JP3331927B2 - Method for producing valve seat made of Fe-based sintered alloy with excellent wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a valve seat made of an Fe-based sintered alloy, which is a structural member of an internal combustion engine such as a diesel engine or a gasoline engine.

[0002]

2. Description of the Related Art Conventionally, as a valve seat made of an Fe-based sintered alloy for an internal combustion engine, as disclosed in, for example, Japanese Patent Application Laid-Open Nos. 55-16463 and 58-178073, hard particle dispersion is disclosed. There are many proposals made of a type Fe-based sintered alloy.

[0003]

On the other hand, in recent years, the output and the size of the internal combustion engine have been remarkably increased, and accordingly,
The valve seat, which is a structural member of the internal combustion engine, must be operated in a higher temperature environment.
When many other valve seats, such as valve seats made of e-based sintered alloy, are used in a higher temperature environment, the wear progresses rapidly and the service life is relatively short. It is the current situation.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the viewpoints described above, even when exposed to high-temperature environments,
As a result of conducting research to produce a valve seat exhibiting excellent wear resistance, the results are shown in terms of% by weight (% by mass). As the forming alloy powder, C: 0.2 to 3%, Mo: 2 to 12%, Co: 2 to 12%, Cr: 0.5 to 8%, Ni: 0.3 to 3%. Alloy steel powder containing one or two of Nb: 0.1 to 2% and Si: 0.1 to 1.5%, with the balance being Fe and unavoidable impurities. (B) a composition containing 20 to 35% of Mo: 5 to 10% of Cr and 1 to 4% of Si as an alloy powder for forming the hard particles A of the Co-based alloy, with the balance being Co and unavoidable impurities. Co-based alloy powder composed of a Co-Mo-Cr-based alloy having: (c) Mo-based alloy hard particles B Alloy powder containing 20 to 50% of Fe, with the balance being Mo-Fe based alloy powder having a composition of Mo and unavoidable impurities, and (d) calcium fluoride (hereinafter, CaF _2). Using the above (a) to (d) as raw material powders, C: 0.5 to 2%, Si: 0.05 to 1%, Mo: 6 to 15%, Co: 5 to 15 %, Cr: 1 to 6%, Ni: 0.5 to 2%, Nb: 0.05 to 1%, and CaF ₂ : 1 to 15%, with the balance being Fe and inevitable impurities. Co-based alloy hard particles A made of a Co-Mo-Cr alloy and M made of a Mo-Fe alloy
The o-base alloy hard particles B are distributed and distributed at a ratio of 6 to 26 area% in total when observed with an optical microscope structure photograph, and 25 to 7 in a ratio of the hard particles A to the hard particles.
5% by area, and the CaF ₂ particles are also 3 to 45%.
When a valve seat composed of an Fe-based sintered alloy having a structure dispersed and distributed at a ratio of area% and a porosity of 5 to 25% by volume is manufactured, the resulting valve seat made of an Fe-based sintered alloy is obtained. In particular, since the hard particles A have excellent high-temperature wear resistance, excellent wear resistance is ensured even when used at higher temperatures, and the hard particles B have excellent normal-temperature wear resistance. The wear resistance is further improved by the lubricity improving effect of the CaF ₂ particles, and the lubricity improving effect and the room temperature wear resistance improving effect are combined, especially during the initial operation of the internal combustion engine and The wear resistance at low speed operation is improved, and as a result, excellent wear resistance is exhibited over a long period of time, and when copper or copper alloy is infiltrated into this, Conductivity and strength is improved, when the further infiltration of lead or lead alloy lubricity, damping property, and it is the machinability was obtained findings that becomes improved.

The present invention has been made on the basis of the above research results. (A) As a base forming alloy powder, C: 0.2 to 3%, Mo: 2 to 12%, Co: 2 -12%, Cr: 0.5-8%, Ni: 0.3-3%, Nb: 0.1-2%, Si: 0.1-1.5% (B) alloy steel powder for forming high-temperature wear-resistant Co-based alloy hard particles A, comprising one or two of the following, and the balance being Fe and inevitable impurities: Mo: 20 to 35 %, Cr: 5 to 10%, Si: 1 to 4%, and a Co-based alloy powder made of a Co-Mo-Cr-based alloy having a composition consisting of Co and inevitable impurities, and (c) normal temperature resistance. As an alloy powder for forming wearable Mo-based alloy hard particles B, Fe: 20 to 50%, Mo-based alloy powder composed of a Mo—Fe alloy having a composition consisting of Mo and unavoidable impurities, (d) calcium fluoride powder, and using the above (a) to (d) as raw material powders, C: 0. 5 to 2%, Si: 0.05 to 1%, Mo: 6 to 15%, Co: 5 to 15%, Cr: 1 to 6%, Ni: 0.5 to 2%, Nb: 0.05 to 1%, CaF ₂ : 1 to 15%, the balance being Fe and unavoidable impurities, and a high-temperature wear-resistant Co-based alloy hard particle A made of a Co—Mo—Cr alloy in the base material. And a room-temperature wear-resistant Mo-based alloy hard particle B made of a Mo—Fe alloy are dispersed and distributed at a ratio of 6 to 26% by area in a total amount, as observed with an optical microscope structure photograph, and the hard particle A the ratio is 25 to 75 area% as a proportion of the hard particles, further CaF ₂ particles Axis 3-45 area% ratio in disperse distribution organization,
Fe-based sintered alloy having a porosity of 5 to 25% by volume and, if necessary, further infiltrated with copper or a copper alloy or lead or a lead alloy. The present invention is characterized by a method of manufacturing a valve seat made of a base sintered alloy.

In the method of manufacturing a valve seat according to the present invention, the reason why the overall composition of the Fe-based sintered alloy constituting the valve seat, the ratio of hard particles and CaF ₂ particles, and the porosity are limited as described above. explain. (A) Overall composition (a) C In addition to a solid solution in the matrix and strengthening of the C component, a carbide dispersed in the matrix is formed to improve the wear resistance of the matrix, and hard particles A, B has an effect of improving abrasion resistance by being contained in each of them, but if its content is less than 0.5%, the above effect cannot be obtained as desired, whereas if its content exceeds 2%, Since the aggressiveness of the opponent suddenly increases, the content is set to 0.5 to 2%, preferably 1 to 1.5%.

(B) Si The Si component has the effect of forming a solid solution in the base material and increasing its hardness, thereby improving the wear resistance. Does not have the desired effect,
On the other hand, if the content exceeds 1%, the strength decreases, so the content is set to 0.05 to 1%, preferably 0.3 to 0.7%.

(C) Mo The Mo component has a function of solid solution strengthening in the base material and a function of forming carbides in the hard particles A and B to improve wear resistance. If it is less than 6%, the desired effect of improving wear resistance cannot be obtained. On the other hand, if its content exceeds 15%, the aggressiveness to the opponent increases, so that its content is 6 to 15%, desirably. 8-12
%.

(D) Co In the Co component, the solid base is solid-solution strengthened and the hard particles A
Has an effect of improving the high-temperature wear resistance and strengthening the hard particles B by solid solution. However, if the content is less than 5%, the desired effect cannot be obtained in the above-mentioned effect, while the content is 15%. If the ratio exceeds the limit, the wear resistance of the valve seat itself decreases, so its content is set to 5 to 15%, preferably 7 to 12%.

(E) Cr The Cr component forms a solid solution with and strengthens the base material and the hard particles B, and the hard particles A form carbides with Mo and further form intermetallic compounds. In the presence of Co, it has the effect of contributing to the improvement of high-temperature wear resistance. However, if its content is less than 1%, the desired effect cannot be obtained, whereas if its content exceeds 6%, sintering will occur. The strength is reduced, and the desired strength cannot be ensured in the valve seat. Therefore, the content is 1 to 6%, preferably 2.5 to 4.
It was determined to be 5%.

(F) Ni The Ni component has a function of forming a solid solution in both the base material and the hard particles A and B to strengthen it, but if its content is less than 0.5%, the Ni component has the above effect. If the desired effect cannot be obtained, and if the content exceeds 2%, the abrasion resistance is reduced, so the content is 0.5 to 2%, preferably 1 to 1.5%. I decided.

(H) Nb The Nb component has a function of improving the heat resistance of the Nb component and contributing to the improvement of the high-temperature wear resistance, but its content is less than 0.05%. In the above case, the desired effect cannot be obtained in the above-mentioned action. On the other hand, when the content exceeds 1%, the aggressiveness to the opponent increases, so that the content is 0.05 to 1%.
%, Preferably 0.3 to 0.7%.

(H) CaF _{2 In addition} to improving the lubricating properties and hence the abrasion resistance, the CaF ₂ component is used in the initial operation of the internal combustion engine and at a low speed, especially in the presence of the hard particles B, as described above. There is an effect of improving the wear resistance during operation, but if the content is less than 1%, the ratio of dispersion and distribution in the base material is less than 3% by area, and the desired effect of improving the effect cannot be obtained. If the content exceeds 15%, the ratio of the dispersed distribution on the base material exceeds 45 area%, and the strength is reduced. Therefore, the content is 1 to 15%, preferably 3 to 10%. %.

(B) Proportion of Hard Particles As described above, the valve seat has the respective hard particles A,
B provides excellent high-temperature wear resistance and normal-temperature wear resistance. Therefore, if the ratio of the hard particles A to the hard particles is less than 25 area%, the desired high-temperature wear resistance can be secured. On the other hand, if the ratio exceeds 75 area%, the ratio of the hard particles B becomes relatively too small, so that the desired wear resistance at normal temperature and the coexistence with CaF ₂ particles are required during the initial operation and low-speed operation of the internal combustion engine. Since the abrasion resistance at the time cannot be secured, the ratio of the hard particles A is 25 to 75 area%, preferably 40 to 6 area%.
It was determined to be 0% by volume. On the other hand, if the total proportion of the hard particles is less than 6 area%, the desired abrasion resistance cannot be ensured. On the other hand, if the total proportion exceeds 26 area%, not only the aggressiveness of the opponent increases sharply, but also the strength increases. Therefore, the total ratio is determined to be 6 to 26 area%, preferably 10 to 20 area%.

(C) Proportion of CaF ₂ Particles As described above, the CaF ₂ particles have a lubricating property-improving effect to improve wear resistance, and the hard particle B also has a room-temperature abrasion resistance improving effect. In combination, there is an effect of improving the wear resistance during the initial operation and low-speed operation of the internal combustion engine. However, if the ratio is less than 3 area%, a desired improvement effect cannot be obtained in the above operation, while the ratio is 45 area. %, The strength is reduced, so the ratio is set to 3 to 45 area%, preferably 9 to 30 area%.

(C) Porosity If the porosity is less than 5% by volume, not only the lubricity improving effect due to the oil retaining effect cannot be expected, but also the infiltration of copper and copper alloy or lead and lead alloy becomes non-uniform. These effects due to infiltration cannot be sufficiently exhibited, while the porosity is 2
If the content exceeds 5% by volume, a decrease in strength and abrasion resistance cannot be avoided. Therefore, the porosity is set to 5 to 25% by volume, preferably 10 to 20% by volume.

[0017]

Next, a method for manufacturing a valve seat according to the present invention will be specifically described with reference to examples. First, base material forming alloy powders M-1 to M- having the average particle diameter and component composition shown in Tables 1 to 3, respectively, as raw material powders.
15, preparing hard particle A forming alloy powder A-1 to A-6, and hard particle B forming alloy powder B-1 to B-3,
These are combined in a predetermined ratio in the combinations shown in Table 4,
-200me prepared as a raw material powder
The CaF ₂ powder having a particle size of sh respectively blended in a predetermined ratio, zinc stearate: After mixing for 30 minutes at 1% addition mixer, pressure at a predetermined pressure within the range of 5~7ton / cm ² Press molding into a powder, holding this compact at 500 ° C. for 30 minutes to degrease, and sintering in an ammonia decomposition gas atmosphere at a predetermined temperature in the range of 1170 to 1250 ° C. for 1 hour the present invention method and the comparative method carried out by, (measured by an image analyzer based on 100 × optical microstructure photograph of) the overall composition, the proportion of the hard particles and CaF ₂ particles are shown in Table 5-8, as well as pores The valve seats 1 to 15 of the present invention and the comparative valve seats 1 to 4 which are made of a Fe-based sintered alloy having an outer diameter of 34 mm, a minimum inner diameter of 27 mm, and a thickness of 7.2 mm are manufactured. did. The comparative valve seats 1-4
Is the ratio of the hard particles, the hard particles and CaF
The ratio of the _two particles is out of the range of the present invention, whereby the overall composition is also out of the range of the present invention.

Further, the valve seats 1 to 15 of the present invention described above.
And comparison valve seats 1 to 4 as a main body, and pure copper and a Cu-3% Co alloy (hereinafter, referred to as Cu
Alloy-3), Cu-3% Fe-2% Mn-2% Zn
Alloy (hereinafter referred to as Cu alloy 2) or Cu-30%
An infiltrant of a Zn alloy (hereinafter, referred to as Cu alloy 3) was placed in a combination shown in Table 9, and in this state, copper or copper alloy was maintained in a methane-modified gas atmosphere at a temperature of 1100 ° C. for 15 minutes. The invented copper infiltration valve seats 1 to 15 and the comparative copper infiltration valve seats 1 to 4 of the present invention were produced by performing the method of the present invention and the comparative method, respectively. Also, the valve seats 1 to 15 of the present invention and the comparative valve seats 1 to 4 are used as main bodies, and pure lead, a Pb-4% Sb alloy (hereinafter, referred to as a combination) shown in Table 10 are added thereto.
Alloy a) or a Pb-5% Sn alloy (hereinafter referred to as alloy b) immersed in a heating bath for 1 hour in a nitrogen atmosphere with a pressure of 8 kg / cm ² applied to the bath surface The method of the present invention and the comparative method were carried out by performing infiltration treatment of lead or a lead alloy under the following conditions, to produce lead infiltrated valve seats 1 to 15 of the present invention and comparative lead infiltrated valve seats 1 to 4, respectively.

Next, for the various valve seats obtained as a result, using a valve seat table abrasion tester, the material of the valve: SUH-3, the heating temperature of the valve: 750 ° C., the number of times of seating of the valve: 3000 times / Min Atmosphere: Propane gas at a pressure of 0.4 kg / cm ² and flow rate: Combustion gas by oxygen gas at a rate of 1.5 l / min, Heating temperature (water cooling) of valve seat: 350 to 450 ° C, Seating load: 22 kg Test time: A wear test was performed under the following conditions: 20 cycles, one cycle consisting of one hour of continuous operation and 10 minutes of stop, and the maximum wear depth of the valve seat and the maximum wear depth of the valve as the mating material were measured. The results of these measurements are shown in Tables 7 to 10.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

[Table 7]

[0027]

[Table 8]

[0028]

[Table 9]

[0029]

[Table 10]

[0030]

From the results shown in Tables 4 to 10, the valve seats 1 to 15, the copper infiltrated valve seats 1 to 15 of the present invention, and the lead infiltrated valve seat 1 of the present invention manufactured by the method of the present invention. No. 15 to No. 15 show low opponent aggression and show excellent wear resistance under high-temperature operating conditions, whereas Comparative Valve Seats 1 to 4 manufactured by the comparative method.
As seen in the comparative copper infiltrated valve seats 1-4 and the comparative lead infiltrated valve seats 1-4, the Fe
Percentage of hard particles in the base sintered alloy, furthermore hard particles and CaF
_When the proportion of the _two particles is out of the range of the present invention, it is apparent that the abrasion resistance decreases and the aggressiveness of the partner increases. As described above, according to the method of the present invention, the high-temperature and normal-temperature wear resistance is remarkably improved by the hard particles A and B, and the hard particles B and CaF ₂ particles simultaneously coexist during the initial operation of the internal combustion engine and It is possible to manufacture a valve seat made of an Fe-based sintered alloy that has improved wear resistance during low-speed operation. Therefore, the resulting valve seat can be used not only for normal operation but also for internal combustion engines that operate at high temperatures. Excellent wear resistance is exhibited over a long period of time.

Continuation of the front page (56) References JP-A-2-163351 (JP, A) JP-A-2-163350 (JP, A) JP-A-61-64857 (JP, A) JP-A-63-290245 (JP) JP-A 9-242516 (JP, A) JP-A 8-134607 (JP, A) JP-A 5-202451 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C22C 38/00 304 C22C 38/48 F01L 3/02

Claims (2)

(57) [Claims] 1. (a) As a base forming alloy powder, C: 0.2 to 3%, Mo: 2 to 12%, Co: 2 to 12%, Cr: 0.5 to 8%, Ni: 0 And Nb: 0.1 to 2%, Si: 0.1 to 1.5%, and one or two of the following, with the balance being Fe and inevitable: (B) alloy powder for forming high-temperature wear-resistant Co-based alloy hard particles A, Mo: 20 to 35%, Cr: 5 to 10%, Si: 1 to 4%, Co-based alloy powder comprising a Co-Mo-Cr-based alloy having a composition comprising Co and inevitable impurities, and (c) an alloy powder for forming the normal temperature wear-resistant Mo-based alloy hard particles B, Fe: Mo-Fe based alloy containing 20 to 50%, with the balance being Mo and unavoidable impurities Mo-based alloy powder consisting of: (d) calcium fluoride powder, using the above (a) to (d) as raw material powder, C: 0.5 to 2%, Si: 0.05 to 1%, Mo: 6-15%, Co: 5-15%, Cr: 1-6%, Ni: 0.5-2%, Nb: 0.05-1%, Calcium fluoride: 1-15%, The balance is the entire composition of Fe and inevitable impurities [All the percentages related to the composition indicate weight% (mass%)]. The base material of the alloy steel is a high-temperature wear-resistant Co-based material of a Co-Mo-Cr alloy. The alloy hard particles A and the room-temperature wear-resistant Mo-based alloy hard particles B made of a Mo—Fe alloy are dispersed and distributed at a ratio of 6 to 26 area% in total by observing with an optical microscope structure photograph, And the ratio of the hard particles A to the hard particles is 25 to 75 area%, Made of Fe-based sintered alloy with excellent wear resistance, composed of a Fe-based sintered alloy having a structure in which the calcium particles are also dispersed and distributed at a rate of 3 to 45 area%, and a porosity of 5 to 25% by volume. A method of manufacturing a valve seat. 2. (a) As the base forming alloy powder, C: 0.2 to 3%, Mo: 2 to 12%, Co: 2 to 12%, Cr: 0.5 to 8%, Ni: 0 And Nb: 0.1 to 2%, Si: 0.1 to 1.5%, and one or two of the following, with the balance being Fe and inevitable: (B) alloy powder for forming high-temperature wear-resistant Co-based alloy hard particles A, Mo: 20 to 35%, Cr: 5 to 10%, Si: 1 to 4%, Co-based alloy powder comprising a Co-Mo-Cr-based alloy having a composition comprising Co and inevitable impurities, and (c) an alloy powder for forming the normal temperature wear-resistant Mo-based alloy hard particles B, Fe: Mo-Fe based alloy containing 20 to 50%, with the balance being Mo and unavoidable impurities Mo-based alloy powder consisting of: (d) calcium fluoride powder, using the above (a) to (d) as raw material powder, C: 0.5 to 2%, Si: 0.05 to 1%, Mo: 6-15%, Co: 5-15%, Cr: 1-6%, Ni: 0.5-2%, Nb: 0.05-1%, Calcium fluoride: 1-15%, The balance is the entire composition of Fe and inevitable impurities [All the percentages related to the composition indicate weight% (mass%)]. The base material of the alloy steel is a high-temperature wear-resistant Co-based material of a Co-Mo-Cr alloy. The alloy hard particles A and the room-temperature wear-resistant Mo-based alloy hard particles B made of a Mo—Fe alloy are dispersed and distributed at a ratio of 6 to 26 area% in total by observing with an optical microscope structure photograph, And the ratio of the hard particles A to the hard particles is 25 to 75 area%, A Fe-based sintered alloy having a structure in which the calcium particles are also dispersed and distributed at a rate of 3 to 45 area%, and a porosity of 5 to 25 volume%, and comprising copper or a copper alloy, or lead or a lead alloy For producing a valve seat made of an Fe-based sintered alloy having excellent wear resistance by infiltrating a steel sheet.