JPS6040497B2 - Vacuum heat treatment furnace with highly clean atmosphere generation mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum heat treatment furnace having a mechanism for generating a highly purified atmosphere, and provides a vacuum heat treatment furnace that can highly purify the heat treatment atmosphere.

In non-oxidizing heat treatments such as Ro-yabu and Akatsuki, the partial pressure of moisture (day 20) and hydrocarbon-based substances (Cm
It is well known to those skilled in the art that it is important to maintain the Hn) partial pressure below a certain value, and the following measures have been conventionally used for this purpose: {a- Inert gas introduced into the heat treatment chamber Gases and reducing gases are purified using gas purifiers.

[b} The heat treatment chamber is evacuated to about 10-4 to 105 torr for a long time and heated in a vacuum.

{c) A method in which a small amount of high-purity inert gas is blown into a vacuum heat treatment chamber and the object to be treated is heated in a stream of high-purity, low-density inert gas within the range of 1 to 10-3 Torr (carrier gas method). ).

However, the above-mentioned conventional means have various drawbacks as explained below: In the method {a}, the ratio ○, CmHn in the atmospheric gas, etc. below a certain value (for example, day 2)
Therefore, measures such as flowing a large amount of high-purity gas to lower the concentration of contaminated gas have been taken, which increases costs and requires the use of high-purity gas. There is a need to reduce consumption.

Method [b-] above may cause contamination in the system due to oil used in the oil diffusion pump used for vacuum evacuation, or the pumping capacity may not be sufficient for a ratio of 0. When the total pressure is 5 x 10-4 Torr, the gas partial pressure is about 4 x 10-4 Torr, which is an insufficient atmosphere for vacuum brazing of aluminum or its alloys, for example. For this reason, a vacuum pump with a larger diameter is used to maintain the total pressure at about 5 x 10-5 Torr to lower the partial pressure of the contaminated gas.

Therefore, the exhaust cost becomes high and the maintenance management is complicated, and improvements in these areas are desired. In the method described above, the CmHn partial pressure can be maintained at about 10-6 Torr, but the CmHn partial pressure can be maintained at about 10-2 Torr due to the oil released from the processed material.
As a result, the heat treatment chamber may be contaminated with oil, carbon may adhere to the surface of the workpiece, impeding the brightness of the product, and when brazing aluminum or its alloys, brazing material may not be used. There are cases where fluidity deteriorates and brazing becomes impossible. For these reasons, effective measures to prevent oil contamination are currently strongly desired. The present inventor has successfully developed the present invention as a result of various studies to eliminate the various drawbacks of the above-mentioned subordinate means, and the gist of the present invention is as specified in each claim of the above-mentioned claims. The principle of atmosphere purification in the present invention is that when the CmHn partial pressure and CmHn partial pressure in the same space are in an equilibrium state, they are determined at the lowest temperature in the space, that is, condensation at the temperature of the cryogenic surface. This is based on the knowledge that the equilibrium vapor pressure of CmHn on solidified day 20 determines the partial pressure of CmHn on day 20 in the heat treatment chamber.

The equilibrium vapor pressure table for day 20 is shown in Table 1 below: Table 1 Equilibrium vapor pressure temperature (oK) for 40 Pressure (Torr) 170 8.6×10-61
80 4×10-5190
2.4×10-4200
1.25×10-3210
5.2×10-3220
1.95×10-1230
6.9xlo-2 cryopanel ratio ○, pumping speed for CmHn: When the temperature of the cryopanel is low enough, these gases that have been condensed will hardly evaporate again, so the theoretical pumping speed S ratio is the same as that of gas molecules. It can be easily derived from kinetic theory: Marshal: 3 skins.

In the above equation, Q is the condensation coefficient, which is the probability that the gas will collide with the cryopanel and be captured, and is 0.6 to 0.8 according to experiments.

A is the surface area (ground) of the cryopanel, T is the ratio 0, CmH
n is the temperature, M is the ratio ○, and the molecular weight of CmHn. Figure 1 is a graph showing the relationship between the theoretical pumping speed of the cryopanel and the cryopanel surface temperature when the cryopanel surface area is 1 and the glue is 0.
It is clear that the pumping speed is approximately 2.2 times the pumping speed (curve PFL) of the Type 22 oil diffusion pump. The present invention will be explained based on specific examples shown in the accompanying drawings. However, the present invention is not limited to the specific examples described below, and changes and modifications within the gist of the present invention are included in the present invention. FIG. 2 is a schematic cross-sectional view showing an example in which a cryopanel 4 is arranged in a space 1' which is connected to a heat treatment chamber via a bypass. It is arranged in the vacuum heat treatment chamber 2 by well-known means. 3 indicates a heater.

4 is a cryopanel, which is a cryogenic refrigerator (not shown)
It is cooled to a low temperature of 1730K to 214oK.

Reference numeral 5 indicates a foot Azusa fan, and reference numeral 6 indicates a gas cooler. During the heat treatment, a part of the atmosphere is sucked in by the Watanabe fan 5, passed through the gas cooler 6, and guided to the cryopanel 4, where the gas is purified.
Circulate that gas.

The vacuum heat treatment furnace shown in FIG. 2 is operated by operating the furnace pressure within the range of 1 to 760 Torr using argon gas or nitrogen gas, and increasing the surface temperature of the cryopanel 4 to 173° K.
By adjusting to the range of 1214oK, the partial pressure of glue and CmHn in the furnace atmosphere can be adjusted to between 1×10-5 torr (equivalent to a dew point of 173oK) and 1 torr regardless of the partial pressure inside the furnace.
×10-2 Torr (equivalent to a fog point of 214oK) can be easily adjusted within the range of The atmosphere necessary for non-oxidizing heat treatment can be easily obtained without lowering the total pressure of the internal atmosphere to 5 × 10-5 Torr, which has previously been impossible to implement industrially due to poor yields. Brazing operations of aluminum or their alloys in Thor's inert gas could be easily carried out. In addition, as another application example of the reduced-pressure atmosphere heat treatment furnace having the structure shown in Fig. 2, argon gas or nitrogen gas is introduced (from G) to maintain the total pressure in the furnace at about 1 to 10-2 Torr. In the system used as a carrier gas method (combined with carrier gas method), the partial pressure of 200 CmHn in the furnace atmosphere is set to 10-6
Tor (corresponding to a fog point of 1600K) can be maintained.

FIG. 3 shows a schematic cross-sectional view of a reduced-pressure atmosphere heat treatment furnace that uses a combination of a vacuum exhaust system and a cryopanel, and a shut-off valve 7 is provided in the bypass to shut off the vacuum heat treatment chamber I and the space 1' in which the cryopanel 4 is arranged. It is configured so that it can be done.

In this furnace, by utilizing the large capacity exhaust characteristic for cryopanel glue 0 explained in FIG. 1, when exhausting from atmospheric pressure, it was possible to shorten the exhaust time in the pressure range of 10-1 to 10-3 Torr. Figure 4 shows a comparison of exhaust times, and A
indicates an exhaust system using both a cryopanel and an oil diffusion pump, B indicates an oil diffusion pump exhaust system, the vertical axis indicates pressure [left side: Torr, right side: Pascal (Sa)], and horizontal axis indicates the exhaust time ( minutes). Also, according to this configuration, the CmHn partial pressure in the furnace atmosphere could be reduced to 10-7 Torr or less at about 10-5 Torr. FIGS. 5 to 7 are schematic cross-sectional views showing a specific example in which a cryopanel is disposed in the same space as a heat treatment chamber via a heat shield and a large pulp. Fifth
The figure shows a heat shield 9 and a large-diameter pulp 10 placed between the cryopanel 4 and the heater 3 to prevent heat influence from the heater 3 on the cryopanel 4, and an oil diffusion pump 8 placed on the back of the cryopanel 4. Here is an example.

This heat treatment furnace is a heat treatment furnace that can carry out the three methods described above, {b) reduced pressure evacuation and vacuum heat treatment method, 'c) carrier gas method, and method using the cryopanel of the present invention, either singly or in combination. . FIG. 6 shows a specific example of a heat treatment furnace having a cryopanel 4 and an oil diffusion pump 8, and a heater 3 disposed inside the heat treatment chamber via a heat shield 9 and a large-diameter valve 10. This is a device that combines the method described above with cryopanels.

FIG. 7 shows a specific example in which a cryopanel 4 is disposed in the same space via a heat shield 9 and a large-diameter valve 10, and shows an apparatus that uses a carrier gas method and a cryopanel in combination.

As detailed above, according to the present invention, a vacuum heat treatment furnace with a highly clean atmosphere is obtained, and the vacuum heat treatment furnace is particularly effective for non-oxidation heat treatment of aluminum or aluminum alloys, etc. It is something.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between cryopanel pumping speed and surface temperature with respect to QO when the cryopanel surface area is 1; Fig. 2 is a cross-sectional schematic diagram showing a preferred embodiment of the present invention; Fig. 3, Fig. 5- Fig. 7 is a schematic cross-sectional view showing another specific example, and Fig. 4 is a graph comparing the evacuation times of an evacuation system A using both a cryopanel and an oil diffusion pump and an oil diffusion pump evacuation system B. is the object to be treated, 2 is a vacuum heat treatment chamber, 3 is a heater, 4 is a cryopanel, 5 is a fan for flies, 6 is a gas cooler, 7 is an on-off valve, 8 is an oil diffusion pump,
9 represents a heat shield, and 10 represents a large-diameter bulb. Figure 3 Figure 4 Figure 5 Figure 6 Groove diagram

Claims (1)

[Scope of Claims] 1. A vacuum heat treatment furnace having a highly clean atmosphere generation mechanism in which a panel cooled by a cryogenic refrigerant is provided in a space that is the same as or communicates with a heat treatment chamber. 2. A vacuum heat treatment furnace having a highly clean atmosphere generating mechanism according to claim 1, wherein a panel cooled to an extremely low temperature is disposed in the same space as a heat treatment chamber via a heat shield. 3. The highly clean atmosphere generating mechanism according to claim 1, which comprises a panel cooled to an extremely low temperature being disposed in a space communicating with at least two parts of the heat treatment chamber via a vacuum valve, and a fan is provided. A vacuum heat treatment furnace with 4 The cryogenic temperature ranges from approximately 230°K (-43°^c) to 130°C.
A vacuum heat treatment furnace having a highly clean atmosphere generating mechanism according to claim 1, wherein the temperature is within the range of °K (-143 °^C).