SU1761314A1 - Strip rolling method - Google Patents

Abstract

The essence of the invention: the rolling is carried out in work rolls with concave profiling and bending. The force of the opposing force and the arrow of the concavity of the generator of the work roll are set such that the axes of the rolls are convex to each other, while the active generator remains concave. The method improves the flatness of the strip. 2 members, 1 tab.

Description

The invention relates to rolling production and can be used on hot plate and cold rolling mills for producing strips with increased flatness requirements.

To obtain a flat strip, it is necessary that the stretch width be equal in its width at the deformation zone. Usually, equalities of stretching are achieved by the similarity of the roll gap and profile of the strip by acting on the active forming roll due to machine and / or forced (counter bending, additional bending) profiling. An important factor in obtaining a flat strip is the effect of self-leveling of stretching across the width, due to the developing processes of cross-flow of metal in the deformation zone (Grigor n GG, Kotsar S.L., Zheleznoe Yu.D. No. 7, pp.8-92).

There is a known method of rolling in a quarto stand with convex supporting and concave work rolls for increasing, sustaining the process and improving the quality of rolled metal. The essence of the method is to change the rigidity of the roller set in the middle of the roll barrels as they wear out at the point of contact, which allows redistribution of the stretch across the width of the strip when rolling from edge waviness to central (warping). A significant disadvantage of the method is the long duration in the possibility of redistributing the extracts across the strip width (the campaign for the development of support rolls), as well as the neglect

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Qs

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the cross-flow of the metal in the alignment;

There is a known method of rolling sheets in a quarto stand with convex supporting and concave work rolls to ensure uniform distribution of contact forces along the length of the roll barrels with the aim of obtaining sheets of constant cross section. This method allows to obtain a strip with a constant cross section, but it does not allow alignment of the draws to the width of the strip in the deformation zone due to the transverse flow of the metal and, as a result, reduction of the flatness of the strip.

The closest in technical essence and the achieved result to the proposed is a method of rolling strips in quarto stands with convex supporting and concave work rolls for expanding technological capabilities when using a forced bending device. However, in this case, there is no intensification of the cross flow. metal in the deformation zone, and therefore the improvement of the slagosity, rolled strip is not achieved.

The aim of the invention is to improve the quality of rolled strips with lenticular cross-section, mainly due to the improvement of their flatness due to the developing processes of cross-flow of metal in the deformation zone during thin-sheet rolling.

This goal is achieved by the fact that in the proposed method of rolling strips, including rolling with anti-bending of work rolls, made with concave profiling, boom BOI-naught forming the work roll and. The magnitude of the bending force during rolling is set within the limits ensuring that the axes of the work rolls are convex to each other while retaining the active forming concave shape.

The proposed method expands the bending force range and sets the quantitative level of the bending force depending on the rolling force and concavity of the work roll, thereby transferring the impact of the bend from the active part of the work roll, known from

prototype axis.

and analogs, on its deflection

0

five

Thus, the claimed method meets the criterion of Novelty. These signs form a new property of the proposed rolling method that does not coincide with the properties of the known solutions, namely, intensifying the cross-flow of the metal in the deformation zone and self-leveling stretching across the width of the strip, which is crucial in achieving the goal. Technical solutions with similar features that distinguish the proposed solution from the prototype have not been found, therefore, the claimed method of rolling strips has significant differences.

It is known that the difference in stretching across the strip width can lead to the appearance of residual stresses exceeding the critical stresses at which the strip loses its flat shape. The level of residual stresses in the band is less than that calculated by the plane strain scheme, which is explained by the cross flow of the metal.

0 in the focus of deformation. The nature of the cross slip of the metal over the roll depends on the magnitude of the bending of the work rolls. When reinforcing bending, ensuring the rotation of the axes

5 working rolls convex to each other 1) a ;, the horizontal component of the speed of the roll in the direction from the middle of the strip to its edge contributes to the cross flow of the metal. In this way, the non-uniformity of stretching in the middle of the strip and at its edges decreases, reducing residual voltages, the magnitude of which does not exceed the critical buckling value (Fig. 16). With bending forces, the work rolls' axes that do not rotate, the horizontal component of the speed of the roll interferes with the cross-flow of the metal from the center of the strip to its edge (Fig. 2a). In this case, the unevenness of stretching increases and the magnitude of the residual voltage (exceeds the critical value of the formation of undulation (Fig. 26).

To account for the transverse metal flow in the deformation zone, the coefficient 0 Р 1 is introduced. It characterizes

five

0

five

attenuation of residual stresses in the strip.

, Ј E,

where AbosT is the value of residual stresses;

Е - elastic modulus of the STRIP material;

L1 is the difference between the stretch at the current point along the width of the strip and the average stretch; 1 - medium stretch width

stripes.

When representing the non-uniformity of relative stretches in the deformation zone by decomposition

 ... "|

the coefficient P, which takes into account the transverse flow of the metal, will be written as

one .

(2)

where A -, and i - amplitude and harmonic number of non-uniformity of relative stretches

6T31

Jq

15

C6

energy of residual stresses (deformations), in turn reducing the amplitude of the relative non-uniformity of these stresses (deformations). Implement this way of rolling

 it is possible by using an anti-bending of the work rolls, ensuring that the axes of the work rolls are convex to each other. Then the additional alignment of the exhaust, obtained from the principle of the minimum of the total power spent on rolling and the accumulation of residual stresses in the strip, has the form -,

(-H (Ki-H

(3)

Where

 hiai2.§ 2h0b2

S is the deflection arrow in the center of the barrel of the work roll relative to the edge of the strip, R is the radius of the work roll. The strip after rolling does not lose its flat shape, if

EO

DSOST + & G00n GKP

(four)

K2

. sixteen

E 1 h cp

L

where / is the coefficient of friction;

h0 is the output thickness

hcp- average thickness;

1 l - the length of the deformation zone, 40 4h - absolute compression,

B - half-width of the strip, 5 - plastic resistance

deformation of the strip material.

y - coordinate.45

Creating conditions to facilitate cross-flow of the metal increases. leveling ability of the deformation center. One of these conditions is the longitudinal stretching of the roll forming line 50 from the inlet to the outlet section of the deformation zone. In this case, the speed of transverse sliding of the metal over the surface of the work roll is reduced, and, as a result, the friction losses, which impede the transverse flow of the metal, decrease, the power consumed by the potential accumulation of the strip decreases.

E (-4)

 ffOn

where GKP is a critical flatness buckling voltage.

To ensure that the axes of the work rolls are convex to each other, the necessary bending force is divided by the following relation

c. AZ.

to,

n KI P

h --- i,

de Q - force of bending, t;

P - rolling force, t;

Kj - flexibility of the work roll for bending under the effect of rolling force, mm / t;

To the work roll flexure under the action of bending force, mm / t, d - boom of the concavity forming the work roll in the unloaded condition, mm.

7

The lower limit corresponds to the straightening of the work roll axis, the upper one - to the straightening of the active generatrix of the work roll. The coefficients K1 and K depend on the design features of the stand and on roll rolls. Obviously, with an increase in the convexity of the support roll, the coefficient decreases, and K increases.

The proposed strip rolling method is implemented as follows.

When rolling after the front end of the strip is gripped by the work rolls, the force of the anti-contraction is increased to a value falling within the limits indicated in Expression 5. At the same time, the axes of the work rolls are curved towards each other. In the process of rotation, the forming work roll moves from the compressed state in contact with the support roll to the stretched state in contact with the strip at the exit of the deformation zone, thereby facilitating the transverse flow of the metal from the middle of the strip to its edge. concave, thereby preserving the lenticularity of the rolled strip.

Example: Strip rolling 2 x 1200 mm is produced in the last stand of the seven-mill finishing group of the 2000 mill with the following parameters absolute reduction Ah 2 mm, plastic deformation resistance § 10 kg / mm2, friction coefficient f 0.3, rolling force P 600 t, radius working roll R 00 mm, the modulus of elasticity of the roll Eg 2 хУжг / mm2, the modulus of elasticity E 10 kg / mm2.

The dependence of the decrease in residual stresses on the edge of the strip due to the additional alignment of the extracts in expression 3 when rolling the lentils of the figurative profile on the counter31 forces

bending working table.

8 rolls represented

five

0

five

0

The reduction of residual stresses in the strip, depending on the effort to prevent bending of the work rolls, is given

in the table.

The proposed method allows rolling strip with increased flatness requirements.

Claims (1)

Invention Formula A method of rolling strips with a lenticular cross-section, preferably in a four-roll stand, including rolling with bending of work rolls made with a concave profile, characterized in that, in order to improve the quality of the strips on flatness by facilitating cross-flow of metal in the deformation zone, an arrow the concavity of the working roll forming and the amount of the anti-bending force during rolling are set within the limits ensuring the rotation of the axes of the work rolls by convexes FRIEND to a friend while research of the active generatrix of the concave shape, in accordance with the dependence: “2 R 4AL K2  l K2 R, V where Q is the force of bending, t; P - rolling force, t, Flexibility of the work roll for bending under the action of rolling force, mm / t; K2 flexibility of the work roll for bending under the action of the force of bending, mm / t-, dj - boom of the concavity of the forming work roll in the rifled condition, mm. About 110 250 400 600 The known method is +0.04 +0.001 The proposed method -0.1520,022 -0.2340, p34 -0.34307050 cpaZ. 2