JP2016140912A - Continuous casting equipment for molten steel of high carbon steel and continuous casting method for molten steel of high carbon steel using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide continuous casting equipment for molten steel of high carbon steel which can produce a product with preferable productivity and preferable work efficiency, and a continuous casting method for molten steel of high carbon steel using the same.SOLUTION: Continuous casting equipment 10 for molten steel of high carbon steel is provided that comprises a plurality of casting molds 11 to 13 arranged for one tundish. Each of the casting molds 11 to 13 has a casting mold space part 20 formed with short edges 16, 17 and long edges 18, 19, and receives and cools the molten steel for the high carbon steel containing 0.6 mass% of carbon poured into the casting mold space part 20 to produce cast metal. A width of the casting mold space part 20 on the short edge 16, 17 side is set to be 300 to 500 mm and a width on the long edge 18, 19 side is set to be 360 to 650 mm, and an inclination part formed in such a way that the interval thereof becomes gradually narrower in a cast metal pulling direction and in accordance with a solidification shrinkage amount of a cast metal shell is formed in each of the opposite surfaces of the short edges 16, 17 and in each of the opposite surfaces of the long edges 18, 19. The continuous casting method for the molten steel of the high carbon steel is also provided in which the cast metal is produced while a casting time is set to be 24 h or more and a casting speed is set to be 0.8 m/min to 1.2 m/min.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a continuous casting facility for molten steel for high carbon steel and a continuous casting method for molten steel for high carbon steel using the same.

  Conventionally, a rail (rail) is manufactured by continuously casting molten steel for high carbon steel adjusted to a predetermined chemical composition with a mold, and hot rolling the obtained slab (for example, Patent Document 1). 2).

JP 2014-101583 A JP 2008-50684 A

However, wrinkles may occur in the manufactured rail (product).
This flaw is caused by fine internal cracks in the slab that occurred during continuous casting. When this internal crack occurs, for example, the mold is suddenly replaced, or the casting speed is made slower than the current state. To prevent the occurrence of wrinkles on the rail. In addition, the internal crack of the slab has occurred mainly in the vicinity of the corner portion of the slab, for example, in the range from the surface of the slab to 5 mm.
For this reason, generation | occurrence | production of the fine internal crack of slab invited the fall of productivity and the deterioration of workability | operativity.

  The present invention has been made in view of such circumstances, and is a continuous casting facility for molten steel for high carbon steel capable of producing products with good productivity and good workability, and continuous molten steel for high carbon steel using the same. An object is to provide a casting method.

The continuous casting equipment for molten steel for high carbon steel according to the first invention in accordance with the above object has a pair of short sides arranged to face each other with a gap between them and the short sides sandwiched from both sides in the width direction. A mold for producing a slab was prepared by injecting molten steel for high carbon steel having a carbon content of 0.6% by mass or more from a tundish into a mold space formed by a pair of long sides to be cooled. In continuous casting equipment for molten steel for high carbon steel,
The width of the short side of the mold space is 300 mm or more and 500 mm or less, and the width of the long side of the mold space is 360 mm or more and 650 mm or less, and each of the opposed short sides of the pair of short sides Each of the molds formed on each of the surfaces and the opposing surfaces of the pair of long sides has inclined portions whose intervals gradually narrow in accordance with the amount of solidification shrinkage of the slab shell in the direction in which the slab is pulled out. A plurality of tundishes are arranged.

  The continuous casting method for molten steel for high carbon steel according to the second invention in accordance with the above object is a continuous casting method for molten steel for high carbon steel using the continuous casting equipment for molten steel for high carbon steel according to the first invention. Then, the casting slab is manufactured at a casting speed of the molten steel for high carbon steel by the mold of 0.8 m / min to 1.2 m / min.

  The continuous casting method for molten steel for high carbon steel according to the third aspect of the invention that meets the above object is a continuous casting method for molten steel for high carbon steel using the continuous casting equipment for molten steel for high carbon steel according to the first aspect. Then, the slab is manufactured by setting the casting time of the molten steel for high carbon steel by the mold to 24 hours or more.

The continuous casting equipment for molten steel for high carbon steel according to the present invention and the continuous casting method for molten steel for high carbon steel using the same, each of a pair of short sides and a pair of long sides forming a mold space portion of a predetermined dimension Since the molten steel for high carbon steel is cast on the surface using a mold in which an inclined portion whose interval gradually narrows following the amount of solidification shrinkage of the slab shell is cast, the inner surface of the mold and the casting formed in the mold are cast. The contact state with the one shell can be improved. Thereby, substantially uniform cooling is performed over the circumferential direction of the slab shell, and the solidification delay in the vicinity of the corner portion is improved, so that the occurrence of fine internal cracks in the slab can be suppressed, and even if it occurs However, the generation location can be moved (deepened) from the surface to the inside (a position where wrinkles are not generated on the surface of the product).
Therefore, by arranging a plurality of such molds for one tundish, it is possible to manufacture a product of good quality free from wrinkles with good productivity and good workability.

  In particular, by using the continuous casting equipment for molten steel for high carbon steel including the mold having the above-described configuration, for example, casting can be performed without suddenly changing the mold and without reducing the casting speed. . Accordingly, the slab can be stably manufactured by setting the casting speed to 0.8 m / min or more and 1.2 m / min or less and casting time to 24 hours or more.

It is a top view of the continuous casting equipment of the molten steel for high carbon steel which concerns on one embodiment of this invention.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a continuous casting facility (hereinafter also simply referred to as a continuous casting facility) 10 for molten steel for high carbon steel according to an embodiment of the present invention has a carbon content of 0.6% by mass or more. It is equipped with three (multiple) molds 11 to 13 for injecting molten steel for steel (hereinafter, also simply referred to as molten steel) from a tundish (not shown) and cooling them to produce cast pieces, and good without flaws Products of high quality can be manufactured with good productivity and good workability. Here, the product is obtained by rolling a slab obtained by casting molten steel for high carbon steel. For example, there is a rail (rail for rail), but it is not limited to this. Absent.
This will be described in detail below.

The three molds 11 to 13 have the same configuration.
These molds 11 to 13 are arranged side by side with a space therebetween, and are positioned and fixed by being attached and fixed to a pair of opposed back plates (frames) 14 and 15 while being sandwiched therebetween. . The back plates 14 and 15 are made of stainless steel or steel.
Thereby, three molds 11-13 can be arranged to one tundish, and molten steel can be poured (supplied) from one tundish to each mold 11-13 simultaneously.

  The mold 11 (the same applies to the molds 12 and 13) includes a pair of short sides 16 and 17 disposed to face each other with a gap therebetween, and a pair disposed to face each other with the short sides 16 and 17 sandwiched from both sides in the width direction. The pair of short sides 16 and 17 and the pair of long sides 18 and 19 form a square-shaped mold space 20. In addition, each of the short sides 16 and 17 and the long sides 18 and 19 is made of copper or a copper alloy, and the surface (molten steel contact surface side) is plated in accordance with the use application (type of molten steel) of the mold 11. Layers and sprayed coatings are formed.

On the back side of the short sides 16 and 17 and the long sides 18 and 19, a large number of water guide grooves (not shown) are provided in the casting direction (the direction in which the slab is pulled out) at a predetermined pitch in the width direction. ing. A back plate (not shown) is attached and fixed to the back surfaces of the short sides 16 and 17, and the back surfaces of the long sides 18 and 19 are attached and fixed to the back plates 14 and 15, respectively.
Thereby, cooling of the short sides 16 and 17 and the long sides 18 and 19 at the time of continuous casting can be implemented by flowing cooling water through the water guide groove.

The short sides 16 and 17 have a thickness of about 10 mm to 100 mm, a width (a width on the short side 16 and 17 side of the mold space 20) of 300 mm to 500 mm, and a length in the casting direction of about 600 mm to 1200 mm. . The short sides 16 and 17 are mirror-symmetric and have the same configuration.
The long sides 18 and 19 each have a thickness of about 10 mm or more and 100 mm or less, and the distance between the pair of opposed short sides 16 and 17 (the width on the long side 18 and 19 side of the mold space 20) is 360 mm or more and 650 mm. Hereinafter, the length in the casting direction is about the same as the short sides 16 and 17.

Here, the width of the short sides 16 and 17 is 300 mm or more and 500 mm or less (particularly 400 mm or less), and the distance between the pair of opposed short sides 16 and 17 is 360 mm or more and 650 mm or less (particularly 500 mm or less). The reason for this is to obtain a slab of a size necessary for producing a high carbon steel product (especially a rail), and with this width and interval, the carbon content is 0.6% by mass or more. This is because when molten steel for steel (particularly, molten steel for rails) is cast, fine internal cracks are likely to occur near the corner of the slab.
Therefore, the shape of the mold 11 (same for the molds 12 and 13) is changed to the following shape.

A slab in the casting direction from the meniscus position to the mold outlet on each of the opposing surfaces (slab contact surface) of the pair of short sides 16 and 17 and each of the opposing surfaces (slab contact surface) of the pair of long sides 18 and 19 An inclined portion whose interval is gradually narrowed is formed following the amount of solidification shrinkage of the shell (solidified shell) (the mold space 20 is tapered (tapered)).
The surface shape (inner cross-sectional shape) of the inclined portion is substantially the same shape in the width direction, and the shape in which the increase rate of the taper rate decreases with increasing distance from the meniscus position, that is, Multi-taper.

This multitaper uses the curve (specified by multiple functions) and / or multiple straight lines for the solidification shrinkage profile of the slab in the mold (from the meniscus position (metal surface) to the mold outlet). It is approximated and applied to the surface shape of the inclined portion.
In addition, the taper ratio is obtained by dividing the difference between the upper end position and the lower end position of the inner surface (slab contact surface) by the length in the vertical direction when the short side and the long side are respectively viewed in plan. It is the value shown by. Here, for example, it is about 0.9% / m or more and 2.0% / m or less.

Hereinafter, the multitaper determination method will be briefly described.
Multi-taper is based on FEM analysis (analysis using finite element method) considering solidification shrinkage of 3D slab and thermal deformation of mold based on the following measured conditions and actual measurement results. The same shall apply hereinafter. Specifically, the shape of the slab, the size of the slab, casting conditions (for example, casting temperature, drawing speed, mold cooling conditions, etc.), physical quantities derived from the components of the cast steel type (for example, liquidus temperature, solid phase temperature) , Transformation temperature, linear expansion coefficient, rigidity value, etc.), the amount of contact heat transfer between the mold and the slab (the amount of shrinkage of the slab is greatly influenced by this amount), and the like.

The amount of contact heat transfer described above is greatly influenced by, for example, the type of lubricant used during casting and the surface shape of the slab (depending on the steel type, oscillation conditions, and lubricant type).
Therefore, it is necessary for determining the multitaper to grasp the actual amount of contact heat transfer for each casting condition as accurately as possible.
Moreover, when processing the shape of the some casting_mold | templates 11-13 to the said shape, it is preferable to process at once, in the state which attached and fixed the member used as the long side 18 of each casting_mold | template 11-13 to the backplate 14. FIG. Accordingly, the long side 18 having the same shape can be efficiently manufactured, and the multitaper shape can be processed with high precision (the same applies to the back plate 15 and the long side 19).

Then, the continuous casting method of the molten steel for high carbon steel which concerns on one embodiment of this invention is demonstrated using the above-mentioned continuous casting equipment 10 of molten steel for high carbon steel.
First, the amount of carbon adjusted to a predetermined chemical composition using a commonly used melting furnace such as a converter or an electric furnace is 0.6 mass% or more (the upper limit is, for example, 1.2 mass%). Manufactures molten steel for carbon steel.
Next, after supplying this molten steel to a tundish, it inject | pours into each casting_mold | templates 11-13 from a tundish, and cools and manufactures a slab.

  Thus, by casting molten steel using the mold 11 having the above-described configuration (the same applies to the molds 12 and 13), the contact state between the inner surface of the mold 11 and the slab shell formed in the mold 11 is as follows. Can be good. Thereby, since the solidification delay in the vicinity of the corner portion is improved, the thickness in the vicinity of the corner portion of the slab shell can be made substantially equal to the thickness of the other portion (side portion) in the mold 11.

In the continuous casting of the slab of the size described above, the casting speed of the molten steel by the molds 11 to 13 is 0.8 m / min or more and 1.2 m / min or less (preferably, the lower limit is 0.9 m / min, The upper limit is 1.0 m / min.
Here, when the casting speed is less than 0.8 m / min, the casting speed is too slow, and the productivity may be lowered. On the other hand, when the casting speed is over 1.2 m / min, the casting speed is too high and non-uniform solidification occurs at the corners in the mold, which causes fine cracks and bleeds. May cause trouble.

In continuous casting of a slab, the casting time is 24 hours or longer (preferably 26 hours or longer, more preferably 28 hours or longer, and the upper limit is, for example, about 36 hours).
Thus, by continuously casting for 24 hours or more, the productivity of the slab can be increased. In addition, by using the mold 11 (same for the molds 12 and 13), as described above, the solidification delay in the vicinity of the corner portion is improved. Further, it can be carried out stably while preventing.

The slab obtained by the above-described method can suppress the occurrence of fine internal cracks in the slab, and even if it occurs, the generation location is from the surface to the inside (for example, a thickness position of 5 mm or more from the surface). Can be moved to.
For this reason, even when the above-described slab is further hot-rolled, a product free from defects can be produced.

Here, in order to increase the productivity of the product, in the continuous casting facility 10, three molds 11 to 13 are arranged for one tundish. However, if wrinkles occur in the product, As described above, for example, it is necessary to change the mold suddenly or to make the casting speed slower than the current state. When such an operation is performed for a plurality of molds 11 to 13, the operation becomes complicated and the productivity is reduced.
From the above, by using the continuous casting equipment 10 for molten steel for high carbon steel of the present invention and the continuous casting method for molten steel for high carbon steel using the same, the high carbon steel has good productivity and good workability. Products (especially rails) can be manufactured.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, in the case where the continuous casting equipment for molten steel for high carbon steel of the present invention and the continuous casting method for molten steel for high carbon steel using the same are configured by combining some or all of the above-described embodiments and modifications. Is also included in the scope of rights of the present invention.
In the above-described embodiment, the case where three molds are arranged for one tundish has been described. However, a plurality of molds may be used, for example, two, or four or more.

Moreover, in the said embodiment, although the mold space part (inner cross-sectional shape) of the three casting_mold | templates arrange | positioned at one tundish was made into the same shape, the inner width of a mold space part exists in the above-mentioned size range. And if the inclined part of the above-mentioned structure is formed in each opposing surface of the short side and long side which comprise a casting_mold | template, it can also be set as a different shape.
Here, the different shape includes, for example, a case where the shape of the inclined portion (multi-taper) is different, or a case where the cross-sectional dimensions of the cast pieces cast in each mold are different.

10: Continuous casting equipment for molten steel for high carbon steel, 11-13: Mold, 14, 15: Back plate, 16, 17: Short side, 18, 19: Long side, 20: Mold space

Claims (3)

In a template space formed by a pair of short sides opposed to each other with an interval and a pair of long sides opposed to each other with the short sides sandwiched from both sides in the width direction, the carbon content is 0. In a continuous casting facility for molten steel for high carbon steel equipped with a mold for injecting molten steel for high carbon steel of 6% by mass or more from a tundish and cooling it,
The width of the short side of the mold space is 300 mm or more and 500 mm or less, and the width of the long side of the mold space is 360 mm or more and 650 mm or less, and each of the opposed short sides of the pair of short sides Each of the molds formed on each of the surfaces and the opposing surfaces of the pair of long sides has inclined portions whose intervals gradually narrow in accordance with the amount of solidification shrinkage of the slab shell in the direction in which the slab is pulled out. A continuous casting facility for molten steel for high carbon steel, characterized in that a plurality of tundishes are arranged.   A method for continuously casting molten steel for high carbon steel using the continuous casting equipment for molten steel for high carbon steel according to claim 1, wherein the casting speed of the molten steel for high carbon steel by the mold is 0.8 m / min or more. A continuous casting method for molten steel for high carbon steel, characterized in that the slab is produced at a rate of 2 m / min or less.   A continuous casting method for molten steel for high carbon steel using the continuous casting equipment for molten steel for high carbon steel according to claim 1, wherein the casting time of the molten steel for high carbon steel by the mold is 24 hours or longer. A continuous casting method for molten steel for high carbon steel, characterized by producing pieces.

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