SEMI-CHEMICAL SEMI-MECHANICAL SEALED ULTRA-LOW OXYGEN CONTENT ATOMIZING DEVICE

Abstract

 The invention generally relates to a water atomization equipment, especially a water atomization or water-gas atomization equipment. This invention which is used for preparing metal or alloy powder is related to the field of powder metallurgy. Compared with other designs in China, the water atomization equipment in accordance with this invention is safer and the oxygen content of the powder produced by the invention is in the range of 50 to 500ppm. The invention provides a water atomization equipment that includes three characteristics:
(1) This invention applies semi-chemical method (such as eject reducing gas like CO, inert gas or vacuumizing, where the last two method has relatively high oxygen content compared with the first method) and mechanical seal method (such as using movable separator) to reduce the oxygen content in the smelting chamber.
(2) This invention applied mechanical seal method to separate the smelting chamber and the atomization chamber. The special mechanical seal method could allow metal drops to enter the atomization chamber meanwhile prevent water vapor from entering the smelting chamber to avoid explosion or reducing the vacuum degree.
(3) By vacuumizing as well as ejecting reducing gas or inert gas, the smelting chamber is separated from external air.

Description

TECHNICAL FIELD

[0001] The invention generally relates to a water atomization equipment, especially a water atomization or water-vapor atomization equipment. This invention which is used for preparing metal or alloy powder is related to the field of powder metallurgy. Compared with other designs in China, a water atomization equipment in accordance with this invention is safer and the oxygen content of the powder produced by the invention is in the range of 50 to 500 ppm.

BACKGROUND

[0002] Low oxygen content water atomization equipment has been reported in the literatures. A water atomization producing method of alloy powder (Patent: CN02149116.x, China) was reported in the latest technology report GN2012fj161 published by science and technology information institute of Fujian province in China. The method was invented by Li Puming et al. from Laiwu Iron & Steel Group Powder Metallurgy Ltd. The inert gas protection method was applied during the process of water atomization, drying and high temperature reduction. The powder produced by this method without the help of vacuum annealing furnace treatment still has low oxygen content which is around 0.15wt%. The method is capable of producing high quality powder, simplifying the procedure, saving the investment and reducing the cost. The iron powder produced with the water atomization method (Patent: TW083104452, Japan) invented by Japan's Kawasaki Industries Ltd has oxygen content around 1.0wt%.

[0003] For now, there are two kinds of water atomization equipment in China, which are the opening style and the close style. The equipment is produced by Hunan Jiutai Company, Handan Rand Company and so on. The high pressure water vapor atomization method of producing low oxygen content alloy powder (Patent: CN201110076808.4, China) invented by Changsha Tuozhi Metal Materials Technology Company Ltd is capable of keeping the powder having low oxygen content, small grain size, controllable morphology and homogenous composition. High pressure water atomization equipment invented by Hunan Jiutai Technology Company Ltd has inert gas protection system. To keep the metal and alloy powder from oxidation, the inert gas is ejected into the atomization tower. The oxidation is mainly happened during the melting process, thus the oxygen content of the powder produced with this method is in the range of 10000-3000 ppm (as shown in Fig.1).

[0004] Water atomization equipment invented by the Handan Rand Company, which the upper part of the crucible is covered to separate the air and the molten metal, could avoid the oxidation of the metal melt. However, this method cannot separate the crucible and external air completely, thus the oxygen content of the powder produced with this method is in the range of 2000-3000 ppm (as shown in Fig.2).

DESCRIPTION OF THE INVENTION

[0005] To reach higher oxygen isolation ability than the equipment mentioned before has, this invention applies semi-chemical method (such as eject reducing gas like CO, inert gas or vacuumizing, where the last two method has relatively high oxygen content compared with the first method) and mechanical seal method to reduce the oxygen content. The mechanical seal method could completely separate the smelting chamber and the atomizing chamber. The special mechanical seal method could allow metal drops to enter the atomization chamber meanwhile prevent water vapor and so on from entering the smelting chamber to avoid explosion. As the smelting chamber can be completely separated from the externalair and the smelting chamber and atomization chamber is separated(as shown in Fig. 3), the oxygen content of the powder produced by the equipment is reduced by nearly an order of magnitude lower than the powder produced by the equipment mentioned before has. The oxygen content of the powder is in the range of 50 to 500 ppm. This project was officially approved in 2013 by the Jinjiang Municipal Science and Technology Bureau of Fujian province in China (2013J0107, Jincai index 2013, No.195). It should be noticed that the seal method to separate the smelting chamber and the atomizing chamber mentioned in the embodiments is to use movable separator, where there are other seal methods included in this patent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig.1-1 and Fig.1-2 is the top view and the side view of the open-type water atomization equipment, respectively. The middle circle part is the smelting crucible. It can be found that the smelting crucible is directly in touch with the external air. Therefore, the powder produced by this method has high oxygen content. Fig.2-1 is the top view of the close-type water atomization equipment and Fig.2-2 is the side view of the close-type water atomization equipment. Compared with Fig.1-1, the smelting crucible has a cover on the top to separate smelting crucible from the external air. However, this method cannot separate the smelting chamber from the externalair completely. There is still a small aperture between the upper part of the smelting crucible and the cover and some of the oxygen in the air will enter the smelting crucible. Therefore, the oxygen content of the powder produced by this equipment is relatively high. Fig.3 is the water atomization equipment mentioned in this invention. Fig.3-1 and Fig.3-2 is the top view and the side view of the invention, respectively. The whole smelting equipment is put into a closure container. By vacuumizing and ejecting reducing gas or inert gas, the smelting chamber is separated from external air as well as the atomizing chamber. Meanwhile, the reducing gas would reduce the oxygen content. Therefore, the powder produced by the equipment has the lowest oxygen content.

EMBODIMENTS

[0007] The reducing gas used in the embodiments is CO and NH₃, respectively. However, the reducing gas included in this patent is not limited to the above two.

Embodiments 1: Firstly, put the stainless steel into the furnace and then vacuumize to 10^-3 Pa. Secondly, ejecting CO into equipment to one atmospheric pressure. Smelt at a certain temperature and then atomize. Finally, screen the powder and measure the oxygen content. By comparing with powder produced by two other kinds of water atomization equipment, it's found that the surface oxygen content of the stainless steel powder produced by the invention is only 1/50 of that of the powder produced by close-type equipment.

Embodiments 2: Firstly, put the nickel piece into the furnace and then vacuumize to 10^-3 Pa. Secondly, ejecting NH₃ into equipment to one atmospheric pressure. Smelt at a certain temperature and then atomize. Finally, screen the powder and measure the oxygen content. By comparing with powder produced by two other kinds of water atomization equipment, it's found that the surface oxygen content of the stainless steel powder produced by the invention is only 1/20 of that of the powder produced by close-type equipment.

Claims

1. The invention provides a water atomization equipment that includes three characteristics:

(1) This invention applies semi-chemical method (such as eject reducing gas like CO, inert gas or vacuumizing, where the last two method has relatively high oxygen content compared with the first method) and mechanical seal method (such as using movable separator) to reduce the oxygen content in the smelting chamber.

(2) This invention applied mechanical seal method to separate the smelting chamber and the atomization chamber. The special mechanical seal method could allow metal drops to enter the atomization chamber meanwhile prevent water vapor from entering the smelting chamber to avoid explosion or reducing the vacuum degree.

(3) By vacuumizing as well as ejecting reducing gas or inert gas, the smelting chamber is separated from external air.

2. The reducing gas used in the embodiments is CO and NH₃, respectively. However, the reducing gas included in this patent is not limited to the above two.

3. The seal method to separate the smelting chamber and the atomizing chamber mentioned in the embodiments is to use movable separator, where there are other seal methodsincludedin this patent

Drawing