JPH0633201A - Iron-based sintered alloy for valve seats - Google Patents

Abstract

(57) [Summary] [Purpose] A ferrous sintered alloy for valve seats, which has excellent wear resistance, heat resistance, and corrosion resistance at high temperatures. [Structure] An Fe-based matrix structure containing 0.3 to 1.5% of C and forming a matrix, Co, Ni, Mn or V
Since 3 to 30% was made to form a solid solution, the strength was improved and excellent heat resistance and corrosion resistance were obtained. Moreover, since 3% to 15% of Fe-Mo and Fe-W were dispersed in the matrix structure as hard particles, the wear resistance could be improved. Furthermore, by dispersing CaF ₂ , MoS ₂ , or MnS as a solid lubricant, seizure resistance and machinability can be improved, and the upper limit of 2.0% of the solid lubricant can be regulated and Since the open porosity was set to 1% or less, the corrosion resistance and the oxidation resistance could be remarkably improved without impairing the machinability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered alloy for valve seats of automobile internal combustion engines.

[0002]

2. Description of the Related Art Fe is a conventional valve seat material.
-C-Co-Ni-based materials, Fe-C-based materials and intermetallic compounds such as ferromolybdenum (Fe-Mo) and ferrochrome (Fe-Cr) or Fe-C for the purpose of improving wear resistance.
A material to which a --Cr--Mo--V alloy or the like is added is used.

Further, Fe-containing Cr and Mo
Impregnated with a sintered alloy (Japanese Patent Laid-Open No. 60-224762), Pb alloy, etc., in which iron-based hard particles composed of Cr, Mo, V, etc. are dispersed in the C base structure to improve wear resistance and opponent attack. Fe-C in the formed Fe-C-Co-Ni matrix structure
-Cr-Mo-V alloy sintered particles in which hard particles are dispersed (JP-A-60-251258), Fe-C
There is disclosed a sintered alloy (JP-B-62-202058) in which ferro-molybdenum and ferro-tungsten particles are dispersed in a —Co—Ni-based material, sintered, and further impregnated with Pb.

[0004]

However, recently, in automobile engines, there has been an increasing demand for improvement in long life, high output, high rotation, exhaust gas purification measures, or fuel consumption improvement measures. For this reason, it has become more unavoidable than ever to withstand harsh operating environments for engine valves and valve seats in automobile engines, further improving heat resistance and wear resistance, and at high temperatures. There is a growing need to improve the corrosion resistance of aluminum.

The present invention was invented to meet the demand for higher performance of conventional sintered alloys for valve seats, which accompanies the recent increase in output of automobile engines and improvement in fuel consumption. It is also an object of the present invention to provide an iron-based sintered alloy for valve seats, which is further improved in wear resistance and has excellent corrosion resistance at high temperatures.

[0006]

In order to improve the corrosion resistance and wear resistance at high temperatures, the inventors of the present invention have investigated the chemical composition of the matrix of the iron-based sintered alloy material for valve seats and the kind of hard particles. We conducted intensive studies on the mixing amount, texture, etc. As a result, by finding a specific composition range of the matrix that exhibits excellent heat resistance and corrosion resistance, by dispersing a specific intermetallic compound and a lubricant, and controlling the open porosity below a certain level, extremely high temperature The present invention has been completed by discovering that corrosion resistance and oxidation resistance can be retained, and finding that it is excellent in industrial mass production without causing deterioration in machinability.

The iron-based sintered alloy for valve seats of the present invention is
In a weight ratio, 3 to 30% of one or more elements selected from Co, Ni, Mn, and V, 0.3 to 1.5% of C are contained, and the balance is substantially Fe. At least one of the intermetallic compounds consisting of -Mo or Fe-W is 3-1
The gist is that 5% and one or more kinds of lubricants composed of CaF ₂ , MoS ₂ , and MnS are dispersed in an amount of 0.3 to 2.0%, and the open porosity is 1% or less.

[0008]

[Function] The Fe-based matrix structure that constitutes the matrix has C
Since 3 to 30% of o, Ni, Mn, or V was solid-dissolved,
The strength was improved and excellent heat resistance and corrosion resistance were obtained. Further, as hard particles, Fe-Mo and Fe-
Since W was dispersed in the matrix structure in an amount of 3 to 15%, the wear resistance could be improved. Further, as a solid lubricant by dispersing the CaF _2, MoS ₂ or MnS,, it is possible to improve the seizure resistance and machinability, both restricted to the upper limit of 2.0%, the sintered body Since the open porosity is 1% or less, machinability is not impaired,
The corrosion resistance and the oxidation resistance could be remarkably improved.

Next, the reason for limiting the composition range of the components constituting the sintered alloy in the present invention will be described. One or more elements selected from Co, Ni, Mn, and V; 3 to
30% In the present invention, Co, Ni, Mn and V are added for the purpose of strengthening by solid solution in the matrix (heat resistance, corrosion resistance, strength improvement). If the total content of these elements is less than 3%, the above-mentioned effect is insufficient and the purpose cannot be achieved. If it exceeds 30%, no strength improvement is recognized for the content, and it is economically disadvantageous. Therefore, the content is set to 3 to 30%.

C: 0.3 to 1.5% C has the effect of forming a solid solution in the matrix to strengthen it and form carbides to improve wear resistance, but the content is 0.3. If it is less than 1.5%, the desired effect due to the above action cannot be obtained. On the other hand, if it exceeds 1.5%, coarse cementite may precipitate to cause embrittlement. It was set to 0.5%.

One or more kinds of intermetallic compounds consisting of Fe-Mo or Fe-W; 3 to 15% Fe-Mo containing 60 to 70% Mo (Hv600 to
1300), and Fe-W containing 75 to 85% W.
(Hv500 to 1000) has a high hardness, and when these are uniformly dispersed, it has an effect of acting as hard particles to improve wear resistance, but if it is less than 3%, the effect is small, and 15%. If it exceeds, the other valve material is greatly attacked and the other material is abraded, and the machinability is deteriorated. Therefore, the dispersion amount is set to 3 to 15%.

[0012] CaF _2, MoS _2, 1 or more lubricant consisting of _{MnS; 0.3~2.0% CaF 2, MoS} 2 and MnS, by dispersing in the matrix, the excellent sliding properties In addition to showing the effect of improving seizure resistance, it has a great effect on improving the machinability. If the added amount is less than 0.3%, the effect is small, and if it exceeds 2%, the effect is not improved, and the corrosion resistance, which is an important valve seat property, is deteriorated. It is necessary to make it 3 to 2.0%.

Open porosity: 1% or less Open porosity plays an important role in controlling corrosion resistance and oxidation resistance at high temperatures. If the open porosity exceeds 1%,
Corrosion resistance and oxidation resistance decrease due to rapid progress of corrosion and oxidation.

[0014]

EXAMPLES Examples of the present invention will be described in comparison with comparative examples,
The effect of the present invention will be clarified. As the raw material powder, commercially available pure iron powder for powder metallurgy, cobalt powder having a particle size of 75 μm or less, nickel powder, ferromanganese (75% M
n) powder, ferrovanadium (80% V) powder, intermetallic compound Fe-Mo powder, intermetallic compound Fe-W powder and calcium fluoride (CaF ₂ ) powder, all of which are natural graphite powders having a particle size of 45 μm or less, Molybdenum disulfide (MoS ₂ ) powder, manganese sulfide (MnS) powder and lubricant zinc stearate powder were prepared, and these raw material powders were blended so as to have the composition shown in Table 1, and a lubricant was added to the blended powder. After adding 0.8%, mixing was performed by a powder mixing device.

Next, various test piece green compacts were molded under a molding pressure in the range of 392 to 686 MPa. Then, in a reducing atmosphere, at a temperature in the range of 1393 to 1473K, 1
Sintering was performed by holding for 800 seconds to 3600 seconds.

The obtained sintered body is heated in a non-oxidizing atmosphere.
After heating to a temperature in the range of 3K to 1373K, 490 to 14
By applying a compressive force with a pressure of 70 MPa, test pieces having open porosities shown in Tables 1 and 2 were produced. The open porosity of the obtained test piece was measured according to JPMA (Japan Powder Metallurgy Association Standard) M02-1992.

In Table 1, No. Nos. 1 to 13 are examples of the present invention. Nos. 14 to 22 are comparative examples, and No. 14
Is a comparative example in which the alloy elements contained in the matrix are few, and No. No. 15 is a comparative example in which many alloy elements are contained in the matrix. No. 16 is a comparative example in which the C content contained in the matrix was small, and No. 16 was used. No. 17 is a comparative example in which the C content contained in the matrix was large, and No. 17 was used. 1
No. 8 is a comparative example in which the amount of the solid lubricant dispersed in the sintered body was small, No. 8 No. 19 is a comparative example in which the amount of the solid lubricant dispersed in the sintered body was large, and No. 19 was used. No. 20 is a comparative example in which the amount of hard particles dispersed in the sintered body was small, No. 20. No. 21 is a comparative example in which the amount of hard particles dispersed in the sintered body is large, No. 21. 22
Is a comparative example in which the porosity of the sintered body is 1% or more.

[0018]

[Table 1]

Examples 1 to 13 and Comparative Examples 14 to
For the 22 test pieces, the Ogoshi abrasion test was performed as the evaluation of wear resistance, the lead oxide corrosion test was performed as the evaluation of corrosion resistance, and the lathe processing test was performed as the evaluation of machinability, and a comprehensive evaluation was performed. The test conditions are as follows. The obtained results are summarized in Table 2.

(1) Ogoshi abrasion test Counterpart material (rotor) SUE50 block material Example and comparative example Sliding speed 0.3 mm / sec Friction distance 100 m Final load 24.5 N Measurement item Abrasion mark width (2) Lead oxide corrosion test Heating Condition 1023K × 10.8Ks Measurement item Weight change (3) Machinability test Lathe test Feed rate 0.1mm / rev Cutting speed 50mm / min Cutting stroke 0.4mm Tip Carbide measurement item Cutting resistance

[0021]

[Table 2]

As shown in Table 2, in Comparative Example 14, the alloying elements such as Co, Ni, Mn, and V that contribute to the corrosion resistance and heat resistance were less than 3%, so that the corrosion resistance was 11. 3m
The corrosion resistance was inferior to g / cm ^2, and Comparative Example 15 contained many of these alloy elements, but the wear resistance and the corrosion resistance did not improve much in comparison with the addition of the alloy elements, and the machining resistance was as large as 216N. . No. In the comparative example in which the C content contained in the matrix of No. 16 was small, the wear width was 4.12 mm and the wear resistance was inferior. The comparative example in which the C content of the 17 matrix contained a large amount was excellent in wear resistance and corrosion resistance, but was inferior in machinability because the machining resistance was 262N.

Comparative Example No. In No. 18, since the amount of the solid lubricant dispersed in the sintered body was small, the cutting resistance was 262N.
And inferior in machinability, Comparative Example No. In No. 19, since the amount of the solid lubricant dispersed in the sintered body was large, the corrosion started from this and the corrosion resistance deteriorated.
No. No. 20 is a comparative example in which the amount of hard particles dispersed in the sintered body was small, but the wear scar width was 7.91 mm and the wear resistance was inferior. In No. 21, since the amount of hard particles dispersed in the sintered body was too large, the mating valve material (rotor) was worn, and the wear of itself increased with it, resulting in poor wear resistance and a machining resistance of 316N. It was also inferior in machinability. Comparative Example No. No. 22 is inferior in wear resistance because the amount of open pores is beyond the scope of the claims of the present invention, so that corrosion progresses through the pores.

On the other hand, according to the embodiment No. 1-1
No. 3, which has a wear scar width of 2.17 to 2.95 mm and is excellent in wear resistance, has a small corrosion amount of 4% with the addition amount of the alloy element being No. 3. 7.22 mg / cm ^{2 of} 1 had a relatively large amount of corrosion, but the others were 3.59 to 5.16 mg
/ A cm ² excellent in corrosion resistance and that is excellent in machinability a 152~197N also cutting resistance was able to confirm the effects of the present invention was found.

FIG. 1 is a diagram showing the relationship between the open porosity and the corrosion weight loss mg / cm ² obtained in this example. As is clear from FIG. 1, when the open porosity exceeds 1%, which is the claimed range of the present invention, the corrosion weight loss is significantly increased. Further, FIG. 2 is a diagram showing the relationship between the total amount of the solid lubricant added%, the corrosion weight loss mg / cm ² and the cutting resistance N obtained in this example. As is clear from FIG. 2, when the amount of the solid lubricant added is outside the lower limit of the claims of the present invention, the cutting resistance becomes large, and when the amount of addition of the solid lubricant exceeds the upper limit of the claims of the present invention, the corrosion weight loss is caused. Increases rapidly. 1 and 2, the effect of the present invention is clarified.

[0026]

As described above in detail, the iron-based sintered alloy for valve seats of the present invention contains 3 to 30% by weight of one or more elements selected from Co, Ni, Mn and V, and C. 0.3 to
Containing 1.5%, the matrix balance being substantially Fe, 1 or more intermetallic compounds consisting of Fe-Mo or Fe-W 3 to 15% and CaF _2, MoS _2,
One or more lubricants made of MnS are dispersed in an amount of 0.3 to 2.0%, and the open porosity is 1% or less, wherein C is 0.3 to 1. The Fe-based matrix structure containing 5% and forming the matrix contains Co, Ni, and M.
Since n or V was solid-dissolved in 3 to 30%, strength was improved and excellent heat resistance and corrosion resistance were obtained. Further, Fe-Mo and Fe-W as hard particles are 3-1.
Since it was dispersed in 5% matrix structure, abrasion resistance could be improved. Furthermore, as a solid lubricant, Ca
By dispersing F ₂ , MoS ₂ , or MnS,
The seizure resistance and machinability can be improved, and the upper limit of 2.0% is regulated, and the open porosity of the sintered body is set to 1% or less, so that the machinability is not impaired and corrosion resistance is maintained. The resistance and oxidation resistance could be significantly improved.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between corrosion weight loss and open porosity obtained in this example.

FIG. 2 is a diagram showing the relationship between the total amount of solid lubricant added, corrosion weight loss, and cutting resistance obtained in this example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadataka Kaneko 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Yoshihiko Ito 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. ( 72) Inventor Hiroshi Okajima 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Takashi Maejima 5-1 Kurisuno-Kitsuka-cho, Yamashina-ku, Kyoto City

Claims (1)

[Claims] 1. A weight ratio of 3 to 30% of at least one element selected from Co, Ni, Mn, and V, and C of 0.3 to 1.5.
% Contained in the matrix the balance being substantially Fe, 1 or more from 3 to 15% of an intermetallic compound consisting of Fe-Mo or Fe-W, and CaF _2, MoS _2, Mn
An iron-based sintered alloy for valve seats, wherein one or more kinds of S-based lubricants are dispersed in an amount of 0.3 to 2.0% and the open porosity is 1% or less.