Cold rolling mills. Stans. Rolling mills. Roll entry rack

A rolling mill is a complex of equipment in which metal is plastically deformed between rotating rolls. In a broader sense - a system of machines that performs not only rolling, but also auxiliary operations: transportation of the original billet from the warehouse to heating furnaces and mill rolls, transfer of the rolled material from one caliber to another, tilting, transportation of metal after rolling, cutting into parts , marking or branding, straightening, packaging, transfer of finished products to the warehouse, etc.

Elements of the main line of the mill cold rolling(SHP)

The main line of cold rolling mills generally consists of the same elements as hot rolling mills: working stand, beds, rolling rolls, spindles, gear stand, main clutch, gearbox, motor coupling, electric motor.

On cold rolling mills, both individual and group drives of rolls are used, both working and supporting and intermediate, depending on the type of mill and its assortment. The most widely used scheme is an individual drive of the rolls. Its application allows to reduce the number of types of electric motors and to choose the optimal gear ratio for NSCP stands. In the case of using an individual roll drive, there is no gear stand, and the torque from the engine is transmitted through a combined gearbox. As a rule, a 1:1 gear ratio is not used on combined gearboxes.

For high-speed SHP, toothed spindle connections with a barrel-shaped tooth profile are used. The largest angle of misalignment at full operating torque for such a connection is 10-30° (with roll changes up to 2°).

Also, cold rolling mills have a spindle connection, consisting of two toothed bushings, planted at the end of the shafts of the combined gearbox; two clips connecting the bushings; four bushings planted on the spindle shafts; two shafts; two half-couplings put on the ends of the work rolls; balancing device (used only during transshipment of work rolls for their fixation).

Barrel-toothed gear couplings are used as the main couplings on the SHP. They consist of two bushings and two clips connected by a connector with horizontally located bolts.

The design of the working stands is determined mainly by the range of rolled strips, the nature of the work and the number of rolls. For cold rolling mills for sheet products, four-roll stands are used. The work rolls are mounted in roller bearings with tapered four-row rollers. The rolling force is perceived by the work rolls, transferred to the barrels of the backup rolls, then to the HPU necks. The chocks of these work rolls do not come into contact with the chocks of the back-up rolls; therefore, the elastic deformations of the work rolls in the vertical plane occur according to the scheme of a beam on elastic foundations.

The HPU provides greater accuracy of working out control actions due to the exclusion of backlash and elastic tightening of the pressure screw when it is rotated under load, which are typical for electromechanical NL. In addition, HPU has low wear, high reliability and ease of maintenance. It is more compact and less metal intensive, which makes it possible to make the working stand compact and increase its rigidity. The HPU, located at the top, is more convenient and 10-15% cheaper than devices located under the bottom pad of the back-up roll.

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Introduction

1. a brief description of technological process and mechanical equipment LPTs-11

1.1 Purpose, arrangement and operation of the cold rolling mill 2000

1.2 Analysis of existing designs of cold rolling mill 2000

1.3 Rules for the technical operation of cold rolling mill units 2000

1.4 Measures to improve the reliability of the units of the cold rolling mill 2000

1.5 Types and methods of metal quality control

1.6 Lubrication of the drive units of the cold rolling mill 2000

1.7 Occupational health and safety during the operation of the cold rolling mill 2000

1.8 Environmental protection under the conditions of HPC-11

Conclusion

Sources used

Appendix

Introduction

IN last years the production of cold-rolled sheet, sheet metal and strip is increasing more and more. This is due to the fact that in many sectors of the national economy there is a constantly growing demand for thin sheet steel with high mechanical properties, precise dimensions, and good surface quality. Cold rolling combined with heat treatment makes it possible to produce steel sheets that meet these requirements. In 1977, the share of cold-rolled sheet

The modern method of cold rolling of sheet steel is the roll method, in which the metal in the form of long strips is wound into rolls of a large mass. For rolling thin sheet steel in coils, mainly continuous mills are used, and with a small amount of production, single-stand reversing mills with a four-roll stand and multi-roll ones. Roll rolling on continuous and single-stand mills occurs with strip tension. Sheet cold rolling is much less frequently used on single-stand reversing mills (without tension).

Improvement of cold rolling technology is on the way to improve the accuracy of finished products due to: the rigidity of the working stands; application of means of elastic anti-bending of rolling rolls; improving the quality of rolls and equipping the mills with systems for automatic control of sheet thickness during the rolling process.

The relevance of undergraduate practice is due to the fact that increasing the efficiency of industrial production and reducing costs in all parts of the metallurgical cycle largely depend on the rational organization of the production process, repairs, as well as the rationality of various technical solutions.

The purpose of the undergraduate practice is to test the professional readiness of the future specialist for independent work and to collect materials for writing a graduation project.

1 . a brief description oftechnological process and mechanical equipment LPTs-11

Technological process

The five-stand tandem mill is connected to a continuous pickling line and includes a double winder (two tension drums) and a built-in control station at the exit section. The configuration of the 4-roll CVC stand allows for rolling in accordance with the requirements of economy and quality.

Handling of work backup rolls requires stopping the entire line (Pl - TCM). As a rule, transshipment is carried out during downtime due to Maintenance or pickling/oiling (P/O) when the strip is not on the line. metal rolling unit

Actuators of process control systems include:

Hydro-fluidic AGC in stands №№1-5

Positive and negative bending of work rolls in stands No. 1-5. Axial shift of working rollers in stands No. 1-5 (CVC - 4PLUS)

Multi-zone cooling device in the flatness control system with closed loop in cage No. 5

Strip thickness control model, thickness control, flatness control, seam detection and tracking device.

To guide the front end of the strip during threading and cutting the strip and to fix the strip when changing backup rolls, the following equipment is installed on the support frame immediately in front of stand #1:

Strip clamp / cut clamp;

Cross cut scissors;

Side guide strip.

In addition, additional supports and guides are installed for

the following measuring devices located at the inlet:

Tensiometer;

Thickness gauge;

Detector weld.

mill stands

On the stands No. 1-5 are installed:

Hydraulic roll gap control cylinders are quick response with low friction. Hydraulic cylinders in all stands are equipped with pressure sensors:

Single stand control system for continuous control of the rolling line;

Cassette-type frame window with an integrated balancing system for the upper back-up roll and the system; positive/negative work roll bending with servo control

System of dynamic axial shift of work rolls with servo-hydraulic regulation;

Drive of work rolls by means of universal drive articulated spindles, gear reducers, gear coupling and one modern AC main drive motor per stand;

Modular mill stand piping for reduced installation time and quick start-up of the mill (all-in-one design).

Etching unit

Etch inlet

The roll transport system, located between the hot roll storage bays and before pickling and the pickling unit inlet, is mainly composed of: a walking beam for moving rolls in a vertical position, a roll transport trolley, a roll turntable, a second roll transport trolley, a walking beam with a preparation station, a shuttle trolley and two roll trolleys. In the hot roll storage aisle, the rolls are loaded onto the roll platforms by means of a crane installed in the aisle.

With the help of the first walking beam, the bales (in vertical position) are transported in the transfer position (stationary bale rack), from where the first transport trolley picks up the bales and transfers them to the turner.

The turner turns over the bales and the second bale transport trolley picks up the bales in a horizontal position and transports them to the second walking beam conveyor. The walking beam transports the bales step by step to the bale platform, which is then the transfer point for the bales to the shuttle trolley.

entrance area

After uncoiling the decoiler drum #1 and #2 as described below, the strip is transferred to the waiting position in front of the welding machine: the dressing table is raised and moved towards the bale, while the shock roller is actuated.

With the help of the unwinder, the front end of the strip moves forward to the separating shears. After that, the rollers of the pull rollers unit and the straightening machine will close, and the head of the strip will be tucked into the separating shears. The head of the strip is detected by means of a sensor, and the length of the strip is measured by a pulse generator at the inlet of the pull rollers. After centering the front edge of the strip, the trimming pull rollers are activated and the front part of the strip is automatically cut on the dividing shears.

Before the exit of the tail of the strip of the previous roll, the unwinder automatically slows down the work of the input section. When the tail extension speed is reached, the

rollers of the straightening machine, shock-absorbing rollers of the directing roller block No. 1 and tension station No. 1. As soon as the tail section leaves the decoiler, the drum is compressed. As soon as the tail section of the strip passes through the leveler, the pull roller unit and the straightener rollers move apart. After that you can

carry out the same procedure as described above for loading the next roll. A measuring device is provided for measuring the thickness of the strip. The straightened tail of the strip moves towards the No. 2 dividing shear, where it will be cut into pieces that are approximately 1 m long.

After the strip is separated, the tail section moves towards the welding machine, and the drive roller of the roller guide block and the take-up device located in front of the strip accumulator will be stopped before the strip tail stops, so that the welding machine and the guide roller No. 1 can to form a loop of the strip.

The separated tail in front of the dividing shear will be cut into non-conforming sheets. During this cutting cycle, by calculating the remaining length of the tail section, the minimum length of the last non-conforming sheet will be limited according to the preset data of the total cut length.

During the cutting operation on the trimming shear, the upper pull rollers of the pull roller units are lowered to trim in front of the shear. Non-conforming sheets fall onto the turntable (top pass line) or directly fall into the cut chute (bottom pass line). The turntable on the top line of the aisle will tilt upward to guide the trim in the scrap box located in the scrap bin area.

Strip welding

The welding process starts after positioning the head and tail in the welding machine. For more detailed information about the welding process, please refer to the corresponding item of the technical specification.

Upon completion of welding, a hole will be made with a punch press to detect welding seam. The strip is then released and the inlet section is ready to start operations again.

Input storage area

During the start of acceleration of the inlet section, the shock rollers of the roller guide block No. 1 and the idler roller No. 1 are raised. At this point, the strip passes through guide roller #1, roller tensioner #1 and deflection rollers into the strip transport area, where it will be guided along the long section to the main bay of the pickling unit. In this section, the strip will pass through guide roller #2, deflector roller and take-up roller station #2 to the inlet looper.

The guide roller No. 1 compensates for the deviation of the strip movement from the center in the inlet section, as a result of which, after passing the tension roller station No. 1, the strip is fed to the conveying section in a centered position. The guide roller No. 2 compensates for the deviation of the strip from the center of the upper conveyance section, as a result of which, after passing the tension roller station No. 2, the strip enters the input looper in a centered position.

The deviation of the strip movement from the center in this looper is compensated by the directional roller No. 3, 4 and 5, which allows the strip to be transferred to the deflecting roller in front of the straightening machine in a centered position.

Strain gauges are provided on the deflecting roller to control the tension of the strip in front of the stretching bending block.

Correct-stretching machine

The strip passes through a straightening-stretching machine. In this section, the bending stress is superimposed on the tensile stresses in the material due to the bending of the strip around the relatively small diameter roller. The two rollers are designed to bend the strip in both directions, the edges being stretched until a long-lasting deformation is obtained. Tensile stress is created due to the difference in speed of the idler rollers, which are in front of the existing block. The stretching speed corresponds to the speed difference between rollers #3 and #4.

The tensile stress is generated due to the speed difference between the tension rollers that are in front of and behind the existing tensile bending block. The stretching speed corresponds to the speed difference between spans #3 and #4.

After the correct stretching machine, the strip is sent to the pickling area.

Pickling/Chemical Processing Area

Due to the high operational flexibility and efficiency, the pickling area is divided into separate pickling chambers with different concentrations of metals and acids. They are separated from each other by means of two rubber rollers, which are connected to the intermediate section.

Each pickling bath belongs to one circulating tank, which ensures the supply of acid in the pickling bath. These tanks are also used as acid holding tanks if acid is drained from the pickling baths during strip downtime. Also, the acid cascade works through these circulation tanks.

The circulation tanks are connected by a common pipeline for accelerated filling of the acid drain tanks.

The top edge on both sides of the pickling baths is shaped like a water run-off trough in order to ensure a perfect pressure, the bath covers are on top. They are made of plastic. This submerged part forms the profile of the vortex etch section.

Both covers (top cover and dip cover for pickling channel) are driven by hydraulic cylinders.

The pickling solution temperature is controlled automatically.

The spent acid is automatically pumped to the regeneration unit. The waste acid flow is pre-calculated using a feed-forward model.

The washing section on the pickling line will be in the form of a cascade. The upper edge of the washing bath is a trough for draining water and forms one line with the pickling baths. The lids are the same as those on the pickling tank, except for the immersed parts of the lids.

Acid circulating collection tanks are built into the rinsing water circulation system. They also have horizontal centrifugal systems.

The rinsing water obtained in the rinsing section I is collected in the rinsing water collection tank.

Before the first pickling bath, a special pre-flushing bath will be installed, which will perform the function of washing the strip in the event of a reverse run.

Slots are provided on the pickling and washing baths, from which the necks of the rubber rollers come out. These openings are closed by means of double sliding shutters.

The drying device, installed after the washing section, consists of two sections: a high-pressure zone and a low-pressure zone, which are supplied with air by means of a fan. The low pressure zone is created by a hot air recirculation system.

Aggressive vapors that form due to high temperatures on the remaining surface of the baths in the pickling and washing area, as well as inside the acid recirculation tanks, are sucked off in order to exclude their occurrence in the line. Before removing this aggressive vapor from the coating level, it must be neutralized, i.e. clean up in accordance with the standards for the composition of industrial emissions, which are developed by the competent authorities for the proposed facility.

Section of the intermediate storage

After chemical treatment, the strip passes through the centering roller block No. 6 and the tension roller block No. 6 into the loop accumulator of the output section No. 1. In front of looper No. 1, a tension measuring device is installed at the exit section, which controls the tension of the strip. This loop accumulator in order to ensure a constant pickling speed in the pickling area during the measurement of the strip width in the edge shear area.

After the looper No. 1, the strip is directed through the control devices No. 7 and 8 to the section of the edge-shaped scissors.

Trimming shears

The section of edge cutters consists of 2 turntables, on which 2 pairs of edge cutters and edge crumblers are installed. The quick change of the trimming shears is done by turning the platform on. During the operation of the line, it is possible to replace the knives of the trimming shears and trimmers with the help of special devices. In this section, if it is necessary to change the width of the strip, the strip is stopped by means of a weld detection device and an automatic strip stop device so that the weld is in the zone of the side die-cutting press.

After the notch is made, the strip is directed to the edging shears.

As soon as the strip width is changed, the weld passes through the tensioner #4 and the deflection roller and guide roller and is directed to the output looper #2. Also, a device for automated quality control of edge trimming was installed at the section of edge trimming shears. In addition, an automated strip surface inspection device is provided in this section.

Output storage area

A device for measuring strip tension is provided near the deflecting roller in front of the output loop accumulator No. 2.

The output looper No. 2, which has the form of a 6-thread store, is located under the roller floor, under the section of the edge trimming shears. Guides #9, 10, 11 and 12 align the strip to the center of the looper area before it is routed into tensioner #8.

The output looper No. 2, located between the edge trimming shears and the input section of the TCM, performs two main functions:

Accumulates streak during tandem bale change at overlapping tasks,

Guarantees tandem operation during edge trimming when combining tasks.

Also, both outlet loopers can be used together to accumulate strip when changing work rolls on a tandem cold rolling mill.

In this case, both accumulators are released before the start of transshipment, and the pickling rate decreases. Thanks to this, it becomes possible to continue the work of the pickling section at a low speed, but without stopping the line.

Under normal circumstances, the storage carts of both loopers are set to an intermediate position. This allows for a certain time to continue the operation of the line in different sections in case of any problems or unplanned stops.

connection area

The strip is fed through the guide device No. 13 to the joint area.

Guide roller #13 executes wrong strip position before. How it will be directed through the tension device No. 7 to the mill - tandem cold rolling.

The last tensioner is used to create the required strip tension for the first stand of the tandem.

Assortment LPTs-11

Geometric dimensions of the strip rolled on the tandem mill 2000:

strip thickness: from 0.28 to 3.00 mm;

strip width: from 880 to 1880 mm (without cutting side edges), from 850 to 1850 mm (with cutting side edges).

Parameters of cold rolled coils:

the inner diameter of the cold-rolled coil is 610 mm. It is allowed to produce cold-rolled coils with metal or cardboard sleeves;

outer diameter of cold-rolled coil: 1200 - 2500 mm;

weight of cold-rolled coil: no more than 43.5 tons.

Rolls with a diameter of less than 1200 mm are considered defective.

The parameters of cold-rolled coils must meet the requirements:

STO MMK 2305, STO MMK 2259, STO MMK 2095, VTI 101-P-KhL 11-39, VTI 101-P-KhL 11-40 or ND for shipment.

It is allowed to roll with reductions that do not comply with Table 1, provided that the cold-rolled steel will comply with the requirements of regulatory documentation and the load on the equipment will not exceed the allowable. The decision on rolling is made by the senior foreman of the mill or the shift foreman of the rolling section, provided that the conditions of the order are met.

In terms of dimensions, maximum deviations in thickness, width, flatness, telescopicity and surface quality, cold-rolled coils must comply with the requirements of the current shipping regulations.

Production cold-rolled steel on the tandem mill 2000, it is carried out strictly in the sequence specified in the task of the shop PRB for pickling and rolling, taking into account the formation of installations in accordance with this TI.

1 .1 Purpose, device and workcold rolling mill 2000

Elements of the main line of the cold rolling mill (SHP)

Barrel-toothed gear couplings are used as the main couplings on the SHP. They consist of two bushings and two clips connected by a connector with horizontally located bolts.

1 .2 Analysis of existing designs of cold rolling mill 2000

Classification of cold rolling mills

By appointment: rolling, skin training, rolling skin skinning.

By the nature of the work: continuous, reversible, sheet, roll, endless.

According to the number of rolls: four-roll, five-roll, six-roll, twelve-roll, twenty-roll, thirty-two-roll, thirty-six-roll, special.

According to the number of stands: single-stand, two-stand, three-stand, four-stand, five-stand, six-stand.

Annex 1 shows the classification of cold rolling mills according to the number of rolls and the working stand.

1 .3 Technical rulesoperation of cold rolling mill units 2000

On modern rolling mills, scale from under the roller tables is removed by hydraulic, dry or combined methods. A channel is made in the foundation under the roller table, into which scale falls from the rollers of the roller table during the transportation of rolled products along them. From the channel, the scale is washed off with water (hydraulic method) into a settling well or removed by a conveyor (dry method) into a common collection. With the combined descaling method, both of the first methods are combined: hydraulic - for cleaning fine scale and dry - for cleaning large pieces of scale.

Care must also be taken to ensure that the rollers do not come into contact with the deck slabs due to shearing of improper laying of the latter, as this may cause premature wear of the rollers or their jamming.

It is very important to ensure regular, timely supply of lubricant to the friction units of the roller tables and in sufficient quantities, since otherwise heating of the parts and their failure is inevitable.

The most accelerated wear in roller tables with a group drive is subjected to bevel gears and plain bearing shells. This is especially observed in furnace and working roller tables of swaging mills, which, in contact with hot metal, become clogged with scale falling off the metal.

The use of a centralized lubrication system on roller tables prevents rapid wear of bearing shells, reducing their consumption by several times.

Therefore, when caring for roller tables, the main attention should be paid to their systematic cleaning of scale and the provision of bearings with lubricant.

To avoid mixing liquid oil with grease, it is recommended that roller bearings adjacent to gear oil baths be lubricated with the same oil as bevel gears.

To reduce the effect of heating, it is advisable to cool the rollers with water, placing sprinklers under it in the form of tubes with drilled holes.

When accepting a shift, check:

whether all rollers rotate;

is there any runout of the rollers in the bearings;

whether the inter-roller plates are shifted and whether they are in contact with the rollers;

serviceability and fastening of guide lines;

serviceability of cooling systems of rollers;

the flow of thick lubricant to the friction units by actuation of the feeders;

oil level in gearboxes according to oil indicators: if necessary, add oil;

the flow of thick and liquid lubricant to the roller bearings, transmission shaft, gearbox shafts. If necessary, adjust the amount of lubricant supplied to the friction units using the feeder pistons, as well as clean the oil channels and trays from contamination;

through the inspection hatches in the covers of the gearboxes, check the reliability of the fastening of the gears on the shafts, as well as the radial and axial clearances of the shafts in the bearings; to eliminate the detected faults in accordance with the "Rules for the operation of standard parts".

Transfers are made in the following order:

at the end of the shift, the drivers of control stations, operators and equipment repairmen handing over the shift are required to record in the shift acceptance log data on the condition of the equipment being serviced, malfunctions,

that were discovered during work or, violations of the Rules and measures taken to eliminate them, as well as notify the host of the shift about this:

the shift receiver and shift taker jointly inspect the equipment they service, eliminate the detected malfunctions, after which they report to the foreman (foreman) that the shift has been accepted and what condition the equipment is in;

malfunctions detected during shift acceptance and not recorded in the log to the shift hander are recorded by the shift taker.

In case of detection of malfunctions in which the operation of the equipment is prohibited, the shift host informs the head of the shift personnel of mechanics or the shift supervisor (the equipment can be put into operation only after the complete elimination of malfunctions and obtaining permission to start); the transfer of the shift is confirmed in the log of acceptance and delivery by the signatures of the persons accepting and handing over the shift, after which the shift is considered transferred (accepted).

Inspection of equipment during the handover of shifts should be started by personnel taking over the shift with the equipment in operation (at the end of the previous shift). When inspecting the equipment of the mill during the transfer of shifts, it is necessary to check:

the condition of parts, assemblies and mechanisms, during the operation of which faults were found in the previous shift, and eliminate them;

are there any characteristic noises, shocks and increased heating in bearing assemblies, couplings, resulting from the development of their parts or poor lubrication; eliminate the detected faults;

the state of gearing in gearboxes, gear stands, open gear transmissions - by the nature of the noise (before the mill stops for shift transmission), as well as by the presence of abnormal vibrations and shocks in the drive elements; eliminate the detected faults;

the condition of pipelines and flexible hoses for supplying water, lubricants and compressed air to the mechanisms; if necessary, repair or replace pipelines, hoses and fittings;

supply of lubricant to friction units from centralized grease lubrication systems - according to the operation of feeders; from liquid lubrication circulation systems to bearings - according to oil flow indicators (URZh), the diameter of which should not be within 3 - 8 mm, depending on the lubricated points; to gears - according to oil flow indicators (UTZh), the flags of which must be open; if necessary, adjust the amount of lubricant supplied to the friction units;

the level of lubricant in gearboxes and transmission baths in accordance with production and technical instructions;

the serviceability of the operation of individual manual lubricators and the presence of lubricant in them; if necessary, refuel with lubricants;

are there any oil leaks from couplings, gearboxes and other units in the places of their seals;

the presence of lubricant in oil baths, if necessary, add lubricant to them;

fastening of couplings, spindles, gearboxes, bearing frames, levers on shafts, axle holders, counterweights and other parts and assemblies, the weakening of which during operation can cause equipment to stop or crash;

operation of pneumatic cylinders and air distributors; in case of air leakage, tighten or replace the seals;

serviceability of braking devices, limit and limit switches, alarm systems, interlocks and instrumentation;

the serviceability of the operation of starting, blocking, braking devices and devices;

if necessary, eliminate malfunctions or adjust the operation of these devices and devices;

availability and serviceability of fences;

cleanliness of equipment and workplace;

Availability and serviceability of tools and fixtures of spare parts.

Gears with tooth wear exceeding 30% of the nominal thickness, or with cracks on one or more teeth, must be replaced. Also, rollers with damaged necks or with wear of more than 10% of the nominal size should not be allowed to work. The wear of roller barrels is allowed no more than 30% of the original thickness. Rollers with these defects should be replaced. The gap between the shaft neck and the liners is allowed no more than five times against the tolerances and fits provided for by the system, and the wear of the transmission shaft necks is no more than 12% of the nominal size.

During the revision of the roller table, it is aligned with the geometric axes; check mutual arrangement axes of the transmission and roller axes and adjust the position of the transmission shaft to ensure proper meshing of all bevel gear pairs.

To reduce the repair time of the roller table, it is recommended to use the nodal method, replacing the following nodes:

separate gearbox shafts with gears and rolling bearings;

assembled rollers (axles, bevel gears, barrels of rollers and rolling bearings);

assembled transmission shafts (with bevel gears, coupling halves and rolling bearings).

For a particularly quick replacement, it is recommended to have several assembled rollers in stock, the first gear shaft assembly with a half-coupling and rolling bearings, separate transmission shafts assembled with gears, half-couplings and rolling bearings.

1 .4 Measures to improve the reliability of cold rolling mill units 2000

Reliability - the property of an object to perform the specified functions, maintaining the value of the established performance indicators within the specified limits, corresponding to the specified modes and conditions and use, maintenance, repairs, storage and transportation over time.

Durability is the property of an object to continuously maintain operability for some time or some operating time.

An analysis of the factors affecting the strength of parts, as well as the operating experience of the machine, makes it possible to establish measures that can improve the performance properties of parts, Bad influence elastic deformations can be reduced by increasing the rigidity of the parts. It is more expedient to increase rigidity by changing their cross-sectional shapes, loading conditions, type and arrangement of supports, using structures in which elements work in tension and compression, and not in bending.

Care of the cold rolling mill usually comes down to timely periodic cleaning of them from scraps of metal, scale, used grease and other contaminants. Care must also be taken to ensure that the rollers do not come into contact with the deck plates due to shifting or improper laying of the latter, as this may cause premature wear of the rollers or their jamming.

The use of a centralized lubrication system on roller tables prevents rapid wear of bearing shells, reducing their consumption by several times. To avoid mixing liquid oil with grease, it is recommended that the transmission shaft bearings and roller bearings adjacent to the gear oil baths be lubricated with the same oil as the bevel gears.

To increase the wear resistance of the pins of the roller shafts and transmission shafts operating under normal conditions, they are subjected to surface hardening by high-frequency currents or flame hardening to bring their hardness to 45-50 HRC. The trunnions of rollers operating in difficult conditions are surfacing with PP-3X 2V 8 flux-cored wire. Roller barrels are also hardened by surfacing with PP-3X 2V 8 flux-cored wire.

When transporting hot metal, a sudden stop of the roller table should not be allowed, since the motionless hot metal on the rollers of the roller table causes excessive and one-sided heating and distortion, leading to failure of the roller table.

To reduce the effect of heating, it is advisable to cool the rollers with water by placing sprinklers under them in the form of tubes with drilled holes.

Roller table bevel gears are made of grade 45 steel with bulk hardening to a hardness of 320-380 HB, forged gears are made of grade 50 steel with surface hardening to a hardness of 40-50 HRC.

The Interfactory School for Hardening Parts of Metallurgical Equipment recommends manufacturing roller table gears from steel grades 20 and 20X with carburizing and hardening to a hardness of 32-38 HRC.

1 .5 Types and methods of metal quality control

After the production of cold-rolled steel on a sample 7 m long, the quality of the manufactured products is monitored after the transfer of work or backup rolls, as well as periodically every fourth hot-rolled coil with the entry of control thickness measurements in the production report of the tandem mill 2000.

The sample for control is cut out by drum shears of a cross cut in the output section of the mill when dividing the strip into rolls. The cut sample is stopped on the magnetic belt conveyor No. 2 or by means of the magnetic belt conveyor No. 1 - No. 3 and transferred to the belt conveyor No. 4 with a device for clamping and turning the strip.

The cut sample is clamped and stretched on the strip tilter device.

On the selected sample, the quality control of the following parameters of rolled products is carried out:

The thickness of the rolled strip is measured with a micrometer, in accordance with GOST 19904. The inspection operator, the senior roller operator, controls. The result of the control measurement is recorded in the production report of the tandem mill 2000.

The width of the rolled strip is measured with a tape measure. Supervised by the inspection operator, senior roller operator. The result of the control measurement is recorded in the production report of the tandem mill 2000.

Rolled surface quality from above and below (visually). Inspection of the lower surface of the strip is carried out by turning the clamped sheet by 180°. Inspection of the surface of the strip is carried out in good light. In case of revealing surface defects, corrective measures are taken in accordance with the DD LPTs-11-3. Supervises - a shift foreman, a senior roller operator, an inspection operator, an OKP controller.

The surface roughness parameters of the strip are measured with a portable surface roughness measuring instrument. If there are no requirements for the direction of measurement of the roughness parameter in the RD, order or current technological letters, measure the roughness parameters Ra and Pc in the transverse direction of rolling on the front side of the rolled product. The report of the production of the tandem mill 2000 contains the results of measurements of the roughness parameters of the upper (front) side. Supervises the inspection operator, the senior roller for compliance with the requirements of the RD for products, TI (VTI) and current technological letters.

In the absence of a portable device for determining the roughness parameters, it is allowed to transfer a sample of hard-worked steel with dimensions of 100x100 mm to the laboratory for physical, mechanical and metallographic testing of the Rolling Shop-11 section with a written application from a shift foreman to determine the roughness parameters.

The contamination of the surface of the upper and lower sides of the rolled strip is determined by the method of replicas according to the method M 3-CLK-3-2198-2007. In the production report of the tandem mill 2000, the result of determining the contamination of the upper (front) side in points is entered. Controls the inspection operator, the senior roller for compliance with the requirements of the RD for products, TI (VTI) and current technological letters. Selected replicas from the upper and lower sides are stored for 2 months from the date of production on the tandem mill 2000. The assessment (assignment of a contamination score) is carried out by OKP employees.

To carry out additional control, it is allowed to carry out additional selection of strip sections on the inspection production line according to the capabilities of the tandem mill 2000 (depending on the product range).

The quality of the coiling of the rolled products produced must comply with the requirements of the RD for products, STO MMK, and current technological letters. Supervised by the inspection operator, senior roller operator. If a discrepancy is detected, the deviations are fixed, the rolls are sent to the NP insulator for further processing.

If a discrepancy is found, the previous rolls before sampling are marked by the OKP controller in the transfer passport with a special character "X" describing the discrepancy.

The cut sample is removed from the table of guillotine shears with a gripping device. The cutting of the cut sample to specific geometric dimensions is carried out on the guillotine shears of the UPiNO section using a sample cutter.

After the quality control of the manufactured products, a 7 m long sample is cut on the guillotine shears of the in-line strip inspection unit into technological trimmings.

1 .6 Lubrication of the drive units of the cold rolling mill 2000

Lubrication - the action of a lubricant located between rubbing surfaces.

Lubricants serve to reduce friction and wear of machine parts. Their use also reduces energy consumption and ensures reliable operation of the equipment for a long time. The lubricant completely or partially separates the rubbing surfaces from each other. In this case, the dry friction of the contacting parts of the mechanism is replaced by one of the types of fluid friction, which eliminates or reduces direct contact between the assembly parts. At the same time, the lubricant protects the rubbing surfaces from corrosion, and when using liquid oils, it removes excess heat from them, preventing overheating of machine components.

To lubricate friction units of rolling equipment, depending on their operating conditions and design features, liquid, thick (consistent) and solid lubricants are used. The vast majority of them are products of oil refining. In some cases, to improve the performance of lubricants, animal or vegetable fats, or special alloying substances that improve certain properties of lubricants, are added to them in a small amount.

Liquid lubricants (mineral oils) are widely used to lubricate the main and auxiliary equipment of rolling shops. Its great advantage is the possibility of continuous lubrication of friction units of machines with the same lubricating oil for a long time.

At the same time, it not only lubricates the rubbing parts of the assembly, but also removes wear products, dirt and other harmful exceptions. The main properties of oils that serve as a criterion for their selection for lubrication of rolling mill equipment are: viscosity, lubricity (lubricity), flash and pour points, acidity, and the content of mechanical impurities. The grade of oil for lubricating friction units is selected from the conditions of their operation (loads, speeds, temperature conditions), the properties of the lubricant and the characteristics of the lubrication system.

In general, the greater the load on the friction surfaces and the temperature of the assembly, the higher the oil viscosity should be.

Thick (grease) lubricants in rolling shops are used to lubricate machine assemblies mounted on rolling bearings, plain bearings with a small shaft revolution, swivel joints, low-speed gears, guides and all other friction units of machines. When the use of liquid oils is not beneficial for structural or economic reasons. Thick lubricants protect the working surfaces of parts from the penetration of dust and moisture much better and do not require such expensive seals to seal friction units.

The effect of the physicochemical properties of greases on their performance is similar to the effect of such properties on the quality of mineral oils.

Solid lubricants used in the form of briquettes in rolling production are mainly used to lubricate open necks of rolls of thin-sheet mills, which heat up to 2500 and above during operation.

Typically, briquettes are a fused mixture of fresh and used petroleum bitumen 5 in a ratio of 1: 1 to 1: 4 with small additions of 1-2% solid antifriction filler (fine-flake graphite, talc). Sometimes pure petroleum pitch or rubrax is added to briquettes to improve their lubricating properties. The briquettes are laid directly on the necks of the rolling rolls. Under the influence of high temperature, the briquette mass melts and covers the journals and bearing shells, lubricating them.

It should be noted that the presence of mechanical impurities in greases is more dangerous than in oils, since, due to the higher density of lubricants, impurities are worse removed by filters and, therefore, fall between the friction surfaces, causing their wear.

Purpose of systems:

decrease in the coefficient of external friction during cold rolling;

removal of heat released during the rolling process;

regulation of the thermal profile of the rolls;

obtaining strips with a surface quality that meets the requirements of standards and specifications.

Requirements for the emulsion:

lack of delamination;

lack of toxic compounds;

the possibility of removing residual emulsion products on the strip during annealing.

The preparation of an emulsion based on emulsols "Kvekerol-1914", "Rinol-1" and similar consists in mixing the emulsol with chemically purified water or condensate.

The working temperature of the emulsion is 40-58. The temperature of the emulsion is constantly monitored by the senior roller according to the readings of a digital thermometer.

The fat content of the emulsion (mass fraction of total oils in the emulsion) and the temperature of the emulsion are monthly reflected by the senior roller in the production book.

The temperature regime of the rolls is controlled by the amount of emulsion fed to the barrels of the rolls. When the mill stops, the emulsion supply stops, but the emulsion is continuously circulated through the internal emulsion cycle.

To protect the emulsion from contamination, if necessary, wash the stands, wires, rolls, cushions, rolls with hot water, before washing the equipment, the pumped systems must be switched to drainage. During preventive maintenance, a thorough cleaning of the mill, flushing of pipelines, crankcases and collectors, and emulsion tanks is carried out. As a washing solution, an aqueous solution with a mass fraction of calcined salt of 2-4% or detergents that do not contain phosphates is used. The temperature of the solution should be 40-60.

After washing with a cleaning solution, all equipment and the emulsion system are washed with hot water. After washing all the equipment, the washing solution is fed through the drainage system to the installation for the regeneration of oil-emulsion wastewater and is cleaned according to TI - 101-P-KhL-8-321-2004.

1 . 7 Labor protection and industrial safety during the operation of the cold rolling mill 2000

Under the labor duties of an employee, directly related to the labor function, are understood, among other things, the duties provided for in Art. 211 of the Labor Code of the Russian Federation - the obligation to comply with the requirements for labor protection by legal and individuals when they carry out any kind of activity. Therefore, violation of labor protection rules can be qualified as a disciplinary offense.

Responsibilities for ensuring safe conditions and labor protection in the organization are assigned to the employer. A list of these duties is given in Art. 212 TK.

Furthermore, in accordance with Art. 212 of the Labor Code of the Russian Federation, the employer is obliged to ensure that persons who have not been trained and instructed in labor protection, internships and tested knowledge of labor protection requirements are not allowed to work.

The employer should remember that the employee cannot be considered guilty of violating labor protection requirements with which he was not familiar. The obligation of the employer to provide briefings on labor protection, organize training in safe methods and techniques for performing work and providing first aid to victims with all employees of the organization, including the head, is enshrined in Art. 225 of the Labor Code of the Russian Federation. If the employer has not fulfilled this obligation, he has no grounds for concluding that the employee is guilty; moreover, he himself may be held liable for failure to fulfill this duty.

All hired persons undergo an introductory briefing in accordance with the established procedure. It is carried out by a labor protection specialist or an employee who is entrusted with these duties by order of the employer. In addition to the introductory briefing on labor protection, primary briefing is carried out at the workplace, repeated, unscheduled and targeted briefing.

Conducting labor protection briefings includes familiarizing employees with the existing dangerous or harmful production factors, studying the labor protection requirements contained in the organization's local regulations, labor protection instructions, technical, operational documentation, as well as the use of safe working methods and techniques.

The briefing on labor protection ends with an oral test of the knowledge and skills acquired by the employee of safe working practices by the person who conducted the briefing.

Induction training .

Before concluding an employment contract, all applicants must undergo an introductory briefing on labor protection and a briefing on fire safety.

Introductory briefing is carried out with all newly hired, regardless of their education, length of service in this profession or position, with temporary workers, business travelers, students and students who have arrived for industrial training or practice.

An introductory briefing in the organization is carried out by an occupational safety engineer or a person who is entrusted with these duties. In accordance with federal law dated 30.06.2006 N 90-FZ, if the number of employees in the organization is less than 50 people and if there is no position of an occupational safety engineer in the staffing table, the duties of an occupational safety engineer are assigned to one of the employees of the enterprise.

An introductory briefing is carried out in a labor protection office or a specially equipped room using modern technical training aids and visual aids (posters, exhibits, models, films, videos, etc.).

To conduct an introductory briefing, a program and instructions are developed taking into account the specifics of their production, which are approved by the employer of the organization.

Introductory briefing can be carried out individually or with a group of incoming workers. An entry is made about the induction briefing in the introductory briefing registration log with the obligatory signature of the instructed and the instructing person, as well as in the employment documents. Along with the journal, a personal training card can be used.

Initial briefing at the workplace is carried out before the start of production activities: with all newly hired to the unit, including employees performing work on the terms of an employment contract concluded for a period of up to two months or for the period of seasonal work, in their free time from their main work ( part-time workers), as well as at home (homeworkers) using materials, tools and mechanisms provided by the employer or purchased by them at their own expense; with employees of the organization transferred in the prescribed manner from another structural unit, or employees who are entrusted with the performance of new work for them; with seconded employees of third-party organizations; with builders performing construction and installation work on the territory of the operating enterprise; with students and students educational institutions corresponding levels, passing industrial practice (practical training), and other persons participating in the production activities of the organization.

Persons who are not associated with the maintenance, testing, adjustment and repair of equipment, the use of tools, the storage and use of raw materials and materials, do not undergo initial training at the workplace. The list of professions and positions of employees exempted from primary briefing at the workplace is compiled on the basis of the Decree of the Ministry of Labor of Russia and the Ministry of Education of Russia dated January 13, 2003 N 1/29 "On Approval of the Procedure for Training in Occupational Safety and Testing Knowledge of Occupational Safety Requirements for Employees of the Organization".

Rental Features

Hot

Metal (alloy) is easier to process, therefore, with this rolling method, thinner sheets or a smaller section bar can be obtained.
For the manufacture of products by hot rolling, low-grade, cheaper steel is mainly used.
There is a need for further processing of products, as they are often covered with scale.
The geometry of hot-rolled specimens does not differ in severity (for example, unevenness at the corners of sheets, uneven thickness), since it is impossible to accurately calculate the limits of deformation during metal cooling.

Calculation of the mass of hot-rolled and cold-rolled sheets according to GOST 19903-90, 19904-90:

Reinforcing (reinforcing).
Bearing (foundation).

Cold

This method of rolling allows you to accurately maintain the specified dimensions of the products.
The surface of the resulting samples is smoother, even, so their subsequent processing is minimized (and sometimes not required at all).
Cold-rolled metal becomes harder and stronger (for bending, stretching, tearing) with a uniform structure over the entire area.
Goes into production.
The higher quality of cold rolled steel increases its cost.

Output

If in the first place is the cost of rental, then preference should be given to hot. When is the determining factor appearance, strength, quality, then cold-rolled samples should be purchased.

The cold-rolled steel sheet produced by the cold rolling process is characterized by high surface quality and dimensional accuracy. Such rolling is recommended when processing sheets of small thickness.

1 Cold-rolled sheet - GOST and general information

Cold rolling is used in cases where it is required to obtain thin (less than 1 mm) and high-precision steel sheets and strips, which is unattainable using hot-rolled technology. Also, cold rolled products provide high quality of physical and chemical characteristics and surface finish of the product.

These advantages determine the active use of this type of sheet metal in both non-ferrous and ferrous metallurgy today (about half of the sheet metal now is cold-rolled sheets).

The disadvantage of this scheme is that it is much more energy intensive than hot rolling. This is caused by the phenomenon of work hardening (in other words, deformation) of steel during rolling, which reduces the plastic parameters of the final product. To restore them, it is necessary to additionally anneal the metal. In addition, the described type of rolled products has a technology with a considerable number of different processing stages, which require the use of diverse and technically complex equipment.

In non-ferrous metallurgy, the cold-rolled process is indispensable for the production of copper, strips and strips of small thickness. Most often, it is used for processing structural low-carbon steels up to 2300 mm wide and no more than 2.5 mm thick, which modern automotive industry cannot do without. Almost all types of tinplate are produced by cold rolling, as well as:

structural low-alloy steels (in particular, transformer and dynamo electrical and stainless steel) - 45, 40X, 09G2S, 20, 65G, 08kp, 08ps, etc.;
roofing sheets;
etched and annealed decapir (metal for the manufacture of enameled products).

According to GOST 9045-93, 19904-90 and 16523-97 sheet products are divided into different types depending on:

flatness: PV - high, PO - extra high, PN - normal, PU - improved;
accuracy: VT - high, AT - increased, BT - normal;
surface quality: high and extra high, as well as increased finish;
type of edge: O - edged, BUT - unedged;
type of holiday to consumers: in rolls and sheets.

2 How is cold rolled sheet metal made?

Such rolled products are obtained from (their thickness can reach 6 mm, at least 1.8 mm), which are fed in rolls to the cold rolling section. The starting material has oxides (dross) on its surface. They must be removed without fail, since oxides reduce the quality of the surface of the cold-smoked sheet due to being pressed into it. Scale also causes early failure of the rolls. It is clear that the first stage of the technological operation for the production of cold rolled products is the removal of this very scale from hot-rolled sheets using one of two methods:

mechanical: the essence of the method lies in the application of shot blasting of the surface of the strip or the implementation of its plastic deformation;
chemical: scale is dissolved in acids.

As a rule, now both of these methods are used in combination. First, mechanical processing of sheets is carried out (preliminary stage) in plastic stretching units, then chemical (basic) processing in pickling baths containing hydrochloric or sulfuric acid. Etching with hydrochloric acid looks more effective. It quickly copes with harmful oxides, having greater activity. And the quality of the metal surface after its use is much better. Among other things, in washing baths, it is more complete and easier to remove from the strips, which reduces the cost of cold-rolled sheet products.

After pickling, the coiled material is fed to a continuous cold rolling mill (with four or five stands), which includes:

unwinders;
scissors;
winders;
looping mechanism;
butt welding unit;
flying scissors.

On the chain conveyor, the steel coils are sent to the decoiler, where they are pulled into the pull rollers. From there, the strips go to the rolls of the stand, equipped with a strip thickness control complex and a pressure hydromechanical installation (hydraulic cylinders, a pressure screw, a thickness gauge, a pulper, a pump, a regulating and controlling device).

The strips pass through all the stands provided on the mill, in which they are reduced according to the specified parameters, and then sent to the winder drum (winding on it is carried out with the help of a whip). After that, the equipment begins to operate at full capacity with a rolling speed of at least 25 meters per second (all previous operations are performed at a speed of up to 2 m/s, which is called a filling speed). When no more than two turns of the strip remain in the decoiler, the mill is again switched to the filling speed mode.

To restore the ductility of steel and eliminate hardening on cold-rolled sheets (it is inevitable after the cold deformation procedure), recrystallization annealing is performed at a temperature of about 700 degrees Celsius. The procedure takes place in broaching ovens (they work on a continuous basis) or in bell-type furnaces.

Then the steel is subjected to training - a small (from 0.8 to 1.5 percent) final reduction necessary to give cold-smooth sheets set parameters. Stripes with a thickness of 0.3 mm are dressed in one pass. This operation is characterized by the following positive properties:

increase in steel strength;
reduction of warping and waviness of metal strips;
creation of high-quality surface microrelief;
reduction (slight) of the yield strength.

The most important thing is that after skin pass shear lines do not appear on the surface of the sheets (otherwise they will definitely appear during the stamping process).

3 Possible defects in the production of sheets by cold rolling

The flaws of cold-rolled sheets are diverse, often they are inherent in a certain type of cold-rolled products. Due to the fact that the thickness of such sheets is significantly less than that of hot-rolled ones, most often their defects are associated with waviness, longitudinal and transverse thickness variations, warping, and some other factors due to non-observance of the accuracy of the shapes and parameters of rolled products. Variation in thickness, in particular, is caused by the following reasons:

rolling without the required tension of the end of the strip;
change (due to heating) of the cross section of the rolls and the temperature of the workpiece;
inhomogeneous roll structure.

Often there is such a defect as a violation of the continuity of steel (the appearance of captivity, cracks, holes, delaminations, torn edges). It is usually due to the low quality of the initial workpiece. Also, deviations in the physicochemical parameters and the structure of the metal are often recorded, which arise due to violations of the heat treatment modes of the sheets.

A rolling mill is a set of equipment designed to perform plastic deformation of metal in rolls (rolling itself), as well as transport and auxiliary operations. The structure of rolling shops or departments generally includes equipment of the main line of the rolling mill, consisting of roughing, intermediate and finishing working stands and transmission mechanisms, as well as heating furnaces, systems for hydrodescaling, equipment for transportation, cutting, heat treatment, finishing, straightening, coiling, marking, packaging of rolled products, etc.

The main tasks of rolling production are to obtain finished rolled products of a given size and shape in the required quantity, at the lowest possible cost, with high level physical and mechanical properties and surface quality.

Section rolling mills are divided into single and multi-strand.

According to the location of the rolls, the stands are divided into horizontal, vertical and universal, but the direction of rolling is divided into continuous and reversible.

Depending on the parameters of the manufactured products, section rolling mills are divided as follows.

· Medium grade Circle up to? 75 mm;

Shaped profiles up to 90 mm

· Small-sized Circle up to? 30 mm;

Shaped profiles up to 40 mm

· Wire rod? 6-10 mm

In modern rolling production, increased requirements are placed on obtaining products with the required properties, ensuring compactness, versatility, efficiency, maintainability and energy intensity of equipment.

Along with increased requirements for the dimensional accuracy of rolled products and the quality of its finish, much attention is paid to the production flexibility of equipment, the possibility of prompt reconfiguration to a different assortment, and the reduction of downtime associated with repairs and maintenance.

There is a tendency to cast billets with a shape and dimensions close to the parameters of the finished product, which introduces significant changes in the rolling process: the number of required passes and rolling stands is reduced with a corresponding simplification of the design, a decrease in dimensions and specific energy consumption, however, a decrease in the elongation coefficient imposes increased requirements on the structure of the resulting rolled products and necessitates the widespread use of heat treatment.

Trends in the modern metal products market are manifested in a decrease in the range of finished rolled products and in a greater variety of steel grades. In any case, in order to obtain the highest productivity, it is necessary to ensure the minimum duration of the changeover process when switching to rolling a different size, profile or steel grade, as well as to reduce the downtime associated with equipment maintenance.

The main products are building fittings, wire rod, wire, angles, hexagons, etc.

Cold rolling mills for ferrous and non-ferrous strips

Cold rolling mills for ferrous and non-ferrous strips are equipment for rolling material in cold form by cold deformation. This means that the raw material is not heated in a furnace before rolling.

TO this method rolling is used in order to obtain a thin strip or strip with minimum thickness values, with an even shiny plane, precise cross-sectional dimensions and high homogeneity of material properties. During cold rolling, it is possible to change the mechanical properties of the metal being processed by choosing the necessary parameters of reductions and temperature effects. Rolling of materials in a cold state by cold deformation is widespread, and cold-rolled products are now widely used in almost all areas of our industry.

When obtaining the finished product, the properties completely obtained by cold rolling are sometimes used, such as the precision of the dimensions of the strip with a thickness of up to max. 0.002 mm, improved during rolling strength. Sometimes, when hardening thick strips, the aim is to obtain improved mechanical properties of the strip obtained by rolling. Modern developments Cold rolling mills today are much more advanced in terms of rolling speed or improved axial or radial load carrying capacity of various types of back-up and work roll bearings, as well as their service life. Also, new systems for measuring and regulating the tension of the rolled strips created between the stands, automatic regulation of the strip thickness and elimination of thickness differences have also appeared.

The above developments can be partially implemented on already operating cold rolling units, as a result of which the productivity of already operating units of the mill will be increased without any special financial costs.

The concept of "tape" is related to the thickness of the strip, because up to a certain point there were difficulties with rolling a wide strip with a thickness? 0.2 mm, in this regard, the rolls that needed to be rolled into a strip of thickness? 0.2 mm, it was necessary to dissolve before rolling, i.e. longitudinal division into several lanes. After that, the longitudinally cut strips were rolled on mills with rolls of a smaller diameter and a smaller barrel.

Today, with the existence of multi-roll rolling lines, where the number of rolls can reach up to 20, there is no point in longitudinal dissolution of the coil, because it is possible to roll thinner and wider strips on a multi-roll unit. One must think that in the near future strips with a width of min. 1000 mm and 0.05 mm thick. And only after that the strip will go to the dissolution, where it will be divided longitudinally into strips of the desired width. However, very thin strips, special alloys and materials will be rolled on narrow strip mills.

In connection with the production of extremely thin strips, the requirements for the constancy of their thickness have become much more stringent; to its uniformity. The concept of a strip profile is interconnected with the concept of thickness variation, which refers to the average difference between the thickness of a strip in its center and the thickness within a certain distance from the edge of the strip or its edge.

It is understood that the profile of the cold rolled strip depends on the flatness of the original roll from the hot rolling line. For example, the convex profile of a cold-rolled product almost completely repeats the profile of the source material from a hot-rolled production.

Temperature effects on the strip, the speed of the deformation process, a constant gap in the deformation zone and the strip tension parameter, respectively, affect the thickness variation of the metal along the entire length of the strip. This effect on the thickness variation is not limited, since the precision of grinding the barrel of the back-up rolls is also important. The design of the support unit and the configuration of the roll pin (in the form of a cylinder or a cone) determine which method of control is preferred in determining the accuracy of the dimensions achieved during grinding.

There are a number of other factors influencing the differences in metal thickness along the entire length of the strip. Obviously, fluctuations in the thickness of the material can also be caused by a change in speed during rolling. And this is simply impossible to avoid, especially during the processes of braking or accelerating the unit.

The coefficient of friction generated between the rolls and the rolled material changes, thereby causing thickness fluctuations. Consistency in the rolling mode contributes greatly to the stability of the strip thickness reading. Rolls should be fed to the mill with minimal interruptions. Then an almost continuous rolling process is created, which entails the establishment of the required temperature regime, which affects the profile of the rolls. Significant breaks between rolls contribute to the violation of the established regimes, their adjustment is required, and the parameters of the finished strip leave much to be desired. Variation in thickness of cold rolled steel can be caused by poor quality back-up rolls on the mill. When grinding barrels of rolls, it is necessary to maintain the accuracy of grinding, which also leads to minimizing the parameters of thickness variation. The runout of the rolls in the stand can also contribute to the presence of thickness differences along the entire length of the strip.

The thickness of the material to be rolled and the accuracy of rolling allow for a certain eccentricity of the rolls and their runout.

Invisible defects of the rolls hidden inside also lead to thickness differences. As a result, the roll can bend quite strongly under heavy load. The roll is checked for the presence of internal defects by ultrasonic flaw detector.

The creation of sufficient rigidity in the stand also helps to reduce the thickness variation of cold-rolled steel. Rigidity can be increased by prestressing the stand by equipping the stand with a large number of rolls, rolls made of hard materials and alloys with a small diameter.

In order to reduce the thickness variation of the rolled material, cold rolling mills are equipped with thickness regulators operating in automatic mode, which subsequently corrects the strip profile. There is an impact on the HPU, on the bending and negative bending of the rolls, the tension of the strip, on the methods of cooling the rolls and the rolling speed.

The composition of the rolling mill equipment and the method of the rolling process determine the type of mill.

This is either a non-reversible, or, conversely, a reversible, or continuous rolling unit.

A mill with one stand (single-stand), schematically shown in Fig. 1, can be attributed to the non-reversing mill. The direction of rotation of the rolls does not change. The rolled strip is always fed from the side of the winder, and at the exit is always transported from the decoiler. Such equipment is used for rolling sheet material or strip in rolls, when rolling can be carried out in one pass. This is typical for rolling aluminum foil or for rolling on a temper mill (Fig. 2).

The reversing mill can also include a mill with one stand (single-stand), schematically shown in Fig.3. The direction of rotation of the rolls is reversed. The strip is rolled first in one direction, then in the other, making several passes, which determine the final parameters of the finished product.

A continuous mill includes a mill with multiple stands (multi-stand), schematically shown in Figure 4. The stands on the mill follow each other, the rolling process goes on continuously, across all the stands at once. The cold rolling mill can consist of 6 stands (for sheet metal and thin strip) or up to 20 stands for small sections of special steels. The direction of rotation of the rolls does not change. The rolled strip is always fed from the side of the winder, and at the exit is always transported from the decoiler.

Today, all cold continuous rolling mills are equipped with rolling process controllers that operate in automatic mode and allow the process to be carried out continuously, without stopping the unit. At the moment of removal of the finished roll at the exit, the next roll is loaded at the inlet (Fig. 5).

The input part of such mills is equipped with a group of decoilers, consisting of 2 decoilers, a straightening-stretching machine 2, shears 3, a welding machine 4, loop accumulators 5, necessary for the unit at the time of the weld at a slow speed, tension S-rollers 6. At the exit of the continuous mill 7 there are flying shears 8 and two winders 9.

When the rolls reach the predetermined length, the flying shears, working on the principle of a guillotine, cut off the strip, and the end of the roll goes to the second winder. When the shears are working, the rolling speed is 5 m/s.

Today, combined lines consisting of a pickling line and a cold rolling mill deserve great attention.

The pickling line has a speed matched to the high material processing speed of the cold rolling line. A high-quality acid and emulsion vapor suction system operates on the trawling line and on the camp, which is gentle on the equipment of both lines. The strip accumulator can be vertical, which reduces the length of the combined line as a whole.

Combined lines have their advantages:

reduction of the total composition of equipment;
· one warehouse of rolls;
reduction in the number of staff.

Rolling mill design

Working stands of a strip mill.

Requirements for cold-rolled strip are constantly becoming tougher. This also applies to the precision parameters of the thickness, flatness of the strip, and the cleanliness of its surface. These requirements form the basis for the design of rolling stand equipment, mill entry and exit, and other auxiliary equipment.

Structural changes concern the rolling stands of the mill. To create a prestress in the stand, higher rolling forces are used, pressure devices have become hydraulic, PZHT have become more advanced, etc. The system of bending and anti-bending of work and back-up rolls improves strip flatness and increases roll life between regrindings.

To help control the flatness of the strip, tension meters are installed on the rolling units, which measure the tension of the strip within its width. The GNU system plus the system of bending and anti-bending of work and backup rolls, axial shift also contribute to achieving accuracy in terms of strip or strip thickness.

Two roll mills

The rolling stand is equipped with a certain number of rolls, which subsequently determines the name of the rolling unit. Two-roll stands are suitable for rolling sectional profile material, narrow strips and strips, for flattening wire, and for skin pass processes. The technology of these processes requires a certain constructive equipment of the stand with two rolls. The load that falls on the rolls and the speed of the rolling process determine the choice of bearings for equipping the stand: rolling, sliding, roller bearings, etc. They are constantly being redesigned to last longer and reduce frictional heat loss.

Two-roll mills can be non-reversible, reversible, continuous. On continuous two-roll mills, foil is rolled and the wire is flattened. An example of such a mill is shown in Fig. 6. The composition of the equipment is quite simple: decoiler, material rolling stand and coiler.

The stand for rolling material is shown in fig. 7. The stand is installed on the base 3. Roll pillows, the lower ones are indicated under pos. 5 and upper under pos. 4 are fixed together with the rolls in such a way that the cushions on the service side are fixed along the axis of the base. With the help of strips, which, as a rule, are fixed with bolts on the frame located on the right. On the pillows of the rolls there are recesses in which the strips are installed. This design firmly fixes the pillow, thus preventing its displacement along the axis and giving the cage as a whole additional rigidity.

The chock, as a whole, mounted together with bearings, spacer, bearing cover, hydraulic clamping ring, is pulled onto the roll trunnion. On the drive side, the pillows are called floating, so they do not remain unsecured. The roll handling procedure is thus faster, since the strips and fasteners only have to be dismantled from the maintenance side. During rolling, especially at high speed, the temperature balance increases, as a result of which the roll lengthens, and its fastening on both sides could lead to jamming of the roll. This situation, in turn, could lead to overloading of the bearings. The pillows of the lower rolls are installed not directly on the frame, but on gaskets with a hardened surface 6. The lower part of the pillow rests on the gasket plane, and when the roll is bent, the bearing self-aligns in the pillow.

The strip enters the cage along the guide table 7. The table is equipped with side guides mounted on rollers 9. The guides can be adjusted depending on the width of the strip or tape, for a narrower or wider tape. During transportation, the strip does not touch the guides themselves, but the rollers, which prevents wear of the guides due to constant contact with the strip. A clamping device 10 is fixed on the wiring table, which fixes the strip or tape between the oiled felt and wood pads. The strip is being cleaned. Before transshipment of the rolls, the screw 11 is unscrewed, and the guide table is freely extended beyond the frame opening, so as not to impede the dismantling of the roll and cushion from the frame.

So that dirt does not get on the rolled material, the rolls are cleaned by a bar, or a scraper 12, which is pressed against the roll, collecting dirt from it.

The strip is transported from the cage to the outlet of the unit, first falling on the receiving table 13, and, supported by a pressure roller 14, is directed to the unit winder. To raise the rolls in preparation for transshipment, a screw mechanism 2 is used.

The pressure devices of any rolling unit are used for precise control of the thickness of the rolled material. They can be electric or hydraulic. Since the hydraulic pressures of two-roll and four-roll rolling mills are structurally performed almost the same, we will touch on their description when familiarizing ourselves with the four-roll stand.

We will consider all pieces of equipment that are the same for 2 and 4-roll stands when describing the 4-roll mill.

Four-roll mills

Today, four-roll mills are the most common rolling equipment for the production of cold-rolled material. In the stand of the 4-roll mill there are 4 rolls: two working rolls and two support rolls. The rolling process takes place between the work rolls, and the support rolls increase the rigidity in the stand, which is facilitated by different types installation of work rolls. Usually back-up rolls are larger in diameter than work rolls. This eliminates the deflection of the work rolls. On four-roll machines, usually only the work rolls are driven.

In order for the work roll to be pressed against the support roll in the non-reversible rolling mode, which saves the work roll from deflection, the work rolls are placed slightly ahead of the support rolls. The rolls can be located without axial displacement, but then the support rolls have a two-sided arrangement. How the rolls can be arranged in the stand can be seen in Fig. 8.

By choice, depending on the technology, both rolls on a four-roll rolling unit can be controlled. It is better to make back-up rolls drive rolls rather than work rolls. If the roll length to diameter ratio is > 5:1, then back-up rolls are selected as drive rolls. On such stands, thin material is rolled, where the content of C or Si is high, stainless steel, i.e. where it is necessary to create a large rolling force. The mill, on which the drive rolls are supported, we see in Fig. 9. In its stands, thin material with a high content of C or Si, stainless steel, high-alloy alloys are rolled, and the thickness of the rolled strip can be up to 0.2 mm.

When rolling softer material with driven back-up rolls, higher reductions can be achieved.

The rolling stand bed bears the main loads present during rolling. The beds are made of cast steel. The base plates for the beds are made of steel. Special tightening mechanisms connect the beds and give them additional rigidity. Back-up rolls are installed in the openings of the beds.

Inserts are attached to the beds, thanks to which the position of the pillows of the work rolls and the HPU is set. Rolls with each grinding lose in diameter. Therefore, below, under the pillows of the backup rolls, there are mechanisms that regulate the position of the roll with a new diameter after grinding relative to the rolling line.

The upper chocks of the back-up rolls are equipped with rolling force meters. GNU regulate the gap between the work rolls in the deformation zone.

Roll bearings withstand very high loads. They are located in huge pillows that are installed in the frame opening. In the pillows of the backup rolls there are liquid friction bearings (FBR). The work roll chocks run on roller bearings (cylindrical).

Depending on the load on the backup rolls and the speed of the rolling process, bearings are selected for the backup rolls. On high-performance rolling mills with a high process speed (10--15 m / s), rolling bearings will not last long. Therefore, the diameters of the backup rolls are increased in order to use standard roller bearings or PZT. PVT is more preferable:

They are small in size
trunnion diameter can be increased up to 0.75 of the back-up roll diameter,
· do not demand careful maintenance, as roller bearings.

Six-roll mills

On fig. 10 shows the layout of the rolls of a six-roll mill with a friction drive of the NS type rolls. The intermediate rolls are the driving ones in this mill. The ends of the intermediate rolls are tapered: one roll has a taper on the drive side, the other on the operator side.

Intermediate rolls have the possibility of axial displacement relative to the edges of the strip, which helps to improve the flatness of the strip. Intermediate rolls rotate in different directions. At high speed rolling friction coefficient becomes lower. The transverse variation in the thickness of the strip or strip from the NS mill is also significantly less than on four-roll stands.

rolling mills

On fig. 11a are the positions of the rolls in the six-roll stand. The advantage of six-roll mills over four-roll mills is that the position of the work rolls is more fixed. Since the pillows are in most cases sliding, the handling of the work rolls proceeds at the lowest cost in terms of time.

Disadvantages:

the number of rolls in the stand (support, working, intermediate) makes their inspection less accessible, which makes it impossible to carefully conduct a visual inspection of their surface;
· the difference in the diameter of the support roll and the work roll is 2.5:1;
The more back-up rolls in the stand, the more difficult it is to maintain the stand, because the back-up rolls must be parallel for the normal operation of the rolling unit;
Roll setting device moves four pressure screws in six-roll mills

To install the screws correctly, there are wedge devices that serve to install them and install the pillows. This ensures that the necessary parallelism is achieved between the top and bottom back-up rolls.

When installing rolls, high precision is very important, because it provides a technologically normal operating mode of the mill. The appearance of axial forces causes malfunctions in the functioning of the main components of the rolling unit. The control rolls in the six-roll stand are the work rolls.

Rice. eleven. b shows us one of the possible designs of backup rolls: the execution can be solid or stacked. In this case, individual rollers (4 - 8 pieces) with supports are mounted on the axle as backup rolls.

Multi-roll mills

Multi-roll rolling units are produced in Lately wider distribution, which is associated with a change in demand in the metal products market. There has been an increase in demand for thin high-carbon strip and strip made of stainless steel and special steels. On conventional mills, these orders are not so easy to fulfill: a large number of passes and intermediate heat treatments are required.

Due to the use of a large number of rolls of small diameter, it is possible to roll a strip or strip with a minimum thickness.

There are many benefits associated with investing in multi-roll mills:

Reducing the weight characteristics of rolling equipment;
metal savings;
Reducing the cost of equipment;
· workshop cranes of smaller lifting capacity serving multi-roll mills;
Reducing the height of the building itself during the construction of the workshop;
· a significant reduction in investments made in the construction of a shop for the production of cold rolled products as a whole.

And the main advantage of multi-roll mills is to obtain a high-quality strip or strip, since there is practically no or only a small degree of transverse thickness variation on the material.

These stands can be either non-reversible, i.e. rolls constantly rotate in one direction, and reversible. Here, two work rolls with a small diameter are driven, all other rolls with a large diameter serve as support rolls and are idle during the rolling process. The tapes or strips rolled on such mills are quite long and are wound into coils or rolls.

To reduce the thickness tolerance and improve the surface flatness parameters in the stand, various devices are used to control the roll profile:

By heating the barrel of rolls;
· anti-bending of working and back-up rolls;
supply of lubricant across the entire width of the rolled material to the deformation zone itself;
· differentiated supply of emulsion.

The thickness of the edge of the strip is always different from the thickness of the strip in the middle. On duo or quarto mills, where large diameter rolls are used and the equipment creates increased stiffness in the stand, tight product thickness tolerances are more easily met.

On multi-roll mills, for example, a strip or strip 1220 mm wide with a thickness of 0.125 mm is rolled with a thickness tolerance of ± 3%. In this case, the length of the strip in a roll or a strip in a riot is about or more than 10,000 m.

However, multi-roll mills, especially those with 20 or more rolls, have a number of disadvantages when compared to duo or quarto mills that use larger diameter rolls. These disadvantages are as follows:

· low rates of rolling force in the deformation zone;
· limited rolling speed and associated low productivity;
high temperature during rolling and difficulty in removing heat from the stand;
increased complexity in the operation of the mill;
complex setup;
Requires precision in the preparation of rolls, in particular, during their grinding;
high energy costs associated with the operation of drive systems.

However, the choice of the type of rolling unit and its further design depends directly on the needs and demand of the market and customer satisfaction.