JPS63123B2 - - Google Patents

Description

[Detailed description of the invention]

In the rolling of a plate material using a reversible rolling mill, the present invention uses a rolling pattern that maintains the shape of the plate well during rolling in the latter half of the rolling pass, and a rolling pattern that maximizes the capacity of the rolling mill in the first half of the rolling pass. The present invention relates to a rolling control method for rolling. In general, when rolling plate materials, it is important to perform rolling so as to obtain a rolled product with good plate thickness accuracy and good shape. The good shape here refers to a flat plate without waves such as ear waves or medium waves. Conventionally, as a rolling method to obtain a good shape, a method has been used in which the crown ratio (ratio of plate crown amount to plate thickness) is constant in each rolling pass.For example, in rolling thick steel plates, , the first half of the rolling pass is rolled with a rolling pattern that provides the maximum rolling amount within the range of rolling capacity (hereinafter referred to as the full load pattern), and the second half of the rolling pass is rolled with a rolling pattern that provides a constant crown ratio in each pass ( (hereinafter referred to as shape path)
Conventionally, a rolling control method has been used in which rolling is performed. The problem with this rolling control method is that
The problem is which pass should bring the boundary between the full load pass and the shape pass, but the conventional method is to determine the target crown of the rolled product (the target crown in the final pass), and then set the crown ratio at a constant value. Using the conditions, determine the rolling reduction amount of the upstream passes sequentially from the final pass, and stop the shape pass when either the rolling load or the rolling torque exceeds the capacity of the rolling mill.
This is a method of determining a total path schedule with the remaining upstream paths as fully loaded paths. In such conventional methods, the number of shape passes varies even if the dimensions of the plate are the same, depending on how the final pass aims to give the crown and the state of the roll profile at that time, making it difficult to obtain a good shape. Sometimes I can't. This situation is shown in FIG. Curve A in the figure is an example when the target crown is large or the roll crown is large, and the curve A is an example when the target crown is large or the roll crown is large. The number of shape passes that can be obtained is 2, and curve B is an example when the target crown is small or the roll crown is small, and the number of shape passes that can be taken within the rolling mill load limit is 5. The reason why the number of shape passes changes depending on the aim crown and roll crown will be briefly explained next.
In general, the crown CR of a rolled plate is calculated using the following crown calculation formula CR = f ₁ (F, W) + g ₁ (CW) + g ₂ (CB) ... f ₁ (F, W): Sheet crown caused by roll bending due to rolling load However, F: Rolling load, W: Strip width g ₁ (CW): Strip crown caused by work roll crown. However, CW: Work roll crown in the strip width portion g ₂ (CB): Strip crown caused by back-up roll crown. , CB: Calculated by the back-up roll crown of the plate width part. As the rolling load (F) increases, the plate crown (CR) increases, and as the roll crown (CW or CB) increases, the plate crown (CR) increases.
is in a relationship that becomes smaller. The rolling load when determining the amount of reduction in the shape pass is determined based on the above formula, so if the target crown of the final pass is set large, the rolling load during the final pass will be increased, and as a result, as shown in Figure 1. The pattern looks like curve A. Even if the target crown is the same, if the roll crown is large, the rolling load must be increased, resulting in a pattern similar to curve A. In the opposite case to the above, a pattern like curve B in FIG. 1 will result. The number of shape control passes required to obtain a good shape during rolling depends on the material and dimensions of the plate (product thickness,
If the number of shape passes determined by the conventional method described above is less than the required number of shape control passes, it will not be possible to obtain a good shape, or conversely, the required shape control will not be possible. If it is larger than the number of passes, the total number of passes will increase and the rolling efficiency will be reduced. The present invention is a shape control method in plate rolling that eliminates the drawbacks of the conventional method as described above. As a control pass, the number of passes of the shape control pass is determined according to the material of the rolled material and the dimensions of the rolled product,
Based on the target crown of the rolled material in the final pass and the reduction rate of the crown ratio (crown amount/plate thickness) of the rolled material in the shape control pass, the crown calculation formula including the rolling load, the exit plate thickness and the reduction amount are included. Using the rolling load calculation formula, calculate the rolling amount for each shape control pass sequentially from the final pass, and for each pass upstream of the shape control pass, calculate the rolling amount that results in a load close to the load limit value of the rolling mill. A shape control method in plate rolling, characterized by determining a pass schedule and rolling based on the schedule. Hereinafter, the method of the present invention will be explained in detail based on an example in which it is applied to rolling of a thick steel plate. First of all, the dimensions of the rolled product (thickness and width)
Separately, the required number of shape control passes is determined as shown in Table 1.

[Table] The required number of passes is determined empirically; if the product board thickness is large and the product board width is small, the number of passes required is small; if the product board thickness is small and the product board width is large, the required number of passes is many. The reason for this is that when the board thickness is small and the board width is large, the shape is likely to collapse, and vice versa, the shape is difficult to collapse. Next, the target crown of the rolled product, that is, the target crown (hereinafter referred to as target crown) CRn of the rolled material in the final pass (n pass) is determined, and the rolling load Fn at the final pass is determined from the above-mentioned formula. From the rolling load Fn during this final pass, the following rolling load calculation formula F=f ₂ (H, DH, T, R, K)... H: Output plate thickness DH: Reduction amount T: Plate temperature R: Roll diameter K: The inlet side plate thickness of the final pass, that is, the outlet side plate thickness H _o-1 of the (n-1) pass, is determined using a parameter representing the hardness of the plate material. In addition, the formula is
"Plasticity and Processing" Vol.16 no 168 (1975-1) p10~
This is similar to equations (1) and (26) in ``Mathematical model for thick plate rolling'' in Section 17. In order to obtain a good plate shape, the crown ratio (CR/
Since H) must be within a certain range, the following crown rate calculation formula is used: CRi/Hi=CRn/Hn+δ.(n-i)...where δ is the crown rate reduction rate described later, and n is the final pass. The number i is an arbitrary pass number (other than the final pass) among the shape control passes to determine the target crown CR _o-1 in (n-1) passes. Here, the crown ratio reduction rate δ is the amount of change in crown ratio per pass that can be changed while maintaining a good shape within the number of shape control passes specified in Table 1 above, and These are predetermined according to the dimensions of the finished product. Once the target crown CR _o-1 for the (n-1) pass is determined, the rolling load F _o-1 for the (n-1) pass is determined from the formula, and the exit plate thickness H for the (n-2) pass is determined from the formula. _o-2
seek. Thereafter, repeat the same process for the required number of shape control passes to determine the exit plate thickness, that is, the amount of reduction in each shape control pass, and determine the pass schedule. Then, within the load limit of the rolling mill, use the formula to determine the pass schedule for the full load pass. stipulate. When determining the pass schedule for the shape control pass above, if the rolling load calculated based on the formula before reaching the required number of passes exceeds the load limit value of the rolling mill, the predetermined target crown or crown ratio reduction rate may be Considering that the method of determination was inappropriate, the target crown CRn and/or the crown ratio reduction rate δ are modified to be smaller by an appropriate amount, and the calculation is recalculated so that the required number of passes can be obtained in the shape control pass.
This target crown and how the recalculation is performed by correcting the crown rate reduction rate are shown in Figures 2a and 2b. Figure 2a shows a plate whose size requires 5 passes for the shape control pass, where the target crown in the final pass is CRn, the crown rate reduction rate in the shape control pass is δ, and the number of passes is sequentially upstream from the final pass. When setting the pass schedule for the pass,
In the (n-3) pass, the rolling load exceeds the load limit value, indicating that under these conditions (CRn and δ), the number of shape control passes cannot be taken three times. FIG. 2b shows that the above conditions have been modified, that is, the target crown in the final pass has been modified to CRn', the crown rate reduction rate has been modified to δ', and the required number of passes has been secured. In both figures, curves A and A' indicate the rolling load in each pass, curves B and B' indicate the crown ratio in each pass, and curve C indicates the load limit value of the rolling mill. In this way, in the method of the present invention, the required number of shape control passes is determined according to the material and dimensions of the rolled product, and the pass schedule is determined to ensure the required number of passes. A rolled product with a good shape is always obtained, and the number of passes is not increased unnecessarily and rolling efficiency is not reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a path schedule determination method according to the conventional method, and FIG. 2 is an explanatory diagram of a path schedule determination method according to the present invention.

Claims (1)

[Claims] 1. In rolling a plate material using a reversible rolling mill, multiple passes including the final pass and closer to the final pass are defined as shape control passes, and the shape control passes are controlled according to the material of the rolled material and the dimensions of the rolled product. The number of passes is determined, and the crown calculation formula including the rolling load is calculated based on the target crown of the rolled material in the final pass and the reduction rate of the crown ratio (crown amount/plate thickness) of the rolled material in the shape control pass. Using a rolling load calculation formula that includes the exit plate thickness and the amount of reduction, calculate the amount of reduction for each shape control pass sequentially from the final pass, and each pass upstream from the shape control pass has a load close to the load limit value of the rolling mill. 1. A shape control method in plate rolling, characterized in that a total pass schedule is determined by determining the amount of rolling reduction, and rolling is performed based on the schedule. 2. When calculating the rolling reduction amount for each shape control pass sequentially from the final pass, if the load exceeds the load limit value of the rolling mill in an intermediate pass of the shape control pass,
Claim 1, characterized in that either or both of the target crown in the final pass and the reduction rate of the crown ratio in the shape control pass are corrected to a small value, and then the reduction amount of each shape control pass is determined. The shape control method in plate rolling according to item 1.