JPS6016843B2 - Steel plate rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of rolling a steel plate in a hot strip mill, cold strip mill, etc., with the purpose of reducing mid-direction thickness variation (crown, edge drop) of the steel plate.

In hot strip mills and cold strip mills, thickness variations occur in the longitudinal and mid-length directions of the steel plate.

The factors contributing to this thickness variation are different in the longitudinal direction of the steel plate and in the middle direction. Thickness variation in the middle direction is caused by deformation due to roll bending, roll flattening, worn shape of backup rolls and work rolls, and elastic recovery of the strip. It is thought that this occurs as a result of the combined effects of Depending on these conditions, the strip can be medium convex, flat, medium concave,
Furthermore, various profiles such as wedges (different thicknesses on the left and right sides in the direction of the sheet) and edge drops occur due to non-uniformity in the roll gap in the middle direction. In these profiles, the convexity in the middle of the strip is called the plate crown, and the crown diameter from the edge to the center is 40 to 100.
This value varies depending on the size. This is said to occur due to the deflection phenomenon of the rolling rolls. Also, edge drop refers to the part of the board where the thickness suddenly decreases from around the edge 30 to 4 scale to the edge.The degree of this edge drop varies depending on the size, but it can be as much as 90" in the large ones.The plate crown Various methods are used to prevent edge drops. Examples include changing the load distribution to reduce the load on the rear stand, roll pending, which bends the roll using hydraulic pressure from the outside, and bending the upper and lower work rolls. Skew rolling, which involves cross-rolling, and control using an HC mill (thin I) with an intermediate roll interposed between the work roll and backup roll, etc. are used. However, all of these methods require a high installation cost or control amount. In addition, although the conventional method is relatively effective for plate crowns, it is not sufficiently effective for edge drops.This invention aims to solve the above-mentioned problems. This paper proposes a method that is inexpensive to install and can effectively reduce plate crown and edge drop.By the way, during rolling, each part of the steel plate receives the rolling load of the rolling mill, and tension is applied to each part of the steel plate. acts, but the magnitude of this tension changes depending on the magnitude of the load.

The relationship between tension and load is inversely proportional, meaning that if the tension applied to each part of the steel plate is large, the load applied to that part will be small, and this is already known empirically. be. Therefore, if the tension of each part in the middle direction of the steel plate is changed during rolling, the load that the steel plate receives will change in inverse proportion. This invention focuses on the relationship between tension and load as described above, and proposes a rolling method for improving the flatness, edge drop, and other profiles of a steel plate.

In other words, since a steel plate generally has a convex shape in the middle as described above, a predetermined rolling load is applied directly to the center of the steel plate, and the load applied increases from the center to the edges.
- If it is made smaller, the crown amount of the steel plate will be smaller and edge drops can be eliminated. Therefore, in order to change the load on each part in the direction of the steel plate, the tension acting on each part is changed. In other words, the tension may be distributed so that the closer the tension is from the center to the edge of the steel plate, the greater the tension. As a specific method, the present invention sets the center of the roll of the rolling mill at the bus line height, and sets the roll chock height so that either the driving side or the working side is higher than the bus line, and the other side is lower than the bus line. It is characterized by adjusting the tension distribution in the middle direction of the steel plate.

FIG. 1 shows an application example of a tandem mill, and by changing the height of the roll chocks on the working side and the driving side, the roll 2 is slightly inclined with respect to the bus line. Then, the steel plate 1 is rolled by shaking it between the stands, and as shown in FIG. 2, which will be described later, the steel plate 1
The unit tension (tension per unit area) at the center and edge portions changes, and accordingly, the load that the steel plate 1 receives becomes smaller as it approaches the edge portions. As a result, the thickness of the steel plate 1, which is convex in the middle due to the rolling load, is uniformly distributed in the middle direction and rolled. In addition,
Here, in order to maintain the tension balance of the steel plate 1 during rolling in a tandem mill, for example, in the front rolling mill, if the height of the roll chock on the drive side is set higher than the bus line and lower on the working side, then the rear rolling mill will roll the drive side lower than the bus line. The tension of the rolls of the milling machine is alternately arranged symmetrically with respect to the bus line by lowering the height and raising the working side. FIG. 2 shows the tension distribution acting on the steel plate during rolling. That is, the tension distribution of the steel plate 1 increases from the center to the edge, as shown by the arrows. Therefore, the load on the edge portion of the rolled material is 4.0 mm lower than that on the center portion, and plate crown and edge drop are reduced. In this invention, the roll chock height can be adjusted independently on the driving side or the working side electrically or hydraulically.

Further, the crown amount is controlled by, for example, installing a profile meter on the exit side of the final stand, and adjustment can be made in conjunction with the control amount of the roll chock height. Next, embodiments of this invention will be described.

After rough rolling, the steel plate with a thickness of 3.2 mm and 1005 mm skin is rolled into a steel plate with a thickness of 3.2 ribs and 1000 ribs in the middle using 7 finishing mills (body length: 178 mm) shown in Figure 3. did.

At this time, two stands of the finishing rolling mill are set up, and the center of the rolling roll is set at the height of the bus line, and the front stand Fn-1 is
The driving side of the roll was set higher than the bus line and the working side was set lower than the bus line, and finish rolling was performed without changing the roll height of the rear stand Fn. The distance between the stands of the finishing rolling mill is 5.5.
W, a presser roll 3 and a looper 4 were provided between the stands, and two types of distances between the front stand Fn-1 and the presser roll 3 were adopted: 500 mm and 100 mm. The results are shown in Figure 4. FIG. 4 shows the unit tension between the edge and center portions and the amount of improvement in plate crown and edge drop with respect to the difference in distance between the edge and center portions.

Here, the distance difference between the edge and the center section is the distance between the rolling roll centers between the stands and the rolling roll edge section when the height of the roll chock is changed from the driving side to the working side and the steel plate is shaken. It is the distance difference between In the figure, a indicates the edge unit tension, and b indicates the center unit tension. As is clear from this diagram, according to the present invention, plate crown and edge drop can be significantly reduced. For example, when the difference in distance between the edge and center is 0, the unit tension is the same for both the edge and center, 0.5k9/kite2, which is effective.
0 & gunboard, roll chock height distance from the bus line is 3 broadside, ZIOO portside, roll chock height distance from the bus line is 45 ribs, the edge and center distance difference is 1.0
It becomes a rib, and the improvement effect of edge drop and plate crown is 30 peaks. As explained above, according to the present invention, plate crown and edge drop can be easily and effectively reduced by simply adjusting the height of the roll chock and changing the roll heights on the drive side and work side. Therefore, the profile of the strip can be improved with lower equipment costs than conventional methods.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram showing the tension distribution in the same, FIG. 3 is a front view schematically showing the finishing rolling mill in the embodiment of the invention, and FIG. The figure is a chart showing the results of the same example. In the figure 1... Steel plate, 3... Presser roll, 4... Looper, Fn,
Fn-11...Stand. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. When rolling a strip using one or more rolling mills, the pass line height is set at the center of the rolls of the rolling mill, and one of the driving side and the working side is higher than the pass line, and the other is lower than the bus line. A method of rolling a steel sheet, characterized in that the crown and edge drop of the strip are reduced by adjusting the height of the roll chock to change the tension distribution in the width direction of the strip.