JPH0598368A - Production of high density powder sintered titanium alloy - Google Patents

Abstract

PURPOSE:To produce a high density powder sintered titanium alloy capable of being made highly densified. CONSTITUTION:At the time of producing the high density powder sintered titanium alloy by mixing a titanium powder and a previously alloyed alloy powder and subjecting the resulting powder mixture to compacting and to sintering, a powder prepared by crushing spongy titanium in a solvent capable of dessolving NaCl or MgCl2 is used as the titanium powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high density powder sintered titanium alloy suitable for automobile parts and the like.

[0002]

2. Description of the Related Art Titanium alloys are lightweight and have high strength, and since they are excellent in corrosion resistance, they are expected to have a wide range of applications from industrial parts to consumer parts. In particular, it is being studied to apply the above properties to automobile parts. However, since titanium is a difficult-to-process material, the method of manufacturing it from a molten material by machining or cold working can provide excellent mechanical properties, but has the drawback of high cost. In order to avoid such drawbacks, it has been attempted to apply a powder metallurgy technique in which elementary powders of a titanium alloy are mixed, shaped into a predetermined shape, and then fired in a vacuum to obtain a sintered body.

However, when powder metallurgy is used, voids remain in the product, and mechanical properties, particularly fatigue strength, are reduced. In order to eliminate the voids, secondary processing such as HIP (hot isostatic pressing) may be used after sintering, but if such a method is adopted, the cost will increase and the merit of powder metallurgy will be obtained. I will lose.

As a notable technique for obtaining a high-density titanium sintered body without increasing the cost, Japanese Patent Publication No.
There is a method disclosed in -50172. According to this method, a prealloy (master alloy) having a predetermined particle size is prepared in advance from alloying elements that constitute a titanium alloy, and the prealloy and titanium powder having a predetermined particle size are mixed to obtain a theoretical value of 80 to 90% A green compact having a density of 1 is formed, and the green compact is sintered at a temperature below the temperature at which a liquid phase occurs.

[0005]

By the way, the Japanese Patent Publication No. 2-
Not limited to the technique disclosed in 50172, sponge titanium is generally used as a titanium raw material when producing a sintered alloy by a powder metallurgy technique. However, when sponge titanium having a predetermined particle size is used as the titanium raw material as it is, the density can be increased to some extent, but a sufficient density cannot be achieved yet.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a high-density powder-sintered titanium alloy capable of achieving sufficient densification.

[0007]

In order to solve the above-mentioned problems, the present invention provides a high-density structure in which titanium powder and pre-alloyed alloy powder are mixed and the mixed powder is molded and sintered. A method for producing a powder-sintered titanium alloy, comprising sponge titanium as NaCl or Mg as the titanium powder.
Provided is a method for producing a high-density powder-sintered titanium alloy, which is obtained by pulverizing in a solvent in which Cl ₂ is soluble.

The inventors of the present invention have made extensive studies as to the reason why sufficient density cannot be achieved by using titanium sponge as a titanium raw material as it is, and as a result, the following findings have been obtained.

(1) Titanium sponge contains TiCl ₄ as Na
Alternatively, since it is produced by reducing with Mg, it is
Cl or MgCl ₂ remains. In the case of the Hunter method using Na, the amount is 0.10 to 0.2 as Cl.
0%, Cl in the case of the chlorination method using Mg is 0.1.
It is about 08%. Since this Cl generated by the decomposition of NaCl and MgCl ₂ does not dissolve in Ti, pores are generated in the structure due to the Cl gas generated during sintering, and this remains as it is to increase the density as shown in FIG. Interfere with. (2) When titanium powder having a large particle size is used, the density is hampered due to nonuniform mixing with the master-alloy and lack of contact area (reaction area).

The present invention was made based on the findings of the inventors of the present application. That is, by crushing titanium sponge as titanium powder in a solvent in which NaCl or MgCl ₂ is soluble, C
l can be removed, and the titanium powder can be made finer.

The solvent used in this case is NaCl.
Alternatively, MgCl ₂ may be soluble, for example, water in the case of NaCl, and alcohols in the case of MgCl ₂ . Further, the pulverizing method is not particularly limited, but a ball mill, an attritor or the like can be preferably used.

[0012]

Embodiments of the present invention will be described in detail below.

As the Ti raw material powder, a sieve of titanium sponge reduced with Na (average particle size of about 100 μm, referred to as sponge fine) was used. 1 kg of this sponge fine was charged into a ball mill (volume: 5 liters) containing 10 kg of steel balls together with 1 liter of pure water and pulverized for 2 hours. As a result of measuring the amount of Cl contained in titanium sponge before and after the pulverization, it was 0.20% before the pulverization, whereas it was 0.05% after the pulverization, and the chlorine content existing as NaCl was dissolved in water. It was confirmed that it was removed. The average particle size of the titanium powder after pulverization was 70 μm.

A master alloy (60A) was added to this titanium powder.
1-40V), mixed with a V blender, and mixed with Ti
A raw material powder of -6Al-4V was prepared. The master
The average particle size of the alloy was 5 μm. 6 of this raw material powder
ton / cm ² 12 × 12 × 60mm when molded with pressure
The molded body of 1 was obtained, and this molded body was sintered at 1260 ° C. to manufacture a sintered titanium alloy.

For comparison, a raw material powder was similarly prepared using titanium sponge which was not crushed in pure water,
6ton / cm ² Was molded at a pressure of 1600 ° C. and sintered at 1260 ° C. to produce a sintered titanium alloy. The characteristics of the sintered body at this time are shown in Table 1.
Shown in.

[0016]

[Table 1]

As shown in Table 1, the sintered body produced according to the present invention has higher density and tensile strength than the sintered body using titanium sponge as it is. That is, by using the method of the present invention, the pores due to Cl are reduced, and since the titanium powder is made finer, sintering is promoted, resulting in an increase in density and an increase in tensile strength. Was confirmed.

[0018]

According to the present invention, there is provided a method for producing a high-density powder-sintered titanium alloy capable of achieving sufficient densification.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between Cl content and density.

Claims (1)

[Claims] 1. A method for producing a high-density powder-sintered titanium alloy, which comprises mixing titanium powder and a pre-alloyed alloy powder, shaping the mixed powder and sintering the mixture, wherein the titanium powder is sponge. A method for producing a high-density powder-sintered titanium alloy, which comprises using titanium pulverized in a solvent in which NaCl or MgCl ₂ is soluble.