JPH02122048A - Sintered tungsten alloy having high ductility at low temperature - Google Patents

Abstract

PURPOSE:To obtain a high-density sintered W alloy having high ductility at low temp. by specifying a composition consisting of W with a specific grain size as a principal component and the balance Ni and Fe and also specifying the compositional relations among the above components. CONSTITUTION:In a sintered W alloy having a composition consisting of, by weight, 85-97% W with <40mum grain size and the balance Ni and Fe, the quantitative relations among the above components are regulated so that they satisfy an inequality 5/6X-20<=100Y/(Y+Z)<=-5/12X+115 (where X, Y, and Z represent W, Ni, and Z contents(wt.%)), respectively. By this method, the sintered W alloy, in which Ni and Fe are rapidly infiltrated through the W grains at the time of sintering and act as binder and sufficient ductility is provided even at low temp. while maintaining prescribed high density, can be obtained. By using this alloy, projectiles, high-speed rotors, etc., free from fracture even it used in a cold district can be formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a tungsten sintered alloy that has high ductility at low temperatures and is useful for high-speed rotating bodies used in cold regions or projectiles that penetrate protective objects. Regarding.

[Conventional technology]

A high-speed rotating body must have high tensile strength and Young's modulus, and must also have sufficient toughness so as not to break during high-speed rotation. Additionally, the projectile must have a high degree of tensile strength, density, and hardness, as well as sufficient ductility and toughness so that the projectile does not break before completely penetrating the protective material. .

In order to meet these demands, a tungsten alloy with high specific gravity and high ductility is disclosed in Japanese Patent Application Laid-Open No. 185843/1983. This stuff is tungsten powder 85-97%
and the balance is nickel and iron powder.
The powder is compacted under a hydrostatic pressure of ~4 ton/c4, and the resulting compact is liquid-phase sintered in a hydrogen stream.The sintered compact is heated in a vacuum and then rapidly cooled. It is a manufactured tungsten alloy.

By applying heating, rapid, and cold heat treatment in a vacuum after the above sintering, excessive hydrogen solidly dissolved in the sintered body can be removed, and grain boundary precipitation of impurities that can cause embrittlement can be prevented. It is said that high ductility can be obtained.

[Problem to be solved by the invention]

When the above-mentioned conventional tungsten alloy high-speed rotating bodies and projectiles that penetrate protective objects are used in cold regions,
Naturally, a sufficiently high degree of ductility, toughness, tensile strength, etc. is required even under cold temperatures.

However, even if conventional tungsten alloys have sufficient ductility at room temperature, they do not have sufficient ductility at temperatures as low as -40°C, and may break during high-speed rotation or when penetrating protective objects. There was a problem that the

Therefore, the present invention has been made by focusing on the above-mentioned conventional problems, and its purpose is to provide a tungsten alloy that has sufficient ductility even at low temperatures, and to provide a tungsten alloy that can be used in projectiles used in cold regions. The purpose of this invention is to enable the manufacture of high-speed rotating bodies.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a low-temperature method comprising 85 to 97% by weight of tungsten with a particle size of less than 40 μm, the balance being nickel and iron, and the quantitative relationship of each component is expressed by the following formula: It is a tungsten sintered alloy with high ductility.

However, X: Tungsten content (wt%) Y: Nickel content (wt%) Z: Iron content (wt%) A more detailed explanation will be given below.

The present invention was made by focusing on the fact that the quantitative relationship between the components of a W-Ni-Fe sintered alloy and the size of tungsten grains in the alloy affect the ductility of the alloy at low temperatures. It is something that

The composition of the W-Ni-Fe based sintered alloy of the present invention is 85 to 97% by weight of tungsten, and the balance is nickel and iron. Higher specific gravity can be obtained by increasing the weight percentage of tungsten. The tungsten content of the present invention is required to be 85% by weight or more in order to maintain a predetermined high density. 8
Below 5 weights, deformation of the alloy occurs during liquid phase sintering. On the other hand, if the tungsten content exceeds 97%, the binder phase consisting of nickel-iron decreases, making it impossible to obtain the desired toughness.

As the tungsten content increases, it is necessary to rapidly fill the tungsten grain boundaries with a binder of uniform composition during sintering, and it is necessary to increase the fluidity of the nickel-iron sintered phase that is the binder.

The inventors of the present invention conducted research by examining liquidus lines and solidus lines for various alloy compositions while taking these points into consideration. As a result, when the relationship (1) 2 above holds between the tungsten temperature χ, the nickel content Y, and the iron content Z, the liquidus and solidus temperatures are the lowest, and the solid-liquid It was found that the region of coexisting phases became narrower.

This shows that when sintering is performed, nickel and iron quickly penetrate between the tungsten grains and act as a binder.

Moreover, since this nickel-iron phase is uniform, it contributes to low-temperature ductility.

The grain size of tungsten changes depending on the temperature and time during sintering, and the tungsten grains grow as the sintering time progresses.

Coarse porosity is likely to occur as the tungsten grains grow. This coarse porosity has a particularly negative effect on low temperature ductility. Therefore, it is necessary for the tungsten grains to have a grain size of less than 40 μm.

Although the method for producing the sintered alloy of the present invention is not particularly limited, it can be produced by the following method.

Namely, first of all, high strength tungsten and nickel.

A mixture of raw iron powders is compression molded under hydrostatic pressure.

The pressing force is preferably about 1 to 4 tons/c+a. When molding is performed at less than l ton /ci, the density of the compression molded product is too small, and even if liquid phase sintering is performed,
% of pores remain, complete densification is not possible, and ductility is reduced. On the other hand, when molding exceeds 4 ton/c+fl, the density becomes too high and closed bores occur in the compression molded product, making it difficult to achieve complete densification.

If hydrostatic pressure is used instead of the usual uniaxial compression during pressurization, the homogeneity of the alloy can be improved by applying pressure evenly from all sides, and the ductility can be improved.

The liquid phase sintering is preferably performed in hydrogen at a temperature of 1430° C. or higher, which is the temperature at which the nickel and iron components form a liquid phase.

The sintering time requires a time necessary for complete densification, that is, 20 minutes or more, and is preferably 60 minutes or less in order to prevent coarse porosity from occurring during sintering.

According to the present invention, in a W-Ni-F based sintered alloy, high ductility can be imparted at low temperatures by setting the component ratio of tungsten, nickel, and iron to a range that satisfies the relationship of equation (1) above. was completed.

〔Example〕

The present invention will be explained in detail below.

Tungsten powder, nickel powder, and iron powder were blended into various compositions and mixed using a ■ type mixer. 2 of the obtained mixed powder
Compression molding was performed under hydrostatic pressure of ton/cffl, and the molded body was liquid-phase sintered at 1530°C in hydrogen. By varying the sintering time, sintered bodies with various tungsten particle sizes were obtained. Subsequently, the sintered body was heat treated in vacuum at 1200°C for 2 hours, and then machined into a tensile test piece.

This tensile test piece was subjected to a tensile test at a low temperature of -40'C.

Table 1 shows the component composition, tungsten particle size, and tensile test results of each test piece.

From Table 1, it can be seen that tungsten sintered alloys whose component composition ratios and tungsten particle diameters are within the ranges of this example exhibit superior low-temperature ductility than those outside the ranges.

However, * is 10Z Those that satisfied the following were marked as O1, and those that did not satisfy were marked as ×.

(Effects of the Invention) As explained above, according to the present invention, the particle size is 40 μm.
The quantitative relationship between each component is as follows: χ: Tungsten content (wt%) Y: Nickel content (wt%) Z: Iron content It was expressed as the amount (% by weight). Therefore, the ductility of the tungsten sintered alloy at low temperatures can be significantly increased, and there is an effect that excellent projectiles and high-speed rotating bodies that can be used in cold regions can be obtained.

Claims (1)

[Claims] (1) A tungsten sintered bond with high ductility at low temperatures, consisting of 85 to 97% by weight of tungsten with a particle size of less than 40 μm, the balance being nickel and iron, and the quantitative relationship of each component is expressed by the following formula: Money. (5/6)X-20≦100[Y/(Y+Z)]≦-(
5/12) X+115 However, X: Tungsten content (wt%) Y: Nickel content (wt%) Z: Iron content (wt%)