METHOD FOR PREPARING METAL POWDER BY WATER ATOMIZATION

Abstract

A method for preparing metal powder by water atomization is disclosed. The method includes the steps of smelting, atomization, separation and drying, and the metal powder is freeze-dried in the drying step. Experiments show that freeze-drying is an important factor affecting oxygen content indexes of copper and copper alloys, and can be applied to the preparation of copper and copper alloy powder and even metal powder with low oxygen content. The method further considers all the details that may cause oxidation during the atomization process, and takes comprehensive measures to greatly reduce the probability of oxidization of copper and copper alloy powder, so that the oxygen content and oxidation of the water atomized powder are effectively reduced, and the water atomized powder is not easy to be oxidized during long-term storage.

Claims

1. A method for preparing metal powder by a water atomization, comprising the steps of smelting, atomization, separation and drying, wherein the metal powder is freeze-dried in the drying step.

2. The method according to claim 1, wherein a protective atmosphere is used in the smelting and/or atomization steps.

3. The method according to claim 1, wherein a protective atmosphere is used from the smelting to atomization steps.

4. The method according to claim 2, wherein the protective atmosphere is nitrogen.

5. The method according to claim 1, wherein the atomization step comprises the use of an atomization liquid, which is an aqueous solution with a corrosion inhibitor added.

6. The method according to claim 5, wherein in the aqueous solution, a mass of the corrosion inhibitor accounts for 0.02-0.1% of a mass of the aqueous solution.

7. The method according to claim 5, wherein the corrosion inhibitor is comprised of mercaptobenzothiazole and benzotriazole.

8. The method according to claim 1, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

9. The method according to claim 1, wherein in the smelting step a molten metal is formed, and charcoal is used to cover a surface of the molten metal.

10. The method according to claim 1, wherein the metal powder obtained after the drying step is sieved to obtain finished metal powder.

11. The method according to claim 1, wherein the metal powder is copper powder or copper alloy powder.

12. The method according to claim 11, wherein the copper alloy powder is bronze powder or brass powder.

13. The method according to claim 3, wherein the protective atmosphere is nitrogen.

14. The method according to claim 13, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

15. The method according to claim 2, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

16. The method according to claim 3, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

17. The method according to claim 4, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

18. The method according to claim 5, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

19. The method according to claim 6, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

20. The method according to claim 7, wherein the atomization step comprises the use of water as an atomization liquid, and a temperature of the water is 0-4° C.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

Comparative Example 1

[0024] 100 kg of electrolytic copper plates were charged into a coreless intermediate frequency furnace for smelting, the electrolytic copper plates were covered with a thick layer of charcoal, and then power was supplied for heating, wherein the charcoal layer could ensure that the molten copper was in a reducing atmosphere to fully remove oxygen from the molten copper. When the quality of the melt met the requirements and the melt was transferred to an intermediate leaking ladle, a leak hole in the center of the leaking ladle, i.e., a diversion pipe, would guide the melt to flow vertically into an atomization tower, and the high-temperature molten metal flow was crushed into powder under the impact of high-pressure water flow (water temperature 25° C.) jet by a jet atomizer. The jet atomizer consisted of an atomizer main body and 4 fan nozzles, every 2 opposite nozzles constituted a group, 2 groups of nozzles were formed in total, and the 2 groups of nozzles were composed of a group of large-diameter nozzles and a group of small-diameter nozzles. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum heat drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The oxygen content of the prepared copper powder was 0.25%, the oxygen content was 0.25% after storage for 2 years, and the yield of −200 mesh powder was 89%.

Comparative Example 2

[0025] 100 kg of electrolytic copper plates were charged into a coreless intermediate frequency furnace for smelting, the electrolytic copper plates were covered with a thick layer of charcoal, then the furnace was sealed by a furnace cover and nitrogen was introduced for protection, and power was supplied for heating after oxygen was displaced by the nitrogen, while it was ensured that no oxygen was in a hearth when the electrolytic copper was heated in a crucible, so that oxygen was isolated from copper. The thick layer of charcoal could ensure that the molten copper was in a reducing atmosphere to fully remove oxygen from the molten copper. When the quality of the melt met the requirements and the melt was transferred to an intermediate leaking ladle, a leak hole in the center of the leaking ladle, i.e., a diversion pipe, would guide the melt to flow vertically into an atomization tower, and the high-temperature molten metal flow was crushed into powder under the impact of high-pressure water flow (water temperature 25° C.) jet by a jet atomizer. The jet atomizer consisted of an atomizer main body and 4 fan nozzles, every 2 opposite nozzles constituted a group, 2 groups of nozzles were formed in total, and the 2 groups of nozzles were composed of a group of large-diameter nozzles and a group of small-diameter nozzles. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum heat drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Comparative Example 3

[0026] The previous operations were the same as those in Comparative Example 2. When the quality of the melt met the requirements and the melt was transferred to an intermediate leaking ladle, a sealed and transparent device was used and nitrogen was introduced in advance to protect the melt, so that oxygen was isolated from the high-temperature melt during the transfer from the intermediate frequency furnace to the intermediate leaking ladle. Once the melt was poured into the leaking ladle, a leak hole in the center of the leaking ladle, i.e., a diversion pipe, would guide the melt to flow vertically into an atomization tower, and the high-temperature molten metal flow was crushed into powder under the impact of high-pressure water flow (water temperature 25° C.) jet by a jet atomizer. The jet atomizer consisted of an atomizer main body and 4 fan nozzles, every 2 opposite nozzles constituted a group, 2 groups of nozzles were formed in total, and the 2 groups of nozzles were composed of a group of large-diameter nozzles and a group of small-diameter nozzles. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum freeze-drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Comparative Example 4

[0027] The previous operations were the same as those in Comparative Example 3. Before the high-temperature melt was transferred to an intermediate leaking ladle, oxygen in an atomization tower was discharged in advance and nitrogen was filled. Once the melt was poured into the leaking ladle, a leak hole in the center of the leaking ladle, i.e., a diversion pipe, would guide the melt to flow vertically into the atomization tower, and the high-temperature molten metal flow was crushed into powder under the impact of high-pressure water flow (water temperature 25° C.) jet by a jet atomizer. The jet atomizer consisted of an atomizer main body and 4 fan nozzles, every 2 opposite nozzles constituted a group, 2 groups of nozzles were formed in total, and the 2 groups of nozzles were composed of a group of large-diameter nozzles and a group of small-diameter nozzles. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum heat drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Comparative Example 5

[0028] The previous operations were the same as those in Comparative Example 4. A mixture of trace amounts of cetylamine, octadecylamine, sodium phosphate, disodium hydrogen phosphate, mercaptobenzothiazole, and benzotriazole was added to high-pressure water as a corrosion inhibitor. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum heat drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Comparative Example 6

[0029] The previous operations were the same as those in Comparative Example 5. While the corrosion inhibitor was added, ice cubes were added to a water inlet tower to ensure the coexistence of ice and water, so that the water temperature of the atomization water was as close as possible to 0° C. After the water atomization was completed, multi-stage jet was used for water-powder separation. After the water-powder separation, the copper alloy powder was dried by vacuum heat drying. The dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Example 1

[0030] The previous operations were the same as those in Comparative Example 6. After the water-powder separation, freeze-drying was used to replace the vacuum heat drying in Comparative Example 6 to dry the copper alloy powder, the dried powder was sieved, and finished metal powder was finally obtained in batches. The corresponding results of the prepared red copper powder were shown in Table 1.

Example 2

[0031] Bronze powder was prepared according to the method of Example 1, and the corresponding results of the prepared bronze powder were shown in Table 1.

Example 3

[0032] Brass powder was prepared according to the method of Example 1, and the corresponding results of the prepared brass powder were shown in Table 1.

TABLE-US-00001 TABLE 1 Performances of copper and copper alloy powder Oxygen content Yield of Name of Oxygen after storage for −200 mesh Embodiment powder content/% 2 years/% powded% Notes Comparative Red copper 0.25 0.25 89 a Example 1 powder Comparative Red copper 0.24 0.24 88 a, b Example 2 powder Comparative Red copper 0.23 0.23 89 a, b, c Example 3 powder Comparative Red copper 0.22 0.22 88 a, b, c, d Example 4 powder Comparative Red copper 0.19 0.20 88 a, b, c, d, e Example 5 powder Comparative Red copper 0.13 0.13 88 a, b, c, d, e, f Example 6 powder Example 1 Red copper 0.015 0.016 88 a, b, c, d, e, f, g powder Example 2 Bronze powder 0.026 0.026 95 a, b, c, d, e, f, g Example 3 Brass powder 0.076 0.076 92 a, b, c, d, e, f, g

[0033] Relevant technical codes for reducing oxygen content used in Notes: a: charcoal layer protection for smelting, b: nitrogen protection for smelting, c: nitrogen protection for melt transfer, d: nitrogen protection for atomization, e: the atomizing liquid using a corrosion inhibitor, f: adding ice cubes to a high-pressure water inlet tower, g: freeze-drying used when the powder was dried.