JPS59104255A - Method for supplying molten metal to twin belt caster - Google Patents

Abstract

PURPOSE:To prevent waving on a molten metal surface in a casting mold and to obtain a thin billet having high quality by disposing a spout so as to decrease the spaces to upper and lower belts and a dam block and adjusting the same so as to make the molten metal in a molten metal pool flush with the surface level of the molten metal in the spout. CONSTITUTION:The bottom surface 10 at the tip of a spout 4 for charging a molten metal is positioned in substantial proximity to the outside surface of a lower belt 2', the outside surface 11 at the tip on the side wall of the spout and the inside surface of a dam block 8 are positioned in substantial proximity to each other and further the tip of the side wall of the spout 4 is extended from the point where an upper belt 2 spaces from a pulley 1 on an inlet side and extends straight forward to the downstream and the space between the top surface at the top of the side wall and the belt 2 is made substantially small. The respective spaces in positioning are made to <=2mm. and a casting mold member are constituted by the above-mentioned members. Then the molten metal surface in a molten metal pool 9 can be adjusted so as to be made roughly flush with the surface level of the molten metal on the spout 4 in a region where the belt 2 is in contact with the pulley 1 on the inlet side. The waving on the molten metal surface in the pool 9 is prevented and the thin billet having a good surface and high quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for supplying molten metal when continuously casting thin metal slabs using twin belt casters.

In recent years, twin belt casters like the one shown in Figure 1 have been put into practical use for casting non-ferrous metal thin sheets such as copper, zinc, and aluminum. , and is expected to be applied in various fields.

What is shown in Fig. 1 is a schematic representation of the cast state of a general twin belt caster, which is an endless bell that moves by the rotation of the upper and lower boots IJ-1 and 1'.
．． Between 2' and skinmer 3. Water heater 5 having gutter 4 etc.
When the molten metal 6 is overflowed and injected, the injected molten metal moves in the same direction as the endless belt moves without causing any relative slip between the belt and is cooled and solidified. The pieces 7 can be taken out continuously, effortlessly, and at high speed. The molten metal is supplied to the hot water supply device 5 using a ladle or a molten metal holding furnace. Also, what is indicated by the symbol 8 is an endless bell l-2
, 2' constitute the mold wall.

Furthermore, recently there has been a growing trend to produce thin sheets (3) directly from steel slabs by cold rolling without hot rolling. Many attempts have been made to apply the above-mentioned twin belt caster, which can be cast in steel, to casting of steel.

By the way, in such a twin belt caster, it is necessary to uniformly inject the molten metal into the gap between the upper and lower belts, which are wide and have an extremely narrow interval, so the caster is designated by the reference numeral 4 in Fig. 1. As such, a molten metal supply device that extended long toward the pouring opening, had low side walls, and had a wide gutter attached to the front was considered essential equipment. FIG. 2 is a schematic perspective view showing the most common example of the gutter.

However, in the method of supplying hot water to a twin-belt caster using a conventional implanted blade-type water heater such as a double-barrel, the total wall thickness of the bottom of the gutter must be made thinner than a predetermined value from the viewpoint of strength. As shown in Fig. 3, a large head difference inevitably occurs between the tip of the gutter 4 and the surface of the molten metal pool 9 in the twin belt caster. In addition to the increased falling energy, the depth of the molten metal pool at the drop point of the injection stream is small in molds with twin-belt casters that are tilted to facilitate the supply of metal into narrow casting holes.
To completely prevent inconveniences such as significant ripples on the surface of a molten metal pool in a twin belt caster, double skin on the surface of manufactured cast slabs, and air bubble entrainment. I couldn't do it.

From the above-mentioned viewpoints, the inventors of the present invention have developed a method to completely prevent ripples on the surface of the molten metal in the twin belt caster mold and to produce thin slabs of good quality without double skin or bubble entrainment. solidified the recognition that all of the molten metal in the planting soil should be supplied into the mold without any head difference, and repeated numerous experiments and research in order to find a means to eliminate the head difference when pouring molten metal. As a result, as shown in Figs. 4 and 5, the bottom surface 10 of the tip of the molten metal injection gutter is brought sufficiently close to the outer surface of the lower belt 2',
In addition, the outer surface 11 of the tip of the gutter side wall and the inner surface of the dam block 8 are made to be sufficiently close to each other. In addition to the upper and lower bells and the dam block on the right, the gap between the top surface of the end of the side wall and the lower belt has been made sufficiently small. In addition, if the tip of the gutter is also used as a mold component and the molten metal level in the molten metal pool 9 in the twin belt caster is raised to almost the same height as the molten metal surface level of the planting soil, the molten metal from the molten metal supply surface 12 of the gutter can be raised. (b) In this case, the head of the injection flow can be completely eliminated.
It is not necessary that the tip of the gutter be in complete contact with the outer surface of the upper and lower belts or the inner surface of the dam block.
If the gap is 2 mm or less, the movement of the upper and lower belts or dam blocks will cause the viscous molten metal to be drawn in a direction that prevents it from entering the gap, and no leakage of molten metal will occur. (C) At the tip of the gutter If a gap is provided between the outer surface of the lower belt or the inner surface of the dam block, friction with the gutter will not occur even when the belt or dam block rotates, and therefore it is necessary to take measures for lubrication between the two. (a) By setting the level of the molten metal pool in the mold in the area where the upper belt is in contact with the upper pulley on the entry side, it is set at the highest point of the lower pulley on the entry side (the highest position of the lower belt). Since there is a sufficient vertical distance from the point to the hot water level and the thickness of the refractory material at the bottom of the gutter can be increased, breakage of the gutter will not occur and stable work can be continued; We came to the knowledge shown in (d).

This invention was made based on the above knowledge υ,
In continuous casting of thin slabs using twin belt casters, the tip of the side wall of the gutter extends to a position downstream from the point where the upper belt separates from the upper pulley on the entry side and becomes straight in the normal melt supply position. The gap between the lower surface of the tip of the gutter and the outer surface of the lower belt of the twin belt caster, the gap between the outer surface of the tip of the gutter side wall and the inner surface of the dam block, and the gap between the upper surface of the tip of the gutter side wall and the upper belt. The molten metal pool inside the twin belt caster should be installed so that the surface level is approximately the same as the molten metal surface level on the gutter in the area where the upper belt is in contact with the upper pulley on the entry side. By continuing to supply hot water while adjusting the

This method is characterized by obtaining a high quality thin slab with good surface texture.

The reason why the gap between the tip of the gutter and the outer surface of the upper and lower belts and the inner surface of the dam block was limited to 2 tones or less is because if the gap exceeds 2 tones, molten metal leakage will occur. .

FIG. 4 is a schematic diagram of main parts showing a state in which molten metal is being supplied to a twin belt caster by the method of the present invention, FIG. 5 is a sectional view taken along line A-A in FIG. 4, and FIG. FIG. 1 is a perspective view of essential parts of an example of a gutter used in the method of the present invention.

In FIGS. 4 and 5, the bottom surface 10 of the tip of the gutter is arranged with a slight gap between the outer surface of the lower belt 2' and the outer surface 11 of the tip of the side wall of the gutter and the inside of the dam block. The surfaces also face each other with a small gap between them. Further, the upper surface of the side wall tip of the gutter and the outer surface of the upper belt 2 are also arranged with a slight gap between them. Since the molten metal surface of the molten metal pool 9 is maintained at a height that is almost the same as the upper surface of the molten metal flow on the gutter, there is no head difference in the flow of the molten metal into the mold. In this way, since the head of the injection flow is zero, there are no ripples on the surface of the molten metal pool, and slabs with good surface quality can be obtained. This makes it possible to increase the thickness without causing any negative effects, dramatically reducing the risk of gutter damage and ensuring stable work.

Next, the present invention will be explained with reference to Examples and in comparison with Comparative Examples.

Example Using the conventional method as shown in Figure 3 and the method of the present invention as shown in Figure 4, all of the molten steel whose chemical compositions are shown in Table 1 was used, and the thickness was 40 ttan and the width was 600 mm. All thin cast slabs were manufactured. The inclination angle of the twin belt casters used at this time was 6°, and the average casting speed was 6 m/min.

Table 1 Note that the molten steel used was all low carbon aluminum killed steel melted in a converter, the molten steel injection gutter was made of molten silica, and the width of the molten steel flow path on the gutter was 480 mm. Ta.

In the conventional method shown in Fig. 3, the minimum gap between the lower surface of the gutter and the lower belt is 20 mm, and the vertical distance from the hot water supply surface of the gutter to the surface of the molten steel pool in the mold is 65 mm, as shown in Fig. 4. Compared to the method of the present invention shown in Fig. 1, the ripples on the mold surface were thicker.

On the other hand, in the method of the present invention as shown in FIG. The gap f between the two side walls and the upper belt was 10.5 to 0.9 mm. Also, the tip of the gutter side wall is located 20 mm downstream from the point P where the upper belt 2 leaves the upper pulley on the entrance side (in the opposite direction to the slab drawing). Vertical distance to surface (depth of bath in mold)
The thickness of the gutter was approximately 60 mm, and the thickness of the bottom of the gutter was approximately 40 mm. Even during the supply of molten steel, no ripples occurred on the surface of the molten metal in the mold.

Comparing the two slabs obtained in this way, the one produced by the conventional method has double skin scattered on the surface of the thin slab, and if some surface care is not done, it will not be normal due to rolling. However, the thin slab produced by the method of the present invention had almost no defects, and the quality of the plate obtained by directly rolling it to size was extremely good. .

Furthermore, in the method of the present invention, since the bottom of the gutter was sufficiently thick, troubles such as breakage of the gutter did not occur in other test castings.

Although this example only deals with the casting of steel, it goes without saying that the same good results can be obtained even if the method of the present invention is applied to the casting of non-ferrous metals using twin-belt casters. It is.

According to this invention, it is possible to stably and reliably obtain thin slabs with good surface quality using twin belt casters, which were extremely difficult to manufacture, and the manufacturing cost of thin metal sheets can be reduced. This brings about industrially useful effects, such as making it possible to further reduce the temperature.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the casting state of a twin belt caster, Fig. 2 is a schematic perspective view of molten metal supplied to a conventional water heater, and Fig. 3 is a schematic diagram of molten metal supplied to a conventional twin belt caster. 4 is a schematic diagram showing the method of the present invention, and FIG. 5 is a schematic diagram showing the method of the present invention.
The sectional view and FIG. 6 are perspective views of essential parts of the gutter used in the method of the present invention. In the drawings, 1...upper pulley, 1'...lower pulley, 2...
Upper heald, 2'...Lower belt, 3...Skinmer,
4... Gutter, 5... Water heater, 6... Molten metal, 7...
Slab, 8... Dam block, 9... Molten metal pool, 10... Bottom surface of the tip of the gutter, 11... Outer surface of the tip of the gutter side wall. Figure 1 Leather Figure 2 Figure 3! Rod 4 Decoy 4 4 Gaku 6 Figure

Claims (1)

[Claims] In continuous casting of thin slabs using twin belt casters, the tip of the side wall of the gutter extends to a position downstream from the point where the upper belt separates from the upper pulley on the entry side and becomes straight in the normal melt supply position. The gap between the lower surface of the tip of the gutter and the outer surface of the lower belt of the twin belt caster, the gap between the outer surface of the tip of the gutter side wall and the inner surface of the dam block, and the gap between the upper surface of the tip of the gutter side wall and the upper belt. In addition, the molten metal pool level in the twin belt caster is approximately the same level as the molten metal surface level in the planting soil in the area where the upper belt is in contact with the upper pulley on the entry side. A method of supplying molten metal to twin belt casters, which is characterized by continuing the supply of hot water while adjusting the temperature accordingly.