JPS5948862B2 - Equipment for hardening metal surfaces using glow discharge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for surface hardening of steel materials and the like by glow discharge in a desired gas atmosphere.

Recently, the ion nitriding method using glow discharge has been attracting attention as an excellent surface hardening method and is beginning to be widely used.

However, industrial ion nitriding furnaces differ from experimental furnaces in that when processing long materials or increasing the amount of charge per charge, uneven nitriding and distortion occur due to variations and non-uniformities in the temperature inside the furnace, leading to variations in quality. This results in the problem that there are many In order to eliminate such problems, it is necessary to use dummies, devise jigs, and even manually adjust the current density during processing to equalize the temperature inside the furnace. When the furnace body becomes larger, when the furnace becomes a continuous furnace, or when the shape of the object to be processed becomes complicated or long, sufficient temperature uniformity within the furnace cannot be obtained and variations in quality are inevitable. FIG. 1 is a schematic diagram showing a conventional device, and 1 indicates an airtight container.

A stage 3 insulated from the container by an insulator 2 is placed in this container, and a stage 3 with a diameter of 10 mm and a length of 2
400mm objects to be processed 4a, 4b, 4C, etc.
・Stand up and support more than a dozen of them. An example of the arrangement of the objects to be processed is shown in FIG. The container has pipes 5 and 6.
The pipe 5 is connected to a vacuum pump (not shown) via a valve 7, and is used to evacuate the inside of the container. Further, the pipe 6 is connected via a valve 8 to a tank storing a desired gas (for example, a mixed gas of hydrogen and nitrogen). 9 is a DC power supply, and container 1 (earth potential)
and the objects to be processed 4a, 4b, 4c, .
degree).

In such a configuration, first, the objects to be treated 4a, 4 are placed in the container 1.
b, 4c, . . . are arranged, and the valve 7 is opened to exhaust the air inside.

Next, the valve 8 is opened, a desired gas (mixed gas of hydrogen and nitrogen) is introduced from the tank, and a constant voltage is applied between the object to be treated and the container, causing a glow discharge inside. The positive ions generated by this glow discharge are accelerated and
a, 4b, 4c, . . . , and heat the surface portion, and some of the ions adhere to the skin portion or diffuse inside to generate nitrogen compounds. Therefore, if this discharge state continues for a certain period of time, a nitride layer of a certain thickness is formed. When the temperature of the object to be treated is measured when ion nitriding is carried out using such an apparatus, there is a very large difference between the center and the ends, as shown by curve a in FIG. It can also be seen that there is a considerable temperature difference between the upper end and the lower end, indicating a lack of temperature uniformity. As a result of various experiments and studies, the inventors of the present invention found that the main causes of temperature variations are the relationship between gas pressure and current density, gas flow and gas concentration, and the occurrence of arc discharge. And, each of the objects to be processed in a fixed position does not have a chance to be given the same conditions regarding the above items,
Furthermore, the influence of thermal radiation between the furnace body and the object to be treated is added, and the non-uniformity of temperature becomes very large. The present invention solves the above-mentioned problems by cutting off local arc discharge, making the gas density uniform in the furnace, and ensuring that each part of the surface of the object to be treated is exposed to substantially the same conditions. The feature is that the object to be treated is moved intermittently or continuously within the furnace.

The present invention will be explained in detail below based on the drawings.

FIG. 3 is a schematic diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same constituent objects.

In the figure, a stage 3 is made of a conductive material, and objects to be processed 4a, 4b, 4c, . . . are arranged on the stage 3 so as to be electrically connected to each other. The insulator 2 supporting the stage 3 is taken out to the outside through the bottom plate of the container 1, and a gear 10 is fixed to the end thereof. This gear is connected to a drive device 11 such as a motor. Therefore, when the motor 11 is driven, rotation is applied to the stage 3 via the gear 12, the gear 10, and the insulator 2.
The objects to be processed 4a, 4b, 4c, ... are insulators 2
rotates around its axis. On the other hand, an electrode 13 connected to the stage 3 is embedded in the center of the insulator 2, and the end of the electrode is connected to the negative side of the power source 9. As a result, stage 3 and objects to be processed 4a, 4b, 4C
, . . . are kept at a negative potential with respect to the container 1.
In such a configuration, if a glow discharge is generated in the container 1 as shown in FIG. 1, the surface of the object to be treated will be ion-nitrided. 4a, 4b, 4C, . . . are rotated continuously or intermittently, the gas introduced from the pipe 6 is stirred in the container, and the gas concentration in the container becomes extremely uniform.

Moreover, if arc discharge occurs locally, it has not been possible to prevent this in the past, but in the present invention, even if arc discharge is about to occur, the container and the object to be treated move relative to each other, so the arc can be prevented. Since the cause of the discharge is completely eliminated, the occurrence of arc discharge can be extremely reduced. Because of this, the glow discharge inside the container 1 becomes extremely homogeneous, and therefore the temperature of the objects to be treated 4a, 4b, 4c, . . .
As shown in Figure b, it becomes extremely uniform. In addition, since transition to arc discharge is prevented and the gas concentration can be made uniform, it is possible to arrange objects to be processed more closely than in the past.
Therefore, work efficiency is significantly improved. FIG. 5 shows another embodiment of the present invention, and is a plan view of the stage section. In this example, a small stage 3 is placed on stage 3.
The objects to be processed 4a, 4b, 4C, 4d, . . . are held on this small stage. Stage 3 moves in the direction of arrow A, and small stage 3a
, 3b, 3C, and 3d are rotated in the direction of arrow B, and the objects to be processed 4a, 4b, 4c, . . . are rotated in the direction of arrow C. That is, the rotation of the small stage rotates the objects to be processed 4a, 4.
b, 4C, . . . are rotated as a group, and the rotation of the objects to be processed 4a, 4b, 4c, . . . is rotation. By performing such a combination of rotations, extremely highly uniform glow discharge can be achieved. The embodiment shown in FIG. 6 relates to a continuous furnace, where 14 is a discharge chamber, 5 is a pretreatment chamber for preheating the object to be treated and maintaining pressure equilibrium with the discharge chamber 14, and 16 is a chamber for preheating the object to be treated and maintaining pressure equilibrium with the discharge chamber 14. A post-processing chamber is shown in which pressure equilibrium is maintained and the heated object to be processed is quenched. 1
7a, 17b, 17C, 17d and 17e are stages, which are intermittently linearly moved from the pre-treatment chamber 15 to the discharge chamber and then to the post-treatment chamber.

Each stage holds a plurality of objects 18 to be processed as a group. The stage is rotated within the discharge chamber 14 and rotates the object 18 to be treated if necessary. With such a configuration, the variation in quality that tends to occur in continuous furnaces is extremely reduced. With the configuration described in detail above, the non-uniformity of the temperature on the surface of the object to be processed can be almost completely resolved, and there is almost no transition to local arc discharge, so there is no trace of arc discharge. You can get good quality products.

Furthermore, there is no arc discharge and homogeneous processing is possible.
Compared to the conventional method, objects to be processed can be arranged more closely in the furnace, and therefore, it is expected that work efficiency will be improved. Although the above description has been made using ion nitriding as an example, it can be similarly utilized for ion carburizing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional device, FIG. 2 is a partial plan view thereof, FIG. 3 is a schematic diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing temperature distribution according to the conventional device and the present invention. Diagram showing comparison, 5th
6 and 6 are diagrams showing other embodiments of the present invention, respectively. 1 is an airtight container, 2 is an insulator, 3 is a stage, 4a, 4b
, 4c, ... are objects to be processed, 5 and 6 are pipes, 7 and 8 are valves, 9 is a power source, 10 and 12 are gears,
11 is a motor.

Claims (1)

[Scope of Claims] 1. A container capable of storing a plurality of objects to be treated, means for creating a desired gas atmosphere in the container, and applying a voltage suitable for generating a glow discharge between the objects to be treated and the container. an apparatus for hardening a metal surface using ion bombardment generated by the glow discharge, wherein the plurality of objects to be treated are moved relative to the container continuously or intermittently during the glow discharge. A device characterized by: 2. The apparatus for hardening a metal surface according to claim 1, wherein the movement of the object to be treated is linear. 3. The apparatus for hardening a metal surface according to claim 1, wherein the movement of the object to be treated is a rotational movement centered around a certain point. 4. The apparatus for hardening a metal surface according to any one of claims 1 to 3, wherein the movement of the objects to be processed is performed by grouping a plurality of objects to be processed. 5. The apparatus for hardening a metal surface according to any one of claims 1 to 4, wherein the movement of the object to be processed includes rotation or rotation of the object to be processed.