JPS61169149A - Continuous casting method - Google Patents

Abstract

PURPOSE:To cast continuously a unidirectionally solified ingot having decreased segregation with less internal defects by drawing impulsively the casting ingot in a good heat conductive and refractory casting mold of which one end projects to a molten metal bath and the other end contacts with a cooling structural body. CONSTITUTION:The good heat conductive and refractory casting mold 6 which consists of silicon nitride, silicon carbide, graphite, etc. and of which one end projects to the molten metal bath 1 and the other end contacts with the cooling structural body 5 is installed horizontally or vertically in a melting furnace 2. The casting ingot 3 in the mold 6 is impulsively drawn with the longer stop time then the drawing time. The molten metal in the mold 6 is unidirectionally solidified without the inclusion and cavities and with the decreased segregation and is thus continuously cast and drawn. The quality of the ingot 3 is additionally improved if the intermediate part of the mold 6 is externally heated to eliminate the influence of the outdoor air temp. or if an inert gas 4 is blown thereto.

Description

[Detailed description of the invention] The present invention relates to a continuous metal casting method.

In particular, it relates to a method by which unidirectional solidification can be easily obtained.

In continuous metal casting, according to the conventional method, columnar crystals are obtained by growing dendritic structures in the same direction.

It grows from the side wall of the mold toward the center of the casting, and equiaxed products often grow in the center. Further, foreign matter and the like accumulate inside the casting, causing many internal defects.

For this reason, when compressed in the direction of columnar crystal growth during plastic working, two-grain boundary cracking may occur depending on the two alloys, which is not preferable.

In order to solve this problem, a device has been proposed as in Japanese Patent Publication No. 55-46265, which heats the mold and solidifies it at the mold outlet, but it is easy to cause breakouts during operation, making it difficult to operate. . Furthermore, a heater was built into the hammer mold to heat the mold itself, which was not a desirable structure.

In other words, the material requirements for manufacturing rods and the like as conductive materials for thin objects such as electric wires in equipment are as follows: 1. There should be few internal defects such as foreign objects and pinholes.

2. It must be long and of uniform quality, with little segregation.

3. Columnar crystals should not grow toward the center of the lot.

There is a need for a continuous casting method that can obtain a product without satisfying the following conditions, and that also satisfies safety, which is a necessary item during casting.

The present invention satisfies the above needs.

That is, this is a continuous casting method in which a hammered ingot is pulled out by pulse drawing using a device in which one end of the mold protrudes into a molten metal bath and the other end is in contact with a cooling structure. Furthermore, the following are provided as embodiments of the present invention.

The casting apparatus described above, wherein the material of the mold is a refractory material that is a good thermal conductor.

A casting method in which a heat-retaining heating element is provided between one end and the other end of the mold.

The above-mentioned casting method has a structure in which inert gas and/or neutral gas is blown into the mold wall surface from the molten metal bath side of the cooling structure of the mold.

The present invention will be described in detail below.

Metals to which the method of the present invention is applied include copper, gold, silver, aluminum, zinc, lead, tin, and alloys thereof.

In particular, those with good thermal conductivity are preferred.

One end of the mold of the present invention projects into the molten metal bath.
By making the mold protrude, the mold is heated by the heat of the molten metal. This makes it possible to maintain the solidification surface on the first side of the molten metal without using another heating means or overheating.At the same time, it is possible to solidify in one direction and obtain a special structure with very large crystal grains. It is something that can be done.

Furthermore, the other end of the mold is in contact with the cooling structure.

One-way solidification can be preferably performed by heating one end of the mold and cooling the other end.

At the same time, no molten metal is present at the mold outlet.

This enables continuous casting without breakage. Furthermore, in order to obtain an ingot with large crystal grains without breakout, it has been found that pulse drawing provides stable operation and a product of stable quality. Pulse extraction is a method in which extraction is stopped for a certain period of time and then extraction is performed. For example, this is an intermittent withdrawal in which the material is stopped for 4.5 seconds and then withdrawn for 0.5 seconds. It is better that the stop and pull-out times are short and alternate, and the stop time is longer than the pull-out time.

Preferably, the stop time/pulling time is 5 or more -fz.

Furthermore, the length of one pullout is preferably smaller.

Preferably, it is 3 mm/time or less.

In order to make the above continuous casting apparatus more preferable, it is preferable to use a refractory material with good thermal conductivity as the material for the mold. For example, silicon nitride, silicon carbide, graphite, etc.

Furthermore, it is preferable to provide a heat-retaining heating element between one end and the other end of the mold so that the temperature of the mold is not influenced by the outside air. It is preferable to form the mold so as to surround the entire periphery of the mold.

=4= Also, the structure is such that inert gas and/or neutral gas is blown into the mold wall surface from the molten metal bath side of the cooling structure of the mold.

This structure prevents segregation of the solidified metal and maintains a uniform temperature of the molten metal.
The gas serves at least to stir and mix the solution at the entrance of the molten metal to the mold. From the part of the mold in contact with the cooling structure, at least from the inlet side of the mold,
It is preferable that the structure is such that it can be loaded.

Furthermore, the casting apparatus used in the present invention may be one in which a mold is provided at the lower part of a melting furnace or a holding furnace, or one in which a mold is provided in a side wall tank of a melting furnace or a holding furnace.

As for the size of the product suitable for using the method of the present invention, a product with a very large diameter is not suitable. For example, the diameter is 20m
The size is less than m. This is because the temperature of the mold is preferably within a range that can be transmitted to the molten metal or semi-solid metal in order to enable unidirectional solidification.

By implementing the present invention as described above, the following effects can be obtained.

(1) A long metal lump with a unidirectionally solidified structure can be obtained without the risk of breakout.

(2) It is possible to obtain a long metal lump that is free from foreign matter and pinholes.

(3) A unidirectionally solidified rust mass with little segregation can be obtained.

(4) The surface of the spindle is extremely smooth.

(5) Due to unidirectional solidification, workability is extremely good.

(6) Since a long metal lump with large crystal grains can be obtained, it is suitable for manufacturing rods as materials for thin conductive wires such as electrical wires for equipment (for example, electrical wires for audio equipment).

Example 1 The experiment was carried out using the apparatus shown in FIG.

The end of a pure copper rod with an outer diameter of 10° and 6 mm is placed 1 cm inside the supply side of the molten metal (1) in a graphite mold (6) having an 11 mm diameter hole attached to the bottom side wall of the melting furnace (2).

Put 50 kg and 100 g of molten pure copper into the furnace.
It was kept at ℃. BQI water was passed through the cooling structure (5) installed on the side opposite to the molten metal supply side, and the solidification position of pure copper was set on the molten metal supply side in the mold.

As shown in Figure 1, N2 gas was introduced into the mold from (4) and was ejected into the molten metal while covering the surface of the casting rod (3). It stirred the molten metal and worked to eliminate variations in temperature and metal composition. Nao N
A gas seal (8) was provided so that the two gases were released only to the molten metal side.

The solidified rod was continuously pulled out by 2 mm in 0.5 seconds, and then pulsed with pinch rolls (7), which was stopped for 4 seconds.

The resulting pure copper was unidirectionally solidified and had extremely large crystal grains.

Example 2 In the apparatuses shown in FIGS. 2, 3, and 4, Example 1-
When the procedure was carried out in the same manner as above, a preferable unidirectionally solidified rod was obtained.

In addition, in FIGS. 3 and 4, a device equipped with a heat-retaining heating element (9) was used in order to reduce the influence of outside temperature.

[Brief explanation of drawings]

FIG. 1 shows the present invention applied to horizontal continuous casting. FIG. 2 shows a downward continuous casting apparatus. Third
Figures 1 and 4 show the embodiments of Figures 1 and 2,
It is equipped with a heating element for heat retention. (1) Molten metal, (2) Melting furnace, (3) Casting rod, (4) N2 gas inlet, (5) Cooling structure, (6) Graphite mold It is. Patent Applicant Date: 16th January 16th, 2015, Attorney for the Chestnut Machine Company 1. (7569) Keishi Junyo Figure 1 Figure 2 i H= Figure 3 Figure 4

Claims (4)

[Claims] (1) A continuous casting method characterized in that the cast ingot is pulled out by pulse drawing using a device in which one end of the mold protrudes into a molten metal bath and the other end is in contact with a cooling structure. (2) The continuous casting method according to claim 1, wherein the material of the mold is a refractory material that is a good thermal conductor. (3) The continuous casting method according to claim 1, characterized in that a heat-retaining heating element is provided between one end and the other end of the mold. (4) The continuous casting method according to claim 1, characterized in that the inert gas and/or neutral gas is blown into the mold wall surface from the molten metal bath side of the cooling structure of the mold. .