SU1533785A1 - Method of strip end engaging to continuous rolling mill - Google Patents

Abstract

The invention relates to rolling production and can be used on continuous sheet and strip mills. The purpose of the invention is to increase the durability of the rolls and processing equipment and the rolling accuracy of the front sections of the strip by reducing the impact loads and oscillatory processes. The method includes installation in the cages with a given stiffness of the desired roll gap, setting the filling speed of each stand, the task of the strip successively in each stand. For the period of the strip being captured by the rollers, the rigidity of the stand is increased N times, the reduction of the process resistance forces to the required level of static overload is achieved. This ensures the reduction of shock loads in the drive line of the rolls and oscillatory processes. 5 il. 1 tab.

Description

The invention relates to rolling production and can be used on continuous sheet and strip mills.

The purpose of the invention is to increase the durability of the rolls and the rolling accuracy of the front sections of the strip by reducing the impact loads and oscillatory processes.

FIG. Figures 1-5 show the graphs of the static moment variation with increasing rigidity of the stands, respectively, for five stands.

The method includes installation in cages with a given stiffness of the required

the roll gap, the task of the filling speed of each stand and the task of the strip successively in each stand.

For the period of the strip capture by the rollers of the i-th stand, its rigidity is increased by N the number of times in comparison with the given one, and the value of N is determined from the cell

SL

: o & o 1 eo in

N

1 + 2p

1 - Sk where n SP / SKO stiffness ratio

strip Cn in the deformation zone to a given stiffness C „„ 1st

cages;

to

fik 0.3–0.9 is the relative coefficient, which shows how many times it is necessary to reduce the static overload of the moment of forces of the technological resistance during the period of the strip capture by the rolls of the 1st stand.

The essence of the method is explained as follows.

By increasing the rigidity of the cage by a factor N, one achieves a reduction to the required level of static overload by the moment of the forces of technological resistance. This level is characterized by the value of the coefficient preassigned аемогоk.

An expression for determining the value of N is obtained as follows.

The dependence for the moment of resistance on the angle of rotation of the work roll is presented in the form

N (if) P (, (D

The function (3) is investigated for an extremum, as a result, the angle of rotation of the roll is obtained

..

at which the moment of resistance in the area of the strip capture reaches the highest value

M P Br2 (vg

1 MOX GSR PE H M

Rolling moment t steady state

M,

ace

 РсрВг about ст

Write the expression for the coefficient of technological overload

0

five

M

k

Max

 one

 C1

oL

st

.(four)

Consider that x

H

 R.

 U it r t

st

bh g

ot + Ј “

Rm r

 2 Ј.bh, to

de P

wed

AT

g

oL

P

-the average specific pressure in the deformation zone;

-The width of the line;

-radius rolls rolls;

- current angle of filling with metal of the deformation zone;

- the corner of the meeting strip with rolls.

relationship between

(2)

where x - the current deformation of the cage (movement of the rolls in the vertical direction) when filling the hearth.

Then the expression for the moment (1) is written in the form

M (tp) p Wgf h -H 1-- (3)

A uniform law is adopted to deform the stand in the gripping section.

x () Ј (,

where x0 is the deformation of the stand after the strip has been captured, i.e. in steady state rolling.

where Cko - given the rigidity of the cage; uh - absolute compression; C - strip stiffness.

After transformation (4) receive

one

k

+ C1. c2

1 + 2

about

(five)

This expression reflects the dependence of the static overload coefficient on the rigidity of the cage.

An expression is made for the relative static overload factor.

§K k (CKO) - k (Ck)

k (C, J

(6)

0

where k (CKo) k (cK)

static overload coefficient for a given stiffness of stand C; static overload coefficient when the stiffness of the stand C to N – C o is changed N times.

55 Given (5), transform (6) and get

N

1 + 2p

G + tk -p

(7)

515

where n SP / RMS the ratio of the stiffness of the strip Cn to the given stiffness of the Cco stand. Obviously, it is necessary that the relative coefficient changes within 0: Ј k i 1, because the rigidity of the stand (N 1) should be increased until k decreases.

Thus, specifying the value of Јk, which shows in relative values the degree of the required reduction of the static overload coefficient, the value N is obtained from the relation (7) the value indicating how many times it is necessary to change the rigidity of the cage.

Studies show that with ok 0.3, the resulting decrease in the maximum value of the moment of resistance is not enough for a significant decrease in dynamic loads and oscillatory processes to occur. With an increase of 8k over 0.9, the effectiveness of further reducing the maximum static and dynamic loads becomes insignificant, while it is necessary to significantly increase the rigidity of the stand. A range of frk values of 0.3-0.9 in terms of efficiency is most preferred.

The method is carried out as follows.

In the cages with a given stiffness, the required roll gap is set and the filling speed of each stand is set. For each stand of the continuous mill, the required coefficient Јk is set, the stiffness of the strip in the deformation zone Cn is calculated by the known formulas, the ratio n SL / Sc, 0 and the ratio (7) determines how many times (N) it is necessary to increase the rigidity of each stand compared with a given. Before the front end enters the first stand, taking into account the lag of the strip, an electrical signal from the unwinder (or thickness gauge installed in front of the first stand) enters the hydraulic control system of the mill stands. The stiffness of the stands increases. After capturing the strip with rollers, the stiffness of the stands is restored to the desired value. Since the stiffness of the i-th stand becomes equal to C "; M; T, Ko; , in accordance with

785

this new stiffness, before seizing in each stand, it is necessary to establish the size of the roll gap & determined by the ratio

st

L; - X0; - xGS -: -

 B “01

where b4; - thickness of the strip at the exit

IQ from the i-th stand;

P „st; - rolling force in steady state, necessary to achieve the required reduction in the 1st

(5 years.

Example. The strip is refueled in a five-stand cold rolling mill 1700. Compression mode, rolling force in cages and p

20 other parameters for the known and proposed methods are given in the table. The specified rigidity of the stands is 4500 kN / mm. The width of the strip is 1050 mm, the initial thickness is 2.5 mm, it is finite

25 0.5 mm.

As can be seen from the data in the table and graphs, with the proposed method of filling the strip, the required reduction in technological overload is achieved.

JQ and a significant change in the nature of the increasing moment. This in turn affects the reduction of shock loads in the drive line of the rolls and oscillatory processes, as well as an increase in the rolling accuracy of the front sections of the strips.

With the known method of filling, the dynamic factor characterizing the shock load during the capture, in the cells of the 1700 mill, is 2-3. With the proposed method, the dynamic coefficient decreases to a level of 1.4-1.7, which increases the equipment durability 1.5-3 times.

45 With the known method, the oscillatory process in the equipment, including in the elastic system of the stand, lasts 0.5-5 s. The rolling force fluctuations UP reach 5-10% or 30050 1000 kN. Consequently, with a capture speed of 1 m / s over the length of the front section of the strip equal to 1 m / s (0.5–5) m 0.5–5 m, damped thickness variations with the rigidity of the stand C k, g 4500 kN / mm, the composition t hht ЛР / (K 0.05-0.2 mm. With the proposed method, the oscillation of the rolling force and, therefore, the thickness variation is reduced by 3-5 times.

40

The proposed method can, in principle, also be extended to single-stand cold rolling mills and plate mills. On these mills, rolling is carried out in several passes. In this case, the required rigidity of the stand for the task of the strip is determined before each pass according to the proposed dependence.

Claims (1)

Invention Formula The method of filling the strip into a continuous rolling mill, including installation in the cages with a given stiffness of the required roll gap, setting the filling speed of each adhesive, the task of the strip successively in, each cage, so as to increase the durability of the rolls and the accuracy rolling the front sections of the strip by reducing shock loads and vibrational The proposed method Sk 0.3; ftk 0.6; k 0.9; N ck k N GK kM N WITH W processes, for the period of the strip capture by the rollers of the i-th stand, its rigidity is increased by N times compared to the given one, and the value of N is determined from the ratio N 1 + 2p 1 TO - P, p C, / SI - the ratio of the rigidity of the strip Cn in the deformation zone to the given stiffness Sk 0.3-0.9 ko i-th stand; a relative coefficient indicating how much pa i it is necessary to reduce the static torque load of technological resistance forces during the period when the strip is caught by the i-th stand. 1.35 6100 1.7 2.1 9400 M 1.37 6200 2.14 1, 38 6200 2.8 5.58 25100 1.1 2.19 2.26 9900 10000 1.66 1.97 6.18 6.7 27800 30200 1.17 1.24 1.39 6200 3.0 2.3 10,100 2.1 6.9 31,000 1,3 2tn &. # Xt 900 00 0 VS 01 god h I WO) 90 D 200 0 ib / ttsl About 0.02 0.05 Figm ROS 0 0.02 0.06 4, poff FIG. five