WO2013150639A1

WO2013150639A1 - Hardened layer formation device

Info

Publication number: WO2013150639A1
Application number: PCT/JP2012/059398
Authority: WO
Inventors: 良政高橋; 輝一坪田; 一男種岡
Original assignee: 株式会社東亜精機工作所; 國友熱工株式会社; カインド・ヒート・テクノロジー株式会社; 平田ネジ株式会社
Priority date: 2012-04-05
Filing date: 2012-04-05
Publication date: 2013-10-10
Also published as: JPWO2013150639A1

Abstract

The present invention is equipped with a vacuum chamber (2) into which carbon gas and/or nitrogen gas is introduced, and a container (3) which is arranged in the vacuum chamber (2) and is capable of accommodating multiple small components. In addition, the present invention has: a pulse DC power source (4) that applies an anode voltage to the container (3); a heater (5) provided in the vicinity of the container (3); a drive device (6) that drives the container (3); a gas supply device (7) that supplies gas to the interior of the vacuum chamber (2); and a pressure control device (71) that controls the pressure within the vacuum chamber (2). The container (3) is formed of an electroconductive material, and by using the container (3) to which an anode voltage has been applied as a movable anode during glow discharge, a hardened layer is formed over the entire surface of the small components with a uniform thickness.

Description

Hardened layer forming device

The present invention relates to a hardened layer forming apparatus used for forming a hardened layer on the surface of a small metal part.

Conventionally, various reforming treatments have been performed for the purpose of improving the surface hardening and corrosion resistance of the object to be treated made of steel materials or various alloys.

Among these reforming treatments, in recent years, plasma carburizing treatment and plasma nitriding treatment using plasma as a medium have attracted attention from the viewpoints of resource saving, energy saving, and reduction of environmental load.

In general plasma carburizing treatment and plasma nitriding treatment, glow discharge generated between an object to be processed placed on a cathode electrode and an anode is used in a reduced pressure processing gas atmosphere.

By the way, when plasma carburizing or plasma nitriding is performed on a small object to be processed, it is necessary to process a large amount of object to be processed at a time in order to improve efficiency.

However, in order to perform homogeneous and stable processing on a plurality of objects to be processed, it is necessary to place the objects to be processed on the jig with the cathodes spaced apart from each other. There has been a problem that it takes time and effort to set the workpiece on the jig. Further, if each workpiece is set on each jig, a large amount of workpieces cannot be processed at a time.

Therefore, for example, a method described in Patent Document 1 has been proposed as a method for efficiently performing a surface modification process using plasma discharge on a small object to be processed.

This Patent Document 1 describes a plasma nitriding apparatus and a nitriding method for the purpose of forming a stable and uniform nitride surface layer on an object to be processed such as an ultra-small spherical shape made of various alloys. . Specifically, a plurality of workpieces having a very small spherical shape, such as ball bearings, are placed on one jig base, and the jig base is vibrated or swung to provide stable and uniform. A hardened layer is to be formed.

JP 2008-115422 A

In the plasma nitriding apparatus and the nitriding method described in Patent Document 1, an object to be processed having a very small spherical shape such as a ball bearing is a processing target. However, when processing small parts having a threaded portion (for example, screws, bolts, nuts, etc.) or cylindrical small parts such as a shaft, the threaded portion is not used. In addition to the fact that it is difficult to perform uniform surface treatment on small parts having uneven surfaces with a large difference in height, such as small parts, it is possible to place a plurality of small parts on a single jig base. Since they overlap each other, it is extremely difficult to form a stable and uniform cured layer over the entire surface.

The present invention was devised in view of such circumstances, and provides a cured layer forming apparatus capable of processing small parts in a lump in a large amount to form a stable and uniform cured layer. .

The present invention is an apparatus for forming a hardened layer of at least one of a carburized layer and a nitrided layer on the surface of a small metal part, and at least one of carbon gas and nitrogen gas A vacuum chamber for introducing a gas, a container disposed in the vacuum chamber and capable of accommodating a plurality of small parts, a pulsed DC power source for applying a cathode voltage to the container, and provided in the vicinity of the container A heater, a driving device for driving the container, a gas supply device for supplying the gas into the vacuum chamber, and a pressure control device for controlling the pressure in the vacuum chamber, wherein the container is conductive. Forming a hardened layer with a uniform thickness over the entire surface of small parts by forming a container made of a material and acting as a movable cathode during glow discharge. And features.

Note that the terms carbon gas and nitrogen gas in the present invention include a gas containing carbon and a gas containing nitrogen. Further, the gas introduced into the vacuum chamber includes argon, hydrogen and the like in addition to carbon gas and nitrogen gas.

According to the present invention, a plurality of small parts are accommodated in the container, and the surface hardening process is performed while moving the container in the plasma atmosphere. Therefore, a plurality of small parts can be accommodated and processed in the container. It is possible to process the small parts at once. Therefore, cost can be reduced.

Also, since the container is made of a conductive material and the container to which the cathode voltage is applied acts as a movable cathode during glow discharge, the processing speed is fast and the plasma uniformly covers small parts. Therefore, a cured layer having a uniform thickness can be formed in a short time on the entire surface of the small component.

Furthermore, since a pulse DC power source is used to apply a cathode voltage to the container, arcing and plasma instability can be prevented, and stable pulse plasma discharge can be obtained. Therefore, a cured layer having a uniform thickness can be suitably formed on the entire surface of the small component.

Furthermore, since a plurality of small parts can be accommodated in the container and processed while moving the container, the trouble of arranging the small parts one by one on the jig can be saved. Therefore, cost can be reduced.

In addition to the above, since heating is performed using a heater provided in the vicinity of the container, the temperature around the container can be uniformly increased by using both heating by plasma discharge and heating by the heater. Therefore, the time required to raise the temperature to the predetermined temperature can be shortened.

According to the present invention, in the hardened layer forming apparatus described above, the container is configured by a tray at least a part of which is formed of a multi-hole metal plate or a metal mesh. The tray is driven to swing in the direction.

According to the present invention, since the surface hardening treatment is performed while swinging the small parts on the tray, the small parts roll slowly on the tray. Therefore, it is possible to prevent small parts from being dented.

In addition, since at least a part of the tray is formed of a multi-hole metal plate or a wire mesh, the processing gas is supplied into the tray through the multi-hole. Therefore, since a plasma atmosphere is generated inside and outside the tray, small parts are present in the plasma atmosphere, so that a stable and uniform hardened layer can be formed on the entire surface of the small parts. Moreover, it is possible to design the tray by setting the shape and size of the hole according to the size and shape of the small parts.

In the cured layer forming apparatus described above, a plurality of the trays may be provided. In this case, a large number of small parts can be processed at a time. Further, since the tray can be appropriately arranged according to the shape and quantity of the small parts, the convenience is high.

Further, the present invention is the above-described cured layer forming apparatus, wherein the container is configured by a cylindrical rotating container having a circumferential surface formed of a multi-hole plate or a wire mesh, and the driving device is configured to rotate. The container is driven to rotate.

According to this invention, a plurality of small parts are accommodated in a rotating container, and at least one of carburizing and nitriding is performed in the discharge plasma while rotating the rotating container and stirring the small parts. Is possible.

Therefore, it is possible to form a stable and uniform hardened layer on the entire surface of the small parts, it is possible to process a large amount of small parts at once, and the cost required for plasma carburizing or plasma nitriding treatment, or both processes. Can be greatly reduced.

Further, since the rotating container is a cylindrical body having a circumferential surface formed of a multi-hole plate or a wire mesh, the processing gas is supplied through the multi-holes on the circumferential surface. Therefore, since a plasma atmosphere is generated inside and outside the rotating container, a stable and uniform hardened layer can be formed on the entire surface of the small component.

Also, it is possible to design the rotating container by setting the shape and size of the hole according to the size and shape of the small parts.

Furthermore, since the rotating container is formed of a cylindrical body, it rotates when it is rotated around the central axis of the cylinder (the axis that passes through the center of the circle on both sides) in a horizontal state with the circumferential surface of the cylindrical body as a horizontal plane. Since the small parts accommodated in the container are suitably stirred, a stable and uniform cured layer can be efficiently formed on the entire surface of the small parts.

In the cured layer forming apparatus described above, the driving device may be provided outside the vacuum chamber. In this case, since it is possible to prevent the drive device from becoming high temperature, it is possible to prevent problems due to thermal expansion.

According to the present invention, it is possible to provide a hardened layer forming apparatus capable of forming a stable and uniform hardened layer on the entire surface of a small part and capable of processing a large amount of small parts at once. .

It is the schematic which shows the outline | summary of the hardened layer forming apparatus which concerns on 1st Embodiment of this invention. It is the schematic which shows the tray which concerns on 1st Embodiment of this invention. It is a schematic perspective view which shows the example which has arrange | positioned accessory components to the tray which concerns on 1st Embodiment of this invention. It is the schematic which shows the outline | summary of the hardened layer forming apparatus which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments of the hardened layer forming apparatus 1 according to the present invention will be described.
<First Embodiment>
As shown in FIG. 1, the hardened layer forming apparatus 1 is provided with a metal container 3 capable of storing a plurality of small parts in a vacuum chamber 2, and a pulse DC power source for applying a cathode voltage to the tray 3. 4, a heater 5 provided in the vicinity of the container 3, a motor (driving device) 6 that drives the container 3 to swing in the horizontal direction, and a gas supply device 7 that supplies the gas into the vacuum chamber 2. have.

The vacuum chamber 2 is made of, for example, austenitic stainless steel and is designed to prevent sputtering of excess impurities due to discharge.

In addition, although at least one of carbon gas and nitrogen gas is introduced into the vacuum chamber 2, argon or hydrogen is also included in addition to the carbon gas and nitrogen gas.

The container 3 is formed of a tray 31 of a conductive material (for example, made of stainless steel) having a bottom surface made of a large number of perforated plates (punching metal), and is configured to accommodate a large number of small parts therein.

As described above, since the bottom surface 32 of the tray 31 is formed of a multi-hole plate, the processing gas is supplied into the tray 31 through the multi-holes of the bottom surface 32. Therefore, since a plasma atmosphere is generated inside and outside the tray 31, a stable and uniform hardened layer can be formed on the entire surface of the small component.

Also, it is possible to design the tray 31 by setting the shape and size of the holes according to the size and shape of the small parts.

Furthermore, the tray 31 may be provided with partitions according to the size, shape, and quantity of the objects to be processed to form small baskets or baskets formed in rows.

Note that various small parts can be applied as the object to be processed, and in particular, it is preferably applied to a cylindrical small part such as a shaft. In this embodiment, a case where the present invention is applied to a shaft will be described as an example.

∙ Due to the function of the shaft, the occurrence of convex dents and discharge marks becomes a fatal defect. Therefore, as shown in FIG. 3, by using the hardened layer forming apparatus 1 of the present embodiment, the shaft 8 is arranged like a roller conveyor on the row-shaped cage 33 of the tray 31, and the tray 31 is swung to thereby rotate the shaft. When the plasma carburizing / nitriding treatment is performed such that 8 rolls on the tray 31, the plasma carburizing / nitriding treatment can be performed without generating dents. Further, in the vacuum chamber 2 during the plasma carburizing / nitriding process, a uniform glow discharge is generated around the row of cages 33, so that the occurrence of discharge traces on the shaft 8 is prevented.

This is because the gas can be dissociated at a low voltage by heating the heater 5, which will be described later, so that the temperature of small parts that are the objects to be processed becomes uniform, and glow discharge is uniformly generated.

The container 3 is preferably provided with a plurality of trays 31 as shown in FIG. This is because a large number of objects to be processed can be processed at a time by providing a large number of trays 31.

The pulse DC power source 4 is a power source applied for plasma generation, and is set so that, for example, a voltage within a range of 300V to 800V is applied. Further, a cathode voltage is applied to the container 3 and an anode voltage is applied to the vacuum chamber 2.

The heater 5 is composed of a sheathed heater, for example, and is provided in the vicinity of the container 3. By providing the heater 5 in the vicinity of the container 3 in this way, the temperature around the container 3 can be raised by using both the heating by plasma discharge and the heating by the heater 5 together. Therefore, the time required to raise the temperature to the predetermined temperature can be shortened. Moreover, since there are two heat sources in this way, the dissociation state of the gas by the plasma at the time of processing can be adjusted.

The temperature in the container 3 is measured, for example, by placing a thermocouple near the container 3. Moreover, the heating control apparatus 51 which performs a highly accurate temperature rising control using the sequencer is provided.

The motor 6 reciprocates with the bottom surface 32 of the tray 31 in a horizontal state with a slight inclination from the horizontal direction, and swings small parts (the shaft 8) on the tray 31 in the horizontal direction. It is used as a drive means. As described above, when the small component (shaft 8) on the tray 31 swings in the horizontal direction, the shaft 8 rotates and moves, so that the entire surface of the shaft 8 can be uniformly processed.

The motor 6 is preferably provided outside the vacuum chamber 2. This is because if the motor 6 is provided outside the vacuum chamber 2, it is possible to prevent the motor from becoming hot due to plasma discharge or a heater, and thus it is possible to prevent problems due to thermal expansion.

The gas supply device 7 is for introducing at least one of carbon gas and nitrogen gas into the vacuum chamber 2, and a high-quality valve is used. In addition, in order to ensure excellent surface treatment layer uniformity and quality uniformity between products, a high-quality mass flow controller is used to control the gas flow rate.

Furthermore, in order to control the pressure during plasma discharge, a vacuum gauge (capacitance manometer) that is not affected by the type of gas or plasma is adopted, and the pressure in the vacuum chamber 2 is determined based on the signal of this vacuum gauge. There is provided a pressure control device 71 for controlling the pressure. A vacuum pump (not shown) is also provided.

In addition, the temperature around the container 3 is set so as to be heated within a range of 350 ° C. to 800 ° C., and a hardened layer is formed on the entire surface of the small part.

Further, the processing pressure in the vacuum chamber is set within a range of several Pa to several hundred Pa, and the applied voltage is set within a range of several hundred V to several thousand V.

Next, a cured layer forming method using the cured layer forming apparatus 1 will be described.

First, a plurality of small parts are accommodated on a container 3 (tray 31) provided in the vacuum chamber 2. At this time, for example, the shafts 8 are arranged on the tray 31 like a roller conveyor (see FIG. 3).

Next, after depressurizing the inside of the vacuum chamber 2, at least one of carbon gas and nitrogen gas is supplied, and a cathode voltage is applied to the container 3 in this gas atmosphere to perform plasma discharge. While the container 3 is being swung, the temperature in the container is heated within the range of 350 ° C. to 800 ° C. using the heater 5 to form a hardened layer on the entire surface of the shaft 8.

The carbon gas includes a gas containing carbon gas, and may be a mixed gas of CH ₄ , C ₂ H ₂ and Ar, for example. Further, the nitrogen gas contains a gas containing nitrogen gas, and may be N ₂ H ₂ or a mixed gas of Ar, for example.

Further, the accessory part (shaft 8) may be formed of austenitic stainless steel.

Austenitic stainless steel is excellent in corrosion resistance and toughness, but has a drawback that it is easy to generate adhesive wear due to its softness and inferior in wear resistance. On the other hand, the conventional carburizing and nitriding treatment at a high temperature has a problem that the corrosion resistance of the stainless steel is remarkably lowered. Therefore, in the present invention, by processing at a low temperature of 350 ° C. to 800 ° C., the hard parts are formed by forming a hardened layer without impairing the corrosion resistance, thereby ensuring the toughness and enhancing the wear resistance. It becomes possible to provide.

Here, the reason why the lower limit of the processing temperature is set to 350 ° C. is as follows. That is, when the treatment temperature is lower than 350 ° C., the diffusion rate of nitrogen or carbon becomes low, and thus a very long nitriding or carburizing treatment is required to obtain a hardened layer having a practical thickness. . Thus, if processing requires a long time, cost will increase and it is not practical.

Further, it is preferable that the processing pressure in the vacuum chamber is set within a range of several Pa to several hundred Pa, and the applied voltage is set within a range of several hundred V to several thousand V.

As a result of shaft nitriding treatment, carburizing treatment, or combined treatment of nitriding treatment and carburizing treatment by the above method, no dent was generated and no large discharge trace was generated. Moreover, it was confirmed that the S layer having high hardness and corrosion resistance of uniform thickness was formed on the entire surface, and it had excellent quality.

As mentioned above, although 1st Embodiment of this invention was described, it is not restricted to the example mentioned above.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.

As shown in FIG. 4, the second embodiment is different from the first embodiment in the shape and driving operation of the container. Mainly, different forms will be described, and description of the same forms will be omitted.

The rotary container 300 is formed of a stainless steel cylindrical body having a circumferential surface made of a large number of perforated plates (punched metal), and is configured to accommodate a large number (about 2000 to 3000) of small parts therein. .

Thus, since the circumferential surface of the rotary container 300 is formed of a large number of perforated plates, the processing gas is supplied through the large number of holes on the circumferential surface. Therefore, since a plasma atmosphere is generated inside and outside the rotating container 300, a stable and uniform hardened layer can be formed on the entire surface of the small component.

Also, it is possible to design the rotating container 300 by setting the shape and size of the holes according to the size and shape of the small parts.

Furthermore, the multi-hole plate forming the circumferential surface of the rotating container 300 may be configured to be detachable. In this case, it is possible to prepare several types of multi-hole plates corresponding to small parts and replace them according to the object to be processed, or to replace them when the multi-hole plate deteriorates.

The rotating container 300 is provided with an opening for taking in and out small parts and a lid for opening and closing the opening.

The motor 6 is used as a driving means for rotating the rotating container 300 around the central axis of the cylinder (the axis passing through the center of the circle on both sides) in the horizontal state where the circumferential surface of the cylindrical body is a horizontal plane. is there.

In this embodiment, the small part that is the object to be processed is particularly suitable for processing a small part having an uneven surface such as a screw.

That is, since a number of screws are accommodated in the rotating container 3 and the surface hardening process is performed while rotating the rotating container 300 in a plasma atmosphere, the screws are agitated inside the rotating container 300. Therefore, since the flow of the processing gas and the distribution of the plasma sheath in the vicinity of the screw are changed by stirring, a hardened layer having a uniform thickness can be formed on the entire surface of the screw.

The method and apparatus for forming a cured layer according to the present invention is advantageous in that a stable and uniform cured layer can be formed on the entire surface of a small component, and a large amount of small components can be processed collectively. .

DESCRIPTION OF SYMBOLS 1 Hardened layer forming apparatus 2 Vacuum chamber 3 Container 31 Tray 300 Rotating container 4 Pulse DC power supply 5 Heater 6 Motor (drive device)
7 Gas supply device 71 Pressure control device 8 Shaft (small parts)

Claims

An apparatus for forming a hardened layer of at least one of a carburized layer and a nitrided layer on the surface of a metal accessory part,
A vacuum chamber for introducing at least one of carbon gas and nitrogen gas, and a container disposed in the vacuum chamber and capable of accommodating a plurality of small parts,
A pulsed DC power source for applying a cathode voltage to the container, a heater provided in the vicinity of the container, a driving device for driving the container, a gas supply device for supplying the gas into the vacuum chamber, and the vacuum A pressure control device for controlling the pressure in the chamber;
The container is made of a conductive material, and a container to which a cathode voltage is applied acts as a movable cathode during glow discharge, thereby forming a cured layer having a uniform thickness over the entire surface of small parts. A hardened layer forming apparatus.
In the hardened layer forming apparatus according to claim 1,
The container is composed of a tray at least partly formed of a multi-hole metal plate or a wire mesh,
The hardened layer forming apparatus, wherein the driving device drives the tray so that small components on the tray swing in a horizontal direction.
In the hardened layer forming device according to claim 2,
A hardened layer forming apparatus comprising a plurality of trays.
In the hardened layer forming apparatus according to claim 1,
The container is composed of a cylindrical rotating container having a circumferential surface formed of a multi-hole plate or a wire mesh,
The hardened layer forming apparatus, wherein the driving device rotationally drives the rotating container.
In the hardened layer forming device according to any one of claims 1 to 4,
The hardened layer forming apparatus, wherein the driving device is provided outside the vacuum chamber.