JPS6129805B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for controlling rolled plate thickness.

Generally, in controlling the thickness of a material to be rolled, such as a steel plate, by a rolling mill, a gauge meter type is used as a means for detecting the thickness of the plate at the exit side of the rolling mill.

Since the thickness accuracy of this plate thickness control is affected by the accuracy of the gauge meter type, various studies have been conducted with the aim of improving the accuracy of the gauge meter type.
However, there were limits to the online accuracy of both the theoretical and experimental formulas. In particular, when rolling is performed such that each product has different characteristics such as size, as in the case of thick plate rolling, it is difficult to improve accuracy.

As is well known, the gauge meter type configuration is h=S+F/M+δ+α ………(1) It is expressed by the formula.

Here, h: strip thickness at exit from rolling mill, S: roll gap under no load, F: rolling load, M: elastic modulus of rolling mill, F/M: mill elongation, which is generally corrected by strip width. δ is an oil film thickness correction term calculated from the roll rotation speed and rolling load, and α is an offset term.

Therefore, in order to improve the plate thickness accuracy, it is necessary to accurately detect the gauge meter plate thickness using the above equation (1). However, in reality, deviations may occur between the actual roll gap S and the measured roll gap S due to thermal expansion of the rolls, roll chuck yoke, reduction screw, etc., roll eccentricity, roll wear, thermal expansion of the housing, etc. Otherwise, the accuracy of the above equation (1) is not necessarily high because disturbances are given to the Mill elastic modulus M due to changes in the plate width.

In addition to the above-mentioned reasons, there are many other factors that reduce the accuracy of equation (1), and it is actually impossible to correct all of these factors. Furthermore, even if factors such as roll thermal expansion and wear are considered to have a large effect, it is extremely difficult to accurately correct for these factors, and therefore there is a limit to the accuracy of a gauge meter model. It was hot.

Therefore, it has been reported that the accuracy of the gauge meter type can be improved by correcting the offset term α of the gauge meter type using a thickness gauge. Even in good cases, the accuracy was about 1σ = 60μ. This is due to errors in thickness measurement.In addition to the accuracy of the thickness gauge itself, there are many factors that reduce thickness measurement accuracy, such as scale on the steel plate during hot rolling, descaling water, and roll cooling water. (1σ=60
This is because it is extremely difficult to improve the accuracy of the gauge meter type.

That is, the conventional gauge meter type is expressed as Hy=GM+α. However, Hγ: actual value of plate thickness,
GM: gauge meter thickness, α: offset value. However, the actually measured value H.gamma. of the plate thickness always includes an error .DELTA.H (=H.gamma.-H) with respect to the true thickness H, and this error .DELTA.H becomes the error factor of the offset value .alpha..

Particularly in passes near the end of thick plate rolling, the thickness of the plate becomes thinner, and the accuracy of conventional gauge meters is insufficient to control the shapes of ear waves and abdominal waves, and from the standpoint of improving yield. Improvement in this accuracy was strongly desired.

The present invention was made in view of the above circumstances, and its purpose is to easily roll a sheet with high accuracy even under rolling conditions where the sheet thickness is thin and the length of the steel sheet is relatively long. The object of the present invention is to provide a method for controlling the thickness of a rolled sheet.

The inventor focused on the fact that the plate length can be measured relatively accurately without being affected by the atmosphere, and that the offset value α can be regarded as a constant in two consecutive passes. The present invention has been achieved, and the rolled plate thickness control method according to the present invention is characterized in that the average plate thickness in the longitudinal direction of the gauge meter plate thickness of at least two consecutive passes measured during rolling and the average plate thickness of the gauge meter plate thickness of the passes are measured during rolling. The present invention is characterized in that a gauge meter type offset term is determined based on each measured value of the steel plate length, and the steel plate thickness is corrected using this determined value.

According to the present invention, the offset term of the gauge meter type is determined by each measurement value of the longitudinal average plate thickness of the gauge meter plate thickness of at least two consecutive passes measured during rolling and the steel plate length of the passes. Because of this,
The error is converted from the actual measurement error of plate thickness to the actual measurement error of plate length, and the longer the plate length, the smaller the proportion of measurement error, which can be expected to further improve the plate thickness control accuracy. It has become possible to reduce the amount by approximately half.

That is, in the present invention, the offset term is determined using the measured value of the plate length, which is relatively unaffected by surrounding conditions, instead of using the actual measured value of the plate thickness, which has many error factors as in the past. So,
This made it possible to significantly improve the accuracy of plate thickness control.

The present invention will be explained in detail below using Examples.

The gauge meter formula is the formula (1) mentioned above, i.e. h=S+F/M+δ+α ………(1)′ It is expressed as

The offset amount α in equation (1) is α between at least two passes under rolling conditions in which the rolling width remains the same, such as the thickening pass in thick plate rolling, where several passes are continuous. = can be assumed to be a constant.

Therefore, if the thickness of the i-pass plate is H _i , then H _i is as shown in (1) above.
By transforming the equation, it can be expressed as H _i =GM _i +α (2).

Here, GM _i ; (S+F/M+δ)i, α: constant (offset amount) i: number of passes.

The plate thickness H _i and steel plate length L _i of the i pass and (i+1) pass are expressed as shown in Fig. 1, and the relational expression between these plate thickness H _i and steel plate length L _i is H _i ×L _i /ρ ² (T _i )=H _i +1×L _i+1 /ρ ²
(T _i+1 )...(3) Approximately holds true.

Here, H _i : Average thickness of the entire length in the longitudinal direction of the i-th pass (thermal dimension) H _i+1 : Average thickness (thermal dimension) of the entire length in the longitudinal direction of the (i+1) pass L _i : Center in the width direction of the i-th pass Length of steel plate (thermal dimension) at position L _i+1 ; Length of steel plate (thermal dimension) at center position in width direction of (i+1) path ρ(T _i ); Thermal dimension conversion coefficient at temperature Ti ρ(T _i+1 ); is the thermal dimension conversion coefficient at temperature Ti+1.

Substituting equation (2) into equation (3) above, (GMi+α)*L _i /ρ ² (T _i ) = (GM _i+1 + α) * L _i+1 /ρ ² (T _i+1 )
......(4) holds true and α is calculated from equation (4), α=AGM _i+1 −GM _i /1−A where A=L _i+1 *ρ ² (T _i )/L _i *ρ ² (
T _i+1 ).

According to this result, by measuring the steel plate length and gauge meter thickness in at least two passes during rolling, the gauge meter type correction value α can be determined regardless of the actual value of the plate thickness.

Therefore, find α for every two consecutive passes,
By correcting the gauge meter formula in the next pass, the accuracy of the gauge meter formula can be improved.

According to experiments, for example, using the length meter described in Japanese Patent Publication No. 39-688 (Patent No. 425599), it is possible to measure a steel plate with a length of 30 m with a variation of 1σ = 100 mm, but the accuracy of the length meter is It was found that if the accuracy of the gauge meter type can be converted and the plate thickness is, for example, 10 mm, the following can be obtained as the gauge meter type variation: 1σ = 10 mm x 100 mm/30000 = 0.033 mm≈33μ.

Therefore, since the accuracy of the conventional gauge meter type is about 1σ=60μ even if it is reported to be good, the variation can be reduced to about 1/2 by doing as in the embodiment.

This method can be used even when slab specifications and product specifications differ for each product, such as in thick plate rolling.
Gauge meter type variations can be eliminated.

As described above, according to the rolled plate thickness control method according to the present invention, it is possible to easily obtain a highly accurate rolled plate thickness even under rolling conditions where the plate thickness is thin and the steel plate length is relatively long. You will be able to do this.

[Brief explanation of the drawing]

FIG. 1 is a reference diagram for explaining an embodiment of the rolled plate thickness control method according to the present invention.

Claims (1)

[Claims] 1. In a rolled plate thickness control method in which the gauge meter plate thickness is calculated using a gauge meter formula and the rolled plate thickness is controlled based on this calculated value, the gauge meter plate thickness of at least two consecutive passes measured during rolling is A gauge meter type offset term is determined based on each measured value of the average plate thickness in the longitudinal direction and the steel plate length of the pass, and the steel plate thickness is corrected based on this determined value. Rolled plate thickness control method.