JPH06297107A - Continuous casting method - Google Patents

Abstract

PURPOSE:To raise the frequency of nuclear generation, to develop uniform solidified shell and to remove the basic defect of longitudinal crack, etc., by continuously casting a cast slab while giving a mold intermittent oscillation having a specific value or lower in the different direction to the drawing direction of the cast slab. CONSTITUTION:Molten metal 2 is drawn out while cooling and solidifying in the mold 1 vertically moved with oscillating mechanism 5 to continuously cast the cast slab. While giving the mold the intermittent oscillation having <=1mm in the different direction to the drawing out direction of the cast slab, the cast slab is continuously cast. Further, the oscillating direction is made to be the direction orthogonal to the drawing out direction of the cast slab. Further, as the means giving the mold the oscillation, the oscillation can be given with the simple mechanism using an air hammer. By this method, the basic defect in the cast slab of mainly the longitudinal cracking, etc., in a continuous casting process can be removed or 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 method for continuously casting molten metal.

[0002]

2. Description of the Related Art In continuous casting, molten metal is supplied to a mold from a tundish, the molten metal is cooled in the mold to form a solidified shell, and this is grown to cast a slab. In the production of such slab, in order to reduce friction between the mold and the slab, prevent seizure and perform stable casting, a lubricant such as powder is used and the mold is oscillated. It is called 4 mm and is several tens to 400 c / min.
The vertical movement of is given. This initial shell is further heat-removed with a mold to grow a shell and produce a cast slab from the mold.

However, due to the oscillation,
Solidification proceeds due to nucleation to growth of the molten metal on the mold surface, but this nucleation is not necessarily uniform, and nonuniform nucleation leads to uneven shell thickness. If this shell thickness is non-uniform, tensile stress due to solidification will be applied to the thin shell portion,
When the shell was broken, the slab was cracked in the mild case, and the bleed and breakout were generated in the severe case.

[0004]

In order to make the shell thickness uniform, it suffices that uniform heat removal be performed.
It has been attempted to improve the vertical movement pattern by oscillation and provide a slab cooling support guide mechanism directly below the mold to form a uniform shell. However, when the molten metal is poured into the mold from the tundish, the flow pattern of the molten metal is not always uniform. Therefore, in the conventional method, uniform nucleation could not be surely performed.

Further, in the above-mentioned oscillation, although it serves as a starting point for nucleation of the molten metal on the surface of the mold, it does not have a role to go one step further to uniformly grow nucleation. In the present invention, the quality of the slab is improved by removing or reducing the non-uniformity of nucleation on the mold surface, which is the cause of the fundamental defects of the slab, such as vertical cracks in the continuous casting method. Is intended.

[0006]

The continuous casting method of the present invention is a method for continuously casting molten slabs by drawing molten metal while cooling and solidifying the molten metal in a vertically moving mold by an oscillation mechanism. A feature of the present invention is that the slab is continuously cast while intermittently applying a vibration of 1 mm or less in a direction different from the slab drawing direction.

Further, the present invention is characterized in that the direction of the vibration is perpendicular to the direction in which the slab is drawn out, or that an air hammer is used as a means for applying vibration to the mold.

[0008]

In the continuous casting method of the present invention, when the molten metal is cooled and solidified in the vertically moving mold by the oscillation mechanism while being drawn, vibration is applied in a direction different from the drawing direction. Therefore, in the initial shell in which the molten metal is formed and the portion close to the shell, the frequency of nucleation is directly affected by vibration and the nucleation frequency increases.

Further, the gap between the shell and the mold surface is about 0.5 mm, and the liquefied powder is flowing into this gap, and in this state, intermittent vibration of 1 mm or less is applied to the liquid. Vibration is transmitted to the slab while compressing the powder layer.

Generally, as the solidification shell becomes thicker, a gap is generally formed between the mold and the mold due to solidification shrinkage. When the vibration is about 1 mm or less, unnecessary vibration is applied to the thickened part of the solidification shell. The vibration is directly applied to the thin portion of the shell. It should be noted that the above-mentioned amplitude has the above-mentioned effect when the vibration is 1 mm or less, but since the vibration is transmitted to the shell through the liquid powder layer, the amplitude is preferably 100 μm or more.

Further, since this vibration is intermittently less than 1 mm, the level of the molten metal on the surface of the mold is small and the overflow is prevented, so that the so-called double skin defect is prevented.

Further, if the direction of vibration is perpendicular to the direction in which the slab is withdrawn, the vibration can be applied without affecting the design pattern of the vertical movement of the oscillation mechanism. Furthermore, an air hammer can be used as the vibrating means to apply vibration with a simple mechanism.

[0013]

The drawings show a schematic example of the apparatus for carrying out the method according to the invention. Molten steel 2 is poured into a mold 1 from an immersion nozzle 4 of a tundish 3. An oscillation mechanism 5 is provided to give a vertical movement to the mold 1, and a vibration applying means 6 such as an air hammer is provided above the mold 1.

Table 1 shows a shape of 1500 mm wide and 220 mm wide.
A mold 1 formed of a copper alloy for casting a slab having a thickness, a stroke of 4 mm, a frequency of 120 cpm, a casting speed of 1.5 mpm, a CaO—SiO ₂ system powder (basicity 1.20, at 1350 ° C. It shows an example when casting is performed at a viscosity of 2.1 poise) and a casting temperature of 1538 ° C.

[0015]

[Table 1]

As is clear from the above-mentioned embodiment, the initial shell in which the molten metal is formed and the portion in the vicinity of the shell are directly affected by the vibration, the nucleation frequency is increased, and cracks and bleeding are significantly caused. Improved.

Further, when this vibration is intermittently of a magnitude of 1 mm or more, the surface of the molten metal on the surface of the mold is less likely to be overfilled, resulting in double-skin defects.

If the vibration direction is not perpendicular to the slab drawing direction, it is necessary to prevent the design pattern of the vertical movement of the oscillation mechanism from being adversely affected. It is necessary to consider the timing and so on.

[0019]

As described above, according to the present invention, when the nucleation of molten metal is allowed to grow on the mold surface, the external vibration is applied to the shell through the liquid powder layer, so that the nucleation frequency is increased. Since a uniform solidified shell develops, it is possible to remove or reduce the fundamental defects of the slab, such as vertical cracks in the continuous casting process, and to provide a high quality slab. Have an effect.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the present invention.

[Explanation of symbols]

 1 mold 2 molten steel 3 tundish 4 immersion nozzle 5 oscillation mechanism 6 vibration imparting means 7 cast piece

Claims (3)

[Claims] 1. A method for continuously casting a slab by drawing molten metal while cooling and solidifying it in a vertically moving mold by an oscillating mechanism, wherein the slab is intermittently cast in a direction different from the slab drawing direction. A continuous casting method characterized in that a slab is continuously cast while a vibration of 1 mm or less is applied to the slab. 2. A continuous casting method, wherein the vibration direction according to claim 1 is a direction orthogonal to a cast piece drawing direction. 3. A continuous casting method, wherein an air hammer is used as a means for vibrating the mold according to claim 1 or 2.