JPH059668A - Valve seat made of fe-based sintered alloy having high strength and high toughness - Google Patents

Abstract

PURPOSE:To enhance the strength and toughness of a valve seat made of an Fe-based sintered alloy and used in an internal-combustion engine, etc. CONSTITUTION:A valve seat is made of an Fe-based sintered alloy having a compsn. consisting of, by weight, 0.5-3% Co, 0.5-3% Mo, 0.5-5% Ni, 0.5-1.5% C and the balance Fe with inevitable impurities and having a pearlite structure as sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat made of a Fe-based sintered alloy having high strength and high toughness.

[0002]

2. Description of the Related Art Conventionally, it is well known that many Fe-based sintered alloys have been generally used for manufacturing valve seats of various internal combustion engines including automobiles.

[0003]

On the other hand, in recent years, various types of internal combustion engines have been remarkably improved in performance and speed, and along with this, the environment in which valve seats are used is becoming more severe. The main stream of material development is to improve wear resistance, so many conventional Fe-based sintered alloy valve seats may crack or chip due to lack of strength and toughness depending on the operating environment. At present, it is easier to do.

[0004]

Therefore, the present inventors have
From the above viewpoint, focusing on strength and toughness rather than wear resistance and conducting research to develop a valve seat excellent in these characteristics, the valve seat was
In% by weight (hereinafter% indicates% by weight), Co: 0.5 to 3
%, Mo: 0.5 to 3%, Ni: 0.5 to 5%,
C: 0.5 to 1.5% is contained, and the balance is composed of an Fe-based sintered alloy having a composition of Fe and inevitable impurities, the Fe-based sintered alloy has a pearlite structure as it is sintered. In addition, the fact that the valve seat has extremely high strength and toughness in combination with the fact that there is no distribution of hard particles such as carbides in the matrix has been obtained.

The present invention was made based on the above research results, and Co: 0.5 to 3%, M
o: 0.5-3%, Ni: 0.5-5%, C:
A valve sheet having a high strength and a high toughness, which is composed of a Fe-based sintered alloy containing 0.5 to 1.5% and the balance of Fe and unavoidable impurities and having a pearlite structure as sintered. It is characterized by

Next, the reason why the component composition of the Fe-based sintered alloy constituting the valve seat of the present invention is determined as described above will be explained.

(A) Co The Co component has an effect of improving heat resistance and toughness, so that if the content of Co is less than 0.5%, the desired effect cannot be obtained on the above-mentioned function, while the content of Co is not sufficient. Even if it exceeds 3%, the further improvement effect cannot be obtained due to the wear resistance, so the content thereof is set to 0.5 to 3%.

(B) Mo Mo component has an action of improving wear resistance, so that if the content of Mo is less than 0.5%, the desired wear resistance cannot be obtained, while the content of 3% is contained. If the content exceeds 1.0, the strength will decrease, so the content was defined as 0.5 to 3%.

(C) Ni The Ni component has the effect of improving the toughness, but if the content is less than 0.5%, the desired toughness improving effect cannot be obtained, while the content exceeds 5%. However, since the toughness does not show any further improvement effect, its content is 0.5 to
It was set at 5%.

(D) CC The C component has a function of forming a solid solution in the base material and forming a pearlite structure to improve the strength, but its content is 0.
If the content is less than 5%, sufficient strength cannot be obtained, while if the content exceeds 1.5%, the toughness deteriorates rapidly, so the content should be 0.5-1.5%. I decided.

[0011]

EXAMPLES Next, the valve seat of the present invention will be specifically described by way of examples. As raw material powder, 1 to
Fe powder having an average particle size in the range of 100 μm, Co
Prepare powder, Mo powder, Ni powder, and graphite powder,
These raw material powders were blended to the blending composition shown in Tables 1 and 2, and 1% zinc stearate was added as a lubricant and mixed in a mixer for 30 minutes, and then a powder compact was formed at a pressure of 7 ton / cm ^2. Press-mold, hold this green compact at 500 ° C for 30 minutes to degrease it, and then in vacuum, 1100-1200 ° C.
The Fe group of the present invention having the dimensions of outer diameter: 34 mm × thickness: 7 mm and having substantially the same composition as the composition by sintering at a predetermined temperature within the range of 1 hour. Sintered alloy valve seats 1 to 9 and comparative Fe-based sintered alloy valve seats 1 to 6 were manufactured, respectively.

[0012]

[Table 1]

[0013]

[Table 2]

In each of the comparative Fe-based sintered alloy valve seats 1 to 6, the content of any one of the constituent components is out of the range of the present invention.

Then, the Fe-based sintered alloy valve seat obtained as a result was measured for theoretical density ratio, and for the purpose of evaluating strength and toughness, tensile strength and Charpy impact value were measured, and the resistance was measured. A wear test was conducted for the purpose of evaluating the wear resistance.

For the abrasion test, the valve seat was set on the support base of the abrasion tester, and the valve material was JIS.
SUH-11, valve heating temperature: 600 ° C, valve seating frequency: 3000 times / min, atmosphere: 0.7 kg / cm ²
Propane gas at a pressure of 1, and a flow rate of 0.7 l / min of oxygen-based combustion gas, valve seat surface heating temperature (water cooling): 200 to 250 ° C., test time: 100 hours. The wear depth and the maximum wear depth of the valve, which is a mating member, were measured. The measurement results are shown in Tables 1 and 2.

[0017]

From the results shown in Tables 1 and 2, the present invention F
The valve seats 1 to 9 made of e-based sintered alloy are the same as the valve seats made of a normal Fe-based sintered alloy, which are approximately 40 to 50 kgf / mm.
² shows a tensile strength of ^{2 and} a Charpy impact value of 0.2 to 0.3 kgf · m / mm ² , while showing a much higher value,
It is clear that it has high strength and high toughness, and also with regard to wear resistance, if it shows this level of wear resistance in a state where the wear of the mating valve is small, it is sufficient as a valve seat. As seen in the comparative Fe-based sintered alloy valve seats 1 to 6, even if the content of any one of the constituents is out of the range of the present invention, the strength,
It is clear that the toughness and / or the wear resistance are inferior in properties.

As described above, the valve seat made of the Fe-based sintered alloy of the present invention has particularly high strength and high toughness, and therefore has excellent performance in practical use under severe conditions where these characteristics are required. Is exhibited over a long period of time.

Claims (1)

Claims: 1. By weight%, Co: 0.5-3%, Mo: 0.5-3%, Ni: 0.5-5%, C: 0.5-1. Fe having a high strength and a high toughness, characterized in that it is composed of a Fe-based sintered alloy containing 5%, and the balance of Fe and unavoidable impurities, and an as-sintered Fe-based sintered alloy.
Base sintered alloy valve seat.