JPS5935801A - Cross rolling method of slab - Google Patents

Abstract

PURPOSE:To prevent the formation of fishtails in the preceding and succeeding parts in the stage of changing the width of a slab by a cross rolling method by using a reversible horizontal rolling mill provided with non-driven vertical rolls on inlet and outlet sides. CONSTITUTION:A slab 4 having an initial width W0 is first thrusted between vertical rolls 2 set in a roll gap W1 in the case of subjecting a slab 4 to cross rolling by the reversible hot rolling of horizontal rolls 1 disposed with vertical rolls 2, 3 for cross rolling on inlet and outlet sides. While the slab is rolled with the rolls 1 in a backward direction after the slab passes out through the rolls 1, the slab is thrusted between the rolls 3 having a roll gap W2 and is rolled. The slab is again rolled to a width W3 with the rolls 2 as the 3rd pass and is thrusted between the rolls 4 with the horizontal rolling mill 1 in the 4th pass; finally only the end part of the slab 4 is rolled down in the 5th pass, whereby the formtion of fishtails is obviated and a crop loss is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for width reduction rolling of slabs, and particularly to width rolling of continuously cast slabs (hereinafter simply referred to as slabs).

As is well known, in order to obtain a hot-rolled steel strip of a predetermined width, conventionally the width of the slab was changed during the continuous casting stage and then supplied to the rolling process. In such a supply system, the productivity of the continuous casting machine decreases and the quality of the slab deteriorates at the width changing portion, which are undesirable. Therefore, in recent years, it has been found that it is desirable to change the width by width reduction in the hot rolling process.

However, in width rolling using vertical rolls, the plate width and the diameter of the vertical rolls are approximately the same size, so deformation is localized at the edges of the slab and so-called docks develop. When this dog bone is rolled with horizontal rolls, a square shaped part (fishy tail) is produced at the front and rear ends of the slab. This fusch tail does not disappear until the final rolling, leading to a decrease in yield.

In addition, a phenomenon occurs in which the width at the front and rear ends of the slab becomes narrower than the width near the center in the longitudinal direction of the slab (width drop), which leads to a decrease in yield. Among these factors that reduce yield, many methods have been proposed to reduce clog loss by preventing fishy tails. The main ones are (
1) Piece/base rolling method in which the rolling direction is limited to one side (Japanese Patent Application Laid-open No. 1973
-65152), (2) Method of applying compressive force using a pushing device during width rolling of slab (Japanese Patent Laid-Open No. 55-30366)
, (3) A method in which the width of the front and rear ends of the cis-slab is locally reduced using a special Luss and then rolled (Japanese Patent Application Laid-Open No. 14235-1983)
0), (4) A method of installing two drive-type vertical roll rolling machines on the exit side of a reversible horizontal rolling mill and performing width reduction rolling twice per pass (Japanese Patent Laid-Open No. 55-133801 )
However, the technique (1) tends to have a problem of low rolling efficiency, and the technique (2) requires a special pushing device to apply compressive force. The technology in sentence (3) requires a press device installed on the line side to compress and deform the local part of the front and rear ends of the slab after temporarily stopping conveyance of the slab in the pre-rolling stage.) In addition to requiring a special press device, rolling There is a problem of low efficiency. In addition, technology (4) does not require much capital investment, but the control of each stand is complicated, requiring advanced rolling mill control equipment, and the vertical rolls are driven, so it is still sufficient to reduce loss loss. There are problems such as not being able to obtain

In view of these points, the present invention can achieve both the further reduction of crop loss that occurs due to changes in slab width due to large reduction in the hot rolling process and the prevention of width collapse at the front and rear ends of slabs with a low capital investment. The gist of this system is that when changing the width of a slab using the width rolling method, the operator of a reversible horizontal roll mill and one width rolling mill with non-driven vertical rolls on the exit side are required. By the horizontal force when rolling the slab with a reversible horizontal roll mill, width reduction rolling is performed while pushing the base end of the slab into the non-driven vertical roll, and the rear end side of the slab is rolled. The present invention relates to a width reduction rolling method for slabs characterized in that the vertical rolls provided at the front in the rolling direction do not perform width reduction.

Conventionally, if the vertical rolls were not driven, it would be impossible to roll to a wider width if the horizontal force from the horizontal rolling mill disappeared.
Since the width of the rear end side of the slab (i.e., the side where the bottom is removed) remains unrolled, the width reduction method using non-driven vertical rolls has not been adopted for purposes other than continuous rolling.

The present inventors have discovered that this bottom punching method actively utilizes the disadvantage that the sides cannot be rolled.

In other words, considering the fact that the conventionally known Shiri-nuki has a thick fishy tail crotch on the side, there is no necessity of rolling the Shiri-nuki at all, and it is actually harmful. A width rolling mill without rolling capacity (non-driven vertical rolls) is most suitable.'1.

As a result of the inventors' repeated numerous experiments,
By pushing the tip of the slab into a non-driven vertical roll using a horizontal rolling mill, the slab nip section receives force toward the rear end, causing the fishtail that develops when the rolls are driven to form, as shown in Figure 3. I found that it did not develop. Furthermore, the phenomenon of width drop at the leading and trailing ends of the slab, which occurs when the rolls are driven, is greatly improved by applying compressive force to the slab, as shown in FIG. 4. (In the figure, A shows the method of the present invention, B shows the conventional method, C shows the width and length, D shows the width and length, and E shows the cross-broth.) Furthermore, as an advantage of pushing into a non-driven roll, there is usually a large number of stands. It has been found that the control of the stand height, which is essential in the case of a rolling mill, is not necessary, and that the stand height can be kept constant despite this (determined by the width rolling conditions).

The present invention was completed based on such knowledge, and will be described in more detail below with reference to the drawings.

The layout of a rolling mill for implementing the method of the present invention is shown in FIG.

In Figure 1, 1 is a horizontal roll rolling mill (drive), 2.3
1 is a person of the horizontal roll rolling mill 1, a vertical roll (non-driven) for width reduction arranged on the exit side, 4 is a slab, and 5 is a dogbone produced by the width reduction of the vertical roll 2.

Next, a specific schedule will be explained with reference to FIG. In the first pass, the slab 4 of initial medium W is pushed into the vertical roll 2 set at the roll gap Wl in the horizontal roll rolling mill 1.Once it passes through the horizontal roll rolling mill 1, no further width rolling is possible, so the slab 4 is pushed in the opposite direction. While being rolled in the horizontal roll rolling mill 1, in the second pass, the material is rolled while being pushed into the vertical roll 3 on the opposite side set in the roll gap W2. At this time, the roll gap W2 of the vertical rolls 3 is set closer to the roll gap W1 of the vertical rolls 2. The rear end of slag 4 was unrolled in the first pass, so there was a large amount of width reduction, but the center part, which accounts for most of the slab length, was width rolled in the first pass, so the amount of width reduction was not that much. not many. 2・
The end of the thread, ie, the F side of the slot 1''4, is not rolled by the vertical roll 3, but is rolled by the vertical roll 2 at the next 37th thread.

Then, in the fourth pass, the rear end side of the slab 4, which was not rolled in the previous pass, is rolled while being pushed into the vertical roll 3 with the same roll opening as the F side by the horizontal roll mill 1. At this time, the width of the central portion is reduced by the amount of width expansion caused by each dog run by the horizontal roll mill. i.e. slag 4
Both the leading and trailing ends are width-rolled on the push-in side only, and the central part is width-rolled in each pass.

Then, in the final pass, only the edges of the slab left in the previous pass are rolled down, and the central part is set to a roll guzzle that is not rolled down, thereby completing the series of rolling. If such a non-driving roll and pass method is used, the slab can be rolled only on the side where it engages with the vertical rolls, and there will be no bottom dropout. Furthermore, since the central portion is rolled in the same width in each pass, there is little reduction in rolling efficiency. In the present invention, the driving force for the vertical rolls is provided by the horizontal force of a horizontal roll mill, but the amount of thickness reduction required to make the vertical rolls non-driven varies depending on the amount of width rolling.

That is, as long as the width reduction amount of the 1-'e contact is small, it is sufficient to set the horizontal roll gap to the original slab thickness and use only one so-called dog for passing the slab.

When the width reduction of the y4 stroke 9 becomes a dog, it is necessary not only to cut one line but also to perform an actual reduction that substantially rolls the thickness of the slab.On the contrary, it is necessary to use the reduction by this horizontal pass. It is possible to have the function of redirecting the rolling reduction during rough rolling.

Next, examples will be listed together with comparative examples.

72,210 continuously cast sheets with a width of 1,550 m, a thickness of 245 m, and a length of 9,000 m were heated to 1,100°C, and half of them were cast using the method of the present invention (no vertical roll drive, width pressure IA only on the biting side of the slab) and the conventional method. Rolled using the vertical roll drive method. The rolling pass scale is shown in Table 1, and the width loss (%) and width drop length (m) are shown in Table 2. Incidentally, the conventional strip/black method uses a rolling mill which lacks the vertical rolls 2 shown in FIG. 1 of the present invention.

Table 1 Note 16 Slab size/e 1550 width x 245 thickness x 9
000 length → 1400 width x 244 thickness x 100OO length Note 2.
2. As is clear from Table 2, when the rolling method of the present invention is used, both the crop loss and the width drop length are the same as in the conventional method. This method is a significant improvement over the conventional method, and is extremely useful when changing the width of continuous cast slabs by width reduction rolling.The vertical rolls are not driven, so the capital investment is low. It brings about excellent industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the layout of a rolling mill that implements the method of the present invention. FIG. 2 is an explanatory diagram showing the pass schedule of the method of the present invention. FIG. 3 is an explanatory diagram showing the relationship between the actual width reduction ratio and the cross-cut loss for the rolling method of the present invention and the conventional single-edge rolling method. FIG. 4 is an explanatory view of the shape of the tip of the slab seen from above in the rolling method of the present invention and the conventional one-pass rolling. l...Horizontal roll, 2,3...1H1io
-#, 4...Slab, 5...Dog d
Guin. Figure 1 Figure 2

Claims (1)

[Claims] When changing the width of a slab using the width rolling method, a reversible horizontal roll rolling machine and a width rolling machine each having non-driven vertical rolls on the exit side are installed, and the slab f is reversibly rolled by the width rolling method. Width reduction rolling is performed while pushing the tip of the slab into the non-driven vertical roll (by horizontal force when rolling with a machine), and width reduction is not performed on the rear end side of the slab using the vertical roll provided forward in the rolling direction. A slab width reduction rolling method characterized by: