JP2600352B2 - Valve seat made of copper-impregnated Fe-based sintered alloy with low opponent aggressiveness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention has a very low aggressiveness against a valve as a mating member when used as a valve seat of an internal combustion engine such as a diesel engine or a gasoline engine.
The present invention relates to a valve seat made of a copper-impregnated Fe-based sintered alloy exhibiting excellent wear resistance.

[Conventional technology]

Conventionally, as described in JP-A-58-178073,
In% by weight (% indicates% by weight), Mo: 0.1 to 0.9%, Ni: 0.5 to 2.5%, Co: 4.5 to 7.5%, Cr: 3 to 6.5%, C: 0.5 to 1.7%, W: 1 to 2.7%, with the balance being Fe and an unavoidable impurity in a Fe-based alloy base material, C: 2-3%, Co: 7 to 15%, W: 15 to 25%, Fe: 1 And a Cr-based alloy particle having a composition consisting of Cr and inevitable impurities, Fe-Mo alloy particles: 8 to 12% by volume, and a structure in which is dispersed and contained, and 6 to 14% by volume. BACKGROUND ART A valve seat made of a copper-impregnated Fe-based sintered alloy obtained by infiltrating copper into an Fe-based sintered alloy substrate having a porosity is known.

[Problems to be solved by the invention]

However, in the above-mentioned conventional copper-impregnated Fe-based sintered alloy valve seat, the Cr-based alloy particles and Fe-Mo alloy particles dispersed in the Fe-based alloy base material are extremely hard, and the hardness is Vickers hardness. In some cases, it exceeds 1600, and although this itself exhibits excellent wear resistance, there is a problem that the wear of the valve as a mating member increases.

[Means for solving the problem]

Therefore, the present inventors have conducted research to develop a valve seat made of a copper-impregnated Fe-based sintered alloy having low opponent aggressiveness and excellent wear resistance from the above-described viewpoints.
In a valve seat made of a copper-impregnated Fe-based sintered alloy, the base material of the Fe-based sintered alloy substrate constituting the valve seat was 150 Vickers hardness.
Hard particles dispersed and contained in the base material are made of a Fe-based alloy having a hardness of ~ 500, and the Vickers hardness is also 50%.
When composed of a Co-based alloy of 0 to 1000, the aggressiveness of the opponent is extremely small, and furthermore, it shows excellent wear resistance,
In addition, even if Fe-Mo alloy particles having a hardness higher than that of the Co-based alloy particles, i.e., having a Vickers hardness of 1,000 to 1,500, are dispersed and contained, the hardness is increased by the relaxation action of the Co-based alloy particles. It has been found that the Fe-Mo alloy particles can further improve wear resistance without damaging the mating member.

The present invention has been made based on the above findings, and includes: Mo: 0.1 to 3%, Ni: 0.1 to 3%, Co: 1 to 10%, Cr: 0.5 to 5%, C: 0.5 to 1.5% , Nb: 0.1 to 2%, the balance being Fe and an unavoidable impurity, and a Fe-based alloy base having a structure mainly composed of a pearlite phase and a Vickers hardness of 150 to 500, Co: 5 to 15%, Mo: 20 to 40%, Si: 1 to 5%, the balance being Co and having a composition composed of unavoidable impurities, and a Vickers hardness: 500 to 1000 Alloy particles: 5 to 20%, Fe-Mo alloy particles with dispersed content of, if necessary, Mo: 55 to 70%, and Vickers hardness: 1000 to 1500: 1 to 15%, A valve seat made of a copper-impregnated Fe-based sintered alloy obtained by infiltrating copper into a Fe-based sintered alloy substrate having a structure containing a dispersed content and further having a porosity of 10 to 20% is characterized.

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

A. Fe-based alloy base (a) Mo, Cr, and Nb These components have the effect of improving the heat resistance by forming a solid solution with the base and improving the wear resistance by forming carbides. Mo: less than 0.1%, Cr: 0.5% respectively
If Nb is less than 0.1% and Nb is less than 0.1%, a desired effect cannot be obtained in the above-mentioned action, and it becomes difficult to preserve the hardness of the substrate to Vickers hardness (Hv): 100 or more in relation to the C content. Even if the content exceeds Mo: 3%, Cr: 5%, and Nb: 2%, the effect is saturated, and no further improvement effect is exhibited. 3%,
Cr: 0.5 to 5%, Nb: 0.1 to 2%.

(B) Ni and Co These components have a solid solution in the
It has the effect of contributing to the improvement of the strength of the substrate, but if its content is less than 0.1% Ni and less than 1% Co, the desired effect of improving the strength cannot be obtained.
%, Co: even if it exceeds 10%, a further strength improvement effect cannot be obtained. In consideration of economy, the content is made Ni: 0.1 to 3%,
Co: 1 to 10%.

(C) C As described above, the C component combines with Mo, Cr, and Nb to form carbides, and has an effect of improving hardness. In addition, it forms a base material mainly composed of pearlite, and has abrasion resistance. However, if the content is less than 0.5%, the desired effect cannot be obtained, and the base hardness is also less than Hv: 100, while if the content is more than 1.5%. However, since the base hardness becomes higher than Hv: 500 and the aggressiveness of the opponent increases, the content is set to 0.5 to 1.5%.

B. Co-based alloy particles The composition of Co-based alloy particles is empirically determined to have a hardness of Hv: 500 to 1000, and therefore, Cr, Mo,
And any of the Si content, Cr: 5-15%,
Mo: 20 to 40%, and Si: out of the range of 1 to 5%, Hv:
It is difficult to secure a hardness of 500-1000.

If the content is less than 5%, the desired wear resistance cannot be ensured. On the other hand, if the content exceeds 20%, the aggressiveness to the opponent increases, so that the content is 5%.
It was set to ~ 20%.

C. Fe-Mo alloy particles Fe-Mo alloy particles have the effect of further improving wear resistance in a state where the opponent's aggressiveness is significantly suppressed in the coexistence with Co-based alloy particles. However, if the content is less than 1%, the desired effect of improving wear resistance cannot be obtained. On the other hand, if the content exceeds 15%, the aggressiveness to the opponent sharply increases. The content was determined to be 1 to 15%.

If the Mo content in the Fe-Mo alloy particles is less than 55%, Hv: 1000 cannot be secured, while the Mo content is 70%.
%, The Hv becomes too high, exceeding 1500, and the opponent's aggressiveness increases, so its content is 55-70%
It was decided.

D. Porosity The porosity is for copper infiltration. If the porosity is less than 10%, the copper impregnation becomes insufficient and the desired strength cannot be secured, while the porosity is 20%. Since the wear resistance is remarkably reduced when the porosity exceeds 1, the porosity is set to 10 to 20%.

〔Example〕

Next, the valve seat of the present invention will be specifically described with reference to examples.

As raw material powders for forming the base, all powders have a particle size of -100 mesh Fe powder, Fe-Cr-Nb alloy (Cr: 12%, Nb: 5% content) powder, Fe-Cr alloy (Cr: 62% content) powder , Fe-Nb alloy (Nb: 65% content) powder, carbonyl Ni powder, Co powder, Mo powder, W powder and natural graphite powder of the same -150 mesh, and Co-based alloy particles and Cr-based alloy particle,
Further, as raw material powders for forming Fe-Mo alloy particles, Co-based alloy powders, Cr-based alloy powders, and Fe-Mo alloy powders each having a composition shown in Table 1 and having a particle size of -100 mesh were used.
Prepared alloy powder were blended these raw material powders in the formulation compositions shown in Table 1, respectively, were mixed for 30 minutes by a mixer, to the green compact at a predetermined pressure in the range of 5~7ton / cm ² Press molding, de-oiling the green compact at a temperature of 500 ° C. for 30 minutes, and then in an ammonia decomposition gas (other reducing gas or vacuum) atmosphere at a predetermined temperature in the range of 1100 to 1200 ° C. To form a Fe-based sintered alloy substrate having the hardness distribution and porosity shown in Table 2 and having substantially the same composition as the blended composition. Subsequently, copper infiltration is performed in a methane conversion gas (other reducing gas or vacuum may be used) atmosphere at a temperature of 1100 ° C. for 15 minutes (infiltration rate: 85 to 95%). This was subjected to a sub-zero treatment using liquid nitrogen at a temperature of −130 ° C. for 30 minutes. By performing heat treatment at a predetermined temperature in the range of 670 ° C for 90 minutes, the outer diameter: 48 mm × inner diameter: 40 mm × thickness: 8 mm Valve seats made of copper-impregnated Fe-based sintered alloy of the present invention (hereinafter referred to as copper-impregnated valve seats of the present invention) 1 to 8 and conventional copper-impregnated Fe
Base sintered alloy valve seats (hereinafter referred to as conventional copper impregnated valve seats) 1 to 6 were manufactured, respectively.

Next, these various types of valve seats were set on a valve seat table wear tester. Valve material: SUH-3, valve heating temperature: 900 ° C, valve seating frequency: 3000 times / minute, atmosphere: Propane gas with a pressure of 0.4 kg / cm ² and a flow rate of 1.5 l / m
Combustion gas due to oxygen in, heating temperature of valve seat (water cooling): 250 to 300 ° C, seating load: 30 kg, test time: 100 hours, abrasion test is performed, maximum wear depth of valve seat and mating member The maximum wear depth of the valve was measured.

As shown in FIG. 1 for the various valve seats described above, cooling nozzles 2 and 2 are provided at predetermined intervals with a heating torch 1 interposed therebetween. Two pairs of water cooling holders made of FC25, which reciprocate at a distance from each other, are arranged.
The valve seats 4, 4 are fitted with a 100 μm interference, and the valve seat 4 is heated to 300 ° C. with a combustion gas of propane gas: 5 l / min, oxygen: 20 l / min from the heating torch 1, while The valve seat 3 heated to 300 ° C. by the compressed air from the cooling nozzle 2 is cooled to 100 ° C.
A repetitive thermal shock test was repeated 100 times every second, and the withdrawal load of the valve seat after the test was measured. Table 2 shows the measurement results.

〔The invention's effect〕

From the results shown in Table 2, all the copper impregnated valve seats 1 to 8 of the present invention have excellent abrasion resistance and strong fitting properties (dropout resistance) which are equal to or higher than those of the conventional copper impregnated valve seats 1 to 6. ), And it is clear that the opponent aggression is much lower than this.

As described above, the valve seat made of a copper-impregnated Fe-based sintered alloy of the present invention has extremely low aggressiveness to a valve as a mating member, and has excellent wear resistance and fitting properties. When applied to an internal combustion engine such as an engine, excellent performance is exhibited over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a repeated thermal shock test. 1 ... heating torch, 2 ... cooling nozzle, 3 ... FC water cooling holder, 4 ... valve seat, 5 ... air cylinder.

Claims (2)

(57) [Claims] 1. Mo: 0.1-3%, Ni: 0.1-3%, Co: 1-10%, Cr: 0.5-5%, C: 0.5-1.5%, Nb: 0.1-2%. A Fe-based alloy base having a composition consisting of Fe and inevitable impurities and a structure consisting mainly of a pearlite phase, and having a Vickers hardness of 150 to 500; Cr: 5 to 15%, Mo: 20 to 40 %, Si: 1-5%, Co-based alloy particles having a composition consisting of Co and inevitable impurities and having Vickers hardness: 500-1000: 5-20%, (more than weight% ) Has a dispersed-containing structure, and 10 to
A valve seat made of a copper-impregnated Fe-based sintered alloy having a low aggressiveness of a partner, comprising a copper-impregnated Fe-based sintered alloy obtained by infiltrating copper into a Fe-based alloy substrate having a porosity of 20%. 2. Mo: 0.1 to 3%, Ni: 0.1 to 3%, Co: 1 to 10%, Cr: 0.5 to 5%, C: 0.5 to 1.5%, Nb: 0.1 to 2%. , The remainder is composed of Fe and unavoidable impurities, and a Fe-based alloy base having a structure mainly composed of a pearlite phase and having a Vickers hardness of 150 to 500: Cr: 5 to 15%, Mo: 20 to Co-based alloy particles having a composition of 40%, Si: 1-5%, the balance being Co and inevitable impurities, and having Vickers hardness: 500-1000: 5-20%, and Mo: Fe-Mo alloy particles containing 55-70%, Vickers hardness: 1000-1500: 1-15%, having a structure containing (more than weight%) dispersed therein, and further having a porosity of 10-20% Fe with
Copper impregnated with low opposing aggression, characterized in that it is composed of a copper-impregnated Fe-based sintered alloy obtained by infiltrating copper into a base sintered alloy substrate
Valve seat made of Fe-based sintered alloy.