METHOD FOR REFINING LARGE-PARTICLE-SIZE PURE COPPER OR COPPER ALLOY PARTICLES BY HIGH-ENERGY BALL MILLING

Abstract

The present invention discloses a method for refining large-particle-size pure copper or copper alloy particles by high-energy ball milling, the method comprising the following steps: (1) using large-particle-size pure copper or copper alloy coarse particles as a raw material and cyclohexane or water as a process control agent, and crushing and refining the particles by high-energy ball milling to obtain small-particle-size copper or copper alloy powder; and (2) decreasing an oxygen content in the powder obtained in step (1) in a reducing atmosphere to obtain pure copper or copper alloy powder. In the present invention, by improving the overall process flow of the preparation method and the parameter conditions of each process step, the method greatly decreases energy consumption compared with existing copper powder preparation techniques. In addition, the method features a simple process and low production costs.

Claims

1. A method for refining large-particle-size pure copper or copper alloy particles by high-energy ball milling, the method comprising the following steps: (1) using large-particle-size pure copper or copper alloy coarse particles as a raw material and cyclohexane or water as a process control agent, and crushing and refining the particles by high-energy ball milling to obtain small-particle-size copper or copper alloy powder; and (2) decreasing an oxygen content in the copper or copper alloy powder obtained in step (1) in a reducing atmosphere to obtain pure copper or copper alloy powder.

2. The method of claim 1, wherein the material of grinding balls used in step (1) is selected from bearing steel or copper, and when bearing steel grinding balls are adopted, the small-particle-size copper or copper alloy powder obtained in step (1) is treated with a leaching solution, filtered after leaching to remove impurities introduced by ball milling, and then dried before step (2).

3. The method of claim 1, wherein in step (1), the process control agent and the raw material are mixed at a fluid-to-material ratio of 0.2-2 ml/g, and the sizes of the large-particle-size pure copper or copper alloy coarse particles are 100-650 μm.

4. The method of claim 1, wherein in step (2), pure hydrogen or decomposed ammonia is used as the reducing atmosphere.

5. The method of claim 1, wherein in step (1), the mass ratio of grinding balls to the raw material during the high-energy ball milling is 15:1-50:1.

6. The method of claim 1, wherein in step (1), the ball milling is carried out for 6-20 h at a ball-mill rotation speed of 200-500 rpm.

7. The method of claim 2, wherein the filtration is vacuum filtration, and the drying is vacuum drying.

8. The method of claim 2, wherein the leaching solution is dilute hydrochloric acid, dilute sulfuric acid, an aqueous solution of copper chloride or an aqueous solution of copper sulfate.

9. The method of claim 1, wherein in step (2), a reduction temperature is 300-750° C. and a reduction time is 1-5 h; and for the pure copper or copper alloy powder obtained after reduction, the oxygen content is less than 0.3 wt % and an iron content is less than 0.11 wt %.

10. The method of claim 3, wherein when the sizes of the large-particle-size pure copper or copper alloy coarse particles are greater than 250 μm, the large-particle-size pure copper or copper alloy coarse particles are first rolled into a sheet form before high-energy ball milling is carried out.

Description

BRIEF DESCRIPTION OF DRAWINGS

Description of Drawings

[0024] FIG. 1 is a process flowchart of a high-energy ball milling method for pure copper powder preparation.

[0025] FIG. 2 is a micrograph of fine materials obtained by high-energy ball milling crushing and refinement in Embodiment 2.

[0026] FIG. 3 is a micrograph of fine materials obtained by high-energy ball milling crushing and refinement in Embodiment 6.

[0027] FIG. 4 is a particle size distribution diagram of materials obtained by ball milling refinement under optimal conditions in Embodiment 6.

[0028] FIG. 5 is a micrograph of materials obtained by high-energy ball milling crushing and refinement in a comparative example.

DETAILED DESCRIPTION

Embodiments of the Invention

[0029] In order to make the objectives, technical schemes and advantages of the present invention more apparent, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only intended to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] An embodiment of the present invention provides a method for refining large-particle-size pure copper or copper alloy particles by high-energy ball milling. Hydrochloric acid is used as a leaching agent to leach out iron impurities introduced by ball milling, pure copper or alloy powder is obtained after filtration and drying, and finally the oxygen content in the powder is decreased through reduction to obtain pure copper or alloy powder which can be used in powder metallurgy. The method for refining large pure copper particles to prepare pure copper or alloy powder comprises the steps as shown in FIG. 1.

[0031] At S1, the large-particle-size pure copper or alloy particles and a process control agents are co-ground in a planetary ball mill first, then materials obtained after ball milling are screened by a 200-mesh standard sieve, and the optimal ball-milling parameters are determined by the sieving rate of copper powder.

[0032] At S2, ball milling is carried out on the large-particle-size pure copper or alloy particles according to the optimal conditions obtained in S1, and the process control agent is separated from the copper powder through a vacuum filtration device to obtain fine copper powder.

[0033] At S3, hydrochloric acid, for example, is used as a leaching agent to leach iron impurities introduced by ball milling through chemical leaching, then a leaching solution is separated from the copper powder through a vacuum filtration device, and vacuum drying is carried out to obtain pure copper or alloy powder.

[0034] At S4, the pure copper or alloy powder obtained in S3 is reduced by a reducing gas such as hydrogen to decrease the oxygen content in the powder, thus obtaining pure copper or alloy powder which can be used in powder metallurgy.

[0035] The present invention will be further explained in detail by taking copper particles with different particle sizes as experimental objects, and using a process control agent for in-situ surface modification of the particles, which improves the dispersibility and brittleness of the powder and slows down the soldering between refined particles.

Embodiment 1

[0036] Pure copper particles with particle sizes of 100-250 μm were used as the experimental object. Cyclohexane was used as the process control agent, and the addition amount of cyclohexane relative to the raw material was 1 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 20:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 6 h, and the ball-mill rotation speed was set to be 500 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain copper powder, and then vacuum drying and reduction were carried out successively to obtain pure copper powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 750° C., and reduction time was 2 h. The oxygen content of the pure copper powder was 0.1% and the iron content was 0.08%. In this case, the sieving rate of the pure copper powder through a 200-mesh sieve was 88.1%.

Embodiment 2

[0037] Pure copper particles with particle sizes of 100-250 μm were used as the experimental object. Cyclohexane was used as the process control agent, and the addition amount of cyclohexane relative to the raw material was 1 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 40:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 8 h, and the ball-mill rotation speed was set to be 400 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain copper powder, and then vacuum drying and reduction were carried out successively to obtain pure copper powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 300° C., and reduction time was 5 h. The oxygen content of the pure copper powder was 0.3% and the iron content was 0.08%. In this case, the sieving rate of the pure copper powder through a 200-mesh sieve was over 88.5%. FIG. 2 is a micrograph of the pure copper powder, and the refined powder is granular.

Embodiment 3

[0038] Pure copper particles with particle sizes of 650-250 μm were used as the experimental object, which were mechanically rolled into tablets before ball milling refinement. Water was used as the process control agent, and the addition amount of water relative to the raw material was 1 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 20:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 10 h, and the ball-mill rotation speed was set to be 400 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain copper powder, and then vacuum drying and reduction were carried out successively to obtain pure copper powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 400° C., and reduction time was 2 h. The oxygen content of the pure copper powder was 0.3% and the iron content was 0.08%. In this case, the sieving rate of the pure copper powder through a 200-mesh sieve was over 95.5%.

Embodiment 4

[0039] Copper alloy particles with particle sizes of 100-250 μm were used as the experimental object. Cyclohexane was used as the process control agent, and the addition amount of cyclohexane relative to the raw material was 0.2 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 15:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 20 h, and the ball-mill rotation speed was set to be 500 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain powder, and then vacuum drying and reduction were carried out successively to obtain copper alloy powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 550° C., and reduction time was 1 h. The oxygen content of the copper alloy powder was 0.3% and the iron content was 0.11%. In this case, the sieving rate of the copper alloy powder through a 200-mesh sieve was over 99.5%.

Embodiment 5

[0040] Copper alloy particles with particle sizes of 100-250 μm were used as the experimental object. Water was used as the process control agent, and the addition amount of water relative to the raw material was 2 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 50:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 20 h, and the ball-mill rotation speed was set to be 300 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain powder, and then vacuum drying and reduction were carried out successively to obtain copper alloy powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 550° C., and reduction time was 1 h. The oxygen content of the copper alloy powder was 0.3% and the iron content was 0.07%. The sieving rate of the copper alloy powder through a 200-mesh sieve was over 87.5%.

Embodiment 6

[0041] Pure copper particles with particle sizes of 100-250 μm were used as the experimental object. Water was used as the process control agent, and the addition amount of water relative to the raw material was 1 ml/g. The two were put into a 250 ml stainless steel ball milling tank. The mass ratio of grinding balls to the raw material was 20:1, the diameter of the grinding balls was 5 mm, and the material of the grinding balls was GCr15 steel. High-energy ball milling was carried out in a planetary ball mill. High-energy ball milling time was set to be 7 h, and the ball-mill rotation speed was set to be 400 rpm. After ball milling, the materials were leached by 2 mol/L hydrochloric acid and then filtered to obtain copper powder, and then vacuum drying and reduction were carried out successively to obtain pure copper powder. Pure hydrogen was used as a reducing atmosphere, reduction temperature was 550° C., and reduction time was 1 h. The oxygen content of the pure copper powder was 0.3% and the iron content was 0.08%. The sieving rate of the pure copper powder through a 200-mesh sieve was over 98.8%. FIG. 3 is a micrograph of the pure copper powder, and the refined powder is granular. FIG. 4 is a particle size distribution diagram of the pure copper powder, and the particle sizes are 7-45 μm.

Comparative Example

[0042] The preparation conditions of this comparative example are the same as those of Embodiment 6, except that the process control agent was replaced by ethanol. The product obtained in this comparative example is shown in FIG. 5. The material obtained after ball milling was in the form of large tablets, which shows that it is difficult to refine copper particles with ethanol as the process control agent.

[0043] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not used to limit the present invention. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.