JP2946972B2 - Method for producing sealed Fe-based sintered alloy part with excellent airtightness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sealed Fe-based sintered alloy part having excellent airtightness.

[0002]

2. Description of the Related Art Conventionally, sealed Fe-based sintered alloy parts have been used as structural members such as hydraulic pumps, air conditioners, and compressors which generally require pressure resistance. This sealed Fe-based sintered alloy part is usually formed by sintering a green compact pressed from a mixed powder having a predetermined composition at a temperature of 1100 to 1200 ° C. in a reducing atmosphere. A continuous furnace or a batch furnace is used for a Fe-based sintered alloy substrate having a porosity of 10 to 30%, and a temperature of 500 to 6%.
Under a condition of 50 ° C., a pressure of 5 to 40 mmAq, and a holding time of 1 to 5 hours, a sealing treatment with steam comprising applying a superheated steam to form a dense oxide film of Fe ₃ O ₄ is performed. It is manufactured by providing a pressure resistance of 20 kg / cm ² or more.

[0003]

On the other hand, in recent years, the sintering atmosphere has been reduced in terms of the finiteness of fossil resources, the control of the carbon concentration of the Fe-based sintered alloy substrate, and the life of the sintering furnace equipment. There is a tendency to use a nitrogen-containing atmosphere instead of an atmosphere (for example, a modified gas). However, when the Fe-based sintered alloy sintered in the nitrogen-containing atmosphere is subjected to the above-described sealing treatment with water vapor, sufficient airtightness cannot be obtained, and only a pressure resistance of about 5 kg / cm ² or less can be obtained. There is no present.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, Fe sintered in a nitrogen-containing atmosphere
As a result of conducting research focusing on the sealing treatment of the base sintered alloy substrate with steam, prior to the sealing treatment with steam, the Fe-based sintered alloy substrate with the sintering atmosphere containing nitrogen was used.
When a reforming treatment is performed under a condition of heating and holding at a temperature of 400 to 600 ° C. in a hydrogen-containing atmosphere, preferably an atmosphere containing H ₂ : 10% by volume or more, the solid solution adsorbs and dissolves on the alloy surface during sintering. Nitrogen, which had hindered the progress of the oxidation reaction during the sealing treatment, was removed by the reaction with hydrogen in the atmosphere of the reforming treatment, and as a result, the progress of the oxidation reaction by steam was remarkably accelerated, and the dense oxidation was performed. The formation of the coating resulted in the research result that a sealed Fe-based sintered alloy part having good airtightness of 20 kg / cm ² or more under pressure was obtained.

The present invention has been made on the basis of the above-mentioned research results, and provides a Fe-based sintered alloy substrate having a porosity of 10 to 30% sintered in a nitrogen-containing atmosphere.
After performing a reforming treatment under a condition of heating and holding at a temperature of 400 to 600 ° C. in a hydrogen-containing atmosphere, a sealed Fe-based sintered alloy part having excellent airtightness is manufactured by performing a sealing treatment with steam. The method has features.

[0006] In the method of the present invention, the porosity of the Fe-based sintered alloy substrate is set to 10 to 30%. The press forming apparatus is not practical and is based on the reason that when the porosity exceeds 30%, the strength rapidly decreases.

Further, in the method of the present invention, the reason why the reforming treatment temperature is set at 400 to 600 ° C. is that the temperature is 40 to 600 ° C.
If the temperature is lower than 0 ° C., the binding reaction between the adsorbed solid-dissolved nitrogen in the substrate and the hydrogen in the atmosphere is slow, so that a long time is required for the denitrification reaction. This is because the progress of the denitrification reaction is suppressed.

[0008]

Next, the method of the present invention will be specifically described with reference to examples. As raw material powders, all 20 to 200
A Cu powder, a graphite powder, and an Fe-based alloy powder having a component composition shown in Table 1 having a predetermined average particle size in a range of μm are prepared. And after mixing, 6-7 ton / cm ²
The green compacts A to I are formed by press molding at a pressure within the range of:
(A) N ₂ : 42.2%, H ₂ : 33.4%, CO:
_{24.0%, CH 4: 0.4%} , (b) N 2: 25.
_{0%, H 2: 75.0%} , (c) N 2: 98.0%,
H ₂ : 2.0%, sintered in the nitrogen-containing sintering atmosphere of any of the above (a) to (c) for 20 minutes at the temperature shown in Tables 2 and 3; , 3 are formed, each having a diameter of 50 mmφ × thickness: 5 mm, and a cooling process after sintering (in this case, (I.e., continuous treatment) or once cooled to room temperature (this case is referred to as intermittent treatment);
N ₂ + H ₂ mixed gas (H ₂ : containing 10% by volume), (i
i) Ammonia decomposition gas + N ₂ gas (H ₂ : 30 volume% is contained), (iii) H ₂ gas, (i) to (ii)
i) The Fe-based sintered alloy substrate is subjected to a reforming treatment in any one of the hydrogen-containing atmospheres under the conditions shown in Tables 2 and 3, and then in a continuous furnace at a temperature of 560 ° C. and a pressure of 20 mmA.
q, holding time: 1.5 hours, the present invention methods 1 to 9 comprising performing a sealing treatment with water vapor were performed to produce sealed Fe-based sintered alloy parts. Further, for the purpose of comparison, as shown in Tables 2 and 3, Comparative Methods 1 to 9 were performed under the same conditions except that the above-mentioned modification treatment was not performed, to produce a sealed Fe-based sintered alloy part.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012] Next, various sealing Fe obtained as a result is obtained.
As shown in a schematic longitudinal sectional view in FIG. 1, a lower ring having an O-ring packing on an upper surface and a lower surface around a hole, as shown in a schematic longitudinal sectional view in FIG. 2, the component 3 is placed on the lower ring 2, and an upper ring 5 with a lid having the same O-ring packing on the lower surface and a through hole 4 on the side surface is placed thereon. Further, a cover ring 6 is fitted so as to cover the outer peripheral side surface of the component 3 and attached to the lower and upper rings 2 and 5 with bolts (not shown). Attach one end of the pipe 8 attached to the total 7, and press the bunch 9 to the upper ring 5.
Under a pressure of kg / cm ² , pressurized nitrogen gas is introduced from the hole of the substrate 1 to the lower surface of the component 3, and the flow rate of the nitrogen gas leaked from the upper surface of the component 3 is detected by the flow meter 7. Then, the pressure of the pressurized nitrogen gas at the time when the pressure became 3 cc / min. Was measured and defined as the withstand pressure. The results are shown in Tables 2 and 3.

As shown in Tables 2 and 3, the present invention methods 1 to 1
The sealed Fe-based sintered alloy parts manufactured by the method No. 9 have higher pressure resistance than the sealed Fe-based sintered alloy parts manufactured by the comparative methods 1 to 9 in which none of the modification processes are performed. It is clear to show. As described above, according to the method of the present invention, even a Fe-based sintered alloy sintered by applying a nitrogen-containing atmosphere is subjected to a reforming treatment before the sealing treatment with steam. Sealed Fe with excellent airtightness
Base sintered alloy parts can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a measurement mode of a pressure resistance of a sealed Fe-based sintered alloy part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower ring 3 Sealing Fe-based sintered alloy part 4 Through hole 5 Upper ring 6 Cover ring 7 Flow meter 8 Pipe 9 Holding punch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B22F 3/24 C21D 1/76 C21D 3/08 C22C 33/02 101 C23C 8/18

Claims (1)

(57) [Claims] 1. Porosity sintered in a nitrogen-containing atmosphere:
Prior to subjecting the Fe-based sintered alloy substrate having 10 to 30% to the sealing treatment with steam, the reforming treatment is performed in a hydrogen-containing atmosphere at a temperature of 400 to 600 ° C. under heating and holding conditions. Of producing a sealed Fe-based sintered alloy part having excellent airtightness.