CN108746657B - Preparation method of high-pressure billet strength tungsten powder - Google Patents
Preparation method of high-pressure billet strength tungsten powder Download PDFInfo
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Abstract
The invention discloses a preparation method of high-pressure billet strength tungsten powder. The method comprises the following steps: mixing blue tungsten oxide, purple tungsten oxide and yellow tungsten oxide in a double-cone mixer for 2.0-4.0 hours according to the mass ratio of 1-2: 4-6: 8-10; taking the mixture of the three tungsten oxides as a raw material, flatly spreading the raw material in a boat, and reducing in a reducing furnace; wherein the thickness of the material layer is controlled to be between 10 and 12 mm; setting the heating speed to be 50 ℃/h, setting the hydrogen dew point to be-70 ℃ to-75 ℃, setting the five-zone reduction temperature to be within the range of 700-950 ℃, and setting the retention time to be 170-180 min for carrying out reduction reaction; and sieving the reduced powder twice through an 80/200-mesh sieve to obtain high-compaction-strength powder, and sealing and storing. The invention does not need calcination and other intermediate processes, directly mixes and reduces materials, has simple process and low energy consumption, and is suitable for large-scale production.
Description
Technical Field
The invention relates to the field of tungsten industry, in particular to a preparation method of high-pressure blank strength tungsten powder.
Background
The melting point and the hardness of the metal tungsten are high in the top of all metals, and the high melting point of the tungsten is combined with the high density characteristic, so that the tungsten has special purposes in civil and defense industries, such as manufacturing high-temperature structural parts, electronic components and the like. In addition, the tungsten alloy has a series of excellent physical and mechanical properties, so that the tungsten-based alloy has very wide application in the fields of national defense and military industry, aerospace, energy, metallurgical industry and the like, and plays an important role in national economy.
In recent years, with the rapid development of economy in China, the application of tungsten products is rapidly increased, the demand for large-caliber thin-walled tubes and large-size thin tungsten plates which are difficult to form is increased year by year, and the requirement on the product quality is higher and higher. If the green compact has insufficient strength, cracks, edge chipping, corner chipping, and the like are likely to occur during the forming or processing. The shape, the particle size distribution and the like of the tungsten powder have great influence on the strength of the pressed compact, and the strength of the pressed compact directly has great influence on the physical and mechanical properties of the final tungsten product, so that the tungsten powder with good formability and high pressed compact strength is prepared, and has important practical significance for preparing high-performance tungsten or high-tungsten-content alloy products.
The raw materials for preparing the tungsten powder and the main process thereof are optimized, so that the formability and the compact strength of the tungsten powder are improved and enhanced by improving the particle size distribution and the appearance of the original tungsten powder.
Disclosure of Invention
The invention overcomes the defects, and improves the formability and the compact strength of the tungsten powder by optimizing the raw materials for preparing the tungsten powder and the main process thereof and improving the particle size distribution and the appearance of the original tungsten powder.
The technical scheme of the invention is as follows.
A preparation method of high-pressure billet strength tungsten powder comprises the following production steps:
(1) mixing BTO \ PTO \ YTO (blue tungsten oxide \ purple tungsten oxide \ yellow tungsten oxide) in a double-cone mixer for 2.0-4.0 h according to the proportion of 1-2: 4-6: 8-10;
(2) taking the mixture of the three tungsten oxides as a raw material, flatly spreading the raw material in a boat, and reducing in a reducing furnace;
(3) wherein the thickness of the material layer is controlled to be between 10 and 12 mm;
(4) the temperature rising speed is 50 ℃/h;
(5) the dew point of hydrogen is-70 ℃ to-75 ℃;
(6) the five-zone reduction temperature (the temperature range of a first zone is distributed within the range of 700-740 ℃, the temperature range of a second zone is distributed within the range of 750-790 ℃, the temperature range of a third zone is distributed within the range of 800-840 ℃, the temperature range of a fourth zone is distributed within the range of 850-890 ℃, the temperature range of a fifth zone is distributed within the range of 900-950 ℃), and the residence time of each high-temperature zone is 34-36 min) is distributed within the range of 700-950 ℃;
(7) the residence time in the high-temperature zone is 170-180 min;
(8) and sieving the reduced powder twice through an 80/200-mesh sieve to obtain high-compaction-strength powder, and sealing and storing.
Compared with the prior art, the invention has the advantages that:
(1) the powder produced by the high-pressure green compact strength process has wider particle size distribution, when the powder is pressed and formed, the powder containing more fine particles is easier to self-regulate under the action of external load, and gaps among the particles are easy to fill through movement, sliding and rotation, so that the large porosity in the green compact is reduced; meanwhile, because the powder particles have complicated shapes and rough surfaces, and part of the particles are bridged to form a loose aggregation structure, the particles are mutually engaged in the pressing process of the powder, so that the strength of a pressed compact is improved, and the preparation of a high-performance tungsten product is facilitated.
(2) The invention does not need calcination and other intermediate processes, directly mixes and reduces materials, has simple process and low energy consumption, and is suitable for large-scale production.
Drawings
FIG. 1 is a high pressure billet intensity powder laser particle size spectrum;
FIG. 2 is a conventional powder laser particle size spectrum;
FIG. 3 is a SEM image of high green strength powder; wherein a is x 500; b is x 1000; c is X2000; d is x 5000;
FIG. 4 is a SEM image of a conventional powder; wherein a is x 500; b is x 1000; c is X2000; d is × 5000.
Detailed Description
The present invention will be further described with reference to the following examples.
The preparation method comprises the steps of preparing two kinds of powder by respectively adopting a conventional powder preparation method and a high-pressure blank strength powder preparation method, testing and observing the granularity, the surface appearance and the like of the powder, then respectively pressing and forming the two kinds of powder, testing the strength of the powder, and finally sintering the pressed blank and testing the physical properties of the pressed blank.
Example 1
Conventional powder preparation methods: reducing the YTO serving as a raw material in a reducing furnace, wherein the thickness of a material layer is controlled to be 8-14 mm, the temperature rising speed is 50 ℃/h, and the dew point of hydrogen is-65 ℃ to-70 ℃; the five-zone reduction temperature is distributed within the range of 750-900 ℃, and the residence time in the high-temperature zone is 150-160 min; and sieving the reduced powder twice through an 80/160-mesh sieve to obtain the conventional powder, and sealing and storing.
Example 2
The preparation method of the high green strength powder comprises the following steps: mixing BTO \ PTO \ YTO in a double-cone mixer for 2.0h according to the ratio of 2:5:10, taking the mixture of the three tungsten oxides as a raw material, laying the raw material in a boat, and reducing in a reducing furnace. Wherein the thickness of the material layer is controlled to be 10-12 mm, the heating rate is 50 ℃/h, and the dew point of hydrogen is-70 ℃ to-75 ℃; the five-zone reduction temperature is 720 ℃ in the first zone, 770 ℃ in the second zone, 820 ℃ in the third zone, 860 ℃ in the fourth zone and 920 ℃ in the fifth zone; the residence time in each high temperature zone is 35 min; and sieving the reduced powder twice through an 80/200-mesh sieve to obtain high-compaction-strength powder, and sealing and storing.
Through comparison of the two processes, the high-pressure billet strength powder is mainly reflected in difference of raw materials, wider temperature gradient distribution range, longer retention time in a high-temperature zone, more accurate requirement on the thickness of a material layer, higher requirement on the dew point of hydrogen and finer mesh number after two times of sieving.
Analysis of powder particle size distribution:
the following is a laser particle size comparison of high green strength powder to conventional powder, as shown in fig. 1 and 2.
As can be seen from the high-pressure billet intensity powder laser particle size spectrum (figure 1), a perfect normal distribution curve is not presented, the distribution of intervals at two ends of the coarse (the particle size is more than or equal to 8 mu m) and the fine (the particle size is less than or equal to 1 mu m) is increased by a certain proportion, the particle size distribution is wider, the radial distance reaches 1.964, the wave peak value is lower and is only close to 9; the conventional powder laser particle size spectrum (figure 2) presents a perfect normal distribution curve, the particle size distribution is narrow, the radial distance value is only 1.518, the wave peak value is as high as 10.6, the powder particle size distribution is very concentrated, and the distribution is obviously reduced in both thick and thin end intervals. The surface morphology of the powder;
the following are SEM electron micrographs of the conventional powder versus the high green strength powder, as shown in fig. 3 and 4.
As can be seen by comparing SEM images of the high green strength powder and the conventional powder at 500, 1K, 2K and 5K times, under 500 and 1K times, the high green strength powder has more particle aggregates and the conventional powder has more uniform particle size distribution; and 2K, can see that high green compact intensity powder is thin under 5K times, the coarse grain is more than comparing, the particle shape is complicated, the surface is coarse, like this in the pressing process, because displacement and deformation can wedge each other and collude between the granule, mechanical meshing between the powder granule is more abundant, the coupling force between the powder granule increases, thereby be favorable to making the green compact have higher intensity, and conventional powder surface rule is slick and sly, in the pressing process, be unfavorable for the mechanical meshing between the powder granule, thereby be unfavorable for improving and press blank intensity.
Green strength of powder:
the results of the physical properties of the high green strength W powder and the conventional W powder are shown in tables 1 and 2.
TABLE 1 conventional W powders for various physical properties
TABLE 2 high green strength W powder physical properties
As can be seen from the table, when the particle sizes of the W powders prepared by the two processes are close to each other, the porosity (Poro) of the high-pressure green strength powder is significantly high, which can show that the fine powder interval ratio of the high-pressure green strength powder is large, and the bulk ratio (Scott) of the high-pressure green strength powder is significantly higher than that of the conventional W powder, and that the ratio of the fine powder interval ratio of the high-pressure green strength powder in the coarse powder interval is significantly large, which is inferred from only the difference in the physical properties of the powders.
It can be seen that:
1) the powder produced by the conventional process has narrow particle size distribution and small size change of powder particles, so that gaps among the particles are not easily filled in the pressing process, and finally the green compact strength is low;
after the process is improved, the powder produced by the high-pressure green compact strength process has wider particle size distribution, when the powder is pressed and formed, the powder containing more fine particles is easier to self-regulate under the action of external loading, and gaps among the particles are easy to fill through movement, sliding and rotation, so that the large porosity in the green compact is reduced; meanwhile, because the powder particles have complicated shapes and rough surfaces, and part of the particles are bridged to form a loose aggregation structure, the particles are mutually engaged in the pressing process of the powder, so that the strength of a pressed compact is improved, and the preparation of a high-performance tungsten product is facilitated.
2) The YTO \ BTO \ PTO mixture is directly subjected to hydrogen reduction to prepare the high-compaction-strength tungsten powder, calcination and other intermediate processes are not needed, the materials are directly mixed and reduced, the process is simple, the energy consumption is low, and the process is suitable for large-scale production.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (1)
1. A preparation method of high-pressure billet strength tungsten powder is characterized by comprising the following steps:
(1) mixing blue tungsten oxide, purple tungsten oxide and yellow tungsten oxide in a double-cone mixer for 2.0-4.0 hours according to the mass ratio of 1-2: 4-6: 8-10;
(2) taking the mixture of the three tungsten oxides as a raw material, flatly spreading the raw material in a boat, and reducing in a reducing furnace; wherein the thickness of the material layer is controlled to be between 10 and 12 mm;
(3) setting the heating speed to be 50 ℃/h, setting the hydrogen dew point to be-70 ℃ to-75 ℃, setting the five-zone reduction temperature to be within the range of 700-950 ℃, and setting the retention time to be 170-180 min for carrying out reduction reaction;
(4) sieving the reduced powder twice with an 80/200-mesh sieve to obtain high-compaction-strength powder, and sealing and storing;
the five-band reduction specifically comprises the steps that the temperature range of a first band is distributed in a range of 700-740 ℃, the temperature range of a second band is distributed in a range of 750-790 ℃, the temperature range of a third band is distributed in a range of 800-840 ℃, the temperature range of a fourth band is distributed in a range of 850-890 ℃, and the temperature range of a fifth band is distributed in a range of 900-950 ℃; the residence time in each temperature zone is 34-36 min.
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| CN110722172B (en) * | 2019-11-01 | 2022-08-26 | 厦门金鹭硬质合金有限公司 | Production method of high-pressure billet strength tungsten powder with wide particle size distribution |
| CN112479259B (en) * | 2020-12-14 | 2023-01-03 | 江钨世泰科钨品有限公司 | Yellow tungsten oxide with high specific surface area and low residual ammonia and preparation method thereof |
| CN112846210B (en) * | 2020-12-31 | 2023-08-22 | 崇义章源钨业股份有限公司 | High-pressure blank strength tungsten powder and preparation method thereof |
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