JPH04362144A - Induction melting method - Google Patents

Abstract

PURPOSE:To melt an active metal to a high temp. of excellent castability with high purity by providing a specific heat resistance layer between the skull of the active metal and a crucible constituted of plural water cooling type bar-shaped copper segments at the time of melting the active metal in this crucible. CONSTITUTION:The many water cooling type bar-shaped segments 2 made of copper and a crucible 6 formed of refractories 7 between these segments to a cylindrical shape are used as the crucible and a high-frequency induction current is passed from a power source 9 to an induction coil 1 provided on the outer periphery thereof to melt the Ti in the crucible 1 by the induction current at the time of melting the active metal, such as Ti, by the high-frequency induction current. The current does not flow in the crucible itself as the water cooling bar-shaped copper segments 2 are insulated from each other by the refractories 7. The current flows effectively only in the Ti 4 and the Ti melts with good electric power efficiency. The heat resistance layer 11 consisting of chemically stable Y2O3 and others which have a high m.p. and high thermal conductivity and do not react with the Ti is interposed between the skull 12 as the solidified shell of the molten Ti and the crucible 6, by which the Ti is sufficiently heated to the high temp. with the high purity and the castability is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction melting method for melting materials such as active metals or high melting point metals with high purity.

0002

[Prior Art] Conventionally, methods such as induction melting, plasma melting, electron beam melting, and vacuum arc melting have been used to melt active metals or high-melting point metals. An induction melting method using a split copper crucible has been researched and is being put into practical use. This melting method has many advantages, such as relatively simple equipment, good workability, and the ability to obtain homogeneous molten metal.

FIG. 2 is an explanatory diagram of the conventional induction dissolution method.
) uses an integrated refractory crucible; (b)
This method uses a water-cooled segmented copper crucible (water-cooled copper segment), which has been researched and is being put into practical use in recent years. (a
) shows an integrated refractory crucible 5 placed inside the induction coil 1, and (b) shows the arrangement of a plurality of copper segments 2 with internal cooling channels 8 inside the induction coil 1, and the space between the copper segments 2. A copper crucible 6 made of a refractory 7 inserted into a slit is arranged, and the material to be melted is melted by induction therein. The induction coil 1 is connected to a high frequency power source 9. In the figure, 3 indicates a skull (solidified shell), and 4 indicates molten metal.

[0004] The copper crucible 6 has a vertically long copper segment 2.
are connected in a cylindrical shape via a refractory 7 inserted into a slit, and the upper part of the copper crucible 6 has a discontinuous structure in the circumferential direction. Therefore, when a high frequency current is passed through the induction coil 1, since the copper crucible 6 is divided by the slit, almost no induced current flows in the copper crucible 6, but an induced current flows in the material to be melted in the copper crucible 6. This makes it possible to efficiently melt the material to be melted.

The molten metal 4 in the copper crucible 6 is held molten in a molten metal skull (solidified shell) 3 formed by the cooling effect of the water-cooled copper segment 2, and furthermore, the molten metal 4 is It is stirred by the electromagnetic force from the induction coil 1 (arrow in the figure), and its upper part is held in a parabolic shape as shown in Figure 2(b), so it is melted without contacting the copper crucible 6. Therefore, compared to the refractory crucible 5 shown in Fig. 2(a), the refractory dirt from the crucible is of course
High-purity melting with little contamination from the copper crucible 6 is possible.

[0006]

[Problems to be Solved by the Invention] However, the molten metal obtained by the above-mentioned melting method has a defect in that, in principle, a sufficient amount of superheat (the difference between the molten metal temperature and the melting point of the molten metal) cannot be obtained. There is. This poses a serious problem when manufacturing cast products. In particular, when casting thin-walled products with complex shapes, molten metal with a temperature close to its melting point is highly viscous and solidifies during casting, resulting in the molten metal not being fully filled to the tip of the mold. This will result in defects. Moreover, if there are many skull parts, the yield will decrease and this will directly lead to an increase in cost.

The present invention has been made to solve the above-mentioned problems, and by inserting a heat resistance layer between the skull and the crucible, it is possible to secure a sufficient amount of superheat and to reduce the amount of skull. The purpose is to provide a dissolution method.

[0008]

[Means for Solving the Problems] The first invention provides a method for melting an active metal such as a titanium alloy in a skull induction melting method using a copper crucible composed of a plurality of rod-shaped water-cooled copper segments. This is an induction melting method in which a heat resistance layer is formed and melted.

[0009] The second invention includes Y2O3 and Hf in the heat resistance layer.
2. The induction melting method according to claim 1, wherein one selected from O2, CaO2, ZrO2, Ta, W2, and Mo is used.

0010

[Function] For the heat resistance layer, a chemically stable material is required that has a high melting point, low thermal conductivity, and does not react with active metals, and a material suitable for the material to be melted is selected. Above Y2O3, HfO
2. CaO, ZrO2, Ta, W2, and Mo are all satisfactory as heat resistance layers. Incidentally, all of these melting points are 2400°C or higher.

Further, the thickness of the thermal resistance layer is determined in consideration of the input power, the amount of cooling water, and the amount of material to be melted. In order to increase the effect of the thermal resistance layer, it is possible to make the contact surface between the copper crucible, the thermal resistance layer, and the skull rough to reduce the heat transfer coefficient at the contact surface and increase the thermal resistance. It is essential. As a result, the factors that participate in heat transfer conduction decrease, and the factors that participate in radiation and convection increase, making it easier to obtain superheat.

The contamination of the molten metal of the thermal resistance layer, which is a concern, can be solved by devising a melting method. That is, as shown in FIG. 1, a hollow heat resistance layer 11 is placed on the bottom of the copper crucible 6, and a skull 12 made of a material to be melted is placed on top of the heat resistance layer 11. In this state,
The material to be melted is charged into a copper crucible 6, and a high frequency current is passed through the induction coil 1 from a high frequency power source 9 to melt it. The upper part of the skull 12 begins to melt as the melting begins, but when a thermal equilibrium state is reached, the melting of the skull 12 stops and the skull 12
The lower part of the heat resistance layer 11 of the molten metal 4 remains undissolved.
Contamination from can be prevented. Further, the molten metal 4 is stirred by the electromagnetic force from the induction coil 1, and the upper part thereof is held in a parabolic shape, so that it is melted without coming into contact with the copper crucible 6.

[0013]

[Examples] Examples of the present invention are shown below. T for melting material
Using 20 kg of Ti and Ti-37Al, melting was performed with and without a heat resistance layer. Y2O3 powder was used for the heat resistance layer, and it was spread in the shape of a hollow in the lower part of the copper crucible, and a skull made of the material to be melted was placed on top of it. Table 1 shows the amount of superheat, amount of hot water, and amount of dissolved oxygen at this time. The induction melting furnace shown in FIG. 1 was used as the melting furnace.

[0014]

[Table 1]

As is clear from Table 1, when the heat resistance layer of the present invention is present, the amount of superheat is greater than when there is no heat resistance layer, and the amount of skull is reduced and the amount of hot water is increased. However, the yield has improved. Further, as a result of oxygen analysis, no oxygen contamination of the molten metal from the Y2O3 powder, which is the heat resistance layer, was observed.

[0016]

Effects of the Invention The present invention is an induction melting method that secures a sufficient amount of superheat and reduces the amount of skull by inserting a heat resistance layer between the skull and the crucible. By placing it between the crucibles,
By increasing the amount of superheat, it becomes possible to cast thin-walled products with complex shapes, and it also has the excellent effect of reducing the amount of skull, increasing the amount of hot water coming out, and improving the yield.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the induction lysis method of the present invention.

FIG. 2 is an explanatory diagram of a conventional induction lysis method.

[Explanation of symbols]

1...Induction coil, 2...Copper segment, 3...Skull, 4...
Molten metal, 5... Refractory crucible, 6... Copper crucible, 7... Refractory, 8... Cooling channel, 9... High frequency power supply, 11... Heat resistance layer,
12...Skull.

Claims (2)

[Claims] Claim 1: In a skull induction melting method using a copper crucible composed of a plurality of rod-shaped water-cooled copper segments,
When melting active metals such as titanium alloys, this induction melting method is characterized by forming a heat resistance layer between the skull and the crucible. [Claim 2] The heat resistance layer contains Y2O3, HfO2, C
1 selected from aO, ZrO2, Ta, W, Mo
2. The induction dissolution method according to claim 1, wherein a type of inductive dissolution is used.