JPS63171255A - Non-solidified rolling method - Google Patents

Abstract

PURPOSE:To prevent the development of crack on surface of a cast slab by rolling the corner part of a cast slab by rolls having caliver groove arranged vertically to a thickness rolling-reduction roll before executing rolling-reduction for thickness of the thin cast slab in a non-solidified rolling method. CONSTITUTION:At the time of non-solidified rolling, in the downstream side of a twin-belt caster 3, a cast slab support roll line 4, a non-driving caliber edger roll 11, a non-driving thickness rolling-reduction roll line 5A, a guide roller line 5B and a pinch rolls 6 are in order arranged. The thin cast slab 8, which is continuously cast by the twin-belt caster 3 and remains non-solidified zone in the inside, is drawn by the pinch rolls 6, and the corner parts 9A of the cast slab are rolling reduced by the caliber-edger rolls 11. In this way, the cast slab cross section is made to convex shape and at the time of succeeding rolling-reduction for thickness, the bending deformation of the shell 9A in the end part of width side is facilitated and the non-solidified rolling under high pressure to prevent the crack developed in the upper and lower face shells 9A at the time of the rolling-reduction for thickness can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention is directed to a thin slab cast by a "fit continuous caster" such as a twin belt caster, in which the inside of the slab is in an unsolidified state. The present invention relates to an unsolidified rolling method that performs thickness reduction, and more specifically, to a rolling method that prevents surface cracking of thin slabs, suppresses an increase in internal cracks, and realizes high reduction unsolidified rolling.

(b) Prior art Normally, when producing a hot rolled steel strip with a thickness of 1.5 to 5 μm, first, continuous casting equipment is used to produce a hot rolled steel strip with a thickness of 200 to 300 inches and a width of 100 mm.
A slab of approximately 0 to 2000 m1+ is produced, and this slab is cut into a length of approximately 10z in a continuous casting line. The cut slabs are transported to the hot rolling process, heated in a heating furnace to a predetermined temperature (1050 to 1200°C), and then subjected to continuous rolling or reverse rolling with several rough rolling mills to reduce the thickness. It is rolled to about 30 to 50 zm, and then finished into a hot rolled steel strip with a thickness of 1.5 to 5 J11 using a continuous finishing mill with 6 to 7 stands.

By the way, in recent years, with the development of continuous casting technology for thin slabs such as twin belt casters, which is different from normal continuous casting,
Thin slabs with a thickness (40 to 80 zz) that is a fraction of the conventional thickness are now being manufactured. As a result, when manufacturing the above-mentioned hot-rolled steel strip, the conventional hot-rolling rough-rolling process is no longer necessary, and the thin slab can be directly supplied to the hot-rolling finish-rolling process, which has a significant effect on reducing equipment costs. Brought.

Furthermore, in order to simplify the finish rolling process, it is necessary to manufacture thinner slabs. However, with the continuous thin slab casting technology described above, the hot water supply method is limited due to the need to change the width, and furthermore, when thin slabs are continuously cast, the surface quality of the slab deteriorates due to this hot water supply method. There was a problem.

Therefore, in the continuous casting of thin slabs, the present applicant has installed a reduction device 5 equipped with horizontal rolls, which enables continuous casting at a higher speed than normal continuous slabs, and has developed a method for continuously casting thin slabs with unsolidified parts inside. Japanese Patent Laid-Open No. 60-8 discloses a method and apparatus for manufacturing a thinner material for hot-rolled steel strip by reducing the thickness difference (wedge amount) between the left and right edges by continuously rolling down the slab 8.
This was disclosed in Publication No. 7904 and Japanese Patent Application No. 14044/1983.

In this method, as shown in FIG. 4(a), even after a thin slab 8 having an unsolidified portion 7 is rolled down by a rolling roll 10 disposed in a rolling zone 58 of a rolling device 5, no solidified part 7 remains. This is a method of performing unsolidified rolling so that portion 7 remains. Therefore, the part that is actually rolled down by the rolling roll 10 is only the shell 9^ at the width end, as shown in Figure 4 (11), and most of the shell 9B on the upper and lower surfaces of the slab is rolled down as shown in Figure 4 (c). As shown in the figure, the rolling force and torque during unsolidified rolling are extremely small compared to conventional hot rolling.

Therefore, compared to hot rolling equipment that performs rolling after completion of solidification, unsolidified rolling equipment has very low rolling power and is a small equipment, and is very inexpensive thickness reduction equipment.・Using several table rolls and a device that adjusts the upper and lower roll openings (roll gaps) of the rolls, the slab is lightly rolled down with the Vinci roll 6 installed downstream of the rolling down device 5. Unsolidified rolling can be performed by drawing.

(c) Problems to be Solved by the Invention When performing unsolidified rolling at a high reduction rate using a rolling device 5 having horizontal rolls arranged as shown in FIG. Cracks occur as shown in FIG. 4(a), deterioration of the crystalline quality of the slab, or a breakout in which the shell 9B is torn and the molten metal inside flows out. Therefore, in reality, the rolling reduction ratio of unsolidified rolling was limited to about 20%.

The deformation behavior of a slab during unsolidified rolling will be explained using FIG. 4. As shown in FIG. 4(,), since there is an unsolidified layer 7 inside the unsolidified slab, when this slab is reduced in thickness with the reduction roll 10, the shell 9 at the width end portion Only that portion is compressively deformed and elongated in the rolling direction (Fig. 4(b)).

On the other hand, as shown in FIG. 4(e), most of the shell 9B on the upper and lower surfaces of the slab is not compressed and deformed by the reduction roll 10, but is only bent, and the elongation deformation in the rolling direction occurs at the width end. This is caused by tensile stress in the rolling direction generated in the shell 9B due to the elongation of the shell 9^. Therefore, if the rolling reduction ratio in unsolidified rolling is increased, the tensile stress generated in the shell 9B on the upper and lower surfaces of the slab will increase, and the shell 9B at the center of the width will increase.
A crack occurs in the width direction in B.

Therefore, with the rolling down device 5 having horizontal rolls arranged as shown in FIG. 3, it is not possible to obtain a very large rolling reduction due to the occurrence of cracks in the shells 9B on the upper and lower surfaces of the slab, and this has a great effect on simplifying the hot rolling finishing equipment. It wasn't enough to bring about that.

In particular, the present invention is capable of causing internal cracks in the slab without causing cracks on the slab surface during unsolidified rolling in which the thickness of a thin slab cast by a continuous rin slab casting machine is reduced while the inside of the slab is in an unsolidified state. The purpose of this invention is to obtain a method for performing unsolidified rolling at a high reduction rate while preventing an increase in the amount of steel. It is said that

(d) Means for Solving Problems The unsolidified rolling method of the present invention involves reducing the thickness of a thin slab cast by a continuous thin slab casting machine before the inside of the slab is completely solidified. In unsolidified rolling, where an unsolidified layer remains inside the slab even after rolling is completed,
The above problem is solved by rolling the corner portion of the slab with a roll having a caliber groove arranged perpendicularly to the thickness reduction roll before the thickness reduction.

(E) Function In the unsolidified rolling method of the present invention, the corner of the slab is edge-rolled using a Caliba edger roll to make the cross section of the slab convex, and during the subsequent thickness reduction, the shell at the width end is It facilitates bending deformation, reduces the elongation in the rolling direction of the shell at the width end during thickness reduction, reduces the tensile stress in the rolling direction that occurs in the upper and lower shells 9B of the slab, and prevents cracks that occur in the upper and lower shells 9. , which enables unsolidified rolling under high pressure.

Furthermore, for changes in slab width, Kariba Etsujia
This can be handled by changing the opening of the rolls, and also changes in the R suitable slab corner reduction amount to prevent cracking of the upper and lower shells 9B caused by changes in unsolidified rolling conditions such as unsolidified reduction amount, shell thickness, slab thickness, etc. This can be dealt with by adjusting the opening of the Caliba Edger roll, making it possible to effectively prevent cracking during unsolidified rolling.

(f) Example An example of the unsolidified rolling method of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a v1 schematic illustration of equipment for carrying out the method of the invention.

In FIG. 1, the same numbers as in FIG. 3 represent the same devices and equipment.

In this embodiment, on the downstream side of the twin belt caster 3, there is a slab support roll row 4, a non-driving force lever edger roll 11, a non-driving thickness reduction roll row 5^, a guide roller row 5B, and a pinch roll. 6 will be installed one after another. The thin slab 8, which is continuously cast by the twin belt caster 3 and which leaves an unsolidified layer inside, is pulled out by the pinch rolls 6, and the corner part of the slab is removed by the Caliba Edger roll 11 (see Fig. 2).
It is rolled down as shown in a), and then subjected to unsolidified rolling by a thickness rolling roll row 58.

For example, under the casting conditions shown in Table 1, the reduction rate is 40%.
The present invention will be described in detail in the case where unsolidified rolling is performed.

Table 1 In this embodiment, as shown in FIG.
701x, caliber depth Dc=40mm, caliber bottom length L
-26xyz. Further, as the reduction roll row 5^, an apparatus was used in which six rows of rolls each having a diameter of 100 zz were arranged at a pitch of 180+v. The edger opening degree E c was set to 60611, and the rolling reduction amount of each rolling roll 10 was set to Δh-3.3iv.

Furthermore, at the end of unsolidified rolling, that is, the reduction roll row 5^
The target shell thickness h of the shell 9B on the upper and lower surfaces of the slab at the exit side of
Cooling of the slab was controlled so that s=13 to 14xm.

When we measured the elongation in the rolling direction of the center of the slab width after this unsolidified rolling, that is, the elongation of the shell 9B on the upper and lower surfaces of the slab, we found that the elongation strain was 1.2% with respect to the length of the slab before unsolidified rolling. was occurring. Moreover, no particularly problematic surface cracks were observed on the upper and lower surfaces of the slab.

On the other hand, in the case where the corner of the slab is not rolled by the Caliba Edger Roll 11 under the same conditions as the above-mentioned unsolidified rolling,
The elongation strain of shell 9B on the upper and lower surfaces of the slab is 2.6%, and the upper and lower surfaces of the slab have a maximum depth of approximately 51 mm and a length of approximately 50 yg+.
Cracks were observed, confirming the effect of the present invention on preventing surface cracks.

The effect of preventing surface cracking according to the present invention described above will be explained with reference to FIG. 2. As described above, cracks on the upper and lower surfaces of the slab during unsolidified rolling are caused by tensile stress acting on the upper and lower shells 9B due to elongation in the rolling direction due to reduction of the width end shells 9^.

Therefore, by reducing the elongation of the shell 9^ due to rolling, the tensile stress acting on the shell 9B can be reduced and cracking can be prevented. In the present invention, the elongation of the shell 9^ during thickness reduction is reduced by rolling the slab corner portions and changing the cross-sectional shape of the slab before thickness reduction.

As shown in Fig. 2), when the corner of a slab is rolled down, the slab hardly elongates as in the edging rolling of a normal hot-rolled steel strip, and the rolled metal at the corner of the slab flows in the width direction. As shown in FIG. 2(b), the cross section of the slab has a dog-bone shape. The thickness of the slab at this time is H,>Ho>H, as shown in Figure 2(b), and when a slab with such a cross-sectional shape is reduced in thickness, the thickness reduction roll has a thickness of H,>Ho>H. At the initial stage of thickness reduction, because the contact starts from the thicker part,
A bending force is applied to the shell 9^. As the thickness reduction progresses, a reduction blade in the thickness direction also acts on the shell 9Δ, so in the unsolidified rolling method of the present invention, the thickness of the shell 9^ decreases due to bending deformation and rolling. Therefore, compared to the conventional unsolidified rolling method, the elongation of the shell 9^ in the rolling direction due to thickness reduction is reduced, and the occurrence of separation can be prevented.

For example, when the thickness reduction progresses only by bending deformation of the shell 9^, the elongation of the shell 9^ becomes O, and cracking of the shell 9B can be prevented. However, since a large tensile stress acts on the 9^^ part of the shell 9^ shown in Fig. 2(e),
A crack occurs at the 9^^ part.

Therefore, it is necessary to adjust the bending force acting on the shell 9^ during thickness reduction.

According to the method of the present invention, the above bending force can be changed by adjusting the opening degree of the Caliba edger roll and controlling the amount of reduction of the corner portion of the slab.
Even if unsolidified rolling conditions such as shell thickness and thickness reduction change,
It is possible to prevent cracking.

(g) Effects As explained above, the unsolidified rolling method of the present invention can reduce elongation due to reduction of the shell. Therefore, it is possible to realize unsolidified rolling with a higher reduction ratio than conventional unsolidified rolling. By the way, the unsolidified rolling method of the present invention can also be applied to unsolidified rolling of slabs cast by conventional continuous casting machines. In addition, in order to enhance the effect of preventing cracks caused by corner edge rolling of the slab, additional Caliba edge rolls may be installed between the thickness reduction rolls.

According to the unsolidified rolling method of the present invention, rolling at a high reduction rate is possible, so the hot rolling process can be simplified and a hot rolled steel strip can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of equipment for carrying out the unsolidified rolling method of the present invention. FIG. 2 is an explanatory diagram of the unsolidified rolling method of the present invention, and FIG. 3 is a schematic explanatory diagram of the installation of the conventional unsolidified rolling method for applying burns. FIG. 4 is an explanatory diagram of the cause of cracking during unsolidified rolling. 1: Ladle 2: Molten metal tank 3: Twin belt casters 4: Slab support roll row 5: Unsolidified reduction device 5 8: Thickness reduction roll row 5B = Guide roller row 6: Pinch roll 7: Molten metal 8: Slab 9^, 911 Nigiel 10:
Thickness reduction roll 11: Kariba Etsuya Roll Patent applicant Sumitomo Metal Industries, Ltd. (5 others)

Claims (1)

[Claims] In unsolidified rolling, a thin slab cast by a continuous thin slab casting machine is reduced in thickness before the inside of the slab is completely solidified, and an unsolidified layer remains inside the slab even after the reduction is completed.
An unsolidified rolling method characterized in that, before thickness reduction, a corner portion of a slab is rolled with a roll having a caliber groove arranged perpendicularly to a thickness reduction roll.