JPS62995B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glow discharge treatment method for a conductive member, and particularly to a method for treating a material in a glow discharge state by increasing the temperature using hollow cathode discharge.

A glow discharge surface treatment method, which is a type of surface treatment for metal materials, has been used industrially. A typical example is the ion nitriding method. The ion nitriding method involves introducing a gas body necessary for the treatment into a reduced pressure vessel (hereinafter referred to as the furnace body) whose pressure is reduced to at least 10 ^-1 Torr or less, and installing an electrode so that the product to be treated becomes a cathode ( (The furnace body may be used as a cathode), and a voltage is applied to this from an external DC power source to generate glow discharge and perform surface hardening treatment.
FIG. 1 shows an outline of the ion nitriding process.

Generally, the workpiece 2 serves as a cathode, and the furnace body 1 serves as an anode. The furnace body 1 has a water-cooled structure to prevent various equipment and parts (such as airtight packing) from being overheated due to heating during processing. In the ion nitriding process, the pressure inside the furnace is reduced to at least 10 ^-1 Torr or less using the vacuum evacuation device 9, and a processing gas such as hydrogen gas and nitrogen gas or ammonia gas is introduced to maintain a predetermined pressure in the range of 1 to 10 Torr. Then, a voltage of 300 to 1500 V is applied from the DC power supply 3 to generate glow discharge to perform the nitriding process. In Fig. 1, 4 is an anode terminal, 5 is a cathode terminal, 6 is a gas cylinder, 7 is a gas inlet, 8 is a gas exhaust port to which a vacuum device 9 is connected, 10 is a vacuum gauge terminal, and 11 is an optical pyrometer. , 12 is a control panel.

Since the object to be processed is heated by glow discharge energy, no external heat source is required. Therefore, since the surface generating the glow becomes the heating source, the temperature of the object to be treated changes depending on the ratio of the surface to the volume. In other words, if the workpiece is of the same shape and has a relatively simple shape, the temperature will be almost uniform throughout and uniform processing will be possible, but if the workpiece has a complex shape, especially parts with different surface areas relative to volume, the temperature will vary depending on the location even if the workpiece is the same. However, there is a drawback that the concentration and depth of the diffused atoms fluctuate greatly as a result, making uniform processing impossible.

In particular, this temperature difference tends to increase when processing at high temperatures. Therefore, in carburizing treatment, which is a higher temperature treatment than ion nitriding treatment, the difference becomes even larger, making it difficult to uniformly harden the required areas. As a solution, there are, for example, a method of performing ion treatment in a conventional vacuum heat treatment furnace, or a method of performing ion treatment while applying high frequency heating from the outside. However, in the former case, the object to be processed is heated by a heater such as carbon fiber, so the heating power source requires high output, and the amount of heating by ions is reduced, so conventional processing using only ions is not possible. The ion bombardment energy to the processed product is smaller than that of the ion bombardment, and the amount of ions to the surface is also reduced.
Therefore, the structure and control of the device become complicated, the overall energy consumption is large, and the concentration of atoms involved in processing such as cleaning action by ions and surface hardening is also reduced. In the latter case,
When many parts are charged into a furnace to be heated by induced current generated by high frequency, the temperature at which the individual parts are heated differs depending on the distance from the high frequency coil, and as with the former, Power supply and control become complicated. In addition, a large amount of energy is required for the treatment, and there are also drawbacks in terms of ion cleaning effect and control of surface ion concentration.

On the other hand, depending on the intended use of the article to be treated, it may be necessary to perform a surface treatment with a plurality of functions within the same article, rather than subjecting the entire surface to a surface treatment with the same function. In the above-mentioned ionic surface treatment, such treatment cannot be performed continuously in one process in the same furnace, and is performed in a complicated process.

In the ion surface treatment method, as a method of obtaining partially different surface treatment layers (for example, the depth and hardness of the nitrided layer in nitriding treatment), as shown in Japanese Patent Application Laid-Open No. 47-6956, An additional metal electrode (anode for the workpiece) is placed between the (cathode) and the wall of the vacuum container (anode) via a resistor to the anode power source.
A method is also known in which the potential of this portion is changed to partially change the ion impact energy. In this method, for example, in the case of ion nitriding, additional metal electrodes are provided at parts that require different nitriding, and the potential of these parts is changed by an external circuit to change the ion bombardment energy to the surface parts. The amount of nitrogen adsorbed and diffused is adjusted to form nitrided layers with partially different depths. However, with this method of partially changing the ion bombardment energy using an external circuit, it is difficult to control the bombardment energy and the device becomes complicated. Because of the strong influence of

The purpose of the present invention is to provide glow discharge treatment in which the conductive material to be treated is effectively heated to a certain temperature using an ion treatment power source in the vicinity of the conductive material to uniformly surface-treat the entire surface. The purpose is to provide a method.

The present invention excites a predetermined gas substance contained in the atmosphere by glow discharge in a reduced pressure atmosphere, causes it to collide with the surface of a conductive member connected to a cathode, and causes a certain amount of gas to be generated within the conductive member. In a device that causes a physical or chemical change, an auxiliary electrode that has a hollow cathode discharge effect, that is, an auxiliary electrode that has a double or triple structure and between which a hollow cathode discharge occurs, is covered with a conductive member. The present invention relates to a method for treating a conductive member, characterized in that glow discharge treatment is performed while the treatment section is brought close to the conductive member to the extent that a hollow discharge effect is produced.

By arranging the auxiliary electrode so as to substantially surround the treated portion of the conductive member, glow discharge treatment can be performed effectively. Here, "substantially surrounding" means that the auxiliary electrode almost completely surrounds the part to be processed, or that the same effect as surrounding is achieved by relatively moving or rotating the part to be processed and the auxiliary electrode. say.

By configuring the auxiliary electrode so that the temperature on the side facing the treated portion of the conductive member is higher than the temperature on the opposite side, the energy of glow discharge can be used effectively. .

By subjecting the treated portion of the conductive member to multiple treatments and exposing it to at least two types of glow discharge treatment conditions, the conductive member can be subjected to multiple types of treatments.

In addition, by exposing two or more treated parts of a conductive member to different glow discharge treatment conditions, specifically by applying heating temperature differences, one conductive member can be treated with multiple types of treatment in one treatment. It is possible to provide a functional part.

The present invention also provides a glow discharge treatment method using an auxiliary electrode having a discontinuous surface with holes, slits, etc. formed therein.

The principle of the present invention will be explained below. First, when diffusing atoms from the surface of a workpiece to impart functions such as surface hardening, surface lubrication, corrosion resistance, and fatigue resistance, it is necessary to do so without adversely affecting the workpiece. As long as the amount and depth of atoms to be diffused or adsorbed are appropriate, and the surface concentration is kept constant (generally related to the solid solubility limit of the material or the growth rate of the adsorbate), the treatment temperature is important. play a role. Taking surface hardening of steel materials as an example, when surface hardening is performed with nitrogen, generally 400~
It is in the range of 700℃. Surface hardening by carburizing using carbon is 700-1100℃, and boron is 800-1100℃.
It becomes 1200℃. On the other hand, surface lubrication by sulfurization using sulfur is 150 to 600°C.

As described above, there are appropriate processing temperatures and processing times depending on the atoms to be diffused and the material to be processed. In the ionic surface treatment method, it is possible to efficiently raise the surface temperature of the object to be treated or partially heat it to an appropriate temperature by using an external heat source, but in the present invention, a method using a double or triple structure An auxiliary electrode having a potential of approximately the same as that of the metal material to be processed is placed at a predetermined distance from the surface of the product to surround the part of the product to be processed. By controlling the pressure of the introduced gas, a hollow cathode discharge is generated between the auxiliary electrode and the object to be processed or within the auxiliary electrode to perform processing. Here, heat absorption from the processed items is due to heat exchange of glow discharge energy, radiant heat between processed items and from auxiliary electrodes, etc., and heat loss due to heat release is due to radiant heat, convection of processing gas, and heat from the electrodes. such as conduction (flow from the electrode cooling water). Among these factors, radiant heat between the auxiliary electrode and the workpiece can be used to heat the required part of the workpiece to a predetermined temperature. This is done by setting the distance between the auxiliary electrodes or between the auxiliary electrode and the workpiece to be treated at a constant interval, and setting the introduced gas pressure to a predetermined value to cause hollow cathode discharge between the auxiliary electrodes or between the auxiliary electrode and the workpiece. This can be achieved by making the current density higher than that of other glow surfaces.

Furthermore, if there is a surface part of the object to be treated (cathode) to which a different function is to be imparted, a counter auxiliary electrode having approximately the same potential as this part is separately installed. The surface of the workpiece in this area is heated and kept warm by hollow cathode discharge between the auxiliary electrodes or between the auxiliary electrode and the workpiece. In this case, the ionization density of the gas between the object to be treated and the auxiliary electrode and between the auxiliary electrodes also increases, and the surface reaction with the target active atoms to be diffused becomes active. In order to effectively carry out this phenomenon, important factors are the distance from the surface of the workpiece to the auxiliary electrode or the interval within the auxiliary electrode, and the setting of the gas pressure according to the composition of the gas. First, the distance from the surface of the workpiece to the auxiliary electrode or the interval within the auxiliary electrode varies depending on the gas pressure. Unless a hollow cathode discharge is generated by the action, the desired effect will not occur. This is because the width of the negative glow varies depending on the gas composition and gas pressure, which strongly affects hollow cathode discharge. Furthermore, the shape and structure of the auxiliary electrodes, which are closely related to these, are also important factors. FIG. 2 shows the structure of the double-structured auxiliary electrode. The figure shows an example of a plate-shaped auxiliary electrode. In this case, 111 is the anode side, and 112 is the processed product side. In this processing method, the auxiliary electrode spacing t ₁
is an important factor. In particular, the structure is such that 112 has a higher temperature than 111 within the auxiliary electrode.
The hollow cathode effect occurs between the auxiliary electrodes, i.e. 11
1 and 112 and between 112 and the workpiece. Further, the auxiliary electrode structure may be cylindrical as shown in FIG. FIG. 3 shows an example of a cylindrical type with a triple structure. In this case, by attaching electrode 2' or 3' to 1' as a thinner and smaller piece than 1', changes in the interval between hollow cathode discharges due to deformation due to thermal expansion due to heating by hollow cathode discharge can be reduced. I can do it. Next is the distance between the auxiliary electrodes t ₂ and t ₃ or the distance between the auxiliary electrode and the workpiece. In general ionic surface hardening treatment, if this distance is less than 0.5 mm, the processing gas will not reach the workpiece. reactions tend to be inhibited, while 20
If the distance is more than mm, the influence of the hollow cathode effect between the glows will be weakened, and the heating effect due to radiant heat between the auxiliary electrodes or between the auxiliary electrodes and the object to be treated will be reduced, and the process will be similar to general ion surface treatment.

Here, glow discharge is generated at a pressure of 3.5 Torr using a mixed gas of nitrogen gas, hydrogen gas, argon gas, and methane gas. If there is no auxiliary electrode, use the auxiliary electrode shown in Figures 2 and 3. t ₁ to 30mm
When the distance between 112 and the workpiece is arbitrarily changed, and when t ₂ is 10 mm and t ₃ is 8 mm in Fig. 3, and the interval between the auxiliary electrode and the workpiece is arbitrarily changed, the diameter is 15 mm. The temperature of specimens with a length of 50 mm was measured by processing them simultaneously in the same furnace. FIG. 4 is a graph showing the relationship between the distance from the workpiece to the auxiliary electrode and temperature. The temperature of conventional glow discharge alone without an auxiliary electrode is 570°C as shown in A, but when the auxiliary electrode shown in Figure 2 is used, it becomes as shown in B, and the effect of hollow cathode discharge is remarkable. The area between 2 and 7 mm is heated to a temperature of over 900°C. In addition, when the auxiliary electrode shown in Figure 3 is used, the temperature will be as shown by curve C in Figure 4, and the temperature will be 300°C or more where the hollow cathode discharge effect is noticeable compared to the case without the auxiliary electrode. The temperature is high. This temperature difference varies greatly depending on the gas composition, gas pressure, material, shape, thickness, etc. of the auxiliary electrode. As mentioned above, in order to generate hollow cathode discharge using the auxiliary electrode and heat each individual component or a specific position of each component, the distance at which the hollow cathode discharge is generated is
It can be seen that a range of 1.5 to 7 mm is desirable. Next, regarding the structure of the auxiliary electrode, in the structure shown in FIGS. 2 and 3, the electrode 111 on the surface facing the anode serves as the auxiliary electrode.
Alternatively, if a similar experiment is carried out by making 1' thicker than electrode 112 or 3' on the surface facing the object to be processed, the thickness of 112 or 3' will be thicker, depending on the difference in each thickness. I see, the temperature difference will be smaller with the same power consumption. As a result, a desirable result was obtained for the auxiliary electrode with a structure in which the electrode on the anode side is thick and the electrode on the object to be treated is thin, and the temperature of the electrode on the object to be processed is higher than that of the anode.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Example 1 As shown in Fig. 5 a, b, c, d, and e, the area to be treated of the test piece was surrounded by a double or triple-structured cylindrical auxiliary electrode, and the conventional ion beam as shown in Fig. 1 was used. It was set inside the surface treatment equipment. In FIG. 5, a chromium-molybdenum steel shaft (diameter 15 mm, length 200 mm) of JIS standard SCM21 was used as the workpiece 311. In FIG. 5a, the auxiliary electrode had a double-structured cylindrical shape, and the distance between 312 and 313 was 8 mm, and the distance between 312 and the test piece was 5 mm. A strong hollow cathode discharge was generated between 312 and the test piece. Fifth
In Figure b, the auxiliary electrode 312 is made thicker than 313,
This interval was set to 3.5 mm, and the hollow cathode discharge here was generated stronger than the hollow cathode discharge between the auxiliary electrode and the workpiece. In FIG. 5c, a hollow cathode discharge is generated at the top and bottom of the test piece, and a triple-structured cylindrical auxiliary electrode consisting of 312, 313, and 314 is used at the top end. At the upper end, a strong hollow cathode discharge is generated between 312 and 313, and at the lower end, a hollow cathode discharge is generated between 315 and the test piece. Figure 5 d is 312
was made thicker than 313, and a strong hollow cathode discharge was generated between 312 and 311. Figure 5e is between 312 and 313 at the top and 316 at the bottom.
A strong hollow cathode discharge was generated between and 317. As a result, the article to be treated was heated to a temperature of 850 to 950 DEG C. at the upper and lower ends of FIGS. 5a and 5c and at the upper end of e. Figure 5 b is 680-700℃, d is 670-690℃, e
The lower end of the temperature ranged from 650 to 670℃. The treatment was carried out at that temperature for 1 hour, and then the quenching treatment was performed. FIG. 6 shows the results of measuring the hardness distribution after treatment. As a result, the hardness of the treated items heated to a temperature of 850°C or higher is within the range , and the hardness of the other items is within the range of . As described above, it can be seen that the hollow cathode discharge generated in the test piece and its vicinity is extremely effective for curing. FIG. 7 shows an example of the auxiliary electrode. Diameter 20mm,
When only the cylindrical inner auxiliary electrode 413 with a diameter of 26 mm, a length of 150 mm, and a wall thickness of 3 mm as shown in FIG. In the case of an outer electrode 412, as shown in Fig. 8, a cylindrical inner auxiliary electrode 415 with a diameter of 26 mm and a wall thickness of 3 mm has holes of 1 mm, 2 mm, and 3 mm sequentially provided on the entire surface, and this auxiliary electrode An outer auxiliary electrode 4 with an inner diameter of 36 mm and a wall thickness of 5 mm is placed on the outside of the
In the apparatus shown in Figure 1, the area without the auxiliary electrode is maintained at 580°C with a mixed gas of nitrogen gas, hydrogen gas, argon gas, and methane gas. The temperature of the auxiliary electrode section was measured while varying the pressure. FIG. 9 shows the relationship between gas pressure and temperature distribution. In order to stably perform surface treatment using ions, it is important that the temperature of the object to be treated does not vary greatly even with slight fluctuations in gas pressure. When there is no auxiliary electrode, the heating temperature is 580°C as in 101, but the heating temperature itself is low. A conventional single auxiliary electrode has a high temperature only within a relatively narrow pressure range, as shown by curve 121. If an external auxiliary electrode is used in this case, a curve 131 will appear, and the effect of hollow cathode discharge within the auxiliary electrode will appear. On the other hand, if holes with a diameter of 1 to 3 mm are provided in the inner auxiliary electrode in the correct order as shown in Figure 8, the temperature at maximum heating will be lower as shown by curve 141, but the pressure range where the temperature will remain constant will be wider. Become. In this case, due to pressure fluctuations, a hollow cathode discharge occurs in the hole in the auxiliary electrode according to the pressure,
This is due to the fact that the pressure range of hollow cathode discharge with the object to be treated is widened. Next, when this electrode is further provided with an outer electrode, the curve becomes like curve 151, the maximum temperature becomes higher and the pressure range in which a constant temperature can be maintained becomes wider.

Note that the maximum temperature and the pressure range in which a constant temperature can be maintained can vary widely depending on the shape and structure of the auxiliary electrode and the composition of the gas.

Next, as an electrode with the structure shown in Figure 8, a diameter of 0.5 to 3
The hole sizes were investigated using internal auxiliary electrodes in which holes of 4, 5, 6, 7, 8, and 9 mm were sequentially provided. As a result, it was found that when the maximum hole diameter was 4 mm or more, the maximum heating temperature decreased rapidly, and when the maximum hole diameter was 8 mm or more, the effectiveness decreased significantly. The most effective range is 0.5 to 4 mm in diameter, and a range of 0.5 to 7 mm is also somewhat effective. Next, instead of a hole, length 20mm
A slit was provided. In this case as well, if the width of the slit was within 4 mm, a similar discharge occurred within the slit based on the hollow cathode effect. Next, a similar experiment was conducted with a ceramic layer provided on the outside of the electrode. As a result, it was found that the electrical output can be reduced by approximately 10% when ceramic is provided on the outer electrode of the electrode in the form shown in FIG.

Example 2 A JISSCM21 material with a diameter of 20 mm and a length of 200 mm was used, and 4 types of electrodes shown in Figs. 7 and 8 were used, 50 each, and nitrogen gas, methane gas, hydrogen gas, Using argon gas, the temperature at the position where no hollow cathode discharge occurs was maintained at 600°C, and ion carbonitriding treatment was performed for 50 minutes. After that, it was hardened at 850°C for 1 hour, and its cross-sectional hardness was measured. As a result of measuring the effective hardened layer depth, the method according to the present invention has a value of 0.9 to 1.2 mm, which is larger than other methods and has less variation.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of a general glow discharge treatment device, Fig. 2 is a perspective view showing the structure of an auxiliary electrode used in the present invention, and Fig. 3 is a cross section showing the structure of another auxiliary electrode. Figure 4 is a graph showing the relationship between temperature and the distance from the workpiece to the auxiliary electrode obtained in the example of the present invention, and Figure 5 shows the structure of various auxiliary electrodes used in the present invention. The cross-sectional view, FIG. 6, shows the surface hardness of the treated product obtained in the example of the present invention,
A graph showing the relationship between the distance between the object to be processed and the auxiliary electrode, FIGS. 7 and 8 are cross-sectional views showing the structure of the auxiliary electrode used in the present invention, and FIG. 3 is a graph showing the relationship between gas pressure and temperature.

Claims (1)

[Claims] 1. In a reduced pressure atmosphere, a predetermined gaseous substance contained in the atmosphere is excited by glow discharge and collides with the surface of a conductive member connected to a cathode, thereby causing the inside of the conductive member to be excited. In the method of causing a certain physical or chemical change in the conductive member, an auxiliary electrode with a double or triple structure surrounding the treated portion of the conductive member is provided and connected to the cathode,
A method for treating a conductive member, characterized in that, during the glow discharge, a hollow cathode discharge is generated both between the auxiliary electrodes and between the auxiliary electrode and the treated portion of the conductive member.