SU1217505A1 - Method of hot rolling of plates - Google Patents

Description

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The invention relates to metallurgical production and can be used in the hot rolling of sheets to improve their flatness and increase the productivity of the rolling mill.

The purpose of the invention is to improve the flatness of the sheet and increase productivity by ensuring equality of stretching across the width of the roll.

The method consists in that the roll is crimped with a CONSTANT relative compression to reach a ratio b / h of 120-160, the temperature of the roll in the passage is determined, and the subsequent rolling is carried out with the ratio of relative reductions in adjacent (proportional and previous) passes and proportional stretching and the temperature of the roll in the last euduyush, skip according to 1 dependence

; -;., - S35

; i, -535

(one)

Where

 relative compression

stretching

the thickness of the roll before and after the pass;

temperature roll in

skip, C, 1 - skip number.

It is known that the rolling process in the finishing stand of a plate mill is divided into two stages: rolling with a constant deformation force and rolling with a deformation force decreasing from pass to pass

The first stage provides high performance of the rolling mill to reach a ratio of the size of the b / h roll 120-160. After that, the rolling force must be reduced from pass to pass to ensure the sheet shape. Failure to follow this rule causes the sheet to roll out of the rolls that are non-planar (wavy or box-like) and in order to be able to be put into the hot straightening machine, it is necessary to make one or two progamochnye passes, which leads to a decrease in productivity rolling mill.

Therefore, in the first stage, the peal is compressed with a constant relative

reduction to achieve a b / h ratio of 120-160, which ensures the highest possible mill capacity in the first stage

rolling.

It is established that in finishing passes the dependence

-g: a icorist,

i where P - rolling force;

6 - relative compression in

pass-,

a is a constant value depending on the parameters of the mill and the rolled sheet.

From the above ratio follows

, at Р, .Р const,.

I and

(additional index corresponds to the maximum permissible value).

Rolling in the first stage with a constant relative compression ensures the full use of power

capabilities of the rolling mill.

In the second stage, the temperature of the stock in the pass is determined, and the subsequent rolling is carried out with the ratio of the relative reduction to pass

to the pass, proportional to the stretch and temperature of the roll in the next pass, which ensures equality of stretch width.

It is established that necessary for

ensuring flatness of the sheets, a reduction in the rolling force is ensured by observing the ratio of relative reductions in adjacent passes.

40

 °

(2).

where a is a coefficient depending on

temperature roll. Considering that

45

(

-e

(3)

come after obvious conversions to dependencies

50

 fi

(four)

After statistical processing, we obtain the dependence of the coees | x 1 and |; nent 55 I on the temperature of roll i.

about

i; -, - 535 t: -S35

(five)

After substituting (5) into (4), we have formula (1).

The range b / h is due to the temperature range of the end of rolling sheets.

For conventional technology, the end rolling temperature is within 950-1000 ° C, and the loss of form sheets occurs when the ratio b / I is 160. At controlled rolling (temperature of the end of rolling CCP-HEO C), the sheet's sensitivity to shape loss under other equal conditions increases and the sheet loses its shape already at b / b 120.

An example. On a plate mill rolled four batches of sheets of steel 17G1S: two on the proposed method, (modes II and IV) and two by a known method (mode I and III).

Modes of reductions in the finishing stand are presented in the table.

When rolling on modes I and III, press on passes, choose from the condition

P ,, ,,, -const,

and in 1 mode deformation force

in the final stage of rolling equal

but 28.5 MN, and F mode - 32.5 MN.

Modes of reductions in the finishing mill stand when rolling a sheet of 12x2250 mm from steel 17G1S

Normally known rolling

2 3 4 5 6

15

217305

In both cases, the sheet, fading after the third pass, leaves the rolls in a wavy and smoothing pass is necessary to level it, which reduces the mill's productivity.

According to the proposed method (II and IV), after reaching the ratio b / b of 160 (normal rolling) and 120 10 (controlled rolling), the critical gap no. 3 is fixed, the temperature of the roll in the pass is determined, and the relative reduction in each subsequent critical passes reduce in accordance with

formula derived from (2)

e;

iiii- Of; -

(6)

In this mode of crimping, the sheet is rolled flat, and the number of passes is reduced due to the elimination of the ironing pass.

The proposed method makes it possible to reduce the flatness of the sheets caused by the inequality of stretching across the width of the sheet from 100-150 mm / m across the width of the sheet to 20-15 mm / m, to increase by 2% the productivity of the mill due to the elimination of the skipping pass.

160 Sheet lost stability

214 After the 3rd pass

Table continuation

Claims (1)

METHOD OF HOT ROLLING OF SHEETS, including measuring the width and thickness of the roll in the aisle and subsequent control of the roll gap by the measurement results, characterized in that, in order to increase the flatness of the sheet and increase productivity by ensuring equality of the hoods across the width of the roll, the roll is pressed with a constant relative compression to achieve the ratio b / C equal to 120-160, determine the temperature of the roll in the aisle, and subsequent rolling is carried out with the ratio of the relative compressions in the aisles, proportional nym drawing temperature and races kata subsequent passage, in accordance with the dependence £ -, e, t; -535 '' where h - the thickness of roll after passage; B - roll width after the passage; 5 - relative compression; 'λ - hood; £ - temperature of the roll in the passage; ί - number of the passage.