SU1722625A1 - Method for rolling sheets and strips in vertical reversible stand - Google Patents

Abstract

The invention relates to the processing of metals by pressure, specifically to the rolling of sheets and strips predominantly from continuously cast slabs into reversible vertical cages of thick and wide-strip mills. The aim of the invention is to improve the width accuracy and productivity by reducing the assortment of blanks. The essence of the invention is to set the amount of reduction in each subsequent pass from the condition of equality of the products of displaced metal volumes to the corresponding stress state coefficient in the considered and previous passes. 1 tab.

Description

The invention relates to the processing of metals by pressure, in particular, to the rolling of sheets and strips mainly from continuous slabs into reversible vertical cages of thick and wide-strip mills.

 There is a known method of hot rolling, in which, in order to obtain a desired width of rolling, the billet is compressed in several (up to five) passes in a cage with vertical rolls only for the width dimension. Then, the rolls are rolled in horizontal rolls to remove the edge bulges, after which the billet is rolled according to the conventional technology to a predetermined thickness.

When the side faces of the billet are compressed by vertical rolls in each pass, the contact broadening of the metal occurs, leading to an increase in the contact surface inappropriately, to an increase in loads on the drive of the rolls.

Closest to the invention is a method of rolling sheets, in which the amount of reduction after each reverse of the vertical stand is set to 0.45-0.5 of the amount of reduction of the previous pass. The distribution of reduction between adjacent passages by this method is intended to reduce the loss of metal in the form of side trimming of sheets by eliminating a wedge-shaped roll.

The disadvantages of this method, which involves a sharp decrease in reduction in each successive passage relative to the previous one, are the reduction of the useful effect of the stand with vertical

Xj

GO

you and hl

rollers to align the input misalignment by increasing the number of private breaks to obtain a given final width of the roll, as well as a significant reduction in the ability of the stand to reduce the width of the slab. The second drawback, along with the decrease in mill productivity, when using the method in vertical cages of the CCM-mill complexes, i.e. when the mill is working on continuous slabs, it leads to a decrease in the productivity of the continuous casting machine due to the need to have a large assortment of slabs in width.

The aim of the invention is to increase the accuracy in width and productivity by reducing the assortment of blanks.

This goal is achieved by the fact that, according to a known method, including regulated compression of narrow edges along the aisles, the amount of reduction in each subsequent passage is set according to

TWO |

Two%

Rb; P#{

0)

where D Vb;, A Vb; -. (- absolute compression of the i-th and previous i-1st passes, mm;

Ft ;, Fbj.i is the area of the contact surface of the metal with the rolls in the deformation zone in this and previous passages, mm;

. - stress ratio in this and previous gaps.

The proposed method differs from the well-known fact that the compression of the side edges of the roll in each subsequent pass after reversing the vertical stand establishes the basis of the equality of the product of the displaced metal volumes by the corresponding stress ratio in the passage under consideration to the previous one. This leads to a uniform distribution of breakdowns along the aisles relative to the allowable loads on the drive of the vertical rolls, ensuring full use of the crimping ability of the vertical stand.

The law of distribution of reductions in adjacent aisles of a vertical stand according to equation (1), taking into account the fact that the contact area of the metal with the roller in the deformation zone is equal to

, Fbj HK; -VABbi-Rbj

where Hiq is the average thickness of the roll at the contact of the metal with the rolls in the deformation zone in the i-th passage, mm;

Rbj - the radius of the vertical rolls, mm, can be represented as follows:

(;.by)

The average thickness of the roll in the contact zone, taking the parabolic law of variation along the length of the deformation zone, is determined by the equation

NK | H0) - + - LNK | ,

(four)

where HP | - the thickness of the roll at the entrance to the cage in the 1st pass, mm.

d Nk; - increment of the thickness at the contact from the broadening of the roll when the side edges are compressed, mm.

A quantitative relationship was established experimentally between compression in vertical rolls and an increment in thickness at the contact, defined by the expression

DNK 0.33-DV |.

(five)

The magnitude of the stress ratio in the high-strain conditions of the deformations of the high bands, to which the process in question belongs, is determined by the known formula

u

(6)

Substituting expressions (6), (5) and (4) into formula (3), we have

3/2

AVvg (0.22 V0. + H0;

HL 22LVe;

VABe; -Rg;

40 45 50

55

Two /, They «-,) (7) |

№-,% - - |

The solution of equation (7) with respect to reduction in vertical rolls in the considered i-th passage is carried out, for example, by the method of iterations.

PRI me R. In a stand-alone vertical stand of the hot-rolling mill 2800, three reversing passes are performed to reduce the width as much as possible, then rolling is carried out according to a conventional technique. The radius of the vertical rolls P 600

mm, the initial thickness of the slab H0 is 250 mm, the allowable compression in the first pass, based on the conditions of the allowable torque and rolling force, the grip angle and the resistance of the roll to transverse bending for the first pass is 100 mm, the initial width of the slab B0 is 1500 mm Calculated formulas.

1. Compression in subsequent passes of the vertical cage:

a) the prototype of AB; 0.5-ABbjv ,,

b) by this method according to the equation corresponding to the law (1).

2. Energy rolling parameters: a) rolling force

 ABeH - ABe, of7 "6 ABfe-Ri

/ 0,0) 42

H

(“)

5. Efficiency of the stand with vertical rollers

p -1

l ....... sb

6. The coefficient of alignment of different widths

Ky

one

1h

(AT)

13.9U-kech6v.

Nk, 9-AZZ 4Ј || .thirty

(eight)

where Кс is the coefficient taking into account the effect of the chemical composition of the steel on the deformation resistance (for steel of type StZsp Kc 1.0);

TI is the temperature of the roll in the deformation zone in the i-th passage;

Vb; - rolling speed in the 1st pass.

b) rolling moment40

Mi 2PiVABb -Rbi - $, (9)

where ty i 0,65 - the coefficient of the resultant leverage; .

3. Reducing the width of the slab

. A B A BЈ-AVN,

(ten)

where A Bbj- total compression for three vertical passes, mm;

A Bn is the forced broadening in horizontal rolls due to the sagging formed on the wide faces of the roll, mm.

4. Forced broadening (assuming that fractional deformation does not affect).

0

0

five

0

five

0

The calculated data for the given conditions and accepted (the temperature of the roll T; 1150 ° С and the rolling speed Vbj of 1 m / s) are presented in the table. The maximum reduction in slab width, which is the difference between the total absolute compression in three passes in vertical rolls and forced broadening during subsequent compression in horizontal rolls, for the proposed method is 2 times higher than in the prototype. The alignment coefficient of the input misalignment according to the proposed method is higher than 1.2 times, which allows a 1.2-fold increase in accuracy in width. The load on the drive of the vertical rolls on the moment in the implementation of the proposed law of distribution of compression remains constant in each pass.

Claims (1)

The given data on increasing the accuracy of rolling strips and sheets in width and ensuring the greatest possible reduction of the width of the slab confirm the achievement of the objective of the invention. The invention of the method of rolling sheets and strips in a reversible vertical cage, mainly from continuously cast slabs, including compression of narrow edges along the aisles, characterized in that, in order to improve the accuracy in width and productivity by reducing the assortment of blanks, the amount of reduction in each subsequent aisle set according to AVY A Vm Fbj. State,., Fbi-rig. where A Bbj, A Vc - szhati in vertical rolls of this and previous passes, mm; Fbj. Fb | - the area of the contact surface of the metal with the rolls in the deformation zone in this and previous passages, mm2; Comparative analysis of the results of the prototype and the proposed way mm t tm mm mm 100 y37 yo 50 331 102 73 0, A2 1.72 25 251 0 By. stress ratio in this and previous passes. 90 64 Yo 128 1M 0.53 2.13 82 Yo