KR20030059730A - A method of producing the alloy powder by super low temperature cooling system - Google Patents

Abstract

PURPOSE: Provided is a production process of high alloy by quick condensation spray method using an ultra low temperature cooling system which lowers temperature of spray gas to ultra low temperature, with preventing oxidation and increasing cooling speed so that it contributes to produce alloy powder with excellent mechanical property. CONSTITUTION: The production process of the high alloy by quick condensation spray method using the ultra low temperature cooling system comprises the steps of: (i) keeping a chamber in a vacuum state partially or under nitrogen air; and (ii) spraying ultra low temperature liquefied nitrogen gas through a cooler for ultra low temperature to produce circular high alloy powder with high quality, with inhibiting rise of temperature within the chamber to prevent oxidation on the surface of the produced powder.

Description

A method of producing the alloy powder by super low temperature cooling system

The present invention relates to the production of high alloy (stainless steel, Co-base alloy, Ni-base alloy) powder by rapid solidification gas spraying method using ultra-low temperature gas, especially nitrogen gas rapid cooling method at ultra low temperature (-90 ~ -130 ℃) The present invention relates to a spherical powder production method having a uniform composition and no surface oxidation.

High alloy powders include stainless steel, Co-based alloys, and Ni-based alloys. Many of these powders are made of water-atomizing, irregularly shaped powders, and gas-atomizing. It is manufactured by the manufacturing method, such as spherical powder manufactured. These high alloy powders are excellent in corrosion resistance, oxidation resistance, mechanical properties, marketability, etc., and are molded into products such as powder extrusion, metal injection molding (MiM), and HiP, and are being applied to products. In addition, almost all of the rapid coagulation powders used in Korea depend on imports, and the conventional gas spraying powder manufacturing method is a gas recycling cooling method at room temperature, which increases the cost of producing small quantities of small products due to huge facility investment and fine powder. There is a difficulty in improving the quality, such as mixing, there was a disadvantage that a powder of a predetermined size (250μm) or more is difficult to manufacture.

The present invention is to solve the problems of the prior art as described above,

In the preparation of the powder by the conventional gas injection method, the powder was prepared by the gas recycling at room temperature and the oxidation prevention of the powder through the vacuum and inert atmosphere in the chamber. However, in the present invention, the oxygen content of the vacuum + inert atmosphere in the chamber is higher than that of the conventional method. To keep the temperature of injection gas low and cool down immediately to prevent oxidation, and to produce powder with excellent mechanical properties because of its high cooling rate, and also a method for easily producing a large variety of high alloy powders at low cost. Its purpose is to provide

1 is a schematic diagram of a cooling system used in the present invention.

2 is a detailed view of a gas cooling system used in the present invention, and

3 is a view showing the injection of the present invention

<Description of Symbols for Main Parts of Drawings>

1 alloy melting device 2 tundish

22: cooling column 23: vaporizer

The present invention is composed of a high alloy powder manufacturing method by cryogenic gas spraying is composed of a large alloy melting, gas cooling system, injection and collection, the details of these are shown in Figures 1 and 2 and 3.

The present invention is a rapid solidification method for producing a high alloy powder, there is a high-frequency induction alloy melting apparatus (1) capable of melting the alloy first, the inside of the melting apparatus is a line of a magnetic dry shaft type . In addition, there is a tundish (2) for maintaining the temperature of the molten metal and the molten metal while flowing the molten molten metal at a constant speed, and inside the alumina (Alumina) or magnesia crucible (4), such as carbon (C) It prevents mixing. In addition, it is heated by LPG or LNG burner gas heating method to heat tundish and maintain temperature, and these gas atmosphere can prevent oxidation of molten metal by forming the area of gas atmosphere that prevents oxidation by exposing molten surface to the atmosphere. have.

The molten metal thus melted and maintained in the tundish is introduced into the spray nozzle through the ceramic orifice 5 under the magnesia crucible 4 with a molten stem of a constant thickness. The molten metal introduced through the orifice is injected into the cryogenic liquid nitrogen gas through the gas injection nozzle 3 into powder.

Numeral 18 denotes a liquid nitrogen supply cylinder that is a gas injection gas, and these gases are introduced into the injection nozzle through the gas regulator 16 and the pressure gauge 17.

The powder prepared as described above is finally solidified and collected in comparison with the injection chamber, and the chamber must be completely sealed to maintain a constant atmosphere and a water jacket 6 must be installed for self cooling.

A pressure gauge 7, an oxygen concentration gauge 8, a thermometer 9, a vacuum pump 10, and the like are installed at the upper end of the chamber to measure oxygen concentration, temperature, and vacuum degree in the chamber. A collection vessel 11 is installed at the bottom of the chamber, an exhaust gas outlet 12 is installed at the middle portion, and a secondary collection vessel 13 is installed at the lower portion of the cyclone.

The above has been described with respect to the components for the overall powder manufacturing apparatus, next will be described with respect to the gas cooling system that is an important component in the present patent.

The cryogenic cooling apparatus of FIG. 2 is mainly composed of a gas cooling coil 22, an air cooler 23, and a fan heater 24, and the gas cooling coil 22 has a double structure, and the outside is insulated. The liquid nitrogen from the liquid nitrogen cylinder 21 is introduced into the cooling coil 22 through the double structured tube as in (30), and the liquid nitrogen in the air cooler 23 is passed through the tube of (31). The gas is passed through the gas cooling coil through the inner tube of the cooling coil 22 which is vaporized with gas gas and passes through the gas pipes 32 and 33 in a double structure. Nitrogen gas thus passed is cooled to ultra low temperature (-90 to -130 ° C) by cryogenic (-195 ° C) liquid nitrogen outside the double tube.

The ultra-cooled nitrogen gas is again introduced into the tube for cooling the molten metal and the tube for cooling the inside of the chamber. Each gas is introduced into the nozzle through the gas control valves 26 and 27. The gas to reduce the temperature inside the chamber is directly introduced, but the gas that sprays the orifice melt is too cold. It raises the temperature of -25-40 degreeC through the air cooling coil 25, and injects into a molten metal. At this time, the temperature of the cooling gas can be controlled at an ultra-low temperature by the amount of time passing through the inside of the liquid nitrogen.

The gas thus introduced reaches the gas injection nozzle of FIG. 3. First, cryogenic nitrogen gas is injected into the chamber through the space of the lower end of the nozzle, the gas passed through the air cooling coil 25 is injected into the molten metal flowing through the orifice.

At this time, an ultra-cooling area 37 is formed in the portion just below the orifice 34 (indicated by the dashed line) by the gas injected from the nozzle and the gas injected from the nozzle to obtain a super rapid solidification effect (FIG. 3).

In this patent technology, a high-purity powder is produced using a gas spray method by rapid cooling of ultra-low temperature (-90 to -130 ° C) nitrogen gas through a cryogenic cooling system as described above using a homogeneous component having a surface oxidation degree of 100 ppm or less and no segregation. It is possible to manufacture a spherical powder of various particle sizes of 10 ~ 1000μm, there is a feature that can reduce the manufacturing cost of small quantity production of a variety of varieties.

<Example>

The results of applying this patented technology to Austenite-based 316L alloys, Ni-based alloys, and Co-bases are as follows. First, the mother alloy is melted while the upper portion of the master alloy is inert nitrogen gas atmosphere to prevent oxidation of solutes such as Cr, and then molten metal is poured into a tundish crucible. At this time, the oxidation of the molten metal was prevented by a reducing flame such as LPG & LNG on the top of the tundish crucible. The molten stem introduced through the crucible and the orifice of the tundish was prepared by the injection of the cryogenic cooling gas cooled through the cryogenic cooling apparatus developed in the present patent technology. In order to prevent the temperature rise in the powder manufacturing chamber, ultra-low temperature nitrogen gas was supplied to the lower end of the orifice to increase the cooling effect, thereby preparing a rapidly solidified powder.

At this time, the oxygen content in the chamber should be maintained within 200 PPM, and the injected nitrogen gas and the impulse powder are rapidly cooled by the ultra-low temperature nitrogen cooling gas of -130 ° C, and are dropped in the chamber and collected in the collecting container. The fine powder with the exhaust gas is collected in the cyclone secondary collection vessel.

The high alloy (stainless steel, Co base alloy, Ni base alloy) powder prepared as described above has a size of 10 to 1000 μm, and a high purity powder having a uniform composition and a surface oxidation degree of 100 PPM can be obtained.

As described above, high alloy powder is manufactured by gas spraying method using nitrogen gas of ultra low temperature (-90 ~ -130 ℃) by a new gas cooling method, and has a uniform composition of 10-1000 μm particle size with surface oxidation degree of 100PPM or less Stainless steel spherical powder (flow rate over 50, Apprent density 5g / sec: -150 mesh) is manufactured with high alloy powder with low cost, low oxidation rate, fine structure by chemical solidification and uniform chemical composition Could.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (2)

Each method of making liquid nitrogen into a cooling gas through a cooling coil (22) device formed of a double tube and an air cooling vaporizer (23) for vaporizing the gas thus cooled, and then again cooled to cryogenic temperature through the cooling coil. Particular vacuum + nitrogen atmosphere in the chamber, then spray impingement on the molten metal exiting through the orifice using an ultra-low temperature (-90 ~ -130 ℃) nitrogen gas cooling medium, the particle size of 10 ~ 1000㎛ oxygen content without surface oxidation 100ppm The method of manufacturing the following high alloy (stainless steel, Co base alloy, Ni base alloy) powder.