JPS6354444B2 - - Google Patents

Description

[Detailed description of the invention]

This invention provides a method for reducing the width of a steel slab, for example, by using a rolling mill row consisting of a vertical roll stand and a horizontal roll stand.
The present invention relates to a method for preventing plane bending (camber) of a rolled material when rolling is performed to apply reduction in the width direction and thickness direction of a slab. BACKGROUND ART Recently, in the steel manufacturing process, a process of continuously casting molten steel to directly obtain billets has become popular. In the case of the process of obtaining steel slabs by continuous casting, from the viewpoint of equipment utilization rate and production efficiency of the continuous casting process, it is best to cast large quantities of steel slabs with as few different cross-sectional sizes as possible. preferable. On the other hand, hot strip coils, cold strip coils, and plate products are required to have a wide variety of width sizes. In the conventional process of injecting molten steel into a mold to obtain a steel ingot and then blooming it to obtain a steel slab, it was possible to create slabs of various widths during the blooming process. However, although the process of obtaining steel slabs directly from molten steel by continuous casting has great advantages in terms of yield and energy cost, it is necessary to reduce the casting width to as few types as possible. , an adjustment process is required to match the casting width with the width required for the final rolled product. One such adjustment process is a rolling process in which the width of the steel slab or the material in the intermediate rolling stage is reduced by a rolling mill train consisting of a vertical roll stand and a horizontal roll stand. In such a rolling process, when rolling a steel slab or the like, a plane bending of the material called camber may occur. If the aforementioned camber occurs in the material during the rolling process to reduce the width of the steel slab, the side guide on the exit side of the rolling mill may be damaged, or the next pass may have poor biting, resulting in misrolls. In addition, in the next process such as flaw inspection, it not only impairs work efficiency, but also reduces the problem of deterioration of flaw detection ability due to fluctuations in the distance between the flaw detection end and the side edge surface of the steel slab, etc. cause Furthermore, the camber that occurs in the material makes handling of the material after rolling extremely difficult. This invention aims to solve the above-mentioned problems caused by material camber that occurs during the rolling process by rolling mill rows consisting of vertical roll stands and horizontal roll stands, which reduces the width of steel slabs, etc. The purpose of this work was to obtain a rolling method that prevents the formation of camber in the material during the width reduction rolling process. The feature is that when performing rolling, which mainly applies a reduction in the width direction to the metal material by a rolling mill row composed of vertical roll stands and horizontal roll stands, the temperature at least in the width direction of the metal sheet material is reduced. Rolling is performed by displacing the pair of rolls of the vertical roll stand existing on the exit side of the final horizontal roll stand in the rolling direction at that time to the lower temperature side in the width direction of the metal material by an amount corresponding to the difference. be. This invention will be explained in detail below. The inventors discovered the cause of camber occurring in the material during the width reduction rolling process of steel slabs, etc., using rolling mill rows consisting of vertical roll stands and horizontal roll stands. It was determined that the cause was uneven temperature. Steel slabs are often heated in a heating furnace 1 shown in Fig. 1 and supplied to a rolling mill row, but within the heating furnace there is a temperature distribution in the furnace length direction as shown in Fig. 1. As a result, the steel slab 2 in the heating furnace 1 has a non-uniform temperature distribution in the width direction when extracted from the heating furnace. This is due to the non-uniform distribution of temperature in the length direction of the heating furnace as mentioned above, as well as the fact that the time it takes for the steel slab to be extracted from the point shown in Figure 1 (furnace exit) is due to line stoppages due to rolling troubles. This is due to the fact that the extractable temperature differs depending on the rolling size and is not constant. As a result, the steel slab extracted from the heating furnace has a lower temperature at the outlet side furnace door at the point inside the heating furnace 1. Such steel slabs, for example, are placed on a vertical roll stand.
V ₁ - Horizontal roll stand H - Vertical roll stand
When rolling (sizing) to reduce the width by V ₂ , plane bending (camber) occurs toward the lower temperature side.
will occur. This is because the amount of deformation on the low temperature side is smaller due to the difference in deformation resistance due to the temperature difference in the width direction of the steel slab, and therefore the stretching is also smaller than on the high temperature side. As a result, the steel slab rolled by V ₁ -H-V ₂ is rolled with a bend toward the low temperature side. Figure 2 shows the temperature difference in the width direction {working side (WS)
The cross-sectional profile of the steel slab after width reduction rolling is shown when there is a driving side (DS). The chain line shows the state of the material, and the solid line shows the state of dogbone formation after width reduction. Figure 3 shows the measurement results of the dogbone height and bending when a steel slab with a temperature difference of 60°C in the width direction was rolled at V ₁ -H-V ₂ using the pass schedule shown in Table 1.

[Table] As is clear from Fig. 2, the drive side DS, which is on the higher temperature side in the width direction, is rolled more in the width direction, and therefore is stretched more in the rolling direction.
The cross-sectional shape of the rolled material is a so-called dogbone shape with a bulge in the thickness direction at the side edges. Even in rolling at this stage, bending occurs due to the stretching difference in the width direction of the rolled material, but when this is further rolled horizontally, as shown in Figure 3, in the width direction of the rolled material, the work side WS and the drive side DS dog bone height
Due to the difference in H _W and _HD , it promotes curvature (camber) of the rolled material. The situation is shown in the upper part of Figure 3. In this way, when there is a temperature difference in the width direction of a rolled material such as a steel slab, this is to prevent bending that occurs when rolling it in a rolling mill row consisting of a vertical roll stand and a horizontal roll stand. ,
As a result of conducting research involving experiments, the inventors have discovered that the roll pair in the most downstream vertical roll stand in the rolling process is displaced to the low temperature side in the width direction of the rolled material while maintaining the vertical roll pair spacing. I found that this is important. That is, for example, when rolling in the direction of arrow X with a rolling mill row consisting of a vertical roll stand _V1 , a horizontal roll stand H, and a vertical roll stand _V2 as shown in FIG.
If DS is relatively high temperature, the vertical roll pair of vertical roll stand V2 on the downstream side in the rolling direction is moved vertically from the roll position shown by the dotted line to the roll position shown by the solid line by ₁ on the work side WS which is the low temperature side. If the distance between the roll pairs is maintained and the rolls are displaced, no camber will occur in the rolled material. The amount of displacement l of the roll pair of the downstream vertical roll stand toward the lower temperature side in the width direction of the rolled material is determined by the temperature gradient in the width direction of the rolled material and the downstream vertical roll stand (in the case of Fig. 4, V ₂ )
It is necessary to find it as a function of the amount of reduction in the width direction of the rolled material. That is, l=f(ΔV ₂ , θ _B ) ...... ΔV ₂ : Amount of width reduction in the downstream vertical roll stand θ _B : Temperature gradient in the width direction of the rolled material at the entrance side of the upstream vertical roll stand, and this equation The amount of displacement l of the roll pair in the downstream vertical roll stand in the width direction of the rolled material in the rolling process is determined, and based on this, the roll pair in the downstream vertical roll stand is moved to the low temperature side in the width direction of the rolled material. Displace. The amount of displacement of the roll pair of the downstream vertical roll stand to make the bending of the rolled material zero (0) is l=0 if there is no temperature gradient (temperature difference) in the width direction of the rolled material. In addition, the vertical roll stand on the downstream side
If the rolling reduction amount of V ₂ is 0 (zero), the downstream vertical roll stand V ₂ is made to function as a guide, and l=
0 is fine. Example A steel slab with a thickness of 280 mm and a width of 1900 mm as shown in Table 1, in which the working side WS is 60°C lower than the driving side in the width direction, is used as shown in Fig. 3. In the rolling mill row shown in Figure 4, in the direction of arrow
Rolling was carried out using the pass schedule shown below. At this time, the roll pairs of the downstream vertical roll stand were variously displaced from the high temperature side to the low temperature side in the width direction of the rolled material as shown in FIG. 5, and the camber of the rolled material at that time was measured. The results are shown in FIG. As is clear from FIG. 5, in this example, which was carried out using the pass schedule shown in Table 1, when the roll pair of the downstream vertical roll stand was displaced 150 mm toward the low temperature side in the width direction of the rolled material, I was able to reduce the curvature (camber) to 0 (zero). Since the present invention is configured and operated as described above, it is possible to roll a steel slab or the like for width reduction without causing camber.

[Brief explanation of drawings]

Figure 1 shows the condition of steel slabs in the heating furnace and the temperature distribution in the length direction of the furnace. Figure 3 is a diagram showing the cross-sectional shape of a rolled material that has been rolled to apply a reduction.
A diagram showing the relationship between the difference in dog bone height in the width direction of the rolled material and the bending in the cross-sectional shape shown in the diagram,
Fig. 4 is a diagram showing an example of an apparatus for carrying out the present invention, and Fig. 5 shows the relationship between the amount of displacement of the downstream vertical roll stand in the width direction of the rolled material to the low temperature side and the camber of the rolled material during the rolling process. FIG. 3 is a diagram based on an example;

Claims (1)

[Claims] 1. When rolling a metal plate material by applying reduction in the width direction and thickness direction by a rolling mill row composed of a vertical roll stand and a horizontal roll stand, at least the temperature difference in the width direction of the metal plate material is The roll pair of the vertical roll stand existing on the exit side of the final horizontal roll stand in the rolling direction at that time is displaced by a corresponding amount toward the lower temperature side in the width direction of the metal material, and rolling is performed. A rolling method for preventing planar bending of rolled material in a rolling mill row including a vertical roll stand.