JPS6024721B2 - Method for reducing clotupulos in blooming rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing crop loss in blooming.

Generally, when blooming a steel ingot into a slab using a blooming mill, in order to reduce the crop loss in the length direction and width direction of the slab and improve the blooming yield, it is necessary to
It is known that it is effective to carry out so-called strong rolling, in which the rolling weight per pass is increased.

However, when we look at the metal flow of the material when soul-rolling a steel ingot into a slab, the metal gradually accumulates and flows from the biting side of the material to the biting side, and as a result, the rolling load gradually increases. I'll go.

Therefore, although the amount of reduction in each pass varies depending on the capacity of the rolling mill, the deformability of the material, etc., there is a limit to the amount of reduction that can be detected. In other words, it is ideal to have a large rolling reduction amount and reduction rate that can uniformly deform the material from the surface to the center, but in reality, the metal flow in the surface layer of the rolled material is greater than in the center. Conventionally, as the rolling pass progresses, an overlap is formed in the thickness direction of the slab at both ends, and a so-called fishtail is formed in the width direction, and its growth is gradually promoted during rolling, resulting in an overlap at the end of rolling. The disadvantage was that the crop loss was extremely large. SUMMARY OF THE INVENTION An object of the present invention is to provide an effective method for eliminating the drawbacks of the prior art and reducing crop loss during soul rolling. The gist of the present invention is to provide a method for reducing crop loss during blooming of a steel ingot using a reversible rolling mill, in which at least one opposing end of the head and bottom of the steel ingot is removed during the rolling of the steel ingot. This is a method for reducing crop loss in blooming rolling, which includes the step of forming convex portions on one set of surfaces using rolling rolls, and then applying rolling from the opposite direction.

Prior to explaining the present invention, the movement of metal during rolling, which is relevant to the present invention, will be explained with reference to FIG.

In a reversible rolling mill, the rolling mill alternates between the biting side and the biting side, but the movement of the metal accompanying the reduction in each pass means that on the biting side, the metal that has been collected flows at the end of each pass. A large amount flows to the ends, increasing crop loss, and on the biting side, overlap and fishtail gradually grow as the pass progresses. That is, as shown in FIG. 1A, there are fishtails 2 at both longitudinal ends of the slab 1.
When the fishtail 2 is formed, when the edger roll 3 is bitten and edged first, the fishtail 2 becomes the shape shown in Fig. 1B.
As shown in , it goes around to the inside in the width direction.

Similarly, an overlap 4 is formed in the thickness direction of the slab 1 as shown in FIGS. 2A and B, and when the horizontal roll 5 is inserted and rolled down first, the overlap 4 is
It will go around to the inside in the thickness direction. As the rolling progresses, the movement of the metal is reversed and the Futstale 3 and overlap 4 gradually grow.
These are cut into trout and become clotupulos, and the reduction of clotupulos is extremely important for improving the blooming pressure yield. Details and embodiments of the invention will be explained with reference to FIGS. 3 and 4. FIG.

That is, as shown in FIG. 3A, in the present invention, a convex portion 9 is formed by a rolling roll 8 on at least one set of opposing surfaces of at least one end of the head and bottom of the steel ingot 7 during the early stage of rolling of the steel ingot 7. This is a method in which the material is formed into a T-shape, and then rolling is applied from the opposite direction using rolling rolls 8 as shown in FIG. 3B to eliminate the convex portions 9. A specific method for forming the convex portion 9 is as follows.
As shown in FIG. 3B, the protrusion length Δ1 is after forming the convex portion 9,
When rolling is applied from the opposite direction to eliminate the convex portions, the rolling force is preferably 200 to 30 degrees so as not to increase the rolling load and cause an overload.

If Δ1 is thereby reduced, the formed convex portion 9 may rise toward the crop end 10 side when the convex portion is formed, reducing the effect of the present invention. On the other hand, if △L is increased by this, the steel properties of the convex portion will increase during rolling from the opposite direction and the rolling resistance will increase, so the metal flow towards the crop end 10 side will increase and the effect of the present invention will decrease. be. In addition, the protrusion height of the convex portion 9 △ days is the protrusion height of the convex portion 9
The larger the defect is, the more effective it is for reducing crop loss, as long as it does not leave a two-plate-like defect on the side surface when eliminated. However, based on the experimental results of the present inventors, from the relationship with △L, the following The range expressed by inequality '11 is most suitable. 0.25△LS△day＜△1 ・・・・・・'1
} That is, it is most preferable that △day be smaller than △L and be equal to or larger than 1/4 of △L.

The reason for this is that if △day is smaller than 0.25△L, the steel properties of the convex portion will increase during rolling from the opposite direction, and the metal flow toward the crop end 10 will increase.On the other hand, if △day is △ If it is larger than L, when rolling down from the opposite direction,
This is because the presence of the rolling roll biting limit increases the number of times of rolling to eliminate the convex portions, and the metal flow toward the cropped end 10 increases as the number of times of rolling increases. If such a convex part 9 is formed in the thickness direction of the material 7, it is possible to reduce the overlap, and if it is formed in the width direction of the steel ingot material 7, it is possible to reduce the fishtail.The reason for this is as follows. It is as follows.

That is, after forming the convex part 9, when applying pressure from the opposite direction to eliminate the convex part 9, the convex part 9 gradually becomes the main body of the material 7 as the reduction of the convex part disappearing from the opposite direction progresses. Since the rolling load is gradually absorbed, the rolling load is reduced as it progresses toward the bite-through side. This point is completely different from that in the normal rolling of the secondary steel as described above, where the metal flows from the biting side of the steel ingot material 7 to the biting side, as if gradually accumulating, and the rolling load gradually increases. The opposite results. Therefore, by forming the convex portions 9 according to the present invention, it is possible to effectively prevent the metal from flowing toward the side where the metal is cut through during rolling, resulting in the growth of fishtails that occur in the width direction at both ends of the slab and overlap that occurs in the thickness direction. As a result, crop loss can be suppressed to a minimum.

In addition to the above-mentioned effects of forming the convex portions, according to the present invention, when rolling the convex portions 9 from the opposite direction, it is possible to roll the convex portions 9 with a reduction amount that is greater than that of the subordinate. , it is possible to reduce the number of times the steel soul material is bitten, and as a result, it is possible to minimize the movement of metal toward the biting side.

This effect also prevents the growth of fishtails and overlaps on both ends of the slab, contributing to reducing crop loss. Next, the manner in which the convex portion 9 is formed according to the present invention and the timing of its formation will be explained. Figure 4A,
B, C, D, and E are examples showing how to form a convex portion, and A is a perspective view showing an example in which a convex portion is formed in the width direction at one end of a rolled material, and B is a perspective view showing an example in which a convex portion is formed at one end of a rolled material. This is an example in which a convex portion is formed in the width direction and the thickness direction, and C is an example in which a convex portion 9 is formed in the width direction at one end of the material and the thickness direction at the end of the material.
The figure shows an example in which a convex portion is formed only in the thickness direction at one end of the material 7, and the E figure shows an example in which a convex portion is formed in the width direction at both ends of the material 7. This shape is suitable for materials with high deformability. It is highly effective when applied. Of course, there are various other ways to form these protrusions.

The most effective time to form these convex portions varies depending on the type, shape, etc. of the steel core, but it is generally effective to form them at the early stage of rolling, before the overlap or fishtail starts to grow.

In many cases, the head shape of killed steel ingots is concave.
It is effective to carry out the present invention by forming a convex part on the steel ingot before the start of rolling, but in the case of a capped steel ingot which has a head shape, Alternatively, if the present invention is practiced at a later stage, when shallow concave shapes are formed at both ends as shown in FIG. 1A, excellent effects can be obtained. It should be noted that the time required to form the convex portions on the steel ingot according to the present invention is only about 1 minute from 3 pieces of sand per place, so the effect on productivity is negligible. An embodiment of the present invention will be explained in comparison with a conventional method.

Example 1 This example is an example in which a convex portion is formed only in the width direction at one end of the rolled material, and the convex portion is rolled down from the opposite direction to disappear.

The cross section of the mold is 1232 ribs x 555 sides at the head and 116 at the bottom.
From a killed steel ingot weighing 7 tons obtained by casting molten steel in a mold of 44 mounds, a slab with a cross section of 145 m x 104 moulds, was processed through the steps shown in Table 1 using the method of the present invention and the conventional method. Manufactured. Table 1 Unit: Day in Table 1 of. R. is a horizontal roll, V. R. is a vertical roll.

In other words, in the conventional method, the number of days is reduced due to scale reduction.
R. Pass location by. After reducing 110 ribs in step 1,
Rotate the steel ingot 90 degrees and leave it as is. R. Continue to reduce the pressure at V. R. Edging was performed to reduce the width to obtain a slab with a specified cross section of 145 ribs x 1040 fences. In the method of the present invention, it has been confirmed through experiments that the scale can be removed without the need for edging. In 4 V. R. After forming the convex part and biting back while setting the pass No. to the 1100 side, pass No. In 6 V. R
．． While setting M. to the 1080 side, continue the protrusion formation pass M. Bite back was performed at 7. Another pass ship. At 8 V. R. 1
Complete the formation of the convex part with the V.04 set on the port side. R.
I opened it and made a bite. That is, the protrusions were formed three times in succession, with ΔL of about 20 yen and Δday of 55. Pass the convex part. 9, No. 11 from the opposite direction to eliminate it, and then V. R. Leave it on for 104 days. R. Continuing to reduce the pressure at finally 14
A slab of 5 ribs x 1040 ribs was manufactured. As described above, in this example, a convex portion was formed only in the width direction of one end of the material from the early to middle stage of rolling, and then rolling was applied from the opposite direction to eliminate the convex portion. As a result, the number of subsequent bites was reduced, and as shown in Table 2, the clot loss at both ends was significantly reduced compared to the conventional method. Table 2 Example 2 In this example, a convex portion is formed three times in the width direction of one end of the steel ingot at the beginning of rolling, and immediately after that, rolling is applied from the opposite direction to eliminate the convex portion, and further rolling is performed. This is an example in which a convex portion is formed in the width direction of the other end of the material in the later stage, and the convex portion is eliminated by applying pressure from the opposite direction.

Mold cross section is 1222 side x 810 side at the head, 1 at the bottom
A caff with a weight of 1 milk obtained by casting in a mold of 258 willows x 91 ribs.

When manufacturing a slab with a cross section of 26 x 92 ribs from a steel ingot, the method of the present invention and the conventional method were applied to produce the crop. compared. Details of both rolling processes are shown in Table 3. Table 3 As shown in Table 3, in the conventional method, the steel ingot was R. Pass No. 1 from M. After lowering the pressure to V.3, rotate it 90 degrees, and then lower it in the usual way. Rolling was continued while edging at R to produce a slab of 26 m x 92 m.

On the other hand, in the present invention, Japanese. R. 1170 willow, 11
Pass No. 0 and 1030 are set in sequence. 1, 3
, 5, a convex portion is formed three times in the width direction of one end of the steel soul, and the convex portion is formed into a pass ship. Sun at 8. R. Set on the 1135th rib, pass M. Sun at 10. R. I set it on the 1025 fence and it completely disappeared, and after that it disappeared for days without edging.
R. Continue rolling down by pass M. At 16 V. R. 1
040 sail, pass place. Set to 1000 ribs at 18 and perform edging, pass M. At 19 V. R. The ship's side,
Pass M. At 21 J. R. was set on a 93-meter pillow to form a convex part in the width direction of the other end of the material, and the convex part was set in a V. R. Edging was carried out while erasing at the same time, and a slab measuring 26 m x 92 m was manufactured. Table 4 shows a comparison of the crabs produced by both methods. Table 4 As is clear from Table 4, according to the present invention, the top crop loss is 2.9%, the bottom crop loss is 2.3%, and the sea bream cut is 4.6% higher than the conventional method. % improvement was achieved.

The present invention involves forming convex portions on at least one pair of opposing surfaces of at least one end of the head and bottom of the steel ingot during blooming rolling of the steel ingot, and then rolling the steel ingot from the opposite direction. In addition, by including the step of eliminating the protrusions, metal flow in the thickness direction and width direction at both ends of the rolled material is prevented, and the subsequent rolling to eliminate the protrusions allows for a larger rolling reduction than in the conventional method. Since it can be rolled at 300 degrees, the number of times the material gets caught in the material during the number of rolling passes can be reduced, and the movement of metal toward the biting side can be minimized. It became possible to reduce the overlap in the thickness direction and the fishtail in the width direction, and as a result, the yield when cutting the manufactured slabs was significantly improved compared to the conventional method. In addition,
A secondary effect of the present invention is that the formation and disappearance of convex portions by the method of the present invention can be carried out in an extremely short time, so that there is almost no decrease in the productivity of blooming.

[Brief explanation of the drawing]

Figure 1A, . B is an explanatory diagram showing the growth of a fishtail in the case of the conventional method of split-roll rolling, FIGS. 2A and B are explanatory diagrams showing the formation of an overlap by the secondary method, and FIGS. 3A and B are diagrams showing the formation of an overlap according to the present invention. FIG. 2 is a plan view showing a method for reducing crop loss in blooming rolling according to the present invention, in which A shows a convex part forming process and B shows a convex part disappearing process. FIG. 4 is a perspective view showing an example of an embodiment of a convex portion formed on a rolled material according to the present invention. 7...Rolled material, 8...
Roll for rolling, 9...Protrusion, 10...
Rolled material end. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A method for reducing clotupulos during blooming of a steel ingot using a reversible rolling mill, wherein at least one opposing end of at least one head and bottom of the steel ingot during rolling of the steel ingot is provided.
The protrusion length ΔL is set to 20 by using a rolling roll on the surface of the set.
After forming a convex portion with 0 mm≦ΔL≦300 mm and a protrusion height ΔH of 0.25ΔL≦ΔH<ΔL, reduction of clotsupuros in blooming rolling is characterized by including a step of applying rolling from the opposite direction. Method.