CN108188390B

CN108188390B - Method for preparing pure tungsten metal part

Info

Publication number: CN108188390B
Application number: CN201810107384.5A
Authority: CN
Inventors: 安希忠; 贾倩; 王艳东; 李武发; 张光健; 付海涛; 杨晓红; 张�浩
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2018-02-02
Filing date: 2018-02-02
Publication date: 2020-01-10
Anticipated expiration: 2038-02-02
Also published as: CN108188390A

Abstract

The invention relates to a method for preparing pure tungsten metal parts, which adopts the method that tungsten powder with certain granularity is firstly vibrated to improve the initial relative density and then is molded and sintered at low temperature to prepare the ultrahigh pure metal parts with higher density by a high-temperature sintering method. The method has low energy consumption, and the prepared tungsten metal part is more compact and has higher performance.

Description

Method for preparing pure tungsten metal part

Technical Field

The invention relates to a method for preparing a pure tungsten metal part, and belongs to the technical field of metal processing and preparation.

Background

Tungsten is a refractory metal, has the characteristics of high melting point, high technology, high density, high thermal conductivity, high strength, low expansion coefficient, high corrosion resistance and the like, and is widely applied to the fields of aerospace, electronic information, energy, chemical industry, metallurgy, nuclear industry and the like. However, pure tungsten metal is difficult to densely form and has many defects after forming due to its disadvantages of high hardness, poor toughness and easy fracture.

From the existing method for preparing pure tungsten metal parts, the method for preparing the pure tungsten metal parts mostly adopts the method of adding a forming agent in powder metallurgy, carrying out unidirectional die pressing forming, degumming and then sintering, but because the adopted sintering temperature is high, such as high-temperature sintering at 2300 ℃, a large amount of energy and cost are wasted; the adopted one-way die pressing is directly carried out by loose packing and stacking, and the obtained pressed blank has small relative density and is easy to generate defects; in order to make the grain size of the pure tungsten part finer, as most methods use fine powder for pressing and sintering, the compactness of the pure tungsten metal is reduced, and the quality of the pure tungsten metal is reduced. In addition, the pure tungsten metal is prepared by sintering tungsten powder, so that a bottleneck is generated on how to obtain the high-density pure tungsten metal, and the current processing method is not broken through all the time.

Disclosure of Invention

Technical problem to be solved

In order to solve the above problems in the prior art, the present invention provides a method for preparing a tungsten metal part, which reduces energy consumption and cost waste, and improves the density of pure tungsten metal.

(II) technical scheme

In order to achieve the purpose, the invention adopts the main technical scheme that:

a method of making a tungsten metal part comprising the steps of:

s1, taking materials: weighing tungsten powder with the average particle size of 10-25 mu m, adding absolute ethyl alcohol, and uniformly mixing to enable the surface of the tungsten powder to be slightly wet;

s2, vibration: placing the tungsten powder obtained in the step S1 into a mould pressing mould and then vibrating;

s3, unidirectional die pressing: performing one-way die pressing on the die pressing die vibrated in the step S2, and then taking out the pressing block;

s4, sintering: sintering the pressing block in the step S3, introducing Ar gas for protection, heating to 80 ℃, keeping the temperature to remove absolute ethyl alcohol, and heating to 1600-1800 ℃ for sintering; to obtain pure tungsten metal parts.

In the method, in step S1, the absolute ethyl alcohol is preferably added in an amount of 0.4-0.7 ml per gram of tungsten powder.

In the above method, preferably, in step S2, the inner wall of the mold is coated with the zinc stearate lubricant, and then the tungsten powder is added.

And a zinc stearate lubricant is coated on the inner wall of the mould pressing mould to reduce the friction force between the tungsten powder and the mould wall, so that the pressed block is convenient to take out after pressing.

In the method, in step S2, the vibration amplitude is preferably 0.1-0.2 mm, and the vibration time is preferably 2-5 min after the frequency is 150-250 rad/S.

In the above method, preferably, in step S3, the unidirectional mold pressing pressure is increased to 400 to 500MPa per minute at 200MPa, and then the pressure is maintained for 2 to 10 min.

In the method, in step S4, the time for the 80 ℃ heat preservation is preferably 15-25 min, and the sintering time is preferably 1.5-3 h.

(III) advantageous effects

The invention has the beneficial effects that:

the method for preparing the tungsten metal part adopts vibration, so that the initial bulk density of tungsten powder can be improved, and the product is more compact; the sintering temperature is reduced by about 500-600 ℃ compared with the sintering temperature in the prior art by adopting lower sintering temperature, so that the energy consumption is greatly reduced, and the cost is reduced; the prepared product has low cost and high density, the relative density can reach 98.7 percent, is improved by 3.9 percent compared with the prior art, and can be used for preparing high-performance parts.

Drawings

FIG. 1 shows the results of the effect of tungsten powder having a particle size of 10 μm on the compacting process before and after vibration;

FIG. 2 is an end SEM image of a non-vibrated compact after pressing at a pressure of 480 MPa;

FIG. 3 is an SEM image of the end face of a green compact with vibration after pressing at a pressure of 480 MPa;

FIG. 4 shows the effect of particle size on relative density during compaction;

FIG. 5 shows the effect of particle size and sintering temperature on the density of sintered material.

Detailed Description

The invention mechanism of the invention is: the tungsten powder with the particle size of 10-25 mu m is adopted, so that intermolecular force among the tungsten powder can be reduced, and a more compact structure can be obtained; the vibration step is added, so that the initial bulk density of the tungsten powder can be improved, and the pressed blank and the sintered product or part are more compact; the sintering is carried out at the temperature of 1600 plus 1800 ℃, so that the strength of the pressed blank can be improved, and the residual stress of the pressed blank can be reduced. The method reduces the energy consumption required by the reaction, reduces the cost, and breaks through the difficult problem that the pure tungsten metal is prepared by sintering the tungsten powder and high-density pure tungsten metal is obtained.

For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.

Example 1

This example, which illustrates primarily the effect of applying vibration, was carried out using the following steps:

(1) taking 12 parts of tungsten powder with the mass of 10 mu m, adding the tungsten powder into the tungsten powder according to the amount of adding 5ml of absolute ethyl alcohol into each 10g of tungsten powder, and uniformly mixing to ensure that the surface of the tungsten powder is slightly wet;

(2) the above 12 parts of tungsten powder were mixed with anhydrous ethanol and then placed in cylindrical molds (mold diameter 20mm) each having an inner wall coated with a zinc stearate lubricant. Wherein 6 parts of the raw materials are directly pressed without applying vibration, 6 parts of the raw materials are pressed after applying vibration, and the vibration conditions are that the amplitude is adjusted to be 0.15mm, the frequency is 200rad/s, and then the raw materials are vibrated for 3 min; the vibration is carried out using a three-dimensional vibration apparatus, which is described in CN 102950789A. After measuring the height of the tungsten powder in the mold without applying vibration and after applying vibration using a scale, the relative density thereof at 0MPa was calculated. The calculation formula is as follows: rho-m/(pi r)²hρ₀). Where ρ is the relative density; m represents the weight of the powder; r-radius of the mold; h-height of powder in the mold; rho₀-density of the compact after compaction.

(3) And 6 parts of tungsten powder with vibration and without brake is applied, the pressing pressure during pressing is respectively increased to 80MPa, 160MPa, 240MPa, 320MPa, 400MPa and 480MPa at the pressure of 200MPa per minute and then is kept for 5min, then the density of each pressed blank is measured by adopting a drainage method, and the pressed piece with the pressing pressure of 480MPa is subjected to sample grinding and polishing and then is observed under a scanning electron microscope. The effect of the tungsten powder before and after vibration on the pressing process and the results of the relative density are shown in fig. 1, and SEM images of the end surfaces of the green compacts without vibration (fig. 2) and with vibration (fig. 3) after the pressing at a pressure of 480MPa are shown in fig. 2 and 3, which shows that the relative density of the green compacts can be effectively increased by applying vibration.

Example 2

A method of making a tungsten metal part, the present example illustrating primarily the effects of particle size and temperature, comprising the steps of:

(1) taking tungsten powder with the same mass and the granularity of 1 mu m, 10 mu m and 20 mu m respectively, adding absolute ethyl alcohol according to the amount of adding 5ml of absolute ethyl alcohol into every 10g of tungsten powder, and uniformly mixing to ensure that the surface of the tungsten powder is slightly wet;

(2) vibration: coating a zinc stearate lubricant on the inner wall of a mould pressing mould to reduce the friction force between tungsten powder and the mould wall, conveniently pressing, taking out a pressing block, putting the tungsten powder into the mould, putting the mould on a three-dimensional vibration table for fixing, adjusting the amplitude to be 0.2mm, vibrating for 5min after the frequency is 250rad/s, measuring the height of the tungsten powder in the mould by using a scale after vibrating, and calculating the relative density of the tungsten powder under the condition of no pressure;

(3) unidirectional die pressing: and (3) pressing after applying vibration, keeping the pressure for 5min after the pressing pressure is increased to 100MPa, 200MPa, 300MPa, 400MPa and 500MPa respectively at the pressure of 200MPa per minute during pressing, measuring the density of a pressed blank each time by adopting a drainage method, and observing the influence of the particle size on the pressing process.

(4) And (3) sintering: and (3) putting the 500MPa pressed blank into a sintering furnace, introducing argon gas into the sintering furnace for sintering, sampling once every 100 ℃, measuring the relative density, wherein the sintering temperature range is 25-2300 ℃, and the sintering time of each sample is 1.5h, and observing the influence of the particle size and the sintering temperature on the pure tungsten part. The results are shown in FIGS. 4 and 5. As can be seen from FIG. 4, higher relative densities can be obtained with compacts having a particle size of 20 μm.

As can be seen from fig. 5, when the firing temperature is 1500 ℃, the density is very high, and the larger the particles, the density increases with the increase of the particles. When 20 mu m particles are pressed and sintered, pure tungsten parts with the relative density of 98.6 percent can be obtained, while the relative densities of the pure tungsten parts obtained by tungsten powder with the relative density of 1 mu m and 10 mu m are 98.1 percent and 98.3 percent, and when the pure tungsten parts are sintered, the density is almost unchanged when the temperature is higher than 1700 ℃, so the temperature of 1700 ℃ is selected.

Example 3

(1) Taking materials: weighing tungsten powder with the average particle size of 20 mu m, adding 5ml of absolute ethyl alcohol into every 10g of tungsten powder) and uniformly mixing the tungsten powder and the absolute ethyl alcohol to ensure that the surface is slightly wet;

(2) vibration: coating a zinc stearate lubricant on the inner wall of a mould pressing mould to reduce the friction force between tungsten powder and the mould wall, conveniently pressing, taking out a pressing block, putting the tungsten powder into the mould, putting the mould on a three-dimensional vibration table for fixing, adjusting the amplitude to be 0.15mm, adjusting the frequency to be 200rad/s, and then vibrating for 3 min;

(3) unidirectional die pressing: after the vibration is finished, the die filled with the powder is placed under a press machine, the pressure of the press machine is increased to 500MPa at the pressure of 200MPa per minute, and the pressure is maintained for 5min and then the pressing block is taken out; wherein, 5min here means keeping for 5min under 500 MPa;

(4) and (3) sintering: putting the taken-out pressed block into a sintering furnace for sintering, introducing Ar gas into the sintering furnace for protection, heating to 80 ℃, preserving heat for 20min to remove absolute ethyl alcohol, heating to 1700 ℃, and preserving heat for 2 h; thus obtaining the pure tungsten metal part. The relative density was found to be 98.7%.

Comparative example

With the prior art, in particular,

(1) taking materials: weighing tungsten powder with the average particle size of 1 mu m, weighing kerosene-rubber forming agent accounting for 8 percent of the mass of the tungsten powder, and uniformly mixing the tungsten powder and the forming agent;

(2) unidirectional die pressing: coating a zinc stearate lubricant on the inner wall of a mould pressing die to reduce the friction force between tungsten powder and the wall of the die, conveniently pressing, taking out a pressing block, putting the uniformly mixed powder into the die, putting the die under a press machine, increasing the pressure of the press machine to 500MPa at the pressure of 200MPa per minute, maintaining the pressure for 5min, and taking out the pressing block;

(4) and (3) sintering: putting the taken-out pressed block into a sintering furnace for sintering, introducing Ar gas into the sintering furnace for protection, heating to 800 ℃ firstly, preserving heat for 1h for degumming treatment, and then heating to 2300 ℃ for preserving heat for 2 h; thus obtaining the pure tungsten metal part. The relative density was found to be 94.8%.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art can change or modify the technical content disclosed above into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims

1. A method of making a tungsten metal part, comprising the steps of:

s1, taking materials: weighing tungsten powder with the average particle size of 20-25 mu m, adding absolute ethyl alcohol, and uniformly mixing to enable the surface of the tungsten powder to be slightly wet;

s4, sintering: sintering the pressed block in the step S3, introducing Ar gas for protection, heating to 80 ℃, keeping the temperature to remove the absolute ethyl alcohol, and heating to 1600-1700 ℃ for sintering; to obtain pure tungsten metal parts;

in step S2, after the amplitude of the vibration is 0.1-0.2 mm and the frequency is 150-250 rad/S, the vibration time is 2-5 min;

in step S3, after the pressure of the unidirectional mould pressing force 200MPa per minute is increased to 400-500 MPa, the pressure is maintained for 2-10 min;

in step S4, the heat preservation time at 80 ℃ is 15-25 min, and the sintering time is 1-2 h.

2. The method of claim 1, wherein in step S1, the absolute ethyl alcohol is added in an amount of 0.5ml per gram of tungsten powder.

3. The method of claim 1, wherein in step S2, the inner wall of the mold is coated with zinc stearate lubricant and then tungsten powder is added.