JPS642444B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thick plate rolling method in which a forming rolling process, a tentering rolling process, and a finishing rolling process are sequentially performed, and in particular, the present invention relates to a thick plate rolling method that can obtain a rolled product that does not require finishing by cutting the side edges. This invention relates to a plate rolling method. Generally, when rolling thick plates, especially thick steel plates,
Slabs manufactured using continuous casting equipment or a blooming mill are first subjected to 1 to 3 passes of so-called forming rolling to adjust the thickness of the slab, and then turned 90 degrees to obtain the required width. After performing the required number of passes of tentering rolling to obtain the desired plate thickness, the sheet is further turned 90° to return to its original direction, and the so-called finish rolling is performed the required number of passes to obtain the desired thickness. We are trying to obtain thick steel plates with the same width and thickness. However, in this rolling process, due to the difference in the plastic deformation behavior between the front and rear ends and the center of the slab, the width of the thick steel plate, that is, the rolled product 10, becomes a drum shape with a wider center in the longitudinal direction, as shown in FIG. Or,
Alternatively, as shown in FIG. 2, it becomes a drum shape with a narrow central portion in the longitudinal direction. This is especially caused by forming rolling and tentering rolling, and the shape differs depending on the relationship between slab dimensions and finished dimensions.
As shown in Fig. 3, when the tentering ratio (rolling width/slab width) is about 1.5 or less, the plate width difference S (the average of the plate width M at the center in the longitudinal direction and the plate widths T and B at the front and rear ends in the longitudinal direction) is It is known that the plate width difference S (M-T+B/2) becomes a drum shape with a negative value, and when the width ratio exceeds about 1.5, the plate width difference S becomes a positive value.
The amount can be predicted quantitatively as shown in FIG. Note that this plate width difference has already occurred immediately after tentering rolling, and this amount does not change much until finishing rolling. Conventionally, a drum-shaped or drum-shaped planar rolled product 10 having such a plate width difference is cut into a desired width using a shearing machine or gas, as shown in FIG. 1 or 2. It was set at 12. or,
The side edge portion 10a of the rolled product 10 as rolled has a convex or concave shape as shown in FIG. 4 or 5, and since this portion does not touch the rolls, the surface is rough. It also had to be cut and removed. On the other hand, although hot strip mills and other coarse mills have traditionally been equipped with vertical rolls to control the width of the rolled material, it is difficult to apply this method directly to thick plate rolling. It was hot. That is,
In rolling a thick plate, as described above, it is necessary to perform tentering rolling, which results in the drum shape or drum shape as described above. Therefore, there is a difference in the width of the board between the front and rear ends and the center in the longitudinal direction of the board, and even if you try to control the width of the board to be constant using vertical rolls, the rolling reduction amount at each part in the longitudinal direction will be different, so the rolling reduction in the width direction with the vertical rolls will be different. There is a difference in the amount by which the side edges of the rolled plate are pushed out in the width direction again in the next rolling by the horizontal rolls (so-called width return amount), and it is not possible to sufficiently eliminate the non-uniformity in the width direction. This state of width return is shown in FIGS. 6A and 6B. In Fig. 6A, if the reduction amount of the vertical roll is S _A , the material to be rolled 14
The material to be rolled 14 can be pushed in by S _A /2 at one edge, and a part of this pushed in becomes a dog bone 14a and creates a bulge. When this portion is then rolled with horizontal rolls, a portion of the dogbone 14a expands again in the width direction, resulting in a width return S _B /2 as shown in FIG. 6B. The amount of width return S _B varies depending on the plate thickness and the amount of reduction of the vertical rolls, but if the thickness of the plate is constant, it is natural that it is related only to the amount of reduction of the vertical rolls, and therefore, as mentioned above, If there is a plate width difference S between the front and rear ends and the central part of the plate, the plate width difference S cannot be completely eliminated even if vertical rolls are used in finish rolling. Furthermore, if the amount of reduction of the vertical rolls is increased, buckling of the plate in the width direction will occur, so a very large reduction is not possible. The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and it is possible to reduce the width difference in the longitudinal direction of a rolled product and to improve the shape of the side edge. An object of the present invention is to provide a thick plate rolling method that can obtain a rolled product that does not require finishing by cutting. The present invention provides a method for rolling a thick plate in which a forming rolling process, a tentering rolling process, and a finishing rolling process are sequentially performed. Reduction correction rolling is performed to give a thickness change of , and the longitudinal plate width difference of the rolled material at the end of tentering rolling is set to a predetermined value or less, and the rolled material is rolled in the thickness direction in the finish rolling process. Flat rolling and edging rolling, in which the side edges of the material to be rolled are rolled down in the width direction using vertical rolls at a constant roll opening corresponding to the target width, are performed alternately up to the allowable width difference. The above objective has been achieved. The principle of the present invention will be explained below. As mentioned above,
Even in thick plate rolling, if vertical rolls are installed like in a hot strip mill to roll the material to be rolled in the width direction of the plate, the rolled product can be rolled with a small difference in width in the longitudinal direction and a good side edge shape. However, in the conventional thick plate rolling method, if the edge rolling is performed as is, width reversion will occur as described above, so the width difference in the longitudinal direction of the rolled material must be set to a small value. It is not possible to do so. However, through experiments, the inventors determined that after the width difference in the longitudinal direction of the rolled material at the end of the tentering rolling was set to a predetermined value, for example, 20 mm or less, the side edges of the rolled material were adjusted to the width of the material in the finish rolling. It has been found that by rolling in the longitudinal direction, the longitudinal plate width difference can be reduced to an almost allowable value, for example, 10 mm or less, at the end of finish rolling. Figure 7 shows the finished board thickness of 30mm (solid line A) and 15mm.
(solid line B) and 10 mm (solid line C), measure the strip width difference S ₁ after tentering rolling, and finish by setting the vertical roll reduction amount equal to the strip width difference for each value. The figure shows the results of rolling and measuring the plate width difference S ₂ after rolling. Here, for a plate with a finished plate thickness of 30 mm, five passes of edging rolling and flat rolling are performed using vertical rolls and horizontal rolls, and then one pass of flat rolling is performed using horizontal rolls to obtain a plate with a finished plate thickness of 15 mm. After 7 passes of edging rolling and flat rolling with vertical rolls and horizontal rolls, 1 pass of flat rolling with horizontal rolls is applied to the plate.For finished plate thickness of 10 mm, vertical roll and After 10 passes of edging rolling and flat rolling using horizontal rolls, one pass of flat rolling using horizontal rolls was performed. In addition, in the edge rolling, the opening degrees of the vertical rolls are all kept constant. From Figure 7, regardless of the finished plate thickness, the initial plate width difference S ₁ is
It can be seen that when the width exceeds 20 mm, the plate width difference S ₂ after rolling tends to suddenly increase. Therefore, in order to satisfy the plate width difference S ₂ of 10 mm or less required for rolled products, it is clear that at least the plate width difference S ₁ after tentering should be set to 20 mm or less, and then edge rolling should be performed. be. In general, the smaller the plate thickness, the smaller the effect of edge rolling (that is, the difference between the amount of reduction due to edge rolling and the amount of width return due to flat rolling immediately after that is large), but when the finished plate thickness is The smaller the number of passes of finish rolling, the more the effect of the edging rolling is accumulated, so the difference in strip width after finish rolling becomes smaller. Also, the larger the plate thickness, the greater the effect of edge rolling (that is, the smaller the amount of width return), but if the finished plate thickness is large, the number of passes of finish rolling will be reduced, so the result will be Generally speaking, the effect of edge rolling is the same as when the finished plate thickness is small, and the effect of edge rolling has almost the same value regardless of the finished plate thickness. This is clear from the fact that, as shown in FIG. 7, the relationship between S ₁ and S ₂ does not vary greatly due to the difference in finished plate thickness, and the values are almost similar. On the other hand, in the conventional thick plate rolling method, the width difference in the longitudinal direction of the rolled material at the end of tentering rolling is within a range of, for example, 20 mm or less, as shown in Fig. 3. Although it is in a very limited range around 1.5, if the inventors carry out the so-called correction rolling that has already been proposed in JP-A No. 53-123358, it will be It is possible to control the plate width difference in the longitudinal direction of the rolled material to a predetermined value, for example, 20 mm or less. That is, as mentioned above,
If the width ratio is less than about 1.5, the finished planar shape will be drum-shaped, and if it is about 1.5 or more, it will be drum-shaped. Therefore, in the final pass of forming rolling prior to tentering rolling, a thickness difference is given in the longitudinal direction of the slab,
If this is turned 90 degrees and tenter rolling is performed, the thicker part of the plate will extend extra in the width direction (the rolling direction of tenter rolling). This is because, in rolling thick plates, metal flow during rolling does not occur in the width direction, but mostly occurs in the longitudinal direction. Therefore, if the finished shape is drum-shaped and the tentering ratio is 1.5 or more, if the central part in the longitudinal direction of the slab is made thinner during forming rolling, the front and rear ends of the longitudinal direction will be thinner than the central part after tentering rolling. Since it stretches, it offsets the widening of the center due to the drum shape, resulting in just the right shape. The rolling state in this case is shown in FIG. In the figure, A shows the slab shape, B and C show the end shape of the forming pass, D shows the end shape of the tentering pass, and E shows the finished product shape. In addition, if the finished shape is a drum-shaped width ratio of 1.5 or less, contrary to the above,
It is only necessary to thicken the central portion in the longitudinal direction of the slab during forming and rolling. After performing tentering rolling as described above, the material to be rolled is again turned 90 degrees and finish rolling is performed using vertical rolls. In this case, the opening degree of the vertical roll is set 0 to 10 mm larger than the ordered board width. This extra opening is determined by the required plate width accuracy. Next, a method of controlling horizontal roll reduction during forming and rolling according to the present invention will be explained with reference to FIG. 9. The rolling reduction schedule is calculated by the calculator 20 based on the slab dimensions and rolling dimensions, and at the same time,
A steel plate planar shape prediction model based on Fig. 3 predicts the plate width difference after final finish rolling. Based on this predicted value, the amount of plate thickness change (Δh, li) in the final pass of forming and rolling shown in FIG. 8 is calculated using the calculator 22 according to the constant volume law. Next, in order to apply this value to actual rolling, the horizontal roll rolling position change amount (△
S, li). This value is instructed to the rolling position and rolling speed control device 28. In this state, the load cell 30 detects the biting of the tip of the rolled material 14 in the final pass of forming rolling, and at the same time, according to the target horizontal roll rolling position change amount (ΔS, li), the automatic plate thickness control device 32, Rolling is carried out while controlling the reduction position via the hydraulic reduction control device 34. At this time, the rotation speed of the horizontal roll 36 is detected by the rotation speed detector 38, the advance rate is corrected by the calculator 40, the length from the tip of the material to be rolled 14 to the current rolling position is calculated, and the speed is automatically adjusted. The rolling speed of the material 14 to be rolled is controlled by controlling the mill motor 44 via the machine 42, and by controlling the rolling device 46 via the automatic plate thickness control device 32 and the hydraulic pressure reduction control device 34. Rolling is performed by giving a target thickness shape at a predetermined position in the direction. Next, a method of controlling the edging mill in finish rolling will be explained with reference to FIG. first,
After completion of tentering rolling and before starting finishing rolling, the vertical rolls 50 are set to a predetermined opening degree, for example, an opening degree W that is 0 to 10 mm larger than the ordered sheet width, and
The roll speed of the vertical rolls 50 is synchronized with the rolling speed of the horizontal rolls of the finishing mill. The control of this edging rolling mill does not particularly need to be integrated with the control of the flat rolling mill, and may be controlled independently, but at least the speed control needs to be synchronized with the speed of the horizontal rolls, so that the speed of the horizontal rolls is An input signal is input from a horizontal mill speed indicating device (not shown) to a speed control device for the vertical rolls 50. Based on commands from the controller, the vertical roll motor 52 is driven, and its speed is detected by a roll rotation detector 54 and fed back to the controller 56 to maintain accurate speed. At the same time, the roll opening degree is input to the roll opening degree setting device 58 according to the target finished board width, and is transmitted to the rolling down drive device 60, and is set to a predetermined opening degree. Furthermore, by the pressure down position detector 62,
The rolling position is fed back to the roll opening degree setting device 58 to maintain an accurate roll opening degree.
In the figure, 64 is a choke housing that accommodates the chock of the vertical roll 50, 66 is a load cell that detects the rolling load of the vertical roll 50, and 67 is a chock housing that accommodates the chock of the vertical roll 50.
is a lowering device, and 68 is a main housing. Examples of the present invention will be described below. The pass schedule in this embodiment is shown in Table 1 below.

【table】

[Table] Compatible.
The slab size is 220 x 1580 x 3000 mm, and the rolled product size is 15 x 3300 x 21000 mm. In this case, the width ratio is 3300/1580 = 2.1, and the drum width predicted from Figure 3 and the width shape prediction model is 90.
mm. This is approximately
It is 2.7%. Therefore, the plate thickness difference △h is 2.7% of the plate thickness at the final rolling of forming, that is,
It is sufficient to give Δh=180×0.027=4.8mm at the center. This plate thickness difference Δh extends in the width direction during tentering rolling according to the law of constant volume. Using this value, set the length li of the plate thickness change part to 600 mm (this li
(may be approximately 500 to 600 mm in any case), and rolled in the final pass of forming to obtain the shape shown in Figure 8B, and then rolled according to the pass schedule shown in Table 1. . Further, in this case, the plate width after tentering was 3310 mm, but the vertical roll opening was set to 3305 mm. Opening degree here 5
mm is the allowance. As a result of the above rolling, the finished plate width was almost uniformly rolled to 3305 mm, and the maximum plate width difference was +2 mm. The side edges of the plate were also in a condition suitable for shearing or gas cutting. As explained above, according to the present invention, drums and drums in the width direction of the plate are eliminated, and at the same time, the shape and surface condition of the side edge portions are improved, so cutting the rolled product with a shearing machine or gas is no longer necessary. It has excellent effects such as improving yield and eliminating steps.

[Brief explanation of the drawing]

1 and 2 are plan views showing examples of planar shapes of rolled products in conventional thick plate rolling, and FIG. 3 is a diagram showing the relationship between tenter ratio and plate width difference in thick plate rolling, 4 and 5 are cross-sectional views showing the shape of the side edge of the rolled product at the end of rolling in conventional thick plate rolling. FIG. 7 is a cross-sectional view showing the state of change in the shape of the end portion of the material. FIG. , a perspective view showing the process of reduction correction rolling to reduce the longitudinal plate width difference of the rolled material to a predetermined value or less at the end of tentering rolling;
FIG. 9 is a block diagram showing a reduction control device for performing the reduction correction rolling, and FIG. 10 is a block diagram showing a control device for an edging rolling device used for finish rolling. DESCRIPTION OF SYMBOLS 10... Rolled product, 10a... Side edge part, 12... Finished product, 14... Rolled material, 36... Horizontal roll, 50...
Vertical roll.

Claims (1)

[Claims] 1 In a thick plate rolling method in which a forming rolling process, a tentering rolling process, and a finishing rolling process are performed sequentially, in the final pass of forming rolling, the roll gap is changed during rolling to cause a longitudinal thickness change in the rolled material. In addition, flat rolling is carried out to reduce the width difference in the longitudinal direction of the rolled material at the end of tentering rolling to a predetermined value or less, and to reduce the rolled material in the thickness direction in the finish rolling process. A thick plate characterized in that edging rolling, in which the side edges of the material to be rolled are rolled down in the width direction using vertical rolls at a constant roll opening corresponding to the target plate width, is performed alternately up to an allowable plate width difference. Rolling method.