JPH1119756A - Continuous casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the development of breakout and to relatively lower the cost by arranging the projections contacting with the curving surface of long sides in a mold to a part of a dummy bar head to obtain such a same action as the existence of large strength solidified shells at the outside of small strength solidified shell. SOLUTION: The SPCC-made projections 12 having e.g. 0.5 mm thickness, are fitted to the dummy bar head 10 so as to contact with the surfaces of the long sides in the mold. The size of the projection 12 in the width direction of a cost slab is made to almost the same size as the cast slab. In the estimation with calculation, e.g. the solidified shell thickness at 100 mm below a meniscus is about 2 mm at both stages of the initial stage of casting and in the stationary state, and it is considered that this thickness does not differ so large at both stage. However, in the initial stage of casting, the drawing resistance is large, because the lubrication with powder is insufficient, and it is considered that the strength of the solidified shell is smaller than or the same degree as the drawing resistance. In the case of using the dummy bar head with the projections, since such a same action is obtd. as thickening the solidified shells at the long sides in the mold at the initial stage of casting, the development of the breakout is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting apparatus for continuously producing a long object having a constant sectional shape by continuously drawing a molten metal while solidifying it in a penetrating mold.

[0002]

2. Description of the Related Art When manufacturing a metal plate, it is common to first form a slab (plate-like ingot) of a molten metal by continuous casting and then roll it. The thickness of the slab is generally about 200 mm, but many rolling steps are required to obtain a metal plate of 10 mm or less. On the other hand, in the case of a continuous sheet casting method in which the thickness of a slab is reduced, the number of rolling steps can be reduced.

However, in such a case, it is necessary to increase the casting speed in order to secure the production amount. At the same time, when the thickness of the slab is reduced, the space for inserting the pouring nozzle for supplying the molten metal to the mold becomes smaller, and therefore, a device for widening the pouring nozzle insertion portion has been devised.

[0004] More specifically, it is divided into two types: one in which only the nozzle insertion portion above the long side mold is widened (US Pat. No. 5,319,922), and the other in which the entire long side mold is made into an arc shape (WO 94/07628). You. The former is characterized in that the short side mold is parallel to the casting direction, while the latter is characterized in that the width of the short side mold is narrower in the casting direction. In the latter case, it is necessary to prevent the formation of a solidified shell on the short side mold surface in a region where the width of the short side mold is narrow.

[0005]

In the above prior art, the solidified shell is extracted while being deformed in the mold. Therefore, as compared with the conventional continuous caster, the contact pressure with the mold is increased by the deformation resistance of the solidified shell, and as a result, the frictional force with the mold is increased. In order to reduce the frictional force, a mold powder is generally used in a continuous casting machine of a type in which a mold is vibrated. The mold powder is melted by the heat of the molten steel and exerts a lubricating effect.

[0006] Therefore, immediately after the injection of mold powder in the early stage of casting, the melting is insufficient, and a sufficient lubricating effect is not exhibited. It is highly probable that breakout occurs at the early stage of casting due to this poor lubrication. This is the same with a conventional continuous caster, but is remarkable in the conventional technique (a technique in which a solidified shell is deformed in a mold while being drawn out), which has a large frictional force with the mold. However, the prior art does not give sufficient consideration to this initial trouble.

[0007] The problem to be solved by the present invention is to propose an optimal component for minimizing breakout at the beginning of casting.

[0008]

The above object can be attained by providing a projection which contacts a part of the dummy bar head along the curved surface of the long side mold.

[0009] The above problem can be solved by using a material whose tensile strength of the projections at 1000 ° C or higher satisfies the formula (1).

That is, at the time of insufficient lubrication by the mold powder in the early stage of casting, the frictional force between the mold and the solidified shell is large. In addition, since mold powder does not intervene in the gap between the solidified shell and the mold, cooling is likely to be uneven, and there is a large possibility that a locally thin shell is formed. Furthermore, burning of the solidified shell due to poor lubrication tends to occur. Due to these effects, the solidified shell having originally low strength is in a state of being easily broken. To prevent the solidified shell from breaking, a method of delaying the drawing start time or a method of delaying the speed at the start of drawing may be considered. However, in such a case, the force required to deform the solidified shell increases with the growth of the solidified shell, and the pull-out resistance increases.

If the technique according to the present invention is applied, the effect is equivalent to the presence of a high-strength solidified shell on the outer surface of the low-strength solidified shell (on the contact surface side with the mold). Acts so as not to occur. Further, since the molten steel or the solidified shell does not come into direct contact with the mold, seizure on the mold can be prevented. At this time, it is important that the protrusions are provided along the mold surface. Because the solidified shell grows on the surface of the mold, if the solidified shell is not disposed along the surface of the mold, only the projections are present in the molten metal, and the solidified shell is unrelated to the solidified shell.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic view of a continuous casting apparatus used in the present embodiment. Molten metal is supplied to a fixed mold having a large upper part and a small fan-shaped short-side mold 1 and a long-side mold 2 having a small lower part through a pouring nozzle 3 to form a molten metal pool 4. You. The molten metal is cooled and solidified in the mold to form a slab 5, which is pulled out to the lower part of the mold. At this time, the slab is supported by the support roll 6. The mold was vibrated up and down. In addition, mold powder was supplied to the molten metal surface during casting.

FIG. 2 is a structural view of a dummy bar head used in this embodiment. FIG. 3 is a structural view of a conventional dummy bar head. The dummy bar head 10 has a thickness of 0.
A 5 mm SPCC (JIS G 3141) projection 12 was attached so as to be in contact with the surface of the long side mold. The size of the projection 12 in the slab width direction was substantially equal to the slab. Casting speed 4.5m / mi
n, The slab thickness was 40 mm, and 0.2% C steel was cast.

In the estimation by calculation, 100
Solidified shell thickness in mm is 2
It is about mm and it seems that there is not much difference. However, in the early stage of casting, the lubrication by the powder is insufficient, so that the pull-out resistance is large, and the strength of the solidified shell is presumed to be small or similar. When a dummy bar head with projections as shown in FIG. 2 is used, the same effect as when the solidified shell on the long side of the casting is thickened is obtained. Outs can be reduced.

[0015]

According to the present invention, the occurrence of breakout can be reduced. If a breakout occurs, production will be interrupted and costly to recover.
These lead to an increase in manufacturing costs. According to the present invention, there is an effect that the cost can be relatively reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of a continuous casting apparatus used in Examples.

FIG. 2 is a structural diagram of a dummy bar head used in the embodiment.

FIG. 3 is a structural diagram of a conventional dummy bar head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... short side mold, 2 ... long side mold, 3 ... pouring nozzle, 4 ... molten pool, 5 ... cast piece, 6 ... support roll, 7 ... back plate, 8 ... long side copper plate, 9 ... cooling water hole, 10: dummy bar head, 11: dummy bar, 12: protrusion.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Nishino 3-1-1 Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Hironori Shimogama 3-1-1 Sachimachi, Hitachi-shi, Ibaraki No. 1 Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Mitsunaga Isono 3-1-1 Kochi-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (2)

[Claims] 1. A molten metal is continuously supplied to a space of a fixed mold formed by opposed long side molds and opposed short side molds, and a shell solidified in the fixed mold is continuously drawn. In a continuous casting apparatus in which the width of the short side mold of the continuous casting apparatus for continuously producing slabs is large and the lower part is small in a substantially sector shape, a part of a dummy bar head used at the start of casting has a substantially sector shape. A continuous casting device characterized by projecting along a curve. 2. The continuous casting apparatus according to claim 1, wherein the projection has a tensile strength at 1000 ° C. or higher that satisfies the equation (1). Σ _B ≧ 1−0.005T (Equation 1) where σ _B : tensile strength (kg / mm ² ), T: temperature (° C.)
It is.