JPH0433768A - Method for casting aluminide - Google Patents

Abstract

PURPOSE:To suitably execute filling-up of molten metal into cavity and to easily manufacture a casting having excellent quality of a little pore, etc., by melting a plate material with the molten metal containing the prescribed Al and Ti under the condition of pouring the molten metal above the plate material set at the cavity in the mold. CONSTITUTION:A disk-like recessed part 3 is arranged in a copper-made water cooling hearth (mold) 2 composed of two members as separatable to right and left parts, and further, a columnar hole 4 is formed at center of the recessed part 2. Successively, at the center of bottom face in this recessed part 3, the Ti plate material (cast-in plate) 8 is set. Then, in the recessed part 3, the raw material of Al and Ti is charged in the range of >=25at% and <=75at%, respectively the under the condition of powder or chip, etc., and these raw material is melted under vacuum by using a tungsten electrode 9 to form molten aluminide. Further, the plate material. 8 is melted under the condition of forming the molten aluminide. The molten metal in the recessed part 3 is caused to flow in the hole 4 and the inner part of the hole 4 is filled up with the molten metal to form a thin disk part 10 in a valve. After descending the temp., by separating the cooling hearth 2 to right and left parts, a cast block 11 of the valve shape is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for casting aluminide, which is an intermetallic compound.

[Prior Art] Aluminide (particularly titanium aluminide), which is a type of intermetallic compound, has been attracting attention in the aerospace, automobile, and industrial machinery fields because it is lightweight and has excellent high-temperature strength. For example, engine suction
It is expected to be used as a high-temperature structural material for exhaust valves, etc.

This aluminide has manufacturing difficulties such as being difficult to process and has poor malleability at room temperature, and since it is made of an active metal, melting and casting are limited, so it is not always possible to manufacture it. I can't say it was easy.

For example, when casting aluminide, aluminide has a high melting point and there is no mold made of a suitable material that can withstand casting, so a so-called water-cooled mold, which cools copper, etc. with high thermal conductivity, with water is used. I had to.

[Problems to be Solved by the Invention] However, this water-cooled mold requires a special structure for water cooling, and its cooling capacity is higher than that of a normal mold, so it is difficult to manufacture complicated parts such as intake and exhaust valves for engines. It was difficult to cast parts with large shapes or thin parts.

In other words, when trying to cast a complex-shaped or thin aluminide part using a water-cooled mold, the whole part may not be cooled uniformly, and only a part of it may be cooled first, resulting in uneven solidification. Therefore, in the past, there was a problem in that another process such as HIP treatment was required after casting. Even when attempting to manufacture complex parts such as exhaust valves, there is a problem in that cutting aluminide itself is not easy, and moreover, many chips are generated, resulting in low production yields and high manufacturing costs.

SUMMARY OF THE INVENTION Therefore, the present invention has been made with the object of providing an aluminide casting method that does not cause defects such as bores and has a high yield.

[Means for Solving the Problems] The invention described in Claims made to achieve the above object provides for preparing a raw material containing AQ and T1 in a range of 25 at% or more and 75 at% or less, and dissolving the raw material. A container is placed above the mold, and a hole is provided to communicate the cavity of the mold with the inside of the melting container, and a plate material partially or entirely having the same composition as the raw material is provided to cover the hole. After that, the raw materials are melted into a molten metal in the melting container, and the plate material is melted with a heating device, and the molten metal is poured from inside the melting container into the cavity of the mold. The gist is the casting method of aluminide to be injected.

Further, the invention of claim 2 provides the method for casting aluminide according to the above claim, comprising:
The gist of the present invention is a method for casting aluminide in which the molten metal contains one or more of the following at% components.

0.05　≦Cr≦10゜ 0.05　≦Nb≦10゜ 0.001≦Si≦10 Incidentally, here, at% and (y) indicate the percentage of the number of atoms.

Further, as the heating device, a tungsten electrode for irradiating an arc beam or the like is suitable.

Furthermore, depending on the shape of the mold, negative pressure may be applied to the bottom of the mold to improve aluminide filling.

Further, the raw material in the melting container may be melted by an arc or the like inside the melting container to form a molten metal, but a molten metal manufactured elsewhere may also be poured into the melting container.

[Operation] According to the invention of claim 1, first, a melting container is placed above the mold, and a plate material of a predetermined component is placed in the hole that communicates the melting container and the mold. Then, by melting the plate material with the molten metal in the melting container, the molten metal is poured into the mold.

In other words, if the plate material and the raw material are prepared with almost the same ingredients, and the holes are covered with the plate material, and the plate material is melted using a heating device,
The molten metal quickly flows into the mold placed at the bottom of the melting vessel, forming a good ingot with no bores, etc. However, since the plate material has the same composition as the molten metal, the composition of the ingot is different from that of the molten metal. It becomes the same uniform thing.

Note that when AQ and T1 are within the above ranges, an alloying reaction occurs suitably, and an intermetallic compound can be produced independently.

Moreover, in the invention of claim 2, the molten metal containing the components described in claim 1 within the above range exhibits the following effects.

■Cr Below the lower limit, no improvement in spreadability is observed, while above the upper limit, the improvement in spreadability is saturated.

■Nb Below the lower limit, no improvement in strength is observed, while above the upper limit, the strength is saturated.

(2) S1: Below the lower limit, no improvement in oxidation resistance is observed; on the other hand, above the upper limit, the oxidation resistance is saturated.

[Example] Embodiments of the present invention will be described below based on the drawings.

Figure 1 shows the process of applying the present invention to valve casting,
Figure 2 shows an example of this work. In this embodiment, the melting container is formed into a mold, and this mold consists of two parts that can be separated into left and right sides.

(Mold forming process...1) As shown in Fig. 2, a disc-shaped recess 3 with a diameter of 501 Tm and a depth of 10 mm is formed in a copper water-cooled hearth (mold) 2 consisting of two parts that can be separated left and right. Further, a cylindrical hole 4 with a diameter of 7 rrm and a depth of 120 mm is formed in the center of the recess 3. That is, a bulb-shaped cavity 5 is formed by the recess 3 and the hole 4. Note that a water channel 6 is formed around the cavity 5 of the water-cooled hearth 2 through which cooling water flows.

(Plate arrangement step...I+) Next, in the center of the bottom surface of this recess 3, an opening 7 of the hole 4 is placed.
A T1 plate (left plate) 8 with a diameter of 40 mm and a thickness of 1 mm is placed so as to cover the area.

(Raw material preparation step...111) Then, in the recess 3, AQ and TI raw materials are each added in the form of powder or chips at a concentration of 25 at% or more and 75 at%.
Bid within % and other Cr.

One or more of Nb and Si, each 0°05≦
Cr≦10.0.05≦Nb≦10.0゜001≦Si
Add only the amount within the range of ≦10.

(Raw material melting process...IV) Next, these raw materials are vacuum arc melted using a tungsten electrode 9, and thoroughly melted and homogenized to perform an alloying reaction to form a molten aluminide. , T1
The melting point of the plate material 8 made of is slightly higher than the melting point of the molten metal,
The plate material 8 is not melted by the vacuum arc at this time.

(Plate melting step...■) Then, with the molten aluminide formed, the output of the tungsten electrode 9 is increased to melt the plate 8. When the plate material 8 is melted, the opening 7 is opened, so that the molten metal in the recess 3 instantly flows into the hole 4, and the inside of the hole 4 is filled with the molten metal.

Note that the liquid level of the molten metal is lowered by this movement of the molten metal, thereby forming a thin disk portion 10 of the valve.

(Mold cooling step...Vl) Then, water continues to flow through the water channel 6 of the cooling hearth 2, and the temperature is lowered over 5 minutes.

(Valve removal process...Vll) After that, the cooling hearth 2 is separated into left and right sides, and the ingot 11 in the shape of a valve is removed.

Actually, in order to precisely form the ingot 11 into a bulb shape, finishing treatments such as cutting and polishing are performed thereafter.

The valve ingot 11 thus formed had a smooth and good surface quality with no bores, and a density of 99.5% or more.

Next, an experimental example will be explained.

(Experiment Example) This experiment was an experiment to examine the characteristics of a bulb-shaped ingot cast by the method of the above example, and AQ.

The tensile strength at room temperature, elongation at room temperature, tensile strength at 300'C, and oxidation resistance at 800'C were investigated by changing the type and amount of T1 and added elements. It shows the strength at which the shaft part breaks, and the elongation at room temperature is the breaking strain. Furthermore, the oxidation resistance is compared with term 2 due to oxidation of T1 as 1.

The results are shown in Table 1 below. Incidentally, sample levels 1 to 3 in Table 1 indicate valve ingots cast by the method of the present example, and samples Nct4 to 11 indicate comparative examples.

As is clear from Table 1, the aluminide casting method of this example is suitable for superior tensile strength at room temperature and 300° C., as well as low elongation at room temperature. Also,
It also has excellent oxidation resistance.

On the other hand, some comparative examples show good results in terms of tensile strength at room temperature, etc., but the tensile strength at high temperatures is low and the oxidation resistance is also poor, so it is not desirable after comprehensive evaluation. It has become something that does not exist.

[Effects of the Invention] As detailed above, according to the method for casting aluminide according to claim 1, the molten metal containing a predetermined amount of AQ and Ti is placed on the top of the plate material placed in the cavity of the mold. Since the plate material is melted, the cavity can be suitably filled with molten metal, and excellent cast products with few bores etc. can be easily manufactured.The yield is also high.

In addition, in the aluminide casting method of claim 2 (because the molten metal contains a predetermined amount of Cr, Nb, Si, etc. as components,
It has the effect of improving strength and oxidation resistance at high temperatures.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the order of the aluminide casting method according to the embodiment, and FIG. 2 is an explanatory diagram specifically explaining the aluminide casting method according to the embodiment. 2... Water-cooled hearth 3... Recess 4... Hole 8... Plate material 1]... Ingot

Claims (1)

[Scope of Claims] 1. A raw material containing Al and Ti in a range of 25 at% or more and 75 at% or less is prepared, a melting container for the raw material is placed above a mold, and a melting container is placed in the cavity of the mold. A hole communicating with the inside of the container is provided, and a plate material partially or entirely having the same composition as the raw material is placed inside the melting container to cover the hole, and then the raw material is melted in the melting container. A method for casting aluminide, in which the plate material is melted into a molten metal using a heating device, and the molten metal is injected into a cavity of a mold from inside the melting container. 2. In the aluminide casting method according to claim 1, the molten metal contains one or two of the following at% components.
A method for casting aluminide containing more than one species. 0.05≦Cr≦10, 0.05≦Nb≦10, 0.001≦Si≦10