JPH06101427A - Iron group sintered alloy made valve seat for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a valve seat of excellent abrasion resistance. CONSTITUTION:A valve seat comprises iron group sintered alloy having such a tissure in which 2 to 12% of the high temperature oxide resistance phase of Co-Cr-Mo group alloy having 500 to 1000 of MHv is dispersed and included by the total occupying rate, in the hard base element of Fe-Cr-Mo-V-W group alloy having 400 to 800 of MHv by weight%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrous sintered alloy valve seat for an internal combustion engine, which exhibits excellent wear resistance even in practical use under severe conditions.

[0002]

2. Description of the Related Art Conventionally, a large number of iron-based sintered alloy valve seats have been proposed for various internal combustion engines such as automobiles.

[0003]

On the other hand, in recent years, various internal combustion engines have been remarkably improved in performance and output, and along with this, the operating environment of the valve seat, which is a structural member thereof, has become more severe. In the present situation, further improvement in wear resistance is required to meet this demand.

[0004]

Therefore, the present inventors have
From the above viewpoints, as a result of research to develop a valve seat with excellent wear resistance,
Fe-C having a Micro Vickers hardness (MHv) of 400 to 800 in% by weight (hereinafter,% indicates% by weight).
In the hard base material of the r-Mo-V-W alloy, the high-temperature oxidation resistance phase of the Co-Cr-Mo alloy having MHv: 500 to 1000: 2 to 12% is dispersed and contained in the whole body. It was found from the research results that, when composed of an iron-based sintered alloy, the resulting iron-based sintered alloy valve seat exhibits excellent wear resistance for a long period of time in practical use under severe conditions. is there.

The present invention has been made based on the above-mentioned research results, and Fe-Cr-Mo-V having MHv: 400-800.
An iron-based structure having a structure in which a hard base material of a W-based alloy, in a proportion of the whole, a high-temperature oxidation resistant phase of a Co-Cr-Mo-based alloy having MHv: 500 to 1000: 2 to 12% is dispersed. The present invention is characterized by an iron-based sintered alloy valve seat for internal combustion engines, which is made of a sintered alloy and has excellent wear resistance.

In the valve seat of the present invention,
The hard base material of the iron-based sintered alloy constituting this is C: 0.7 to 2%, Si: 0.1 to 0.5
%, Mn: 0.1 to 0.5%, Cr: 2 to 6%, M
o: 2 to 10%, V: 1 to 6%, W: 1 to 1
Fe-Cr-Mo-V-W having a composition of 0%, and optionally, Co: 0.2 to 10%, with the balance being Fe and inevitable impurities.
The high temperature oxidation resistant phase existing as a system alloy and as a dispersed phase is Cr: 25 to 32%, Mo: 7 to 10%, S
It is desirable to be composed of a Co-Cr-Mo based alloy containing i: 1.5 to 3.5% and the balance being Co and unavoidable impurities.

Therefore, the hard matrix and the high temperature oxidation-resistant phase in the iron-based sintered alloy constituting the valve seat of the present invention are the above-mentioned Fe-Cr-Mo-V, respectively.
The above-mentioned hardness can be obtained by being composed of a -W-based alloy and a Co-Cr-Mo-based alloy, and by setting the content ratio of the high temperature oxidation resistant phase to 2 to 12%, the hardness of these can be improved. An effective hardness balance is formed in the gap, and the valve seat exhibits excellent wear resistance.

Next, the valve seat of the present invention will be specifically described by way of examples. 1 as raw material powder
Atomized Fe-Cr-Mo-VW-based alloy powder having a particle size of 00 mesh or less and having the hardness and composition shown in Tables 1 to 3, and atomization for forming a high temperature oxidation resistant phase Co-Cr-Mo alloy powders were prepared, blended in the blending ratios shown in Tables 4 and 5, and zinc stearate (1%) was added as a lubricant, and the mixture was mixed for 30 minutes in a mixer. The green compact is press-molded at a pressure of cm ² , and the green compact is held at 500 ° C. for 30 minutes to degrease (remove zinc stearate), and then in an ammonia decomposing gas atmosphere, 1100 to 1200 ° C.
The theoretical density shown in Table 4.5, which is composed of an iron-based sintered alloy having a composition substantially the same as the compounding composition, is obtained by sintering at a predetermined temperature within the range of 1 hour. Ratio, and outer diameter: 34 mm × inner diameter: 27 mm × thickness 7 mm valve seats made of iron-based sintered alloy of the present invention (hereinafter referred to as the valve seat of the present invention) 1 to 18, and comparative iron-based sintered alloys Manufactured valve seats (hereinafter referred to as comparative valve seats) 1 to 6 were manufactured.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

[0013]

[Table 5]

In the comparative valve seats 1 to 6, any one of the high temperature oxidation resistant phase and the hardness of the hard matrix and the content ratio of the high temperature oxidation resistant phase in the iron-based sintered alloy constituting the comparative valve seats is in accordance with the present invention. It is out of the range.

Next, regarding the various valve seats obtained as a result of this, valve material: SUH3 base on stellite plating, valve heating temperature: 800 ° C., valve seating frequency: 3000 rpm, atmosphere: 0.4 kg Propane gas at a pressure of / cm ² ;
A wear test was performed under the following conditions: combustion gas with oxygen at a flow rate of 6 l / min, surface heating temperature of valve seat (internal water cooling): 350 ° C, test time: 50 hours, maximum wear depth of valve seat, and mating member The maximum wear depth of the valve was measured. The measurement results are shown in Tables 4 and 5.

[0016]

From the results shown in Tables 4 and 5, all of the valve seats 1 to 18 of the present invention show excellent wear resistance and a small attacking property against the counterpart valve seats 1 to 18. As seen in No. 6, if any of the requirements for forming the iron-based sintered alloy deviates from the scope of the present invention, one of the wear resistance and the opponent attacking property becomes inferior. It is clear that As described above, the iron-based sintered alloy valve seat of the present invention exhibits excellent wear resistance for a remarkably long time even in practical use under severe conditions.

Claims (1)

[Claims] 1. Micro Vickers hardness (MHv): 4
The high-temperature oxidation resistance phase of the Co-Cr-Mo alloy having MHv: 500 to 1000 in the hard matrix of the Fe-Cr-Mo-VW alloy having 0 to 800 is 2 to 2. A valve seat made of an iron-based sintered alloy for an internal combustion engine, which is excellent in wear resistance, and is composed of an iron-based sintered alloy having a structure in which 12% is dispersedly contained.