RU2615670C1 - Hot strip rolling method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method comprises strip rolling by working rolls, measuring temperature of a left T_l and a right T_r of edges of billets by pyrometers and inter-roller gap change based on measured temperature. Wherein inter-roller gap is increased by amount of ΔS/2 from the edge of billet with a higher temperature by changing a position of the upper roller, and it is reduced by amount of ΔS/2 from the opposite edge, wherein the value ΔS is determined from the ratio of

where R is working roller radius, mm; Δh is absolute compression: cage strips, mm; B is width of rolled strip, mm, C_k is rigidity of rolling mill bed, t/mm; Δσ_s=σ_s(T_l)-σ_s(T_r), σ_s (T_l) and (T_r)is resistance to rolled metal plastic deformation at temperatures of, respectively, T_l of the left strip edge and T_r of the right strip edge, kg/mm².

EFFECT: elimination of side wedge-shaped bulges and distortion of rolled material.

2 dwg

Description

The invention relates to rolling production, and more specifically to methods for hot rolling of strips and sheets.

During hot rolling of strips, the distribution of thickness over the width is usually uneven due to the fact that the compression of the strip decreases from a hotter driving edge to a less hot edge on the service (transshipment) side, and the cross-sectional profile becomes wedge-shaped; the thickness of the driving edge of the rolled strip is less than the thickness of the edge on the service side.

There is a method of reducing the wedge-shaped profile when shifting the rolled strip along the barrel of the work rolls (A.S. SU 1652007), in which the compression of the strip from the side of the edge located at the edge of the barrel is increased, and from the side of the edge located in the middle of the length of the rolls, compression reduce.

The disadvantage of this method is its applicability only for the case of lateral displacement of the rolled strip.

A known rolling method (patent UA 20129), in which the reduction of the wedge-shaped cross-sectional profile is achieved by reducing the reduction of the strip from the drive side by changing the profiling of the work or backup roll: make a bevel on the drive side on the work or backup roll, the depth of which is determined by the average value of the measured difference temperature of the edges of the rolled strips.

The disadvantage of this method is the inability to control the parameters of the bevel during the rolling process.

A known rolling method (patent RU 2368443) of targeted impact on the rolled strip by changing the position of the pressing devices of the horizontal rolls in order to equalize the rolling forces from the drive and maintenance side and straighten the resulting crescent shape with powerful high-speed guide bars.

The disadvantage of this method is that the equality of the rolling forces from the drive and maintenance side does not equalize the thickness of the rolled strip along its width.

Closest to the proposed invention in technical essence is the "Device for measuring and regulating the flatness of the strips in the rolling process" (patent RU 2211102).

The device comprises a temperature distribution meter for the width of the strip in the areas of measuring the distribution of tension across the strip width. These temperatures are involved in the calculation of the skew of the rolls to equalize the relative tension after cooling of the strip and align the temperature along its width to improve flatness. However, this device does not change the distribution of the strip thickness over its width and does not take into account the temperature change of the plastic deformation resistance (yield strength) of the strip material.

For the current level of technical equipment of hot strip mills, the object of the invention is to provide a targeted effect on the geometry of the strip billet, i.e. the wedge shape of the cross-sectional profile, when it is rolled in conventional strip hot rolling lines to produce sheets and strips without a wedge shape.

The problem is solved and the technical effect is achieved by the fact that in the proposed method of hot rolling of the workpiece in the form of strips and sheets, including rolling with preliminary measurement of the input temperature of the workpiece, the temperature is measured separately on the left (T _l ) and right (T _p ) edges using pyrometers, moreover, to eliminate the wedge-shaped profile of the cross section of the strip, the position of the upper work roll is changed so that from the side of the edge of the workpiece with a higher temperature the roll gap is increased by ΔS / 2, and from the side of the opposite edge it is reduced by ΔS / 2, where

R is the radius of the work roll, mm; Δh is the absolute compression of the strip in the stand, mm; In - the width of the rolled strip, mm; With _to - the rigidity of the frame of the rolling stand, t / mm; Δσ _S = σ _S (T _l ) -σ _S (T _p ), σ _S (T _l ) and σ _S (T _p ) are the plastic deformation resistance of the rolled metal at temperatures T _l (temperature of the left edge of the strip) and T _p ( temperature of the right edge), kg / mm ² .

In more detail, the details and advantages of the invention are explained below in the examples of the invention with reference to the schematic drawings, which depict:

FIG. 1 is a diagram of the formation of wedge-shaped due to the asymmetry of the temperature field;

FIG. 2 is a diagram of a preset skew of the roll gap.

Depicted in FIG. 1, an unevenly heated strip of rectangular cross section (dashed line) with a thickness of H ₀ has different stiffness in width - on the drive side the metal is hotter, which means it is softer, on the service side it is less hot, and therefore harder. This can be described by springs with different stiffnesses: on the drive side, the spring stiffness C ₁ , and on the service side, the spring stiffness C ₂ , with C ₁ <C ₂ . Springs C _to simulate the rigidity of the left and right stands of the rolling stand.

Z ₁ and Z ₂ are the heights of the loaded roll gap on the drive and service side;

L is the initial height of the roll gap.

F ₁ - the force with which the pressure device of the left frame presses on the hotter left side of the rolled strip, and, accordingly, the strip presses on the pressure device of the left frame;

F ₂ - the force with which the pressure device of the right frame presses on the less hot right side of the rolled strip, and, accordingly, the strip presses on the pressure device of the right frame;

X ₁ - stand stretching from the drive side;

X ₂ - stand stretching from the service side;

ΔX ₁ - absolute compression of the driving edge of the slab;

ΔX ₂ - absolute compression of the edge of the strip on the service side.

The skew of the roll gap is expressed as follows:

ΔS-Z ₁ -Z ₂ = X ₁ -X ₂ .

Let us express the rolling efforts through compression, stretching of the frames and stiffnesses of the frames and rolled metal:

F ₁ = C _to X ₁ = C ₁ ΔX ₁ ;

F ₂ = C _to X ₂ = C ₂ ΔX ₂ .

Then

To compensate for the resulting skew of the roll gap ΔS, it is necessary to create a preliminary skew ΔS * = - ΔS before the strip enters the stand.

Thus, in order to determine ΔS, it is necessary to calculate the values of F ₁ and F ₂ in advance.

The rigidity of the frames can be measured or calculated. The dependences of the plastic deformation resistance σ _{S of the} rolled metal can also be determined by direct measurement in the laboratory or found in reference books on metal science.

The rolling force F ₁ and F ₂ can be estimated using the product of the value of the plastic deformation resistance σ _S at the measured temperature by half the area of the deformation zone:

Then

where Δσ _S = σ _S (T _l ) -σ _S (T _p ),

T _l and T _p - temperature of the left and right edges, measured by pyrometers 2 (Fig. 2);

σ _S (T _l ) and σ _S (T _p ) - resistance to plastic deformation of the rolled metal at temperatures T _l and T _p .

So, the value of the preliminary bias is determined in accordance with the formula (1) as follows:

where R is the radius of the work roll; Δh is the absolute compression of the strip in the stand; In - the width of the rolled strip.

The process of presetting the skew of the roll gap is as follows (Fig. 2).

, а на противоположной стороне

.In a pause between the strips, the upper work roll is set parallel to the lower with the height of the roll gap S in accordance with a predetermined compression. When the head of the rolled strip falls under the pyrometers (2), the temperature of the left T _l and the right edges T _{p is} measured, and the skew value ΔS is calculated by the formula (2). Next, the position of the upper work roll is changed and the skew of the roll gap is set so that on the side of the hotter edge, the position of the upper work roll takes on the value

, and on the opposite side

.

Thus, a technical effect is achieved in the form of eliminating the wedge-shaped profile of the cross section of the rolled strip.

Claims (9)

A method of hot rolling a workpiece in the form of strips and sheets, including rolling by means of work rolls, measuring the temperature of the left T _l and right T _{p of the} edges of the workpiece with pyrometers, and changing the roll gap depending on the measured temperature, characterized in that the side of the workpiece edge has more high temperature by changing the position of the upper work roll, the roll gap is increased by ΔS / 2, and from the side of the opposite edge it is reduced by ΔS / 2, while ΔS is determined from the relation

Where R is the radius of the work roll, mm; Δh is the absolute compression of the strip in the stand, mm; In - the width of the rolled strip, mm; With _to - the rigidity of the frame of the rolling stand t / mm; Δσ _S = σ _S (T _l ) -σ _S (T _p ), σ _S (T _l ) and σ _S (T _p ) - resistance to plastic deformation of the rolled metal at temperatures, respectively, T _l and T _p , kg / mm ² .

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