JPH0446664A - Method for casting aluminide - Google Patents

Abstract

PURPOSE:To manufacture an excellent casting product by producing molten metal containing the specific percentage of Al and Ti respectively and pushing the molten metal into a mold. CONSTITUTION:Recessed part 3 is arranged in a copper-made water cooled hearth 2. Al and Ti in the range of >=25atm% and <=75atm% to each, are charged into the recessed part 3 under condition of powder or chip, etc. These raw material is vacuum-melted by using an electrode 8 to form aluminide. The water cooled mold 4 forming a hole 5 is pushed into the molten aluminide to form the casting product 11. In the molten metal, one or more kinds of atm% of 0.05<= Cr <=10, 0.05<= Nb <=10, 0.001<= Si <=10, are contained. By this method, bore, etc., in the casting product is reduced and the yield can be increased.

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 difficult workability and poor ductility at room temperature, and since it is made of active metal, melting and casting are limited, so it is not necessarily easy to manufacture. However, when casting aluminide, for example, there is no mold made of a suitable material that can withstand aluminide's high melting point, so a so-called water-cooled mold is used to cool copper, which has a high thermal conductivity, with water. etc. had to be used.

[Problem to be solved by the invention] However, this water-cooled mold (surface) 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 complex parts such as engine intake and exhaust valves. It was difficult to cast parts with large shapes or thin parts.

In other words, when trying to cast a complex-shaped or thin part with a water-cooled mold, the whole part may not be cooled uniformly, but only a part of it may be cooled first, resulting in uneven hardening and bore holes. Therefore, in the past, there was a problem that another process such as HIP treatment was required after surface casting.

Also, apart from the above technology], even if you try to manufacture complicated parts such as intake and exhaust valves for engines by cutting,
Cutting aluminide itself is not easy, and moreover, there are problems in that many chips are generated, resulting in low production yields and high manufacturing costs.

Therefore, according to the present invention, defects such as bores do not occur, and
Moreover, the aim was to provide a method for casting aluminide with a high yield.

[Means for Solving the Problem] The invention described in the claim made to achieve the above object is to produce a molten metal containing AQ and Ti in a range of 25 at% to 75 at%, and to the molten metal. The gist is an aluminide casting method in which a cast product is formed by pressing a mold.

Further, the invention according to claim 2 (in the method for casting aluminide according to claim 1,
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, OO1≦Si≦10 Here, at% and (Table) indicate the percentage of the number of atoms.

[Operation] The invention according to claim 1 (first, the raw materials of AQ and Ti are melted to produce a molten metal containing AQ and Ti within a predetermined range capable of forming the aluminide, and then the molten metal is injected into the molten metal). It is used to press the mold.

In other words, instead of pouring the molten metal into a mold, by pushing the mold into the molten metal, the pressure generated during the pushing is used to quickly fill the mold of a complex-shaped or long and narrow member with the molten metal. It is something to do. That is, rapid filling due to this large pressure can prevent defects such as bores from occurring in the mold of complex parts.

Incidentally, when AQ and Ti are within the above ranges, the alloying reaction occurs more preferably and an intermetallic compound can be produced independently.

Furthermore, a molten metal containing the components described in claim 2 within the above range exhibits the following effects.

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

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

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

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

FIG. 1 shows step 2 of applying the present invention to valve casting,
Figure 2 shows an example of this work.

(Mold forming process...1) As shown in Fig. 2, a disc-shaped recess 3 with a diameter of 50 holes and a depth of 10 mm is provided in advance in the copper ice-cooled hearth 2, and a valve-shaped recess 3 is provided in the copper water-cooled mold 4. A shaped hole 5 is provided. Water channels 6 and 7 through which cooling water flows are formed around the recess 3 of the water-cooled hearth 2 and the hole 5 of the water-cooled mold 4, respectively.

(Raw material preparation step...11) First, AQ and Ti raw materials are introduced into the recess 3 in the form of powder or chips in a range of 25 at% or more and 75 at% or less, and other Cr .

One or more of Si and Nb, each at 0°05
≦Cr≦10.0.05≦Nb≦10゜0.001≦8
Add only the amount in the range 1≦10.

(Raw material melting process...111) Next, these raw materials are vacuum arc melted using a tungsten electrode 8, sufficiently melted and homogenized, and an alloying reaction is performed to form aluminide.

(Mold pressing is step...IV) Then, with the aluminide dissolved, the water-cooled mold 4 in which the valve-shaped hole 5 was formed was heated to a pressure of about 5 kg f.
7 cm" into the aluminide from above the recess 3 to fill the water-cooled mold 4 with aluminide.

(Mold cooling process...■) Then, water is continued to flow through the water channels 6° 7 of the water-cooled hearth 2 and the water-cooled mold 4, and the temperature is lowered over a period of 10 minutes.

(Valve removing step...V+) Thereafter, the water-cooled hearth 2 and the water-cooled mold 4 are separated, and the ingot 1 in the shape of a valve is taken out from the water-cooled mold 4.

In actuality, in order to form the ingot 11 precisely into the shape of a bulb, finishing treatments such as cutting and polishing are then performed.

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

Next, an experimental example will be explained.

(Experiment Example) This experiment 1 is an experiment to examine the characteristics of a bulb-shaped ingot cast by the method of the above example, and is AQ.

By changing the type and amount of Ti and added elements, tensile strength at room temperature, elongation at room temperature, tensile strength at 300℃, 80
This tensile strength, which was examined for oxidation resistance at 0°C (indicates the strength at which the shaft portion of the upper ingot breaks), and the elongation at room temperature is the elongation at break. The comparison was made assuming that the amount increased by 1.

The results are shown in Table 1 below. In Table 1, samples Nc] to 3 show ingots of valves cast by the method of the present example, and samples Nc4 to 11 show comparative examples.

As is clear from Table 1, the aluminide casting method of this example has excellent tensile strength at room temperature and 300°C.It also has excellent oxidation resistance.

On the other hand, some comparative examples show good results in terms of tensile strength at room temperature, but the tensile strength at high temperatures is low.
It also has poor oxidation resistance, making it undesirable from a comprehensive evaluation.

[Effects of the Invention] As detailed above, 1: According to the aluminide casting method of claim 1, 1i a molten metal containing a predetermined amount of AQ and Ti is produced, and a mold is pushed into the molten metal to form a cast product. Therefore, it is possible to easily manufacture an excellent cast product with few bores, etc. Also, the yield is 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 sequence of the aluminide casting method of the embodiment. FIG. 2 is an explanatory diagram specifically explaining the aluminide casting method of the embodiment. 2... Water-cooled hearth 3... Concavity 5... Hole 6... Water-cooled mold 11... Ingot

Claims (1)

[Claims] 1. A method for casting aluminide, which comprises producing a molten metal containing Al and Ti in a range of 25 at% or more and 75 at% or less, and pressing a mold into the molten metal to form a cast product. 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