Operation of mill stand roll drive 2030 under conditions of cold rolled stock production and NLMK PJSC coatings

Introduction

PJSC NLMK is an enterprise with a full metallurgical cycle: from the production of raw materials for the smelting of cast iron and steel to the final product - flat metal rolling with high added value. High-quality metal products of NLMK PJSC are used in various strategically important sectors of the economy, from construction and engineering to the production of energy equipment and large-diameter pipes.

The overall production scheme includes the following alterations:

- agglomeration production;

- coke-chemical production;

- blast furnace production;

- steelmaking;

- rolling production.

PJSC NLMK is an enterprise with a full metallurgical cycle: from the production of raw materials for the smelting of cast iron and steel to the final product - flat metal rolling with high added value. High-quality metal products of NLMK are used in various strategically important sectors of the economy, from construction and engineering to the production of energy equipment and large-diameter pipes.

The rolling production is represented by the GWP hot rolling shop (hot rolling production), and the PCPP cold rolling shops (cold rolling and polymer coating production), CAT (transformer steel production), PDS (dynamic steel production).

Theoretical part

1.1 Manufacturing process

The rolling billet is hot rolled etched strips in rolls coming from the hot rolling mill 2000. Strip thickness 1.86.0 mm, width 9001850 mm.

Two continuous etching units are installed in the workshop for removal by mechanical breakage and chemical dissolution of scale in solutions of hydrochloric acid from the surface of hot-rolled strips of carbon steel rolled into a roll.

The main dimensions of the unit: width 12 m, height 10.95 m, length 323 m, deepening 9.6 m. Each unit includes: a roll unwinder, a welding machine, a storage unit, baths for etching, neutralization, washing and cleaning strips, a drying unit, as well as a solution regeneration unit.

Hot-rolled rolls are fed by bridge crane in vertical position to device for transportation, tilted to horizontal position and delivered to receiving part of unwinder.

The device for transporting rolls includes: a 49.2 m long plate conveyor with walking beams for 14 rolls, a width meter, a 440 kN tilter, a transporter with a walking beam for three rolls, a belt removal machine, a loading chain conveyor for five rolls with a total length of 19.4 m (transportation speed 9 m/min), hydraulic installation to provide devices for transporting rolls with hydraulic oil with a pressure of 14 MPa.

Inlet part is intended for unwinding of rolls, cutting of front and rear ends, cutting of defects, welding of strips butt to obtain continuous strip before etching. Loading trolley has lifting drive from two hydraulic cylinders 280/160 and 1200 mm, displacement drive - from 12kW DC motor. The cantilever four-stage unwinder is designed to place a roll, center along the axis of the etching line and unwind the strip from above. The front end of the strip, pulling and correct unit serve to feed the front end of the strip from the unwinder to the guillotine scissors, straighten the strip and after cutting the feed to the welding machine. The thickness of the metal cut on the shears is 6.0 mm, the width is 1950 mm, the maximum cutting force is 625 MN, the stroke of the movable knife is 100 mm.

Type of welding machine SBS 80/1600/19H with welding transformer with capacity of 1.6 MW, draught force of 780 kN at pressure of 10 MPa. The maximum width of the strip to be welded is 1.9 m.

The set of tension rollers serves to unwind the strip from the unwinders after welding and to create tension of the strip in the loop device (four rollers with a diameter of 1.3 m, a barrel length of 2.1 m, three rollers have a diameter of 254 mm, a length of 600 m). The rollers are lined with polyurethane.

Inlet loop device is intended for creation of strip reserve ensuring continuous operation of the unit during transition from one unwinder to another, as well as preparation, welding of strip ends and treatment of welding seam. Horizontal loops (6 branches) are located under etching baths. Lower part of loop is supported by rollers, and upper part is supported by trolley and rollers of turning devices. Three loop trolleys and guide rollers. Strip margin 720 mm, trolley speed 130 m/min, tension created by looped trolley drives 45.884.0 KN. Loop drive from two 0530/530 kW motors, speed 0750/775 per minute.

The auxiliary winch serves to fill the strip and bring the ends together in case of a break. The tensile straightening machine is designed to pre-mechanically remove scale from the strip and create the necessary tablet properties. The number of rollers is four, diameter 1.3 m, barrel length 2.1 m, hardness 15mm of the polyurethane coating HSh 95 ± 3 u. Number of working rolls - three, maximum diameter 76 mm, minimum 67 mm. In one cassette along the axis I - 12 support rollers with a maximum diameter of 134.5 mm, a minimum of 125.5 mm, a width of 120 mm, on the axis II - 11 rollers with a width of 120 mm and two with a width of 30 mm. During the operation of the pulling and regular roller assemblies, the welding machine, and the scale straightening machine, dust and metal particles are sucked by air flow through the sleeve filters down and fed by means of an auger into the nearby boxes.

The acid bath consists of five sections with a total length of 133.275 m, a width of 2.5 m and a depth of 0.9 m. Outside the bath there are stiffeners made of shaped steel, from the inside there is a 4-mm layer of ebonite, the walls are lined with acid-resistant brick and tiles made of melted basalt. Granite blocks and gummed dehydration rollers of etching solution with diameter 345 mm, barrel length 2.3 m are installed between bath sections. Lifting and pressing of rollers from 12 pneumatic cylinders. Technical synthetic 32% hydrochloric acid is used to etch the metal. The composition of the etching solution is 200 g/l of total acid. The amount of circulating solution is 250 m3.

Maximum strip speed, m/min: in the inlet part 780, in the etching 360, and in the outlet 500. Filling speed 60 m/min. At etching of 25 t of strip roll with section of 2.3 x 1350 mm the average capacity of etching unit is 360 t/h.

Continuous etching unit No. 2 in terms of the composition and characteristics of the equipment is made in the same way as continuous etching unit No. 1. Its composition additionally includes passivation section with length of 5.0 m for application of solution protecting metal from corrosion.

Passivation solution composition, kg/m3: 42 soda (NaCO3), 42 trisodium phosphate (Na3P04), 42 borax (Na2S2O3).

Double set of control squeezing rollers is arranged on outlet side of etching bath.

The washing bath is made as a five-stage cascade washing and consists of five sections with a total length of 23.7 m. The set of squeezing rollers behind the bath is similar to the squeezing rollers behind the etching bath.

The outlet of the pickling unit is equipped with two tension rollers with a diameter of 1300 mm, a barrel length of 2100 mm and two pressure rollers with a diameter of 254 mm and a barrel length of 800 mm. The loop device at the outlet is designed to form a strip reserve (450 m). Horizontal loops (four branches) are located under etching baths. The lower part of the loop is supported by rollers, and the upper part is supported by a trolley and rollers of rotary devices. There are two tension trolleys. Tension created by the drives of the loop trolleys, 4568 kN.

The set of tension rollers No. 3 is designed to form strip tension at speeds of < 60 m/min.

Side edges on etched strip are cut on disk scissors. Two disk scissors are installed in the unit, when working with some, they adjust others, which reduces the time for replacing and tilting knives. The diameter of the knife before the shifting is 400 mm, after 360 mm, the thickness of the knife before the shifting is 40 mm, after 20 mm. There are four knives in the installation. The maximum width of the edge to be trimmed on one side is 35 mm, the minimum is 10 mm. The scissors are made in the form of long ones, i.e. with non-driven knife shafts. In the unit - two crumb scissors. To tighten 10.8108 kN of the strip, tensioning and pressing rollers are installed in front of the coiler.

The lubricating machine is designed to lubricate the strip with anti-corrosion protective oil or emulsion of 12 spray nozzles, applied depending on the speed and width directly or through the felt roller. Excess oil is squeezed by a pair of gum rollers with a diameter of 200 mm, a barrel length of 2.1 m.

Technical characteristics of mechanical scissors of transverse cutting of welds, sample cutting and harvesting device from them are similar to scissors of transverse cutting of inlet part.

After cutting, the strip with the help of sets of deflecting rollers No. 1 and No. 2 is supplied to the drum of floating type coilers with an electrohydraulic tracking system. Coilers are driven from 0810/810kW engine (10450/1350 rpm). The maximum permissible weight of the roll is 45 tons, the tension of the strip is 105 kN.

From the reel drum, the reels are transferred by the stripper to a humpback chain conveyor consisting of a movement trolley and a removable fork, and by a device for transportation to a storage of etched reels. The conveying device consists of a discharge double-chain conveyor 40 m for 11 rolls, a muld walking beam for three rolls, a humpback walking beam 14 m for four rolls and a double-chain conveyer 185m for 26 rolls. Transportation speed from 9 to 12.5 m/min.

In a warehouse, rolls are marked, tied with one or two metal ribbons, weighed on 50t scales with a photovoltaic sensing device and a remote printing device. The continuous etching line is automated. As a result of automation using UVM, mechanisms of the unit of input, central and output parts are controlled, sequence of operations for strip transportation, selection and control of technological mode of strip processing, tracking of material from the moment of roll supply to unwinder to its marking with data transfer to UVM of the mill via machine communication.

Technical Operation Description

2.2.1 Maintenance Rules

Preparation and setup of mill:

Before rolling the mill is adjusted and prepared:

1) Input:

- inspection and cleaning of transport devices, unwinders, pressure and deflecting rollers.

- cleaning and blowing of steel structures of the welding machine with compressed air.

- cleaning of photo sensors.

2) Stan:

- inspection and cleaning of wiring valves

- inspection of the surface condition of the drums of the working rolls before filling into the stand for detection of surface damage and defects in the preparation of the rolls.

- check of roughness of working rolls barrels for the 5th stand for compliance with the requirements of NTD.

- inspection of the surface condition of the barrels of support rolls before filling into the stand for detection of damage.

- check of nozzles operation at short-term actuation of emulsion supply: closing of cooling zones on rolls, distribution flare and uniformity of supply. Adjustment of replaced nozzles (row A at an angle of 15 ° to the rolling line, row B and row C at an angle of 45 °).

- checking the condition of strain gauges, pressure and stress rollers for the absence of navels and balls.

- adjustment of thickeners according to the sample.

3) Output part.

- inspection and cleaning of transport devices, coilers, pressure and deflecting rollers.

- cleaning of photo sensors.

- checking the reliability of welding on the welding machine of the internal turn.

Responsibility for the preparation of the mill is assigned to the rolls, the senior roll, the operators, the APCS electrician, the flaw detector. Control of the preparation of the mill is carried out by a replacement foreman, a senior roller maker.

The results of the inspection are recorded in the technological log of the mill with signatures of the responsible performers. The decision to start rolling is made by the replacement master.

The mill setup shall ensure that the strip is of the required thickness and profile in accordance with the standards and specifications.

2.2.3 Reception and delivery of shift.

During shift delivery the main equipment is inspected:

a) Input of continuous rolling line:

- loading step conveyor with centering device.

- loading trolley

- device for vertical alignment of rolls along the axis of the unwinder drum

- device for removal and cutting of packing tape

- unwinder

- bar front end position indicator

- pulling rollers and correct machine

-directing table

- shear cutters of the ends

- conveyor

- double wiring table

-including rollers

-making machine

-feed rollers

-tensioning rollers No. 1

-controlling roller

-belly device

- support roller table

-tensioning rollers No. 2

- rotary "pulling" (stabilizing) roller

b) Inlet part of the board rolling line:

-start step conveyor

-stop trolley

- double-head unwinder

- device for bending and directing the end of the strip with a three-roller feeding machine

-director

-feed rollers

- device for strip clamping and lowering

-centering device

-directing table

- strip hydraulic clamping

- cross-cutting scissors

-meter of thickness

-Binding tape removal device

c) Work stands:

- support plates with prefabricated baths

- grab stands with hydraulic pressure devices

- devices for roll transshipment

-press postings

- device for blowing off the emulsion strip in front of the thickeners and behind the stand No. 5

- intercellular conductor tables

- feeler gages

-Band Tension Detection Appliances

-press rollers

-stressometric roller

d) Outlet of the mill:

- pulling rollers

- volatile drum scissors

-coiler No. 1 with roll collider

- temporary flapper No. 1

- unloading trolley No. 1

-directing roller

-coiler No. 2 with roll collider

- temporary flapper No. 2

- unloading trolley No. 2

-press rollers

-reel conveyor

-reel centering device

-Inspection Table Coiler

-press roller

- device for folding and direction of strip end

-chain conveyor

- scales

-reel binding device

-reel marking device

2.2.4 Interchange service.

Technical maintenance is limited mainly by regular tightness checks of hydraulic pipelines and hydraulic cylinders, cleaning and lubrication of wear plates at the bed before rolling the rolls.

Preventive care is also provided with daily maintenance of the stands:

Give the command "Disassemble electrical circuits and disconnect hydraulics," check the validity of disconnection of mechanisms by test start-up and allow maintenance personnel to repair by transferring the key-tag and token-tag to them.

Inspect the equipment, paying attention to:

- oil leakage through the heels of roll couplings (during transshipment of work rolls);

- condition of roller couplings fasteners;

- presence of clearances in connections of rod rods of all hydraulic cylinders;

- availability of lines, limit switches and their serviceability;

- supply of lubricant to the gear stand;

- supply of lubricant to oil boxes of spindles and level of lubricant in reduction gear box of drum shears;

- supply of lubricant to pulling and deflecting rollers;

- assemble wrenches-tags and tokens, give a command to assemble electrical circuits and check the operation of mechanisms and limit switches by switching on;

- give the command: - "start work";

General Instructions for Technical Care of Rolling Rolls:

- prior to installation of roll sets should be thoroughly cleaned and the sliding surfaces of cushions should be sufficiently provided with plastic grease;

- roll barrels must be thoroughly cleaned of plastic grease and oil before initial rotation. This is essential to ensure that the support rolls do not slip when falling off and that there is no surface damage;

- when rotating the rolls, the bearing temperature should be monitored first;

- immediately upon the start of the rotation of the rolls, the cooling means for the rolls should be supplied, dosed accordingly to the rotation speed;

forged steel rolls used for steel or non-ferrous metal flaring in cold rolling mills have hardened barrels and are very sensitive to temperature and overheating effects;

- At each rolling mill, interference occurs that disrupts the normal working process, the causes of which are damaged surfaces of the rolls, primarily working rolls;

the causes of these interference may be rolling material slippage, welding at strip break points, delamination and coagulation, or electrical maintenance errors of the rolling mill. All this leads to unexpected overheats of the hardened surfaces of roll barrels;

- to avoid such losses due to such interference, the rolls should be removed from the rolling mill and checked well before new installation into the rolling mill;

- damage to the roll as a result of any interference cannot always be determined by eye, and therefore it is recommended to check the batch of barrels with 3% nitric acid, also called "nital," in case of interference, to determine how large the overheating was and what conclusions should be made regarding the grinding.

Types of repairs and their maintenance

2.3.1 Current and overhaul

The current repair of the working stand drive is carried out in accordance with the repair schedule of the mill 2030. The first with a frequency of 30 days with a stop of the mill for seven hours; the second with a frequency of 29 days with a stop of the mill for 34 hours. During repair, scheduled transshipment of all working and support rolls together with supports and cushions is performed; it is necessary to remove the cover of the gear stand, remove the rolls and pillows from the stand; also remove the gearbox covers. Clean all parts from oil, dirt and wipe dry, replace if necessary. The purpose of the repair is to determine defects in the parts, the degree of their wear and suitability for further operation.

Inspect the frames and covers of the gear stand and reduction gears and check if there are cracks, potholes and other defects that violate their strength. Check attachment of working and gear stands.

In oil pumps check the condition of gland packing, density of flange connections and cleanliness of channels, check the condition of the filter and clean it.

Perform check of fillets and working surfaces of inserts of gear roll supports. At increase of clearances in fillets perform surfacing with babbit and install remote rings to reduce run-off.

Inserts shall be replaced if cracks are found in their body, painting on more than 20% of the surface of the insert, delamination of the babbit layer or lag behind the body of the inserts. When the inserts wear less than the maximum permissible standards, the inserts are welded with subsequent boring and pounding.

Gear roll teeth wear shall not exceed 25% of the original thickness. If the wear rate is exceeded, the gear rolls are replaced with new ones.

Overhaul is carried out in accordance with the repair schedule of the mill 2030 with a frequency of once a year with the mill stopping for 5... 10 days; and the following types of work are performed:

- complete disassembly of gear stand and reduction gears, removal of pressure screws and universal spindles;

- detection of defects in parts their elimination or replacement of worn out parts, if they are not subject to repair (gaskets, seals, inserts, bolts, etc.);

- cleaning and washing of all lubrication channels;

- inspection of foundations and slabs;

- assembly of reduction gears, gear stand and its alignment relative to rolling axis and relative to location of working rolls of stand.

Installation of pressure screws and universal spindles.

After repairs, testing is performed with preliminary connection of lubrication and cooling system.

Conclusion

During the course project, the issues of technical operation and repair of the work stands of the continuous mill "2030" in the conditions of operation of PCPP OJSC "NLMK" were considered. Technical map of intermediate shaft repair has been developed. Power calculations of the mechanism drive motor, kinematic calculation were made, strength calculations were training for the performance of the diploma project.

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