CN110453166B - Preparation method for improving plasticity of pure molybdenum block - Google Patents

Preparation method for improving plasticity of pure molybdenum block Download PDF

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CN110453166B
CN110453166B CN201910874706.3A CN201910874706A CN110453166B CN 110453166 B CN110453166 B CN 110453166B CN 201910874706 A CN201910874706 A CN 201910874706A CN 110453166 B CN110453166 B CN 110453166B
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forging
molybdenum
preparation
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plasticity
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CN110453166A (en
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蒋香草
宋久鹏
颜彬游
代少伟
李文彬
陈帅
宋平
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Nanjing University of Science and Technology
Xiamen Tungsten Co Ltd
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Nanjing University of Science and Technology
Xiamen Tungsten Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/17—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by forging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/248—Thermal after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Abstract

The invention discloses a preparation method for improving the plasticity of a pure molybdenum block, wherein the content of molybdenum in the pure molybdenum block is more than 99.95 wt%, and the preparation method of the pure molybdenum block comprises the following steps: selecting molybdenum powder with the purity of more than 99.9 wt% as a raw material; pressing the molybdenum powder to prepare a green body; sintering the green body to prepare a sintered body, wherein the relative density of the sintered body is 94.5% -98%; forging and vacuum heat treating the sintered compact; the oxygen content of the molybdenum powder is below 500ppm, the Fisher-Tropsch particle size of the molybdenum powder is 1.7-3.5 mu m, and the apparent density of the molybdenum powder is 0.75g/cm3‑3.0g/cm3. According to the method, the plasticity of the prepared pure molybdenum block is obviously improved by controlling the performance of the raw materials and combining with process adjustment, and the plastic ductility reaches the level of molybdenum alloy.

Description

Preparation method for improving plasticity of pure molybdenum block
Technical Field
The invention relates to the field of preparation of refractory metal materials, in particular to a preparation method for improving the plasticity of a pure molybdenum block material.
Background
Molybdenum has high melting point, high strength, high thermal shock resistance, strong corrosion resistance and good heat conduction and electric conductivity, so that the molybdenum is widely applied to the fields of aerospace industry, electronic industry, chemical industry and the like, but no matter what application, the molybdenum needs to have certain plasticity, and the capability of continuously generating deformation for as long as possible without fracture becomes more and more important.
The plasticity of the molybdenum and molybdenum alloy block materials is improved by mainly reducing the impurity content (including gas element C, N, O and the like) of pure molybdenum and mainly adding rare metals, rare earth oxides and the like to the molybdenum alloy in terms of chemical components. Generally, the plasticity of the molybdenum alloy added with the rare earth element is improved by a larger extent than that of pure molybdenum, and the elongation of the molybdenum alloy is generally 20-46%, but the molybdenum alloy added with the rare earth element has the defects that pure molybdenum is required to be used in some high-temperature application environments, and the molybdenum alloy added with other substances is not required to prevent impurity outgassing.
In terms of processing mode, pure molybdenum is sintered through powder metallurgy, then is subjected to pressure processing such as forging and rolling, and is subjected to heat treatment to improve the plasticity of the pure molybdenum. However, pure molybdenum has the problems of serious anisotropy and easy delamination in a rolling mode, and the traditional forging mode cannot achieve the high plastic ductility of molybdenum alloy, so that the application of the molybdenum alloy is limited.
Disclosure of Invention
In view of the above situation, the invention provides a preparation method for improving the plasticity of a pure molybdenum block, and the method remarkably improves the plasticity of the prepared pure molybdenum block by controlling the performance of raw materials and combining with process adjustment, and the plastic elongation rate reaches the level of molybdenum alloy.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method for improving the plasticity of a pure molybdenum block material is provided, wherein the content of molybdenum in the pure molybdenum block material is more than 99.95 wt%, and the preparation of the pure molybdenum block material comprises the following steps: selecting molybdenum powder with the purity of more than 99.9 wt% as a raw material; pressing the molybdenum powder to prepare a green body; sintering the green body to prepare a sintered body, wherein the relative density of the sintered body is 94.5% -98%; forging and vacuum heat treating the sintered compact; the oxygen content of the molybdenum powder is below 500ppm, the Fisher-Tropsch particle size of the molybdenum powder is 1.7-3.5 mu m, and the apparent density of the molybdenum powder is 0.75g/cm3-3.0g/cm3。
The invention finds that the plasticity of the molybdenum block is closely related to the performance of the sintering blank, when the grain size of the sintering blank is small, the relative density of the sintering blank is in the range of 94.5-98%, the impurity content of the sintering blank is low, especially under the condition of low oxygen content, and the molybdenum block obtained is subjected to proper forging and heat treatment, the plasticity of the molybdenum block is obviously improved compared with the plasticity of the molybdenum block outside the relative density range.
While the relative density of the sintered compact is directly related to the molybdenum powder forming the sintered compact. The molybdenum powder contains oxygen element, and the oxygen is easy to form MoO in the molybdenum2And the molybdenum is partially polymerized on the grain boundary in the form of a monomolecular layer, so that the bonding strength of the molybdenum on the grain boundary is reduced, and the molybdenum is easily brittle along the grain, therefore, the lower the oxygen content in the molybdenum powder, the better the oxygen content is, at least the oxygen content needs to be controlled below 500ppm, so that the oxygen content can be controlled to a lower level when a blank is sintered, the impurity elements in the gas in the sintering process are less, and the sintering densification is easier to perform; the Ferris particle size and the apparent density of the molybdenum powder have certain influence on the performance of a finished block, the apparent density is matched and suitable for stacking of molybdenum powder particles, so that a sintering blank with better performance is formed after pressing and sintering processes, the particle size of the molybdenum powder is too small, the apparent density is high, the powder activity is high, pores disappear quickly and the sintering is easy, but the surface layer of the sintering blank is easy to shrink and compact to form a shell, the particle size of the powder is too small, the oxygen content of the powder is high, and a brittle oxide phase is easy to form in the sintering process; the Ferrier particle size of the molybdenum powder is 1.7-3.5 μm, and the apparent density is 0.75g/cm3-3.0g/cm3The range of (3) is most suitable for forming a molybdenum bulk material having high plasticity.
The wt% referred to in the present invention is a weight percentage.
Vol% referred to in the present invention is volume percent.
The numerical ranges disclosed herein include all point values within that range.
Detailed Description
In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the following examples, and experimental methods in which specific conditions are not specified in the following examples are generally performed under conventional conditions.
The definition of the Fisher size, apparent density, compositional determination, and plasticity determination mentioned in each example is as follows:
fisher size: the Fisher particle size of the metal and compound powder is measured by a Fisher particle size analyzer according to GB/T3249-2009.
Apparent density: and (3) determining the second part according to GB/T1479.2-2011 metal powder apparent density: the Scott volumetric method adopts a loose density meter to measure.
Component determination: the method comprises the steps of testing impurity components of non-gas elements by using an inductively coupled plasma emission spectrometer, testing the content of C, S gas elements by using a carbon-sulfur analyzer, and testing the content of O, N gas elements by using an oxygen-nitrogen analyzer.
Relative density: the density of the sintered compact is tested by a drainage method, and the relative density is obtained by dividing the density of the sintered compact by the theoretical density.
And (3) plasticity evaluation: according to GBT228-2002 metal material room temperature tensile test method, a SANS-CMT5105 electronic universal tester is adopted to test the tensile strength and the elongation.
In a preferred embodiment, the particles of the molybdenum powder are mainly spherical particles, and the sphericity is 90% or more. The particles of the molybdenum powder are uniform spherical particles, the agglomeration is less, the particles are easy to coordinate with each other, and the uniform sintered blank at each position is more favorably formed.
In a preferred embodiment, the molybdenum powder has a total content of Fe and Ni of 50ppm or less. The crystal is easy to be separated out along the grain boundary when the sintered compact is sintered, so that the sintered compact generates a crack source in the subsequent pressure processing process.
In a preferred embodiment, the molybdenum powder has an S content of 10ppm or less. S can form sulfides with other impurities in the sintering process, and eutectic is generated in the main phase of the molybdenum block and distributed along the grain boundary, so that the molybdenum block shows hot brittleness, and the plasticity is influenced.
In a preferred embodiment, the pressing is performed by cold isostatic pressing; the pressure of the cold isostatic pressing is 180MPa-250MPa, and the pressure maintaining time is 60s-120 s.
In a recommended embodiment, the sintering is carried out in a reducing atmosphere, the sintering temperature is 1500-1800 ℃, and the holding time of the sintering is 3-5 h.
In a preferred embodiment, the sintering comprises: heating to 1100-1300 ℃ at an average heating rate of 0.5-15 ℃/min, and keeping the temperature for 0.5-2 h; and finally, heating up to the sintering temperature at the average heating rate of 0.5-10 ℃/min. In the sintering stage of 1100-1300 ℃, the volatilization of impurities and gas is accelerated, the macroscopic size of the molybdenum blank begins to shrink, the density of the molybdenum blank begins to increase, and the temperature is increased at the average temperature increasing speed of 0.5-15 ℃/min, so that the size shrinkage of each part of the molybdenum blank is relatively stable and uniform. In the final heating and sintering stage, the molybdenum blank density increase rate is slowed down and tends to a stable value, the pore closing process tends to be smooth, closed pores remained in the crystal grains are spheroidized and remain in the molybdenum blank, and the molybdenum blank is heated to the sintering temperature at the average heating rate of 0.5-10 ℃/min, so that the molybdenum blank can be well densified, and the relative density of the sintered blank is 94.5-98%.
In a recommended embodiment, the preparation of the pure molybdenum bulk material further comprises the step of cogging, and the temperature of the cogging is 1300-1400 ℃. The cogging is generally provided at the tip of the forging to process the sintered compact.
In a preferred embodiment, the forging temperature is lower than the sintering temperature.
In a preferred embodiment, the forging is a multi-pass forging, said multi-pass being from three-five passes, i.e. three or four or five passes. The method has the advantages of less passes, insufficient deformation of the material, failure in deformation strengthening effect, excessive passes, more corresponding forging heating times, and easy embrittlement of the material due to repeated heating, thereby affecting plasticity.
In a recommended embodiment, the temperature of each pass in the multi-pass forging is 1000-1100 ℃, which is more beneficial for forging processing and obtaining a molybdenum billet with no crack and good plasticity.
In a preferred embodiment, the forging includes at least one of a quick forging, a rotary forging, a high speed forging, a finish forging, or a free forging. Multiple forging modes can be combined, the advantages of different forging modes are fully exerted, and the material can achieve the effects of compactness and performance enhancement.
In a recommended embodiment, the deformation amount of the first pass in the multi-pass forging is 30-40%, the deformation amount of the second pass is 20-30%, the deformation amount of the third pass is 20-30%, the deformation amount of the Nth pass is 0-10%, N is a positive integer, and N is more than or equal to 4 and less than or equal to 5. The forging frequency of the molybdenum blank is too low and is less than 3 times, so that the total deformation is not enough, and the strengthening effect is weak; if the deformation of each pass is not controlled, the accumulated large deformation can be achieved only by forging for too many passes, and thus the material is subjected to multiple high-temperature hot working, so that the material is in the processes of frequent dynamic recovery and dynamic recrystallization, the deformation energy storage is low, and the strengthening effect is influenced.
In a preferred embodiment, the multi-pass forging is a three-pass forging in which the first pass has a deformation of 30% to 40%, the second pass has a deformation of 20% to 30%, and the third pass has a deformation of 20% to 30%.
In a preferred embodiment, the reducing atmosphere is 99 vol% or more of H2。
In a recommended embodiment, the vacuum heat treatment is heating for 0.5h-1h in an environment with the temperature of 950 ℃ -1050 ℃, and the vacuum degree of the vacuum heat treatment is 10-2Pa or above.
It should be noted that the pressing pressure and dwell time, sintering temperature and dwell time, forging mode selection, and vacuum degree and temperature of vacuum heat treatment are conventional choices in the industry, and therefore, in the examples, the ranges of the above parameters have not been tested and verified.
Example I
1) Preparing raw materials: taking molybdenum powder with the purity of more than 99.9 wt% as a raw material, wherein the oxygen content, the Fisher size and the apparent density of the molybdenum powder are shown in the table 1;
2) pressing: and filling the molybdenum powder into an isostatic pressing rubber sleeve for cold isostatic pressing treatment to obtain a green body. The pressure of cold isostatic pressing is 200MPa, and the pressure maintaining time is 90 s;
3) and (3) sintering: sintering the green body in a reducing atmosphere to prepare a sintered body, wherein the relative density of the sintered body is 97%, the sintering temperature is 1800 ℃, and the heat preservation time is 3 hours;
4) forging: forging the sintered blank to obtain a forged pure molybdenum blank, wherein the forging temperature is 1100 ℃;
5) vacuum heat treatment: the forged pure molybdenum billet is processed at the vacuum degree of 10-2And (3) carrying out heat treatment under Pa to obtain a pure molybdenum block material, wherein the heat treatment temperature is 1050 ℃.
TABLE 1 raw Material Performance parameters for the examples and comparative examples
Figure BDA0002203960230000051
The appearance of the pure molybdenum bulk was observed, and the pure molybdenum bulk of examples 1-8 was crack free, whereas comparative example 1 had edge microcracks. This may be associated with an excessively high oxygen content and the presence of impurity brittle phases in the molybdenum bulk finally obtained, which may lead to cracking of the forged edges.
The performance evaluation was performed on the pure molybdenum bulk obtained in each example and each comparative example, and the performance evaluation results are shown in table 2.
TABLE 2 evaluation of the properties of the pure molybdenum bulk materials of the examples and comparative examples
Figure BDA0002203960230000061
As can be seen from table 2: the oxygen content of the molybdenum powder is too high, and the finally obtained molybdenum block has an impurity brittle phase, so that the plasticity of the material is influenced; the Freund particle size is too small, the apparent density is too small, the molybdenum powder is easy to oxidize, the number of the finally obtained pure molybdenum bulk grains is large, the number of crystal boundaries is large, and more impurity brittle phases are easy to segregate on the crystal boundaries, so that the plasticity of the material is influenced; if the Ferris particle size is too large and the apparent density is too large, the finally formed grain structure is too coarse, thereby affecting the plasticity of the pure molybdenum block.
Example II
1) Preparing raw materials: taking molybdenum powder with the purity of more than 99.9 wt% as a raw material, wherein the oxygen content in the molybdenum powder is 350ppm, the Fisher particle size of the molybdenum powder is 2.7 mu m, and the apparent density is 1.0g/cm3；
2) Pressing: and filling the molybdenum powder into an isostatic pressing rubber sleeve for cold isostatic pressing treatment to obtain a green body. The pressure of cold isostatic pressing is 180MPa, and the pressure maintaining time is 120 s;
3) and (3) sintering: the green compact was placed in 99 vol% H2Under the atmosphere, firstly heating to 1300 ℃ at an average heating rate of 0.5 ℃/min, and preserving heat for 0.5 h; heating to the sintering temperature of 1500 ℃ at the average heating rate of 0.5 ℃/min, keeping the temperature for 5 hours, and sintering to prepare a sintered blank, wherein the relative density of the sintered blank is shown in Table 3;
4) cogging and forging: cogging forging the sintered blank at 1300 ℃;
5) forging: forging the sintered blank subjected to cogging forging to obtain a forged pure molybdenum blank, wherein the forging temperature is 1000 ℃;
6) vacuum heat treatment: the forged pure molybdenum billet is processed at the vacuum degree of 10-2And (3) carrying out heat treatment under Pa to obtain a pure molybdenum block material, wherein the heat treatment temperature is 1050 ℃.
TABLE 3 relative Density of sintered compacts of examples and comparative examples
Figure BDA0002203960230000071
The appearance of the pure molybdenum blocks was observed, and the pure molybdenum blocks of examples 9-11 were crack-free, while the pure molybdenum blocks of comparative examples 4 and 6 were significantly cracked.
The performance evaluation was performed on the pure molybdenum bulk obtained in each example and each comparative example, and the performance evaluation results are shown in table 4.
Table 4 evaluation of properties of pure molybdenum bulk materials for each of examples and comparative examples
Figure BDA0002203960230000072
As can be seen from table 4: the relative density of the sintered blank is lower than 94.5 percent, the strength of the final molybdenum material is lower than 450MPa, and the elongation rate is almost zero; the relative density is lower than 94.5%, the number of pores in the sintered blank is large, the sintered blank can be compacted only by subsequent hot working forging, the material is too hot and fragile, the relative density is higher than 98%, the grain size of the sintered blank is too large in the sintering temperature process, and cracks are easy to appear in the next forging process due to the large grain structure.
Example III
1) Preparing raw materials: taking molybdenum powder with the purity of more than 99.9 wt% as a raw material, wherein the particles of the molybdenum powder mainly comprise spherical particles, the sphericity is more than 90%, the Fisher particle size is 1.7 mu m, and the apparent density is 0.75g/cm3The molybdenum powder was analyzed for its composition as shown in table 5;
2) pressing: and filling the molybdenum powder into an isostatic pressing rubber sleeve for cold isostatic pressing treatment to obtain a green body. The pressure of cold isostatic pressing is 250MPa, and the pressure maintaining time is 60 s;
3) and (3) sintering: the green compact was placed in 99 vol% H2Under the atmosphere, firstly heating to 1100 ℃ at an average heating rate of 15 ℃/min, and preserving heat for 2 h; heating to a sintering temperature of 1760 ℃ at an average heating rate of 10 ℃/min, keeping the temperature for 4.5 hours, and sintering to obtain a sintered blank, wherein the relative density of the sintered blank is 96.5%;
4) cogging and forging: cogging forging the sintered blank at 1400 ℃;
5) forging: forging the sintered blank subjected to cogging forging to obtain a forged pure molybdenum blank, wherein the forging temperature is 1100 ℃;
6) vacuum heat treatment: the forged pure molybdenum billet is processed at the vacuum degree of 10-3And (4) carrying out heat treatment under Pa to obtain a pure molybdenum block, wherein the heat treatment temperature is 950 ℃.
TABLE 5 analysis of raw Material Components in examples
Figure BDA0002203960230000081
The pure molybdenum bulk materials obtained in the respective examples were subjected to performance evaluation, and the results of the performance evaluation are shown in table 6.
Table 6 evaluation of properties of pure molybdenum bulk materials in examples
Figure BDA0002203960230000082
As can be seen from table 6: the total content of Fe and Ni below 50ppm is more beneficial to forming high elongation; the S content is 10ppm or less, which is more advantageous for high elongation.
Example IV
1) Preparing raw materials: taking molybdenum powder with the purity of more than 99.9 wt% as a raw material, wherein the particles of the molybdenum powder mainly comprise spherical particles, the sphericity is more than 90%, the Fisher particle size is 3.2 mu m, and the apparent density is 1.20g/cm3The oxygen content in the molybdenum powder is 450 ppm;
2) pressing: and filling the molybdenum powder into an isostatic pressing rubber sleeve for cold isostatic pressing treatment to obtain a green body. The pressure of cold isostatic pressing is 230MPa, and the pressure maintaining time is 75 s;
3) and (3) sintering: the green compact was placed in 99 vol% H2Sintering the mixture to prepare a sintered blank under the atmosphere, wherein the relative density of the sintered blank is 96.5 percent, the sintering temperature is 1690 ℃, and the heat preservation time is 4 hours;
4) cogging and forging: cogging forging the sintered blank at 1350 ℃;
5) forging: carrying out high-speed forging on the cogging-forged sintered blank by adopting the process shown in the table 7 to obtain a forged pure molybdenum blank;
5) vacuum heat treatment, namely performing vacuum heat treatment on the forged pure molybdenum billet at the vacuum degree of 3 × 10-3Heat treatment is carried out under Pa to obtain a pure molybdenum block material, and the heat treatment temperature is 1000 ℃.
TABLE 7 forging Process for the examples
Figure BDA0002203960230000091
The pure molybdenum bulk materials obtained in the respective examples were subjected to performance evaluation, and the results of the performance evaluation are shown in table 8.
Table 8 evaluation of properties of pure molybdenum bulk materials in examples
Figure BDA0002203960230000101
As can be seen from table 8:
the forging from three times to five times is more beneficial to improving the plasticity of the pure molybdenum block; in the multi-pass forging, the deformation of the first pass is within the range of 30-40%, the deformation of the second pass is 20-30%, the deformation of the third pass is 20-30%, the deformation of the Nth pass is within the range of 0-10%, N is a positive integer and is more than or equal to 4 and less than or equal to 5, and the method is more beneficial to further improvement of the plasticity of the pure molybdenum block; the forging temperature of each pass is 1000-1100 ℃, which is more beneficial to forming a forging blank without cracks.
The above embodiments are only used for explaining the technical solutions provided by the present invention, and the present invention is not limited thereto, and any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention fall within the protection scope of the technical solutions of the present invention.

Claims (7)

1. A preparation method for improving the plasticity of a pure molybdenum block material, wherein the content of molybdenum in the pure molybdenum block material is more than 99.95 wt%, is characterized by comprising the following steps: selecting molybdenum powder with the purity of more than 99.9 wt% as a raw material; pressing the molybdenum powder to prepare a green body; sintering the green body to prepare a sintered body, wherein the relative density of the sintered body is 94.5% -98%; forging and vacuum heat treating the sintered compact; the oxygen content of the molybdenum powder is below 500ppm, the Fisher-Tropsch particle size of the molybdenum powder is 1.7-3.5 mu m, and the apparent density of the molybdenum powder is 0.75g/cm3-3g/cm3The content of S in the molybdenum powder is less than 10ppm, the forging is multi-pass forging, the multi-pass forging is three-five-pass, the forging temperature of each pass in the multi-pass forging is 1000-1100 ℃, the deformation amount of the first pass in the multi-pass forging is 30-40%, the deformation amount of the second pass in the multi-pass forging is 20-30%, the deformation amount of the third pass in the multi-pass forging is 20-30%, the deformation amount of the Nth pass in the multi-pass forging is 0-10%, N is a positive integer, and N is not less than 4 and not more than 5.
2. The preparation method for improving the plasticity of the pure molybdenum bulk material according to claim 1, wherein the preparation method comprises the following steps: the particles of the molybdenum powder are mainly spherical particles, and the sphericity is more than 90%.
3. The preparation method for improving the plasticity of the pure molybdenum bulk material according to claim 1, wherein the preparation method comprises the following steps: the sintering is carried out in a reducing atmosphere, the sintering temperature is 1500-1800 ℃, and the sintering heat preservation time is 3-5 h.
4. The preparation method for improving the plasticity of the pure molybdenum bulk according to claim 3, wherein the sintering comprises the following steps: heating to 1100-1300 ℃ at an average heating rate of 0.5-15 ℃/min, and keeping the temperature for 0.5-2 h; and finally, heating up to the sintering temperature at the average heating rate of 0.5-10 ℃/min.
5. The preparation method for improving the plasticity of the pure molybdenum bulk material according to claim 1, wherein the preparation method comprises the following steps: the temperature of the forging is lower than the temperature of the sintering.
6. The preparation method for improving the plasticity of the pure molybdenum bulk material according to claim 1, wherein the preparation method comprises the following steps: the forging includes at least one of quick forging, rotary forging, high-speed forging, finish forging, or free forging.
7. The preparation method for improving the plasticity of the pure molybdenum bulk material according to claim 1, wherein the preparation method comprises the following steps: the temperature of the vacuum heat treatment is 950 ℃ to 1050 ℃, and the vacuum degree of the vacuum heat treatment is 10-2Pa or above.
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