JPS61213338A - W-ni-fe sintered alloy - Google Patents

Abstract

PURPOSE:To provide high tensile strength, hardness and sufficient toughness, by specifying wt. ratio of Ni to Fe, particle diameter of W, solid soln. quantities of Ni and Fe in W particle and regulating contents of oxygen and carbon in sintered alloy. CONSTITUTION:In sintered alloy composed of 85-98wt% W and the balance Ni and Fe, particle diameter of W is regulated to 40-100mum, and >=0.1wt% Ni and >=0.2% Fe are dissolved into W particle in solid state. Oxygen and carbon contents are regulated to <=0.05%, and <=0.005% respectively in sintered alloy. Oxygen and carbon quantities are decreased by roasting powder mixture having said compsn. in oxidizing atmosphere, then reducing said mixture in reducing atmosphere, etc. By regulating W particle diameter, Ni, Fe are dissolved by suitable quantities into W particle after sintering, and toughness of alloy is improved. The W-Ni-Fe sintered alloy is useful to projectile (piercing body) piercing protector, high speed revolving body, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a high toughness W--Ni--Fe sintered alloy. The alloy according to the invention can be used for projectiles (
It is suitable for use on penetrating objects) and high-speed rotating objects (tiles, etc.).

(0) Prior art and its problems The penetrating body has high tensile strength, density and hardness,
Moreover, it is generally accepted in the art that it must have sufficient toughness so that the projectile does not break before complete penetration. In addition, as a high-speed rotating body, it must have high tensile strength and Young's modulus, and must also have sufficient toughness so as not to break during high-speed rotation.

Conventionally, W-Cu-Nt 1 has been used for such applications.
W--Cu--Fe alloys have been used as projectiles and high-speed rotating bodies, but they only elongate by 0.5 to 2%, making them susceptible to impact fracture. There was a desire to develop a material with higher toughness and greater elongation while maintaining high density and hardness.

(C) Description of the Invention The present invention provides a W--Ni--Fe sintered alloy that has high tensile strength and hardness, and also has sufficient toughness.

That is, the present invention uses W85 to 98 weight percent and weight Ni and F.
e (Ni:Fe weight ratio of 5:5 to 8:2), the tungsten grain size is 40-100 μm, and the tungsten particles contain 0.1% by weight or more of nickel and 0% iron. This is a W-Ni-Fe sintered alloy in which the amount of oxygen in the sintered alloy is 0.05% by weight or less and the amount of carbon is 0.005% by weight or less.

The alloy according to the present invention will be described in detail below.

The alloy composition is 85-98% by weight of tungsten, the rest is nickel and iron, and the Nr:Fe weight ratio is 5:5-8.
=2 range. If the tungsten content is less than 85% by weight, the alloy will deform during liquid phase sintering, and if it is more than 98% by weight, Ni-Fe! This is because the amount of the hardening phase decreases, making it impossible to obtain the desired toughness. Toughness is maximized when the Ni:Fe ratio is 2:1, but a predetermined toughness can be ensured if it is in the range of 5:5 to 8:2. In order to achieve sufficient toughness in these alloy compositions, we conducted various analyzes of impurities, tungsten grain size, and alloy structure, and found that the oxygen in the alloy, carbon content, tungsten grain size, and the content of tungsten grains in the sintered body were It was discovered that iron and nickel content greatly affect toughness. Oxygen and carbon in the alloy form a solid solution in the binder phase and tungsten phase, reducing toughness and forming blisters or pores in the alloy during sintering. This is C+ 1/20. = Go or C+ O, =
This seems to be because gas is generated by the reaction of Cot. If the oxygen content and carbon content are 0.05% by weight or less and 0.005% by weight or less, respectively, blistering and pore formation of the alloy due to the above reaction will not occur (toughness will also be reduced.Ordinary tungsten powder, Iron powder, nickel powder, especially nickel and iron powder contain oxygen and carbon as impurities. For example, nickel and iron made by the carbonyl method,
It contains 0.1% by weight of carbon and 0.07% by weight of oxygen. For this reason, when these powders are mixed to make an embossed sintered body, the density decreases as the sintering time increases due to gas reactions, and in extreme cases, foaming occurs, making it impossible to create an alloy. oxygen,
Carbon reduction is practically achieved by the following method.

That is, powders mixed at a predetermined ratio are roasted in an oxidizing atmosphere at 400 to 800°C. In this step, the powder is oxidized, and the raw materials and carbon introduced during mixing are oxidized and removed. These roasted powders are reduced in a reducing atmosphere at 400 to 800°C. In this step, the amount of oxygen is reduced and a portion of the carbon contained therein is also removed. Another method is to separately prepare two powders of nickel, iron, and tungsten.
Roast in an oxidizing atmosphere at 00-500°C. These roasted powders are reduced in a reducing atmosphere at 400 to 800°C.

Oxygen and carbon can also be reduced by weighing and mixing the powders subjected to these treatments in a predetermined proportion. The sintered body has a two-phase alloy structure consisting of a binder phase and tungsten particles, and the tungsten particle size is 4.
O-100 μm has excellent toughness. As the tungsten particle size increases, the elongation of the alloy improves, and the impact value increases up to a tungsten particle size of about 100 μm, and tends to decrease as the tungsten particle size increases beyond that.

Therefore, the tungsten particle size ranges from 40 to 100 μm, and the impact value is excellent. Tungsten particle size varies depending on temperature, time, and shape during sintering.

For example, in the case of a round bar with a diameter of 45mm, the tungsten particle size will become 40 to 100μ in 30 to 40 hours at a temperature of 1460℃.
It becomes m. In addition, in the case of a round bar with a diameter of 18m + m, 4~
It becomes 40-100 μm in 7 hours. The Nrs Fe content in the tungsten grains after sintering is effective in improving toughness, and it is necessary that the Nrs Fe content be 0.1% by weight or more and 0.2% by weight or more in solid solution, respectively. If the amount of solid solution is small, the toughness will decrease significantly even if the tungsten particle size is 40-100 μm, and the sintered body will be rapidly sintered at a temperature of 500°C/hour or more from a sintering temperature of 20 to [iθ°C higher than a small amount. This can be achieved by cooling. In other words, the present invention is possible by leaving the amount of iron and nickel dissolved in the tungsten particles as they are in the tungsten particles at the sintering temperature, and when slowly cooling, the iron and nickel dissolved in the solid solution are removed. precipitates, making it impossible to obtain a material with high toughness.

Within the range of the alloy composition detailed above, ■ the grain size of tungsten is set to 40 to 100 μm; ■ the amount of oxygen and carbon is each 0.05% by weight, and the amount of O and GO is 5% by weight or less; ■ the solidification of nickel and iron in the tungsten grains; Each dissolved amount is 0.1% by weight or more,
By containing 0.2% by weight or more, a stable high-toughness alloy with an elongation of 20% or more can be achieved. This high-density, high-toughness alloy is useful for applications such as high-speed rotating bodies. In some cases, it may be desirable to further cold-work the alloy in order to improve the hardness of the penetrating body through work hardening. Forging and swaging are effective cold working methods.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example ! Tungsten 191 kg 1 Nickel 8 kg s Iron 3
kg was sieved to remove large aggregates, and mixed in an attritor for 5 hours using alcohol as a solvent. The particle size of the mixed powder after removing the alcohol by vacuum drying is an average particle size of 2.
It was 1 μm. Further, the amount of carbon was o, oos% by weight. This mixed powder was roasted at 500°C in the air. The carbon content was 0.004% by weight. It was further reduced in hydrogen at 800°C. The amount of carbon was 0.001% by weight, and the amount of oxygen was 0.03% by weight. Due to static pressure molding, the diameter is 0-
The treated powder was filled into 15 rubber bags each having a length of 700 mm. After that, put it in a pressure vessel, 0, l Ton
Pressurizes at a speed of 1 inch/1 inch, maximum 1,57 on
and held for 10 minutes. After that, NO, 2Ton/w
The pressure was removed at a speed of 1.5 in. and the embossed body was taken out from the bag. After lathe-machining the stamped body to a diameter of 60mm, it was placed in a hydrogen sintering furnace and sintered at 350°C for 1 hour. The density of the obtained intermediate sintered body was 18.1, which was 39.1% of the theoretical density.

This sintered body was further sintered for 14 hours in a hydrogen atmosphere at 0°C, and then heated from 1460°C to room temperature for 1 hour, 2 hours, and 3 hours.
The mixture was cooled for 4 hours, 10 hours. The dimensions after liquid phase sintering were a diameter of 47 mm and a length of 510 seconds. The average grain size of tungsten, whose microstructure photograph is shown in FIG. 1, was 60 μm.

Example 2 194 kg of tungsten, 4 kg of nickel, 2 kg of iron
The mixture was sieved and mixed in an attritor in the same manner as in Example 1. The average particle size of the mixed powder was 2.1 μm.

Carbon m was o, oto% by weight. 500 ml of this powder
It was roasted in the atmosphere at 800°C and further reduced in hydrogen at 800°C. The carbon content was 0.003% and the oxygen content was 0.02%.

Static pressure molding was carried out under the same conditions as Example 1, and this was made into a diameter of 80 m.
Lathe machined to m. The molded body was pre-sintered under the same conditions as in Example 1. What is the density of the sintered body? The density was 8.3, which was 98.9% of the theoretical density. This product was placed in a hydrogen atmosphere furnace at 146 O and sintered for 32 hours in the same manner as in Example 1.

This sintered body was cooled from 141% 0° C. to room temperature over 1 hour, 2 hours, 3 hours, 4 hours, and 10 hours.

The grain size of tungsten in the sintered body was 52 μm.

Example 3 The alloys produced in Examples 1 and 2 were embedded in resin, and after polishing, the amount of N ilFe in the tungsten grains was point-analyzed using an X-ray microanalyzer and quantitatively analyzed by comparison with a separately determined calibration curve. . In addition, tensile test pieces from the sintered body,
Impact test pieces were cut and their properties were evaluated.

Table 1 shows the results. Tensile properties AST shape
ME 8-79Fig18,! = L, crosshead speed 0.2 cm/n gauge length 25 m. In the impact test, a JIS 222023 test piece was used to determine the impact value.

Table 1 Example 4 The alloy prepared in Example 1 at a cooling rate of 1440° C./hour was subjected to cold working by swaging. The area reduction rate was 8.23.42%. A tensile test piece was prepared for the obtained round bar in the same manner as in Example 3, and a tensile test was conducted under the same conditions to evaluate the tensile strength and elongation.

Further, the end face of the cold-worked bar was measured at 5 points using a Rockwell hardness meter to determine the hardness. The results are shown in Table 2. The structure of an alloy with a reduction in area of 42% is shown in Figure 5I2. The W grains are deformed by cold working, and the tensile strength and hardness are increased by work hardening.

Table 2

[Brief explanation of drawings]

FIG. 1 is a 150 times magnified micrograph of the alloy of Example 1 of the present invention, and FIG. 2 is a tSO times magnified micrograph of another example alloy. Part 1, Figure 2

Claims (2)

[Claims] (1) Consisting of 85 to 98% by weight of tungsten and the balance being nickel and iron, with a weight ratio of nickel and iron of 5:5 to 8.
: In the sintered alloy having the composition of 2, the grain size of tungsten is 40 to 100 μm, and 0.1% or more of nickel and 0.2% or more of iron are dissolved in solid solution in the tungsten grains. , and the amount of oxygen in the sintered alloy is 0.05% by weight or less, and the amount of carbon is 0.005% by weight or less. (2) Oxygen content is 0.05% by weight or less, carbon content is 0.00%
The W-Ni-Fe sintered alloy according to claim 1, characterized in that the W-Ni-Fe sintered alloy is made from powders of tungsten, nickel, and iron containing 5% by weight or less.