JPH06304702A - Method for continuously casting hollow cast billet - Google Patents

Abstract

PURPOSE:To stably produce a hollow cast billet without defect on the inner surface by setting casting condition so as to satisfy a prescribed expression, at the time of continuously casting the hollow cast billet by using a water cooling type columnar core for forming the inner surface of the cast billet. CONSTITUTION:At the time of continuously casting the hollow cast billet by using the water cooling type columnar core for forming the inner surface of the cast billet, the casting condition is set so that solidification constant K1 of core, distance L1 from the meniscus to the lowermost end of core, solidification constant K2 of the mold forming the outer surface of the cast billet, distance L2 from solidification starting position to the lowermost end of the core, casting velocity V and the thickness D of the cast billet satisfy the expression K1X(L1/V)<0.5>+K2X(L2/V)<0.5>>=0.5D. By this method, the problem of development of bleed and breakout on the inner surface of cast billet is solved, and the hollow cast billet having no problem can stably be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting a hollow slab using a columnar core having a water cooling function.

[0002]

2. Description of the Related Art As a method for producing a hollow slab using a water-cooled columnar core for forming the inner surface of the slab, JP-A-3-2
As disclosed in Japanese Patent No. 68843, the upper half is induction-heated by a surrounding heating coil, and the lower half is a refractory mold cooled through a surrounding water-cooled copper mold. The outer surface of the slab is formed while controlling it below the level of the molten metal surface, while the inner surface of the slab is formed by a columnar core with a water-cooling function that is set on the center line of the refractory mold, and hollow slabs are continuously cast. There is a method of manufacturing. Further, some methods for producing a thick hollow cast piece in which the outer surface of the cast piece is formed by using an ordinary mold are also disclosed. However, when a hollow slab is manufactured using a columnar core having a water-cooling function as described above, the inner surface of the slab is cooled in the region where the core is present, but when the core is exceeded, the inner surface of the slab is in a heat-insulated state. Becomes Therefore, there have been many problems such as bleeding and breakout on the inner surface of the slab. Although a method of spray cooling the inner surface of the slab after the core to improve the heat removal ability is also disclosed, steam explosion occurs when a breakout occurs, which is not preferable in terms of safety.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the problems of bleeding and breakout on the inner surface of the slab that occur in the conventional continuous casting of hollow slabs, and the risk of steam explosion accompanying breakout during spray cooling. It is an object of the present invention to provide a method for performing continuous casting of hollow slabs, which has no problem and has no problem.

[0004]

Therefore, according to the present invention, when a hollow slab is continuously cast using a water-cooled columnar core for forming the inner surface of the slab, the solidification constant K _{1 of the} core and the meniscus are used. The distance L ₁ to the lowermost end of the core, the solidification constant K _{2 of the} mold forming the outer surface of the slab and the distance L ₂ from the solidification start position to the lowermost end of the core, the casting speed V, the slab thickness D But,
It is characterized in that the casting conditions are set so as to satisfy the formula (1) described later.

[0005]

In the present invention, a hollow slab is cast using a columnar core having a water cooling function. The effects of core length, casting speed, and slab thickness, which are important parameters in this method, on casting were investigated.

An outline of the apparatus used for the experiment is shown in FIG. 1 (for details of the apparatus configuration, see Japanese Patent Laid-Open No. 3-268843). In this method, the upper half is induction-heated by the surrounding heating coil 33, and the lower half is made of a refractory mold 19 that is cooled via the surrounding water-cooled copper mold 18, and the solidification start position is set to be higher than the molten metal level. The outer surface of the slab is formed while controlling downward, while the inner surface of the slab is formed by the columnar core 24 having a water cooling function set on the center line of the refractory mold 19.
Hollow slab is continuously cast. In this method, an experiment was conducted by changing the core length, the thickness of the cast piece, the casting speed, and the mold structure forming the outer surface of the cast piece. Further, during the experiment, sulfur was added to the mold and the coagulation parameters K ₁ and K ₂ were measured by sulfur printing. As a result, as shown in FIG. 2, the solidification constant K ₁ of the core and the distance L ₁ from the meniscus to the lowermost end of the core, the solidification constant K _{2 of the} mold forming the outer surface of the slab, and the solidification start position to the core Distance to the bottom of
₂ , the casting speed V, and the cast piece thickness D satisfy the following conditions: K ₁ × (L ₁ / V) ^0.5 + K ₂ × (L ₂ / V) ^0.5 ≧ 0.5D (1) By setting
It was found that the frequency of breakouts was extremely low. On the other hand, when the above relationship was not satisfied, defects such as uneven thickness, eccentricity, and bleeding on the inner surface of the slab were observed. No such defects were found.

[0007]

EXAMPLES The present inventors conducted experiments under the conditions shown in Table 1 and investigated the conditions of casting stability and slab internal surface defects.
Two types of molten steel, 18-8 stainless steel and low carbon Al-Si killed steel, were used. In addition, Examples 1 to 5 are the present invention, and Examples 6 to 10 are the results of experiments conducted for comparison. Further, Examples 5 and 10 are the results of casting the outer surface of the cast slab using a normal water-cooled copper mold, and Examples 1 to 4 and 6 to 9 are the results of experiments using a refractory mold.

From the above, the frequency of breakouts is extremely reduced by the method of the present invention, and defects such as uneven shape, eccentricity, and bleeding on the inner surface of the slab, which are observed in the comparative example, are also present. I didn't see it.

[0009]

[Table 1]

[0010]

As described above, in the method of continuously casting a hollow slab using a columnar core for cooling the inner surface of the slab with water, the solidification constant K ₁ of the core and the distance L from the meniscus to the lowermost end of the core. ₁ , the solidification constant K _{2 of the} mold forming the outer surface of the slab, the distance L ₂ from the solidification start position to the lowermost end of the core, the casting speed V, and the slab thickness D satisfy the above equation (1). By setting the casting conditions as described above, it becomes possible to stably manufacture a hollow cast slab having no inner surface defect.

[Brief description of drawings]

FIG. 1 shows an outline of an apparatus used in an experiment.

FIG. 2 shows the relationship among the solidification constant, core length, and cast piece thickness of the present invention.

[Explanation of symbols]

 11 Hot Water Pool 15 Uncooled Mold 18 Cooled Mold 24 Columnar Core 27 Water Transfer Tube 33 Induction Heating Device 34 Induction Heating Coil 41 Immersion Nozzle M Molten Steel P Hollow Slab a, b Solidified Shell

Claims (1)

[Claims] 1. When continuously casting a hollow slab using a water-cooled columnar core for forming the inner surface of the slab, the solidification constant K _{1 of} the core and the distance L from the meniscus to the lowermost end of the core.
₁ , the solidification constant K _{2 of the} mold forming the outer surface of the slab, the distance L ₂ from the solidification start position to the lowermost end of the core, the casting speed V, and the slab thickness D are K ₁ × (L ₁ / V) ^0.5 + K ₂ × (L ₂ / V) ^0.5 ≧ 0.5D (1) A continuous casting method for hollow cast slabs, characterized in that the casting conditions are set so as to satisfy the relationship.