JPH0469022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous casting method for heating and melting slag bears produced during continuous casting.

[Conventional technology]

Slag bears are mold powder that is cooled and solidified by the mold wall. In continuous casting of molten metal, mold powder is used on the surface of the molten metal bath in the mold to prevent surface oxidation of the molten metal in the mold, adsorption of inclusions, and prevention of seizure between the solidified shell in the mold and the mold. It is a powder that is dispersed. The properties of such mold powder should be determined taking into consideration the stability of operation and quality of slabs, but in reality, the optimum mold powder must be set individually for a wide variety of steel types and casting conditions. This is difficult because it hinders the improvement of work efficiency and cost reduction.

In addition, the physical properties of mold powder do not remain constant during use due to the influence of trace elements and the absorption of inclusions such as aluminum oxide in the molten metal, so even if mold powder is set that matches the conditions such as the steel type, It cannot be said that it always maintains suitable physical properties. Such incompatibility of the molding powder results in a lack of smooth flow of the molding powder between the slab and the mold. Then, the mold powder is cooled and solidified by the mold wall surface at the inflow portion, so that
A slug bear will be generated here.

The inflow of the mold powder occurs as a phenomenon in which the upper part of the solidified shell is bent toward the inside of the molten metal by mold oscillation, and the mold powder flows between the mold and the solidified shell. However, particularly in the case of a shot stroke of about 150 cpm or more and a high cycle mold oxidation, the amount of bending of the solidified shell becomes small, and as a result, the amount of mold powder flowing in is reduced. For this reason, when the mold oscillation is about 120 cpm, the decrease in the inflow rate is not very large, but as mentioned above, when it is about 150 cpm or more,
The slag bears will be generated and will grow. This slag bear obstructs the inflow of mold powder and causes operational troubles in continuous casting.

In order to remove such generated slag bears, conventionally, the slag bears were manually crushed using a chisel or the like.

[Problem that the invention seeks to solve]

However, such conventional slag bear removal means is manual and is not only inefficient, but also has the problem of lacking safety because the removal work is carried out at the upper surface of the molten metal.

The present invention has been made in view of these conventional problems, and aims to enable remote control and automation of removal work by removing slag bears using thermal energy.

[Means for solving problems]

In the continuous casting method according to the present invention, during continuous casting of molten metal, infrared rays or laser beams are concentrated in the vicinity of the intersection of the mold powder layer and the mold wall surface to heat the molten metal and thereby melt the metal.

[Effect]

During continuous casting, thermal energy is applied to the slag bear to heat and melt it. Since the melting temperature of commonly used molding powder is approximately 1100° C., slag bears are generally melted by heating to a temperature above this temperature, although it depends on the properties of the molding powder. The melted slag bear flows between the slab and the mold together with the melted mold powder, and acts to prevent seizure between the two. Note that depending on the size and shape of the slag bear, or after the slag bear is melted, the thermal energy is applied to the mold powder, and at this time, it can also act to promote melting of the mold powder. Therefore, by performing the heating before the formation of slag bears, it is also possible to prevent the formation of slag bears and promote melting of the mold powder.

As the heating means, infrared irradiation or laser beam irradiation is used. Note that in the case of a laser beam, since it is point irradiation, the irradiation involves scanning. This scanning is performed by swinging or rotating a mirror that reflects the laser beam.

〔Example〕

1 to 3 show an embodiment using infrared rays as a heating source. In the figure, 1 is a continuously cast slab, and 2 is a mold for forming the slab 1. The mold 2 includes a long side copper plate 2a forming the long side of the slab 1, and a short side copper plate 2a forming the short side of the slab 1.
It has b. Both copper plates 2a and 2b are paired, and each pair of short side copper plates faces each other.
The slab 1 is passed from the immersion nozzle 3 to the mold 2.
It can be divided into an unsolidified portion 1a, which is supplied into the molten metal and remains as molten metal, and a solidified shell 1b, which is cooled and solidified.

The molten metal supplied by the immersion nozzle 3 is formed in the mold 2, gradually cooled, and guided by support rolls 4 to descend.

Mold powder 5 is supplied to the upper surface of the molten metal (unsolidified portion 1a) in the mold 2. This mold powder 5 is melted by the heat of the molten metal and distributed on the upper surface of the molten metal. 6 is the molten mold powder. Then, when the upper part of the solidified shell 1b is bent toward the inside of the slab 1 by mold oscillation, the mold 1 and the solidified shell 1
The molten molding powder 6 flows into the gap between the molding powder 6 and the molding powder 6 to form a film. This film-like mold powder 7 and the molten mold powder 6
This serves to prevent surface oxidation of the molten metal in the mold 2, adsorption of inclusions, and prevention of seizure between the solidified shell 1b and the mold 2.

When the molten mold powder 6 is cooled by the mold 2 around the upper surface of the slab 1 and a slag bear 8 is generated or is about to be generated, thermal energy is generated from the heat source 9. The slag bear 8 generated near the intersection of the wall surface of the mold 2 and the mold powder 5 is irradiated with concentrated irradiation by being reflected by the reflecting plate 10, thereby heating the slag bear 8. In this embodiment, an infrared generator is used as the heat source 9, but a laser beam generator may be used instead. When using infrared rays, by using a heat source 9 with a length corresponding to the dimensions of the slab 1, linear irradiation along the circumference of the upper surface of the slab 1 is possible, but in the case of a laser beam, it is possible to irradiate a line along the periphery of the top surface of the slab 1. Since it is irradiation, the mirror is swung and rotated in a scanning manner.
The heat rays may be irradiated along the entire length of the side of the slab 1, or may be applied only to the portion of the side where the slag bears 8 are generated. Then, the heated slag bear 8 is melted and flows between the slab 1 and the solidified shell 1b.

When the heating is required, that is, the slag bear 8
Examples of means for monitoring when is being generated or when it is about to be generated include means for measuring the temperature of the slab 1 and means for measuring the thickness of the film-shaped mold powder 7. The conditions of the slab 1 and the mold 2 are monitored by these means, and when a local shortage of mold powder 6 is found to be flowing in, the heating is performed.

When the inventor heated the mold powder 6 on the front surfaces of both long sides of the mold 2 using a heat source 9 using infrared rays, it was observed that the slag bears 8 that had been generated there melted and disappeared. Further, the consumption amount of mold powder 5 increased from 0.25Kg/t to 0.45Kg/t, and as shown in FIG.
The incidence of vertical cracking on the surface of the slab 1 was reduced to about 1/4 of that of Conventional A. The conditions at this time are as follows.

"Continuous casting conditions" Dimensions of slab 1...260 x 1900mm Casting speed...1.1m/min Oscillation cycle...230cpm "Composition of mold powder 5 (%)" Silicon oxide 40, calcium oxide 35, aluminum oxide 5. Sodium oxide 10, fluorine 6, carbon 4 "Casting steel composition (%)" Carbon 0.12, silicon 0.28, manganese 0.163, phosphorus 0.02, sulfur 0.005, aluminum 0.35 "Infrared output" 25kw x 2 Next, in Figure 3 When the temperature was monitored using an embedded thermocouple at each point a to f in the mold 2 shown, a decrease in temperature at point b was observed, so the temperature between the mold 2 and the molten mold powder 6 above that position was observed. A laser beam with an output of 1 kW was irradiated near the contact point. This was carried out by scanning irradiation of ±50 mm in the long side direction of the slab 1. As a result,
The inflow of mold powder at point b is improved, and slab 1
The gap between the mold 2 and the mold 2 was filled with the film-like mold powder 7, the heat removal behavior of the mold 2 was improved, and the temperature of the slab 1 increased. FIG. 5 is a graph showing the surface temperature change of the slab 1 at the point b at this time, where C shows the time when casting starts, D shows the time when laser beam irradiation starts, and E shows when laser beam irradiation ends.

As a result, the coagulation shell 1b develops normally,
Prevention of breakout and vertical cracking of the slab 1 was achieved.

〔Effect of the invention〕

As explained above, according to the present invention, during continuous casting of molten metal, a person uses a chisel to melt slag bears stuck to the mold wall by heating with concentrated irradiation of infrared rays or laser beams. Since there is no longer a need to crush the slag bears using a metal slag, the safety of operations can be improved, and heating can be remotely controlled and automated, making it easier to melt and remove the slag bears, making continuous casting easier. This has the effect of improving efficiency. Depending on the size and shape of the slag bear, or after the slag bear has melted, thermal energy may be applied to the mold powder that has not become a slag bear, but in this case, it can also act to promote the melting of the mold powder. . Therefore, if the heating is performed before the formation of slag bears,
It is also possible to prevent the formation of slag bears and promote melting of mold powder.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention;
FIG. 2 is an enlarged view of the main part of FIG. 1, FIG. 3 is a front sectional view of FIG. 1, and FIG. 4 is a graph showing the effects of the embodiment.
FIG. 5 is a graph showing the temperature change at a certain point of the slab in the example. 1... Slab, 2... Mold, 5, 6, 7...
Mold powder, 8...Slag bear, 9...Heat source.

Claims (1)

[Claims] 1. A continuous casting method characterized in that during continuous casting of molten metal, the area near the intersection of the mold powder layer and the mold wall surface is heated by concentrated irradiation with infrared rays or a laser beam.