JPH03211206A - Manufacture of high density titanium alloy sintered parts - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to sintered parts for automobile parts, marine or ship parts, membrane structures, etc., and in particular to the production of high-density titanium alloy sintered parts. Regarding the method.

(Prior Art) Automotive engine parts with complex shapes, such as connecting rods, have conventionally been manufactured by cutting steel materials. In line with recent objectives such as improving fuel efficiency, reducing weight, and increasing efficiency, various parts are being developed using titanium alloy materials instead of steel materials. Similar developments are also underway in marine and marine components and in membrane structural components.

However, conventional titanium alloy parts are first melted in a vacuum arc melting furnace (VAR), then forged, hot rolled,
After going through various processes such as heat treatment, it is manufactured by mechanical processing, and because the process is expensive and complicated, the product price is inevitably high, and it is difficult to use it as a general-purpose automobile part. Ta.

Currently, in order to solve the above problems, near-net shave molding such as powder metallurgy is being used instead of conventional melting. Among the powder metallurgy methods, a mixed powder that is mechanically mixed in advance to form a predetermined alloy component is filled into a flexible mold made of rubber or other material so that it can be molded into a predetermined shape, and cold isostatic pressing is performed. (hereinafter referred to as CIP), the powder is compacted into a predetermined shape, then sintered by heat treatment at high temperature, and then hot isostatically pressed (hereinafter referred to as HIP).
A method for manufacturing titanium alloy parts using the so-called raw powder method is being developed.

According to the above method, it is possible to manufacture automobile parts and the like without going through expensive processes such as melting, forging, or hot rolling. In addition, the additive elements of titanium alloys can be easily blended in any weight ratio, and due to solidification segregation in the melting method and alloy powder method, they cannot be added or there are restrictions on the amount added. There is also the advantage that certain elements can also be added.

However, it is becoming clear that this raw powder method has the following problems.

First, because a flexible mold such as a rubber mold is used during CIP, unevenness due to the powder shape remains on the surface of the powder compact, and similar unevenness remains on the surface after sintering and HIP. . Second, due to non-uniform filling when filling powder into a mold or local non-uniform pressure that occurs during CIP of a complex-shaped product, partially open pores occur on the surface of the powder compact after sintering. Since pressurized gas flows into these open pores during HIP treatment, pressure acts on the open pores, resulting in insufficient sealing of the open pores, and the open pores remain as defects after the HIP treatment. Therefore, it may not be able to withstand use as automobile parts that require high fatigue strength.

Countermeasures such as grinding after HIP treatment have been taken to solve the above problems, but not only is it difficult to grind components with complex shapes by machining, but the characteristics of the raw powder method It is disadvantageous in terms of cost reduction and cost, and a rational solution to this problem is desired.

In addition, in Japanese Patent Application Laid-Open No. 1-159358, the wear resistance and fatigue strength of titanium members are improved by applying electroless plating to the surface of the titanium member, annealing it, and then subjecting it to shot peening. This is a treatment for a titanium member with a smooth surface, and cannot be applied to a sealing treatment for defects on the surface of a sintered body as in the present invention, and is essentially different from the present invention.

(Problems to be Solved by the Invention) In view of the above circumstances, the present invention applies the raw powder method to the production of sintered parts for automobile parts, marine or ship parts, shell structures, etc. The object of the present invention is to provide a method for manufacturing a high-density titanium alloy sintered part that has no surface irregularities or open pore defects and has excellent fatigue strength.

(Means and effects for solving the problems) In order to achieve the above objects, the present invention provides (1) a mixture of titanium powder and one or more metal powders so as to have a predetermined alloy component; The powder is filled into a mold and cold isostatically pressed to form a powder compact, which is then sintered.
A high-density titanium product characterized by performing a sealing treatment by applying Ni, Cu, Co, or Cr plating to a plating thickness of 10 mm or more on the surface of a titanium alloy sintered body obtained by hot isostatic pressing. A method for manufacturing alloy sintered parts, or (2) further at a temperature of 300°C or higher and 900°C.
The gist of the present invention is a method for manufacturing a high-density titanium alloy sintered part, which is characterized by annealing at the following temperature.

In the method of the present invention, a mixed powder that has been mechanically mixed in advance to have a predetermined alloy component is filled into a flexible mold made of rubber or the like, molded into a predetermined shape by CIP, and the powder molding is performed. The sintered body is sintered by heat-treating the body at high temperature and then HIP-treated, and has an uneven surface and locally open pores. Smooth the surface layer and close open pores.

Thereby, surface irregularities can be alleviated and open pores can be eliminated. This made it possible to significantly improve the unevenness and local open pore-like defects of the sintered body after HIP treatment, which had been a problem in the past.

Furthermore, by adding annealing treatment, the interface between the plating and the sintered body can be strengthened and the fatigue properties can be improved.

In the present invention, the metal powder refers to a single powder such as aluminum powder or an alloy powder such as V4oAI)6a.

The plating thickness was limited to 10m or more and 500m or less.
If the plating process is less than 10m, the sealing process will be insufficient.
In addition, plating over 500 m does not contribute to sealing and alleviation of surface irregularities, and also has the disadvantage of unnecessarily increasing the density of the sintered body.Furthermore, the annealing temperature is limited to 300°C or more and 900°C or less. This is because at temperatures below 300°C, diffusion of the plated metal is insufficient, and at temperatures above 900°C, embrittlement may occur at the interface.

Examples of the present invention are shown below.

Example 1 Two types of powder, the composition of which is 99.6% titanium
, titanium powder containing 0.09% oxygen and 0.0005% or less chlorine, and a master alloy powder for addition whose composition was 60% aluminum and 40% vanadium were prepared.

Then, according to the following steps, TI-6AI-4v
A sintered product consisting of the following was manufactured. First step: Titanium powder and additive master alloy powder were mechanically mixed at a weight ratio of 9:1. Second step: The mixed powder obtained in the first step was charged and filled into an elastic rubber mold having a predetermined shape. Third step: The filled powder was compacted by cold isostatic pressing. Fourth step: Press the powder compact into a vacuum degree of 10-4 to 1O-6.
sintering at about 1200°C. The relative density of the obtained sintered body was 95%. Fifth step: Approximately 900℃
Hot isostatic pressing was carried out at a temperature of . Sixth step: The surface of the sintered body was plated by a known electroplating method.

Table 1 shows the type of plating, the main bath composition, the average plating thickness, the sealing condition after plating, the relative density after HIP, and the fatigue strength of the finished product. The fatigue test conditions were axial force, stress ratio R-
-1, frequency f-20Hz, in the atmosphere, at room temperature.

As is clear from Table 1, Ni, Cu, and Co.

C: It can be seen that as a result of complete pore sealing in all cases, products with higher density, less surface irregularities, and improved fatigue strength are obtained compared to conventional manufacturing methods.

Example 2 Two types of powder, the composition of which is 99.6% titanium
, titanium powder containing 0.09% oxygen and 0.0005% or less chlorine, and a master alloy powder for addition having a composition of 80% aluminum and 40% palladium were prepared.

Then, a sintered product made of Tl-6A14v was manufactured according to the following steps. First step: Titanium powder and additive master alloy powder were mechanically mixed at a weight ratio of 9:1. Second Step The mixed powder obtained in the second step was charged and filled into an elastic rubber mold having a predetermined shape. Third step: The filled powder was compacted by cold isostatic pressing.

Fourth step: The green compact is heated to a vacuum degree of 10-' to 1O-6tor
r, and sintered at about 1200°C. The relative density of the obtained sintered body was 95%. Fifth step: Hot isostatic pressing was performed at a temperature of about 900°C. Sixth step: The surface of the sintered body was plated by a known electroplating method.

Seventh step: The plated sintered bodies were heat treated at the temperatures shown in Table 2 for 1 hour each. Table 2 shows the type of plating, main bath composition, average plating thickness, annealing temperature, relative density after HIP, and fatigue strength of the finished product. The fatigue test conditions are axial force, stress ratio R--1, frequency f-2011z, in the atmosphere, and room temperature.

As is clear from Table 2, N1. Cu, Co.

C: It can be seen that in both cases, the annealing treatment further improves the fatigue strength compared to Example 1.

(Effects of the Invention) As is clear from the above description, the present invention can easily eliminate surface irregularities and open pore-like defects, which are problems in the production of titanium alloy sintered parts using the raw powder method, without grinding. It is possible to obtain high-density titanium alloy parts that can withstand automotive parts and the like while maintaining the characteristics of the base powder method.

Claims (2)

[Claims] (1) A powder compact is produced by filling a mold with a mixed powder of titanium powder and one or more metal powders so as to have a predetermined alloy composition, and then cold isostatically pressing the powder. It is characterized by performing a sealing treatment by applying Ni, Cu, Co, or Cr plating to a plating thickness of 10 μm or more and 500 μm or less on the surface of a titanium alloy sintered body obtained by sintering and hot isostatic pressing. A method for manufacturing high-density titanium alloy sintered parts. (2) The method for manufacturing a high-density titanium alloy sintered part according to claim 1, wherein after the plating treatment, annealing is performed at a temperature of 300° C. or more and 900° C. or less.