JPS62196306A - Manufacturing method of multi-layer tungsten alloy - 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 <Industrial Field of Application> The present invention relates to a method for producing a tungsten alloy having high ductility and suitable for making cryle, mandrel, etc., which require particularly high-impact work.

Conventional technology and problems〉 Conventionally, tungsten alloys using nickel or iron as binders
Utilizing its high specific gravity, it was used for weights for automatic watches, shielding materials, balancers, etc., but in recent years, the high specific gravity of this material,
Attempts have been made to achieve high strength and use it in cryle, mandrel, etc. that are subject to impact loads. By increasing the specific gravity of the alloy, it is possible to increase its rigidity, but on the other hand, there is a problem in that its ductility decreases.

In view of this problem, the present inventors previously invented a method for manufacturing a tungsten alloy having high ductility. That is, W
A mixed powder consisting of 85% to 97% powder and the balance being Ni and Fe powder is 1 to 4 ton/c + n'
The powder is compacted under 0 water pressure, and then the compact is heated to 0--60'C.
It is possible to produce a highly ductile tungsten alloy by liquid-phase sintering in a hydrogen stream, followed by heat treatment in which the sintered body is heated in a vacuum and then cooled. Met.

Techniques for solving the Kumagari point El> Subsequent research revealed that as a method to increase the ductility of alloys,
It has been found that by varying the properties of the outer and core parts of the alloy, its performance is further improved compared to that produced by the method described above.

That is, when manufacturing tungsten alloy, outside Il!
The composition of 11 parts is a mixed powder consisting of W powder of 93 to 97% in w amount ratio and the balance of Ni and Fe powder, and
The composition of the core is W powder 85-91% and the balance is Ni and F.
A mixed powder consisting of powder e, which is filled with the above-mentioned mixed powder in the outer part and the core part without mixing with each other at the time of powder filling, and then compacted under zero water pressure of 1 to 4 ton/cfi2, and then The green compact is liquid-phase sintered in a hydrogen stream at 0 to -60°C, and then the sintered body is heated in a vacuum and then 2) cooled. Furthermore, by subjecting the heat-treated body to sueno processing at a processing rate of 5 to 20%, a two-layer tungsten alloy in which the core part is more ductile than the outer part is obtained. It consists of

Next, the (1η formation and effects of the present invention) are as follows.

W, Ni, and Fe powders are used as raw material powders, but in order to maintain the desired specific gravity, Wfi should be 9325 or more in the outer part and W)t should be 85 in the core part.
% or more, but in order to maintain the desired elongation, it is necessary that W @ be less than 97% in the outer part and less than 91!6 in the core part. N
I and Fe are added for the purpose of generating phase formation during sintering, promoting densification, and increasing the ductility of the material.If the content is less than 3% in the outer part, the above effect cannot be achieved. Zu7
If it exceeds 3 to 7%, the desired specific gravity may not be obtained.
If the core part is limited to 9%, the desired elongation cannot be ensured, and if it exceeds 15%, the desired specific gravity cannot be obtained, so each content was limited to 9 to 15%. Regarding the quantitative relationship between Ni and Fe, it is desirable for Fe to account for about 20 to 50% of the entire binder phase, and the reason for this is that within this range, N
This is because the melting point is sufficiently lower than that of i and Fe alone, and effective liquid phase sintering becomes possible.

The particle size of each powder is desirably about 1-10 μm based on the considerations of moldability, sinterability, and ductility of the material.

Further, since liquid phase sintering is possible even when using an alloy powder of N1 and Fe, the same effect as when using a powder of spores can be obtained.

Next, after mixing the above powder, 1 to 4 tons/
It compresses and moves under the hydrostatic pressure of c + n 2.

At a pressure of 1 ton/eta2 or less, 2 to 3% of pores remain even after liquid phase sintering, resulting in a decrease in ductility.

At pressures exceeding 4 ton/c I*2,
The density of the compact is so high that most of the pores become so-called closed bores during the 51-temperature process at 11 o'clock in the firing process.
Reduction and impurity removal by hydrogen cannot be performed effectively. In addition, in order to increase the homogeneity of the material and therefore increase its ductility, it is necessary to perform arithmetic compression instead of the usual uniaxial compression, and the powder is compressed by arithmetic compression at a rate of 1 to 4 tons/C162. I decided to do so.

Next, the green compact is sintered in an aqueous air stream, but the most important point at this time is to maintain the hydrogen dew point between 0 and -60'. This is because the presence of impurities such as oxides at W grain boundaries or W-matrix grain boundaries will impair ductility after liquid phase sintering. not in a hydrogen atmosphere of
The green compact is placed in a hydrogen atmosphere with an extremely low dew point of 0 to -60°C, and the ductility of the material is increased by sufficient reduction and removal of impurities during the sintering process, which involves raising the temperature by about 36°C. This is possible. The above effect is not sufficient in an atmosphere with a dew point higher than 0°C, and the degree of the effect does not improve even if the atmosphere is maintained at 7F in the furnace below -60°C, so the dew point of hydrogen in the sintering furnace is 0 to -GOoC. Of course, in order to keep the hydrogen dew point at the outlet of the sintering furnace within this range, the hydrogen dew point at the inlet must be kept even lower, for example below -70°C, and the furnace material and pressure must be maintained even lower. Naturally, it is necessary to appropriately select the infiltrated hydrogen position, taking into account the amount of powder, the shape of the furnace, etc.

In order to obtain a highly ductile material, sintering is necessary at a temperature at which Ni and Fe at least form a liquid phase and for a time necessary for sufficient alloying and densification to occur. requires a temperature of at least 1450°C or more and a time of at least 30 minutes.

Next, in order to impart desired ductility, it is necessary to further heat-treat the obtained sintered body. If there is a large amount of dissolved hydrogen in the sintered body, it will reduce the ductility of the material, so in order to remove this, the sintered body is placed in a vacuum at a temperature of 700~
It is necessary to heat and hold at a temperature of 1400° C. for 2 to 10 hours, and then 2) cool it down. Cooling the epithelium should be at least 40°C/min up to at least 300°C.

This advanced heat treatment not only reduces the amount of hydrogen in the material as described above, but also prevents the formation of trace amounts of precipitates at grain boundaries and within the material, and also prevents supersaturation in the binder phase. It is considered that ductility can be increased by preventing precipitation of W fixed in the steel.

Next, regarding the ratio of the outer part to the core, as the outer part increases, the specific gravity becomes higher, and on the other hand, as the core part increases, the material becomes more ductile, but there are restrictions on powder filling. From, outer part: core part is 8:
The limit is 2 to 2:8, preferably outer part: core = 6
:4 to 4:6 ratio.

As described above, by combining the raw materials, molding, sintering, heat treatment II, and other processes as in the present invention, and by combining the compositions of the inner and outer alloys as in the present invention, conventional tungsten This makes it possible to obtain a significant improvement in ductility compared to alloys.

On the other hand, for wills and mandrels, it is possible to increase the penetration force by improving the hardness of the outer part, and the most effective method for this is swaning.
As a result of various studies, it was confirmed that in order to improve the hardness of the outer part, if the processing rate is less than 5%, it is not very effective, and if it exceeds 20%, the core part will harden and the alloy will deteriorate. Since the ductility decreases, the processing rate of swaging is 5.
~20% is appropriate.

Hereinafter, the effects of the present invention will be illustrated by examples.

Example 1 W, Ni and Fe powders with average particle sizes of 5.5, 5.0 and 6.2 microns, respectively, were made into 95% W-3
゜5%Hi -1,5%Fe
This, the other one is 88%W-8.4%Ni-3.6%F
B was prepared by adding an appropriate amount of acetone and mixing in a bot mill for 72 hours to prepare a mixed powder. After filling two layers of this mixed powder, Δ powder on the outside of the rubber and B powder on the core of the rubber, without mixing, they were molded in a rubber press and sintered in hydrogen gas at 1470°C for 90 minutes. Then, heat treatment was performed at 1250° C. for 6 hours in a vacuum, and after cooling, the tensile strength and elongation of the material were measured for each of the outer part and the core part.

Experiments Nos. 1 to 4 were produced under the conditions of the chemical compound claimed in the patent, and it can be seen that materials with excellent ductility were obtained.

Experiments Nos. 5 to 9 were manufactured under conditions outside the scope of the claims, and the mechanical properties (especially elongation) deteriorated for the following reasons.

That is, the molding pressure for N014 was too low, and a sufficiently densified material could not be obtained by sintering. In the case of N096, the molding pressure was too high, and most of the pores became closed bores during the external temperature process of sintering, and the W powder surface was not sufficiently reduced and impurities were not removed by hydrogen gas.

In N017 and 8, the dew point of sintering ■, 7 is too high, W
Reduction of the powder surface and removal of impurities were not sufficient.

In No. 9, because the cooling rate after the vacuum heat treatment was slow, the supersaturated solid solution of Wv in the binder phase became a compound with Ni and Fe, and precipitated at the interface between the binder phase and the W particles. There was not enough growth. Fig. 1 shows the metallographic structure (a) of the outer part and the metallographic structure (1'') of the core part of 9N0.2. Core metal K1. fi < l)), it can be seen that the area ratio of the binder phase is higher than that in the outer part.

Based on the product of the present invention, a cryle for internal grinding was manufactured and a performance test was conducted, and it was found that the amplitude of the tool tip was 20 to 30% smaller with the product of the present invention compared to a single-layer product with the same density. As a result, more precise grinding has become possible.

-Top- Example 2 The tensile strength of the material after the heat-treated body of Experiment N002 of Example 1 was subjected to swanong processing at various processing rates,
Table 2 shows the elongation and V hardness.

Experiment No. 2-1 is a heat-treated body, and No. 2-2 to 2
-5 is one in which the processing rate was changed from 3 to 25%.

No. 012-2 has insufficient hardness in the outer part, while No. 2-3 and 2-4 have a slightly increased hardness in the outer part and exhibit high ductility in the core part. ζ), No. 2-5 is 1. due to the processing rate being too high. It can be seen that the core has become brittle.

Based on the present invention, a cryle for internal grinding was manufactured and a performance test was conducted, and it was found that the product of the present invention was able to perform sue song processing at the same density and processing rate! Compared to the It 1'4 product, the amplitude of the tool cutting edge is 10 to 20% smaller,
As a result, more precise grinding has become possible.

Table 2

[Brief explanation of drawings]

Figure 1 shows the metal structure of the alloy produced by the method of the present invention (
It is a figure showing magnification (100 times).

Claims (2)

[Claims] (1) When producing a tungsten alloy, the outer part is made of powder with a composition of 93 to 97% W powder and the balance is Ni and Fe, and the core part is made of W powder of 85 to 91% by weight.
% and the balance consists of Ni and Fe,
After filling the outside part and the core part with the above powders without substantially mixing them when filling the powder into the mold, 1-
The powder is compacted under a hydrostatic pressure of 4 ton/cm^2, then the compact is liquid-phase sintered in a hydrogen stream at 0 to -60°C, and then the sintered body is heated in a vacuum and then rapidly cooled. A method for producing a tungsten alloy in which the core portion is more ductile than the outer portion, the method comprising applying heat treatment. (2) A method for manufacturing a tungsten alloy in which the core part is more ductile than the outer part, characterized by subjecting the heat-treated body obtained in claim (1) to swaging processing at a processing rate of 5 to 20%. .