SU1346285A1 - Method of cooling the rolls of sheet rolling mill - Google Patents

Abstract

The invention relates to ferrous metallurgy, in particular, to sheet-rolling production, and can be used for strip rolling, for example, in continuous broadband hot rolling mills. The aim of the invention is to stabilize the roll forming profile during the rolling process. For this, the method involves feeding in the rolling process on the outer surface of the roll of the cooler, for example, water. During the first (2-6) 10 cycles of loading the rolls of the last stand, a cooler with a temperature of 80-100 ° C is fed to the central portion of the roll, equal to 1.05-1.25 of the width of the rolled strip, after which the temperature of the cooler is reduced to 15-40 ° C and cooling lead to the central portion of the roll, 0.7-0.9 width of the rolled strip, and to the roll sections corresponding to the edges of the rolled strip on a length of 0.1-0.3 strip width from their edge the cooler is supplied with a temperature equal to 1.25-2.5 temperatures of the cooler supplied to the central part of the shaft ka This temperature every

Description

The invention relates to ferrous metallurgy, in particular to sheet-rolling production, and can be used in the rolling of strips, for example, in continuous broadband hot rolling mills.

The aim of the invention is to reduce the transverse thickness variation of the rolled strip by stabilizing the profile of the forming roll during the rolling process.

The drawing shows schematically the deformation zone during the rolling of the strip according to the proposed method and the cooling zone.

roll.

Between the rolls 1 roll strip 2 rolls.

Between the rolls 1 a strip 2 is rolled, width B, which has a cooling zone (i) during the exit to the stable mode, a cooling zone (2) after the stable mode and areas /., To which a cooler with an elevated temperature is supplied: / i ( l, 05-1.25) B; / ,, (0,7-0,8) B; / 3 (0.1-0.3) V.

The dryness of the method is as follows.

The efficiency of heat control of the roll surface by controlling the coolant flow rate supplied during hot rolling to the rolls is usually limited by a certain amount of coolant flow, the excess of which does not lead to a change in the roll temperature. One of the principal differences in the method of charging is that it is understood that thermal regulation is carried out by varying the temperature of the water.

This allows for sufficiently fine control of the thermal profile of the rolls and is explained by the following equation;

.V af L / (if - / o) aF, (P

where; V - MoniHOCTb, retracted (supplied)

chiller, kW;

a - coefficient of heat transfer,

kW / (m hail);

M (is- nerepad temperatures between the temperature of the roll barrel and the temperature of the cooler, ° C;

F is the contact area to which the coolant is supplied, m According to expression (1), depending on the ratio of the temperature of the roll barrel / J and the cooler / o, both heat supply to the roll and its removal can be made. It is precisely this possibility that allows, at the initial moment, due to the heat supply to the roll, i.e., when f; / (), it is possible to heat the rolls intensively, reducing the time they reach the steady-state thermal regime. As and; It is known that the temperature in the finishing group of the mills is different. Therefore, water is supplied at a temperature of 80 ° C to the rolls of the last stand of the finishing group. Temperature

less than 80 ° C does not allow for simultaneous achievement of the thermal regime on all the cells and from the last cage to the first one increases up to 100 ° C. Wherein

in the first cages, the supply of hot water is carried out on the middle portion of the roll, equal to 1.05 V (here B is the width of the rolled strip). A smaller value lengthens the period of heating of the mill rolls to the required mode.

Water supply to a wider area up to 1.25 V is rational on the rolls of the last stands. Water supply at a greater width does not give an additional effect in stabilizing the thermal profile.

5 roll, therefore impractical.

This heating of the rolls is carried out during the first (2-6) -10 cycles of loading the rolls of the last stand of the finishing group of the mill according to

20

P 4-05-0 G / (H-BDg),

(2)

where n is the number of roll loading cycles; G - total mass of rolled sheets

5 (lanes), t;

B and I - pyrin and strip thickness, mm;

Df-diameter roll barrel, mm.

Fewer cycles up to

2-10 it is advisable to use when rolling

in the camp of bands of minimum thickness, so

Q, at the same time, due to maximum reductions in the cages, a smaller amount of metal is required to reach the stationary thermal mode of rolling. However, the number of cycles less than 2-10 even when rolling a sheet with the smallest thickness does not lead

At the end of the increase in the temperature of the rolls and stabilization is not achieved.

The number of cycles, equal to 6-10, it is advisable to appoint when rolling a thick strip, provided for by the range of the mill, since the minimum deformation across the cages

0 leads to the fact that the exit to the stationary thermal regime takes longer. The number of cycles more, PM 6-10, leads to overheating of the rolls and the distortion of the thermal profile.

After reaching the stationary rolling mode, the temperature of the supplied water decreases down to 15 ° C (which is quite realistic during this period of mill operation) and is fed to a roll section of 0.7 V in the first cells of the mill finishing group, for example, continuous wideband mill (NShS). Smaller temperatures, like the smaller width of the ZONE of cooling, are impractical even on the first stand, since they can significantly change the roll profile by increasing the transverse thickness variation of the nozzle. Water supply with a temperature of up to 40 ° C and a roll width of 0.9 V can be applied to the rolls of the last stand, with high temperature and a large cooling zone are not rational, because due to the increased heating can bring the profile roll of the required limits and degrade the accuracy of the cross section of the strip.

With a stable rolling process for the section is continuously thickened: its wear of the rolls The temperature of the water supplied across the width of the roll is different. In this case, in accordance with the uneven nature of the roll wear along its length, the length of the areas of increased wear is 0.1 V in the last stand of the mill and 0.3 V in the first stand. Accordingly, the temperature of the cooler supplied to these areas is 1.25 of the temperature of the cooler supplied to the central part of the strip in the last stand, and gradually reaches a value of 2.5 in the first stand. A smaller temperature increase in these zones, even in the last stand, is ineffective in the thermal control of the heat profile of the roll, and a larger price increase can lead to a distortion of the profile even in the first stand and degrade the accuracy of the strip cross section.

The difference in wear along the length of the roll barrel over time (depending on the loading cycles of the rolls) is aggravated and can be taken into account by the fact that every 2–10 loading cycles of the rolls when rolling thin strips and 4–10 cycles when rolling thick strips temperatures increase by 5-15%.

Such an increase in its minimum value is permissible when rolling thicker strips, and maximum in rolling thin strips, since the specific pressure during rolling and, accordingly, the wear of the rolls increases with decreasing thickness of the rolled strip. A smaller number of cycles, as well as a larger one, leads to an additional distortion of the profile. In this case, in the first case, the roll has a large deflection at a given area of wear, and in the second - a smaller one.

The implementation of the method can be carried out with the help of known devices used, for example, in the NShS 1700. At the same time, steam heaters are introduced into the water supply collectors. During the period of transshipment on the mill, water supply nozzles are adjusted for rolling each strip in accordance with the diagram in the drawing, sections of which are activated by a command from the U.S. console. In this case, the temperature of the water supplied to the surface of the roll is regulated by the flow of water through the nozzles. The method can be implemented with the help of other water and steam supply systems known and used in the mill.

Example. A strip of size 2.4 x 890 mm is rolled from steel 08KP on the NShS 1700. The modes and parameters of the proposed process in the cells of the finishing group NShS 1700 with

o

hot rolling strip, 2.4 x 890 mm are given in table. 1. From the analysis of the result of comparative rolling (Table 2), carried out according to the known and proposed methods, it follows that the output to a stable rolling mode according to the proposed method is carried out at less than 2 times the volume of the metal, which significantly improves the accuracy of the rolled products.

The strips rolled on the NShS 1700 are further cold rolled and annealed. The rejection of cold-deformed strips obtained from hot-rolled coils, rolled in a known manner according to the defect. “The flatness and weldability of the coils” is 0.9%, and according to the proposed -0.4%. The cross-sectional thickness difference of the strips rolled on a hot redistribution using the proposed method at the end of the roll campaign is reduced by 3 times (Table 2).

The general technical and economic indicators of the proposed method are as follows:

reduction in the amount of rolled metal before reaching a stable thermal regime.

reduction of strip thickness variation;

a decrease in the volume of low-grade steel;

increase rolls resistance in one rolling campaign.

The method provides stabilization of the profile of the forming roll according to the measure of its release to the thermal mode of rolling and growth of surface wear.

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Claims (1)

Invention Formula A method of cooling the rolls of a sheet rolling mill, comprising supplying a cooler, for example water, to the outer surface of the roll during the rolling process, characterized in that, in order to reduce the lateral thickness of the rolled strip by stabilizing the profile of the forming roll during the rolling process, ) During loading cycles of the last stand rolls, a cooler with a temperature of 80-100 ° C is fed to the central portion of the roll, equal to 1.05-1.25 pshrins of the rolled strip, after which the temperature of the cooler is reduced to 15-40 ° C and cooled They lead to the central portion of the roll, equal to 0.7-0.9 of the width of the rolled strip, and to the roll sections corresponding to the edge of the rolled strip on d, 1-ni O, -0.3 pshnna strip from their edge, the cooler serves with a temperature equal to 1.25-2.5 temperatures of the cooler supplied to the central part of the roll, and this temperature is increased by 5-15% every (2-4) -10 load cycles of the rolls. Note. All parameters are given by averaged values. T, T, T - the temperature of the water supplied to the zones cooling rolls 1.1 and 1 respectively. Table 1 Rolling method 0.025 0.015 ABOUT 0.015 0.020 0.030 0.035 0.040 0.055 0.065 0.075 table 2 0.015 ABOUT ABOUT 0,010 0,010 0,010 0.015 0.020 0.020 0.020 0.025