JPS5911377B2 - Casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a casting method using a casting material such as a graphite mold that requires lubricity and corrosion resistance.

Well-known materials for casting materials such as molds include metals such as copper and aluminum, and lubricating heat-resistant materials such as graphite and boron nitride.

The latter is mainly used as a material for a mold used in a heated atmosphere, for example, in a known metal purification method using solidification and crystallization.

However, in graphite molds, 1
Due to the long casting time lasting over 0 hours, oxidation consumption is severe and the life is extremely short.

In particular, oxidative consumption becomes severe from about 400°C.

Although it is possible to introduce an inert gas to prevent graphite from being consumed by oxidation, it is difficult to create a completely closed system and is therefore impractical.

In addition, in order to make continuous casting possible, high-grade graphite is required and is expensive.

Boron nitride has advantages over graphite in terms of oxidation consumption, but
It is extremely expensive and practically unusable.

Therefore, Special Publication No. 50-20536, Special Publication No. 38-16
The metal purification method disclosed in No. 604 requires a solidification rate that is slightly lower than that of ordinary casting methods, so there are many issues such as keeping the molten metal warm for a long time, the need for lubrication, and preventing the contamination of impurities. Therefore, graphite is used exclusively as the material for casting materials such as molds, other containers, and tools.

The present invention has been made with the aim of solving the above-mentioned problems caused by the use of such graphite materials. The gist of this invention is a casting method characterized by:

Here, the casting material includes each member that comes into contact with the molten metal during casting, such as a stirrer for the molten metal in a tundish, a mold, and a gutter.

To explain the present invention in more detail based on the drawings, the first
The figure is an explanatory diagram of an example applied to a purification method by continuous casting of metal, and numeral 1 in the figure is a mold impregnated with perforated boron.

A heat insulating material 2 is provided around the outer periphery of the mold 1, and a heater 3 is embedded in the heat insulating material 2, so that the temperature of the molten metal 4 is maintained at an appropriate temperature.

A purified metal ingot 5 is cooled by a cooling medium such as air blown out through a cooling pipe 6 at the bottom of the mold 1.

As a result of this cooling, a solidification interface 7 is formed in the molten metal within the mold 1, and the purified metal is successively solidified and crystallized at this interface.

At this time, the concentration of impurity solutes increases in the molten metal near the solidification interface 7, so the molten metal is stirred by the stirrer 8 to disperse the impurity solutes.

It has been confirmed that by using a material in which the pores of graphite are filled with boron nitride powder as the mold 1, the usable time as a mold is greatly extended compared to when a simple graphite mold is used. It was done.

The results of the test are shown in the table.

As is clear from these results, according to the method of the present invention, the material life is 3 to 4 times longer than when using normal graphite materials, and the lubricity is also improved by impregnating the graphite pores with boron nitride. It was found that casting was possible without any problems even when low-grade graphite with many pores was used.

In FIG. 1, the boron nitride-impregnated graphite material can also be applied to the stirrer 8, and in this case as well, its life has been significantly improved.

An example of the method for impregnating and filling a graphite material with boron nitride is as follows.

That is, a graphite material is housed in a completely sealed container, the inside of the container is kept in a vacuum state, and a treatment liquid made by mixing boron nitride particles of 1 to 3 microns in a solution of a phosphoric acid compound is injected into the container.
．． This is done by applying pressure to sufficiently impregnate boron nitride into the graphite material, then taking it out and drying it.

The method of the present invention can be effectively applied to a horizontal casting method using a mold 1' as shown in FIG. 2, a hot top casting method using a mold 1L as shown in FIG.

In view of the above, the present invention greatly improves the lifespan of graphite materials for casting, which is particularly noticeable in casting in high-temperature atmospheres, and also improves the lifespan of graphite materials for casting, which is particularly noticeable in casting in high-temperature atmospheres. Since graphite can also be used satisfactorily, it is useful for reducing casting costs.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram when the present invention is applied to a metal purification method.
Figure 2 is an explanatory diagram when applied to horizontal casting, and Figure 3
The figure is also an explanatory view when applied to hot top casting. 1.1', 1...mold, 2...insulating material, 3...chemical compound, 4...molten metal, 5...
...Purified metal ingot, 6... Cooling pipe, 7.
... Solidification interface, 8 ... Stirrer.

Claims (1)

[Claims] 1. A casting method characterized by casting using a casting material obtained by impregnating and filling the pores of graphite with boron nitride powder.