JPH06136509A - Plasma carburizing furnace - Google Patents

Abstract

PURPOSE:To reduce the time for the carburizing treatment, and to execute the uniform carburizing of small or complicate-shaped products by connecting a loading table provided in a treatment chamber and the heat insulating material to the high-frequency power source. CONSTITUTION:A treatment chamber 13 surrounded by the heat insulating material 12 is formed in a chamber enclosed by a furnace shell 11. A leg member 22 is extended from a loading table 21 provided in a treatment chamber 13, and the lower end part of the leg member 22 is taken out of the furnace and supported by the furnace shell 11 through the electric insulating material 23. The heat insulating material 12 and the lower end part of the leg member 22 are connected to a high-frequency power source 41 through a matching box 42. A metallic product loaded on the loading table 21 is induction heated by the high-frequency power source 41, and at the same time, the metallic product is plasma-carburized by applying the AC voltage between the heat insulating material 12 and the metallic product. The impedance is appropriately matched by the matching box as necessary, and the insufficient calory is supplemented by an auxiliary heater.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma carburizing furnace. The inside of a metal product, for example, a steel product is kept in its original state and only its surface is hardened, while maintaining the toughness of the steel product, while the wear resistance, fatigue strength and resistance of the steel product are maintained. Carburizing is widely used as a surface hardening heat treatment for improving impact resistance and the like. It is well known that various carburizing furnaces are used for such carburizing treatment, but in recent years, a vacuum carburizing furnace, in particular, a plasma carburizing furnace is drawing attention. The present invention relates to an improvement of the above plasma carburizing furnace.

[0002]

2. Description of the Related Art Conventionally, as a plasma carburizing furnace, a processing chamber surrounded by a heat insulating material is formed in a furnace shell, and the processing chamber is equipped with a mounting table. Is used in connection with a DC power source (Japanese Patent Laid-Open No. 125255/1990). In this plasma carburizing furnace, the metal product on the mounting table is used as a cathode, the heat insulating material surrounding the metal product is used as an anode, a DC voltage is applied between both electrodes, and the glow discharge plasma generated generates the atmosphere supplied in the furnace. Carburizing is performed by ionizing a carburizing gas and causing the ions to collide with the surface of a metal product.

However, in the conventional plasma carburizing furnace as described above, the generated plasma density is low and therefore the ion density of the carburizing gas is low, and the ions collide with the metal product only from one direction. It has the following drawbacks. 1) Carburizing takes a long time. 2) When a small metal product is loaded and carburized, carburization becomes uneven between the outer metal product and the inner metal product. In the case of carburizing a metal product having a complicated shape, carburization becomes uneven between the portion exposed on the outside and the portion hidden on the inside. 3) In order to make carburization as uniform as possible, it is necessary to reduce the filling rate (loading degree).

[0004]

The problem to be solved by the present invention is that the conventional plasma carburizing furnace takes a long time for carburizing treatment, and the case of carrying a carburizing treatment by loading small metal products is complicated. This is because when carburizing a shaped metal product, carburization becomes uneven and the filling rate is low.

[0005]

SUMMARY OF THE INVENTION In the present invention, however, a processing chamber surrounded by a heat insulating material is formed in a furnace shell, and the processing chamber is equipped with a mounting table. The present invention relates to a plasma carburizing furnace characterized in that the mounting table is connected to a high frequency power source.

An important point in the present invention is that the heat insulating material and the mounting table are connected to a high frequency power source. A processing chamber surrounded by a heat insulating material is formed in the furnace shell, the processing chamber is equipped with a mounting table, and the heat insulating material and the mounting table are connected to a high frequency power source. It is said that a carburizing gas supply system and an exhaust system using a vacuum pump are connected to the furnace shell, and normally equipped with, for example, a manhold or the like for uniformly dispersing the supplied carburizing gas into the processing chamber. There is no end.

It is preferable to interpose a matching device in the middle of connection between the heat insulating material or the mounting table and the high frequency power supply. This is to properly adjust the impedance that changes in relation to the shape and size of the metal product to be carburized. Further, it is preferable to equip the processing chamber with an auxiliary heater. This is because when the induction heating by the high frequency power source is insufficient due to the shape, size, etc. of the metal product to be carburized, the shortage is compensated.

In the present invention, an AC voltage is applied between the heat insulating material and the metal product on the mounting table while inductively heating the metal product by the high frequency power source. According to the present invention, due to the characteristics of the high-frequency power source, it is possible to increase the generated plasma density, and thus to increase the ion density of the carburizing gas, and the ions collide with the metal product from multiple directions,
Since the so-called stirring effect of the ions can be obtained, the time required for carburizing can be shortened, and even when carburizing by loading small metal products or carving a metal product having a complicated shape, carburizing is uniform. It is possible to further increase the filling rate.

[0009]

1 is a vertical sectional view schematically showing an embodiment of the present invention. A processing chamber 13 surrounded by a heat insulating material 12 is formed in a chamber hermetically sealed by a furnace shell 11. The processing chamber 13 is equipped with a mounting table 21, from which the foot member 2
2 is extended. The leg member 22 penetrates the heat insulating material 12 and the furnace shell 11 without directly contacting them, and the lower end portion thereof is taken out of the furnace, and is supported by the furnace shell 11 via an insulating material 23. . The processing chamber 13 is equipped with auxiliary heaters 31 and 32.
Is connected to the AC power supply 33.

The heat insulating material 12 and the lower end portion of the foot member 22 extending from the mounting table 21 are connected to a high frequency power source 41, and a matching unit 42 is interposed between the lower end portion and the high frequency power source 41. It is equipped. Although not shown, the furnace shell 11
An opening / closing door is attached to the heat insulating material 12 and the furnace shell 1
1 is connected to a carburizing gas supply system and an exhaust system using a vacuum pump, and the processing chamber 13 is equipped with a manhold or the like for uniformly dispersing the supplied carburizing gas.

While inductively heating the metal product A placed on the mounting table 21 by the high-frequency power source 41, an AC voltage is applied between the heat insulating material 12 and the metal product A to plasma-carburize the metal product A, At this time, the impedance is appropriately adjusted by the matching unit 42 and the insufficient heat amount is supplemented by the auxiliary heaters 31 and 32, if necessary.

[0012]

As is apparent from the above, according to the present invention described above, the time required for carburizing treatment can be shortened, and when carrying out carburizing treatment by loading a small metal product or carburizing a metal product having a complicated shape. Even in the case of treatment, there is an effect that carburization can be made uniform and the filling rate can be increased.

[Brief description of drawings]

FIG. 1 is a vertical sectional view schematically showing an embodiment of the present invention.

[Explanation of symbols]

11 ... Furnace shell, 12 ... Thermal insulation material, 13 ... Processing chamber, 21 ... Mounting table, 31, 32 ... Auxiliary heater,
41 ... High frequency power source, 42 ... Matching device

Claims (3)

[Claims] 1. A processing chamber surrounded by a heat insulating material is formed in a furnace shell, and a mounting table is provided in the processing chamber, and the heat insulating material and the mounting table are connected to a high frequency power source. Plasma carburizing furnace characterized by being made. 2. The plasma carburizing furnace according to claim 1, wherein a matching device is provided in the middle of the connection between the heat insulating material or the mounting table and the high frequency power source. 3. The plasma carburizing furnace according to claim 1, wherein the processing chamber is equipped with an auxiliary heater.