JP4325452B2 - Supporting guide method for short side of slab directly under continuous casting mold - Google Patents

Description

  The present invention relates to a method for supporting and guiding a short side of a slab immediately below a continuous casting mold.

  Immediately under the mold of the continuous casting machine, the solidified shell thickness of the slab is thin, and the slab tries to be bulged by the molten steel static pressure inside the slab, so the slab is intended to prevent breakout or to cool the slab uniformly. A cooling support guide device is disposed immediately below the mold. This device has a copper plate that is attached to the mold and oscillates together with the mold, and a foot roll located immediately below the copper plate. The slab is supported and guided by these, and the slab slab having a constant cross-sectional shape is continuously drawn. It is burned.

  A normal foot roll is a flat type foot roll in which the diameter of the portion that contacts the slab surface is constant on both the long side and the short side of the slab.

On the other hand, in continuous casting of stainless steel, in the case of flat type foot rolls, the cross section of the slab after passing through the foot rolls has a shape in which the short side swells and the long side side of the edge is depressed, and if this is rolled as it is, the product steel plate Since surface defects such as shave (sliver) defects occur on the surface, there is a problem that requires care of the slab surface before hot rolling, and seam defects occur when rolling if the short side is concave. In order to make the long side of the continuous cast slab of stainless steel as flat as possible and slightly indent the short side, the slab long side is a normal flat foot roll. It is known that the short side is a foot roll with a crown (Patent Document 1).
JP-A-3-291130

  The above normal foot roll (flat type on both the long side and short side) is a slab directly under the mold when the casting speed (slab drawing speed) is less than 2.0 m / min. Bulging was effectively suppressed. However, if high speed casting at a casting speed of 2.0 m / min or more is performed, the thickness of the solidified shell just below the mold is further reduced, which increases the amount of bulging on the short side and increases the risk of breakout. There was a problem. Therefore, with reference to Patent Document 1, it has been considered to use a foot roll with a crown on the short side. However, in Patent Document 1, since the foot roll is not in contact with both ends of the mold short side, the width of the slab is reduced. When changing the lower end of the mold short side to the slab width center side, the reaction force from the slab to the short side foot roll becomes insufficient, and the indentation into the center part of the short side becomes excessive. , Found that there is a high risk of breakout. In addition, the foot roll with a crown also has the difficulty that manufacturing cost increases compared with a flat type foot roll.

  Therefore, the present invention has an object to provide a short side support guide method directly under a continuous casting mold that can reduce bulging of the short side of the casting immediately below the mold without causing excessive indentation even in the case of high speed casting. To do.

  The present invention that has achieved the above object is as follows.

(Invention Item 1) In the method for supporting and guiding the short side of a slab immediately below a continuous casting mold using a foot roll, one flat type central roll that abuts the central part of the short side of the slab on the same roll shaft as the foot roll. And two flat-type end rolls respectively in contact with both ends of the short side of the slab so as to be individually rotatable, and the roll radius of the central roll is larger than the roll radius of the end roll. only 1-5% larger, and the slab short side immediately below a continuous casting mold, characterized in that it has a three-part convex foot rolls formed by the barrel length of the central roller 30 to 60% of the cast slab thickness Support guidance method.

  (Invention Item 2) A method for supporting and guiding a short side of a slab immediately below a continuous casting mold according to Invention 1, which is used for continuous casting at a casting speed of 2.0 m / min or more.

  (Invention 3) The slab short-side support guide method directly under the continuous casting mold according to Invention 1 or 2, which is used for continuous casting of medium carbon steel or silicon steel.

(Invention Item 4) In the cast slab short-side support guide device directly below the continuous casting mold having the foot roll, the foot roll has a slab thickness of 30 on the same roll shaft and abutted against the center of the slab short side. 2 having the one flat central role of which is a 60%, only 1-5% smaller roll radius of the slab short side end portions respectively in contact with the central roller of the roll radius slab thickness than A slab short-side support and guide device directly under a continuous casting mold, which is a three-segment convex foot roll that is mounted so as to be individually rotatable with a flat type end roll.

According to the present invention, as the foot rolls on the short side, slab short side and one flat central roller that abuts the central portion, the end of the two flat abutting each slab short side end portions Using a three-segment convex foot roll that is mounted on the same roll axis so as to be individually rotatable, the roll radius of the center roll is 1-5% larger than the roll radius of the end roll , and the center roll Since the cylinder length of the slab is 30 to 60% of the slab thickness , bulging of the slab directly under the mold can be reduced at a low cost without causing excessive pressing even in high-speed casting.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of the present invention. As shown in this figure, the foot roll 10 used in the present invention has one central roll 10C that abuts on the short side center of the slab 1 and two abuts on both ends of the short side of the slab 1 respectively. An end roll 10E is mounted on the same roll shaft 11 via a bearing 12 so as to be individually rotatable, and is a three-segment convex foot roll 10 in which the roll diameter of the center roll 10C is larger than the roll diameter of the end roll 10E.

  The center roll 10C and the end roll 10E are flat rolls. According to this configuration, not only the center part of the slab short side but also both end parts are pressed, so there is no danger of excessive pressing when changing the slab width. In addition, flat type rolls can be obtained at low cost because they are less expensive to manufacture than rolls with crowns.

In the present invention, the contact width between the short side center portion and the center roll 10C (the trunk length of the center roll 10C) is preferably 30 to 60% of the slab thickness.

  In order to suppress bulging of the short side of the slab, the roll diameter D2 of the central roll 10C is set to be 2 × δ larger than the roll radius D1 of the end roll 10E. In the present invention, this δ (= the central roll 10C The roll radius (D2 / 2) −the roll radius (D1 / 2) of the end roll 10E is 1 to 5% of the slab thickness. If δ is less than 1% of the slab thickness, bulging of the short side of the slab on the foot roll exit side cannot be suppressed. If δ is more than 5% of the slab thickness, excessive push-in occurs, and breakout is likely to occur at the portion in contact with the foot roll.

  In addition, since the central roll 10C and the end roll 10E can be individually rotated, wrinkles that occur in the case of integral rotation (from the difference between the roll peripheral speed of the end and the center, either the roll end or the roll center and the slab short side The wrinkles generated by rubbing do not occur in the present invention.

  FIG. 2 is a side view showing an example of the embodiment of the present invention. The AA arrow view of FIG. 2 corresponds to FIG. In this example, the roll shaft 11 of the three parallel type foot rolls 10 is supported by a swing frame 8 hung from a support shaft provided at the bottom of the mold frame 6, and the lower end of the swing frame 8 and the bottom of the mold frame 6 are lowered. The lower end portion of the fixed frame 9 extended in the direction is connected by a disc spring type elasticity applying means 20. The elasticity of the elasticity applying means 20 is adjusted to an appropriate range determined based on results. This adjusted elasticity acts on the three-segment convex foot roll 10 and presses the foot roll 10 against the slab short side with an appropriate force.

  In this example, the three divided convex foot rolls 10 are arranged and used per one short side of the slab 1, but the number used is not limited to this and may be determined appropriately. In addition, what is necessary is just to use a flat type roll as usual for the foot roll of the slab long side.

  Further, as described above, when the casting speed is less than 2.0 m / min, the bulging amount can be suppressed to the extent that there is no problem even when the conventional flat type foot roll is used on the short side, so the effect of the present invention is obvious. Therefore, the present invention is preferably used for continuous casting at a casting speed of 2.0 m / or more.

  In addition, when a conventional flat type foot roll is used on the short side, with medium carbon steel (C: steel containing 0.07 to 0.09 mass%) and silicon steel, the increment of the bulging amount with respect to the increment of casting speed is There is a tendency that it is larger than the steel type, and therefore, for medium carbon steel and silicon steel, it was necessary to regulate the casting speed to be smaller than other steel types. When the present invention is applied to this to reduce the amount of bulging of medium carbon steel and silicon steel, the casting speed of medium carbon steel and silicon steel can be increased to the level of other steel types, and productivity is improved. Therefore, the present invention is preferably used for continuous casting of medium carbon steel or silicon steel.

The slab short-side support guide method according to any one of the first to third aspects of the invention is also provided in the three-segment convex foot roll 10 as shown in FIGS. One flat-type central roll 10C in which the body length abutting on the part is 30 to 60% of the slab thickness, and the slab in contact with both ends of the short side of the slab and the roll radius of the central roll 10C. The slab short side according to claim 4, which has a three-segment convex foot roll 10 in which two flat-type end rolls 10E each having a roll radius smaller by 1 to 5% of the thickness are rotatably mounted individually. It can be easily implemented by the support guide device.

(Example 1, Comparative Example 1)
In Example 1, a vertical bend type continuous casting apparatus was used to continuously cast medium carbon steel (0.08 mass% C-containing steel) to produce a slab slab having a width of 1500 mm and a thickness of 220 mm. The present invention was applied in the form shown in FIG. The three-segment convex foot roll used on the short side had a central roll diameter of 120 mm, a central roll cylinder length of 78 mm, an end roll diameter of 110 mm, and an end roll cylinder length of 51 mm (δ = 5 mm = 2.3% of slab thickness) ). For the long side, a two-part flat foot roll having a roll diameter of 136 mm and roll body lengths of 1192 mm and 842 mm was used. The casting temperature (molten steel overheating temperature in the tundish) ΔT was 25 ° C., and the casting speed was 2.6 m / min. During casting, the width of the slab passing between the short side foot roll closest to the mold and the next short side foot roll is measured with a straight gauge, and the target slab width (converted into a hot piece) is measured from this measured value. Value) was subtracted to evaluate the amount of bulging. Moreover, it replaces with the said 3 division | segmentation convex foot roll, About Comparative Example 1 continuously cast on the same conditions as Example 1 except having used the roll type foot roll of roll diameter 120mm and roll trunk | drum length 223mm, bulging amount similarly Evaluated. As a result, the bulging amount of Example 1 was 25% of that of Comparative Example 1. Based on this result, the casting speed of medium carbon steel could be increased from the conventional 2.6 m / min to 2.84 m / min.
(Example 2, comparative example 2)
In Example 2, using a vertical bending type continuous casting apparatus, silicon steel (0.35 mass% Si-containing steel) was continuously cast to produce a slab slab having a width of 1300 mm and a thickness of 220 mm. The present invention was applied in the form shown in FIG. The three-segment convex foot roll used on the short side had a central roll diameter of 120 mm, a central roll cylinder length of 78 mm, an end roll diameter of 110 mm, and an end roll cylinder length of 51 mm (δ = 5 mm = 2.3% of slab thickness) ). For the long side, a two-part flat foot roll having a roll diameter of 136 mm and roll body lengths of 1192 mm and 842 mm was used. The casting temperature (tundish molten steel overheating temperature) ΔT was 25 ° C., and the casting speed was 2.64 m / min. During casting, the width of the slab passing between the short side foot roll closest to the mold and the next short side foot roll is measured with a straight gauge, and the target slab width (converted into a hot piece) is measured from this measured value. Value) was subtracted to evaluate the amount of bulging. Moreover, it replaces with the said 3 division | segmentation convex foot roll, About Comparative Example 2 continuously cast on the same conditions as Example 2 except having used the roll type foot roll of roll diameter 120mm and roll trunk | drum length 223mm, bulging amount similarly Evaluated. As a result, the bulging amount of Example 2 was 25% of that of Comparative Example 2. Based on this result, the casting speed of silicon steel could be increased from the conventional 2.64 m / min to 3.0 m / min.

  The present invention can be used not only for steel but also for continuous casting operations of other metals or alloys.

It is a cross-sectional view (AA equivalent view of FIG. 2) which shows an example of embodiment of this invention. It is a side view showing an example of an embodiment of the present invention.

Explanation of symbols

1 Cast slab 2 Solidified shell 3 Molten steel 4 Mold (continuous casting mold)
5 Casting short side copper plate 6 Casting frame 7 Casting (drawing) direction 8 Swing frame 9 Fixed frame 10 Foot roll (3 split convex foot roll)
10C Central roll 10E End roll 11 Roll shaft 12 Bearing 20 Elasticity imparting means (Belleville spring type)

Claims (4)

In the slab short-side support and guide method directly below the continuous casting mold using a foot roll, the foot roll is placed on the same roll shaft with a single flat-type central roll that abuts on the center of the slab short side, Two flat-type end rolls that are in contact with both end portions of the side are individually mounted so as to be freely rotatable, and the roll radius of the central roll is 1 to 5% of the slab thickness than the roll radius of the end roll. was large and cast strip short side supporting guidance method immediately below the continuous casting mold, characterized in that it has a three-part convex foot rolls formed by the barrel length of the central roller 30 to 60% of the cast slab thickness.   The method for supporting and guiding a short side of a slab immediately below a continuous casting mold according to claim 1, wherein the method is used for continuous casting at a casting speed of 2.0 m / min or more.   3. The method for supporting and guiding a short side of a slab immediately below a continuous casting mold according to claim 1, wherein the method is used for continuous casting of medium carbon steel or silicon steel. In the slab short-side support guide device directly below the continuous casting mold having a foot roll, the foot roll has the same roll axis, and the body length contacting the center of the slab short side is 30 to 60% of the slab thickness. 1 and flat central role of the two ends of the flat with only 1-5% smaller roll radius of the slab short side end portions respectively in contact with the central roller of the roll radius slab thickness than A slab short-side support and guide device directly below a continuous casting mold, wherein the slab is a three-segment convex foot roll that is mounted so as to be individually rotatable.

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