JPS61144249A - Continuous casting method - Google Patents

Abstract

PURPOSE:To improve casting efficiency by heating and melting the slag bar sticking to the wall surface of a mold by IR rays, laser beam, etc. CONSTITUTION:The mold 2 has steel plates 2a, 2b forming respectively the long side and short side of a billet 1. The molten metal supplied from an immersion nozzle is molded in the mold 2 and descends. Mold powder 5 is supplied atop the unsolidified part 1a thereof and the molten mold powder 6 is distributed on the surface. Heat energy is generated from a heat source 9 for IR rays, etc. and is concentrically irradiated on the slag bear 8 via a reflecting plate 10 to heat the slag bear when the slag bear 8 is formed as the powder 6 is cooled. The slag bear 8 sticking to the wall surface of the mold 2 is melted by the above-mentioned method, by which the slag bear is removed without the aid of man power. The efficiency of continuous casting is thus improved.

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. Mold powder is
In continuous casting of molten metal, powder is sprinkled 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 the body. 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 molten metal, so even if mold powder is set that matches the conditions such as the steel type, It is not possible to maintain suitable physical properties all the time. 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 in the inflow region, and slag bears are generated there.

The inflow of mold powder occurs as a phenomenon in which the upper part of the solidified shell is bent toward the inside of the molten metal due to mold oscillation, and the mold powder flows between the mold and the solidified shell. However, especially 150
In a mold-on-silane silane with a short stroke of about cpm or more and a high cycle, 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-on silane silane has a pressure of about 120 cpa+, the decrease in the inflow rate is not so large, but when the pressure exceeds about 150 cpm as described above, the slag bears are generated and grow. This slag bear obstructs the inflow of mold powder, causing 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 not only inefficient, but also has the problem of lacking safety because the removal work is performed 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]

The continuous casting method according to the present invention melts slag bears stuck to the mold wall by heating them during continuous casting of molten 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., the slag bear is 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. In addition, the size of the slag bear.

Depending on the shape 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, in addition to infrared ray irradiation and laser beam irradiation, various means can be employed as long as they can provide a predetermined thermal energy. 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 has a long side copper plate 2a that forms the long side of the slab 1, and a short side copper plate 2b that forms the short side of the slab 1.

Both copper plates 2a and 2b each form a pair, and the pairs of short-side copper plates face each other. The slab 1 can be divided into an unsolidified portion 1a which is supplied into the mold 2 from the Imagin nozzle 3 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. and,
When the upper part of the solidified shell 1b is bent toward the inside of the slab 1 by mold-on-silane silane, the molten mold powder 6 flows between the mold 1 and the solidified shell 1b and forms a film. This film-like mold powder 7 and the molten mold powder 6 function to prevent surface oxidation of the molten metal in the mold 2, adsorb inclusions, and prevent seizure between the solidified shell 1b and the mold 2.

Molten mold powder 6 is cooled by mold 2 around the upper surface of slab 1, and slag bear 8 is placed there.
is generated or is about to be generated, thermal energy is generated from the heat source 9, reflected by the reflector plate 10, and concentratedly irradiated onto the slag bear 8, thereby heating it.

In this example, an infrared generator was used as the heat source 9, but
Alternatively, a laser beam generator or other heat source may be used. When using infrared rays, by using a heat source 9 with a length that corresponds to the dimensions of the slab 1, linear irradiation along the periphery of the top surface of the slab 1 is possible; Since it is irradiation, the mirror must be swung 1 to scan.
Rotate.

The irradiation with such hot rays may be carried out over the entire length along the side of the slab l, or only on the part of the side where the slag bears 8 are generated, and the heated slag bears 8 are melted and solidified with the slab 1. It flows between the shell 1b and the shell 1b.

The means for monitoring when the heating is required, that is, when the slag bear 8 is produced or about to be produced, includes means for measuring the temperature of the slab 1, and means for monitoring the temperature of the mold powder 7 in the form of a film. There are means to measure the thickness. The condition of the slab 1 and the mold 2 is monitored by these means, and when a local insufficient inflow of the mold powder 6 is found, the heating is performed.

This inventor used a heat source 9 using infrared rays to mold the mold 2.
When the mold powders 3 and 6 on the front surfaces of both long sides were heated, it was observed that the slag bears 8 that had been formed there melted and disappeared. In addition, the consumption amount of mold powder 5 is 0.2
As shown in FIG. 4, the incidence of vertical cracking on the surface of the slab 1 in Example B of the present invention was approximately 1/4 of that of the conventional method. decreased to The conditions at this time are as follows.

"Continuous casting conditions j1 Dimensions of slab 1...260 x 1900 Tsuru casting speed...
...1. l m/sin oscillation cycle...230 cpm "Composition of mold powder 5 (%)
j Silicon oxide40. Calcium oxide 35. Aluminum oxide5. Sodium oxide10. Fluorine6. Carbon 4r casting steel composition (%) Carbon 0.12. Silicon 0.28. Manganese 0.163. Phosphorus 0.02° Sulfur 0.005. Aluminum 0.35 "infrared output" 25 x 2 Next, temperature was monitored using embedded thermocouples at each point (al to ffl) in the mold 2 shown in Figure 3.
Since a temperature drop was observed at point (b), a laser beam was irradiated with an output of -1 to the vicinity of the contact point between the mold 2 and the molten mold powder 6 above the point.

This was performed by scanning irradiation at ±50 tm in the long side direction of the slab 1. As a result, the inflow of the mold powder at point (b) is improved, the gap between the slab 1 and the mold 2 is filled with the film-like mold powder 7, and the mold powder 7 is injected into the mold 2.
The heat removal behavior 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 φ), where C shows the start of casting, D shows the start of laser beam irradiation, and E shows the end of laser beam irradiation. .

As a result, the solidified shell 1b developed normally, and prevention of breakout and vertical cracking of the slab 1 was achieved.

〔Effect of the invention〕

As explained above, according to this invention, during continuous casting of molten metal, the slag bears stuck to the mold wall are melted by heating, so there is no longer a need for humans to crush the slag bears using a chisel. In addition to improving operational safety, heating can be controlled remotely and automated, making it easier to melt and remove slag bears, improving the efficiency of continuous casting. . Note that depending on the size and shape of the slag bear, or after the slag bear has been 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 melting of the mold powder. Therefore, if the heating is performed before the formation of slag bears, it is possible to prevent the formation of slag bears and promote melting of the mold powder.

[Brief explanation of the drawing]

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.
The figure is a graph showing the effect of the example, and FIG. 5 is a graph showing the temperature change at the point where the slab is formed in the example. 1... Slab, 2... Mold, 5.6.7... Mold powder, 8... Slag bear, 9... Heat source.

Claims (3)

[Claims] (1) A continuous casting method characterized in that during continuous casting of molten metal, slag bears stuck to the mold wall are melted by heating. (2) The continuous casting method according to claim 1, wherein the heating is performed by irradiating infrared rays. (3) The continuous casting method according to claim 1, wherein the heating is performed by irradiating with a laser beam.