JPH0323257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously casting an ingot, and when an ingot of aluminum or the like is continuously cast, the structure of the ingot is improved and the rolled material obtained from the ingot is improved. The purpose of this invention is to provide a method that can improve the mechanical properties of.

To continuously cast ingots such as aluminum, generally a frame-shaped metal water-cooled mold that is open in the vertical direction is used, and a pedestal is placed at the bottom of the mold, and the molten metal is poured onto the pedestal. A method is adopted in which the solidified ingot is continuously supplied into the mold, the pedestal is lowered and the ingot is pulled out from the bottom of the mold, and the ingot thus pulled out is subjected to cooling water and solidified. .
However, in such continuous casting methods (including so-called semi-continuous casting), the ingot is cooled sequentially from the outer periphery, and the cooling rate becomes slower toward the center. (called DAS), etc., become coarse. Also, for the same reason, a large number of linkage porosity occurs in the center of a rectangular ingot of medium-high strength alloy.
Such a relationship becomes more pronounced as the thickness of the ingot increases, and as mentioned above, the mechanical strength of the center of a rolled plate manufactured using an ingot with different textures between the outer skin and the center becomes more pronounced. The properties will be inferior to those of the skin, and in any case, it will be difficult to obtain the desired properties.

The present invention was developed through repeated research in view of the above-mentioned circumstances, and is a method of directly casting molten metal supplied into a water-cooled mold into the mold when continuously casting aluminum ingots. It is proposed that the ingot be discharged toward the center of the ingot and be used in conjunction with the distribution nozzle to supply the ingot, thereby forming a nearly uniform and dense structure from the surface to the center. , and also attempts to eliminate the occurrence of the above-mentioned syringe porosity.

To explain the present invention in detail, the attached drawing shows the method of the present invention as described above as an apparatus for obtaining a square ingot, and a tundish 1 has a mold formed in an ingot 5. A nozzle 2 for direct hot water supply is inserted considerably deep below the hot water level in the mold 5 toward the center of the lump 8, and the molten metal from the tundish 1 is directly discharged at the insertion depth position. It's on. Further, on both sides of such a nozzle 2, distributing hot water nozzles 3, 3 for supplying hot water into the mold 5 via a float 4 are arranged symmetrically, and the hot water is supplied at the same time. 6 is provided, and cooling water is fed into the mold 5 to give a cooling effect to the molten metal, and the cooling water is directly supplied to the circumferential surface of the ingot 8 drawn out from a nozzle 9 formed at the bottom of the mold 5 for cooling. It is designed to do so.

To further explain the method of the present invention carried out by the above-mentioned apparatus, the larger the amount of molten metal supplied from the hot water supply nozzle 2, the higher the temperature of the molten metal at the same depth position in the center of the ingot. Since the surface temperature is the same at each position, the cooling rate applied to the center becomes relatively faster, and a dense crystal structure can be formed in the center. However, when the amount of molten metal supplied to the center of the ingot increases in this way, the amount of molten metal distributed and supplied from the distribution nozzle 3 decreases, and the surface layer of the ingot becomes too cold, resulting in cold shatter (constriction due to solidification).
It is inappropriate to increase the amount of hot water supplied from the nozzle 2 to an extreme extent, as this may easily cause floating crystals to occur, and the relationship between these may vary depending on the shape and size of the ingot. However, in general, the amount of hot water supplied by the nozzle 2 is preferably 35 to 70%, particularly 40 to 60%, of the amount of hot water supplied into the mold 5. By doing so, it is possible to maintain a uniform crystal structure throughout the mold. It can be cast as. By doing the above, even if the temperature of the molten metal supplied is the same, the temperature at the surface layer of the mold is lower, so compared to the conventional method in which the entire amount is discharged from a nozzle using a float, feather crystals are formed on the surface layer. It has also been confirmed that it is less likely to occur. Direct hot water supply nozzle 2 has at least float 4
It is necessary to insert the filter into the molten metal in the mold longer than the distribution nozzle 3, and it is effective to use a filter 6 that is coarser than the conventional filter.

Specific embodiments of the invention as described above will be described below.

As shown in Fig. 1, hot water is supplied directly from the tundish 1 through the hot water supply nozzle 2 and the distribution nozzles 3 to the water-cooled mold 5, which is designed to continuously cast an ingot 8 having a rectangular cross section with an internal diameter of 508 x 1060 mm. When the hot water supply nozzle 2 is inserted directly from the molten metal surface in the mold 5 to a depth of 40 mm, 52% of the amount of hot water supplied into the mold is supplied from the nozzle 2, and approximately 24% is supplied from the distribution nozzles 3 and 3, respectively. 99.5% aluminum was semi-continuously cast under the conditions supplied. The ingot drawing speed from the bottom of the mold 5 was 7.5 cm/min.

That is, the crystal structure in the center of the ingot thus obtained is as shown in the micrograph of FIG. 2, and it is clear that it is a fine structure. On the other hand, when the same aluminum is semi-continuously cast at the same speed by the conventional method using only a float nozzle without using the direct hot water supply nozzle 2, the crystal structure at the center of the ingot is as shown in Figure 3. Therefore, the denseness of the crystal structure obtained by the method of the present invention is clear.

According to the present invention as explained above, the crystal structure of the ingot obtained by this type of continuous casting is appropriately formed into a substantially uniform dense state from the surface layer to the center, and the crystal structure of the ingot obtained by this type of continuous casting is appropriately formed into a dense state, and It is possible to provide an ingot of excellent quality by eliminating the occurrence of such ingots, thereby improving the mechanical properties and other properties of plate materials and other rolled materials obtained using such an ingot, This invention has great industrial effects.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and FIG. 1 is a cross-sectional explanatory diagram showing an example of an apparatus for carrying out the method of the present invention, and FIG. FIG. 3 is a micrograph showing the crystal structure of the center of one example of the ingot produced, and FIG. 3 is a micrograph of a comparative example, both of which are shown at 50x magnification. Also, in Fig. 1 above, 1 is a tundish,
2 is a direct hot water supply nozzle, 3 is a distribution nozzle, 4 is a float, 5 is a water-cooled mold, 6 is a filter, 7 is a molten metal, 8 is an ingot, and 9 is a cooling water.

Claims (1)

[Claims] 1. When supplying molten metal into a water-cooled mold to continuously obtain an ingot, the molten metal is supplied through a direct hot water supply nozzle and a distribution nozzle provided in the center of the mold, and the above direct hot water supply nozzle is A continuous casting method for an ingot, characterized in that the ingot is inserted into the molten metal in the mold longer than the distribution nozzle, and the amount of hot water supplied by the direct hot water supply nozzle is 35 to 70% of the total amount of hot water supplied in the mold.