JPH08109450A - Wear resistant sintered alloy for oilless bearing - Google Patents

Abstract

PURPOSE: To produce a wear resistant sintered alloy for high bearing use hard to wear the mating member by dispersing Cu-base metallic grains and alloy particles in which the amt. and hardness are specified into an iron-carbon alloy matrix in which martensite is present and specifying the porosity. CONSTITUTION: This wear resistant sintered alloy for an oilless bearing has a martensitic iron-carbon alloy matrix contg., by weight, 0.3 to 1.5% C, 0.1 to 1.5% Cr, 0.05 to 6% W, 0.02 to 1.8% V, 7 to 30% Cu, and the balance Fe. In the same matrix, Cu or Cu alloy grains are dispersed, the hard grains of an Fe-base alloy contg. 0.6 to 1.7% C, 3 to 5% Cr, 1 to 20% W and 0.5 to 6% V and contg., at need, <=20% of one or more kinds of Mo and Co are dispersed by 5 to 30% and the porosity is regulated to 8 to 30%. Moreover, the particles of the Fe-base alloy may be substituted by the particles of Mo-Fe alloy contg. 55 to 70% Mo or the particles of Co-base alloy contg. 5 to 15% Cr, 20 to 40% Mo and 1 to 5% Si.

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 oil-impregnated bearings which exhibits excellent wear resistance when used under a high load such as sliding bearings for construction machinery.

[0002]

2. Description of the Related Art Conventionally, as sliding bearings used under high load, a machined carbon steel for general structure has been quenched and tempered, and a sintered oil-impregnated product having a similar alloy composition and metal structure. Alloys are used. This is because carbon steel having a martensitic structure exhibits excellent wear resistance in sliding under a high load.

[0003]

The latter sintered alloy requires less frequent replenishment of lubricating oil than the former structural carbon steel, but has low strength and apparent hardness and a relatively large amount of wear. There was a drawback. In order to solve the above drawbacks, sintered alloy steel containing an element that strengthens the iron alloy matrix is conceivable, but since such alloys have many hard intermetallic compounds, the apparent hardness becomes too high, It is not desirable because it will attack and wear the mating member during sliding. It is an object of the present invention to obtain a sintered alloy for oil-impregnated bearings for high surface pressure, which has less wear on the bearing itself and is less likely to wear a sliding counterpart member.

[0004]

In order to achieve the above object, the sintered alloy for a bearing of the present invention has Cu alloy particles or Cu alloy particles in an iron-carbon alloy matrix containing martensite. Are dispersed, and the Cu content is 7 to 30.
In addition, the composition is (1) C: 0.6 to 1.7% by weight and C as a harder phase than the iron-carbon alloy matrix.
r: 3 to 5%, W: 1 to 20%, V: Fe based alloy particles containing 0.5 to 6%, (2) C: 0.6 to 1.7%,
Cr: 3-5%, W: 1-20%, V: 0.5-6%, M
o or at least one of Co: F containing 20% or less
e-based alloy particles, (3) Mo: Mo containing 55 to 70%
-Fe alloy particles, and (4) Cr: 5 to 15%, M
5 to 30% by weight of any alloy particles selected from Co-based alloy particles containing o: 20 to 40% and Si: 1 to 5% are dispersed, and the porosity is 8 to 30%. It is characterized by that.

The present invention will be described in detail below. The composition is% by weight. (A) Iron-Carbon Alloy Base The base is an iron-carbon alloy having a structure mainly composed of martensite, which has been proven in the prior art. Examples of unavoidable impurities of iron include Mn and Si which are usually contained in iron powder. Carbide forming elements such as Cr, Mo and V are not added. C is added in the form of graphite, diffuses into Fe during sintering to become carbon steel, and becomes a structure in which a part of troostite is found in martensite by quenching and tempering, and a moderately strong matrix is formed. It is formed. Micro Vickers hardness at a test load of 25 gf is about 450-7
It is about 50. C content in iron-carbon alloy base is 0.3%
If the addition amount is less than this, improvement in strength cannot be expected so much.
On the other hand, if it exceeds 1.5%, the hardness is increased, the aggression to the mating sliding material is increased, and the strength cannot be expected so much. Considering these points, the addition amount of C is set to 0.3 to 1.5%.

(B) Cu or Cu alloy The particles of soft Cu or Cu alloy dispersed in the matrix serve to suppress attack on the mating material. In addition of Cu, it is necessary to add Cu in the form of copper powder because the method of Cu infiltration blocks pores and reduces the oil impregnating ability. If copper powder is used, even if it melts during sintering,
Since the outflow holes are formed, the oil impregnation capacity is not impaired. During the sintering, a part of Cu diffuses into the iron base, and a part of it melts iron to form a copper alloy.
Alternatively, it becomes a dispersed state in the form of a Cu alloy phase. The copper powder used has the same action and effect even if the particle size is 100 mesh or less, which is commercially available, or if the amount of 350 mesh or less is about 70 to 80% by weight. If the added amount of Cu is less than 7%, Cu diffuses into Fe,
Since the amount of the Cu phase or the Cu alloy phase is too small, the effect of suppressing the attack on the mating sliding material is small. Further, when the content exceeds 30%, the effect of suppressing the attack on the mating sliding material is high, but the base strength is lowered. Therefore, the addition amount of Cu is set to 7 to 30%. In addition, preferably 10 to 20%
And more preferably 16-18%.

(C) Hard Alloy Particles In addition to the above-described structure in which copper or a copper alloy phase is dispersed in the iron-carbon martensite matrix, an appropriate amount of alloy particles having a hardness higher than that of the martensite matrix is dispersed. When included, the hard alloy particles reduce the plastic deformation of the matrix, the load on the matrix alloy during sliding is reduced, and a sintered oil-impregnated bearing alloy exhibiting excellent wear resistance is obtained. If the addition amount of the hard alloy particles is less than 5%, the effect of reducing the wear amount is not remarkable, and if it exceeds 30%, the attack on the mating sliding material becomes large, so the amount of the hard particles is set to 5 to 30%. . However, the hard alloy particles are required to be an alloy that is unlikely to undergo alteration during sintering and has a high hardness after sintering. Inappropriate examples include high carbon tool steels where carbon diffuses into the surrounding matrix during sintering and the hardness becomes uniform,
Examples include Ni-based hard alloys that cause unilateral diffusion from the hard alloys to the peripheral base portion without mutual diffusion to reduce the hardness of the hard alloys, resulting in poor adhesion to the peripheral bases. . Preferred hard alloy particles include the following four types. (1) C: 0.6 to 1.7%, Cr: 3 to 5%, W: 1 to
Fe-based alloy containing 20% and V: 0.5-6%. This alloy has a composition corresponding to high speed tool steel (high speed steel) containing Cr, W and V as elements forming carbides, and is added in the form of alloy powder. (2) C: 0.6 to 1.7%, Cr: 3 to 5%, W: 1 to
Fe-based alloy containing 20%, V: 0.5-6%, and at least one of Mo and Co: 20% or less. This alloy is
It has a composition corresponding to high speed tool steel (high speed steel) containing Mo or Co and is added in the form of alloy powder. (3) Mo-Fe alloy containing Mo: 55 to 70%. This alloy has a composition equivalent to JIS-standardized ferromolybdenum, and if the Mo content is low, satisfactory hardness cannot be obtained, and if the Mo content is high, the hardness becomes too high and aggressiveness to the mating material In order to increase the value of Mo, Mo is set to 55% to 70%. It is added in the form of ferromolybdenum powder with low carbon content. (4) Cr: 5-15%, Mo: 20-40%, Si: 1
Co-based alloys containing ~ 5%. Examples of this alloy include heat-resistant and abrasion-resistant alloy powder (for example, Cabot Co., trade name: Kobamet) which is commercially available for overlay thermal spraying.

(D) Porosity Porosity is required for impregnating with oil, and the porosity is 8%.
If it is less than the above, the amount of oil to be impregnated and the amount of oil that oozes out during sliding are too small to obtain the desired lubricating effect. Porosity is 30
%, The strength of the sintered alloy decreases and the amount of wear increases, so the porosity is set to 8 to 30%.

[0009]

EXAMPLES The present invention will be described with reference to Examples and Comparative Examples. The mixing ratio and composition are% by weight. First, the following powders were prepared. (1) Atomized iron powder: grain size 100 mesh or less (Kobe Steel Co., Ltd .: 300M) (2) Electrolytic copper powder: grain size 100 mesh or less (Fukuda Metal Foil & Powder Co., Ltd .: CE56) (3) Graphite Powder: Grain size 200 mesh or less (4) Alloy powder A: High speed tool steel SKH2 equivalent composition, grain size 2
00 mesh or less, composition Fe-4% Cr-18% W-1%
V-0.8% C (5) Alloy powder B: High speed tool steel SKH51 equivalent composition, grain size 200 mesh or less, composition Fe-4% Cr-5% Mo-6
% W-1% V-0.8% C, (6) Alloy powder C: Composition Fe-65% Mo, grain size 200 mesh or less, (7) Alloy powder D: Composition Co-8.5% Cr-28% Mo-2.
5% Si, grain size 200 mesh or less (manufactured by Cabot Co.,
Product name: Cobamet), (8) Zinc stearate powder

A predetermined amount of various hard alloy powders, graphite powder and 1% zinc stearate powder were added and mixed to a powder obtained by adding 20% electrolytic copper powder to 80% atomized iron powder. Each mixed powder was compacted into a cylindrical shape at a compacting pressure of ² to 4 ton / cm ² , and the compact was sintered at 1100 ° C. in an ammonia decomposing gas atmosphere. Temperature of each sintered body is 850
After holding in a carburizing atmosphere at 60 ° C. for 60 minutes, quenching was performed, tempering was performed at 180 ° C. for 40 minutes, and then a bearing shape was formed by cutting. The impregnated lubricating oil is ISO
It is turbine oil equivalent to VG56. The metallographic structure of each sample is that the matrix portion is martensite, the copper-colored phase is dispersed in the grain boundary of the matrix portion, and the hard alloy powder is added.
The hard alloy phase is dispersed in an area almost commensurate with the addition amount,
Porosity was also observed. The micro Vickers hardness (test load 25 gf) of the hard alloy particles is 800 to 900 for alloy powders A and B, 1400 to 1500 for alloy powder C, and 850 to 950 for alloy powder D. The bearing sample had a density ratio of 80% (porosity 20%) for each material, and was continuously operated for 100 hours using a bearing tester to measure the amount of wear of the bearing and the rotating shaft. The rotating shaft used is carbon steel S45 for machine structure.
The C material was quenched and tempered and had a surface hardness of HRC55. The operating condition of the tester is a peripheral speed of 1
The pressure is 5 m / min and the surface pressure is 30 MPa. Table 1 shows the amount of hard alloy powder added, the overall composition, and the amount of wear of the bearing and shaft.

[0011]

[Table 1]

Sample Nos. 1 to 12 are alloys of the present invention,
Sample Nos. 13 to 15 are comparative samples. Sample 13 contains no hard alloy powder, sample 14 contains little hard alloy powder, and sample 15 contains excess hard alloy powder. It can be seen that the samples 1 to 12 according to the present invention have a small amount of wear of the bearing and the shaft. The data of Samples 4 to 6 and 13 to 15 show the relationship between the amount of hard alloy particles and the wear amount, and those without hard particles (Sample 13) and those with few hard particles (Sample 14) are bearings themselves. The wear of the shaft is large, and the wear of the shaft is also large. Hard particle amount is 4
Sample 0 of 0% has a large amount of shaft wear and, as a result, a large amount of bearing wear. That is, it can be seen that there is a property of attacking the opponent material.

Next, as the hard alloy particles, 20% of the same alloy powder B (corresponding to SKH51) as the sample 5 of the above-mentioned example was used,
A bearing sample having a composition in which the added amount of copper powder was changed in the range of 0 to 35% was prepared and a bearing test was conducted. The sample preparation procedure and the bearing test method are the same as those in the above-mentioned embodiment. In Table 2,
The relationship between the Cu content and the amount of wear of the bearing and the shaft is shown.

[0014]

[Table 2]

Sample 16 has a structure in which hard alloy particles are dispersed in a martensite matrix and does not contain a copper phase. Due to the dispersion of the hard particles, the wear amount is smaller than that of the alloy in which only the copper particles of Sample 13 shown in Table 1 are dispersed. Compared with the sample 16, the sample 17 containing 5% Cu has a smaller amount of wear of the bearing and the shaft.
As can be seen from the large difference in the amount of wear of No. 8, the rate of change of the amount of wear with respect to the amount of Cu is large, and the amount of wear increases as Cu decreases, which is not preferable. The improvement of wear resistance is
It is considered that this is because the base was strengthened by containing Cu, and the action of not attacking the opponent material appeared. When the amount of Cu is 7 to 25%, wear of both the bearing and the shaft is small. That is, it can be seen that the copper phase gives the sliding material familiarity. When the amount of Cu exceeds 30%, the shaft is not worn but the bearing wear amount tends to increase. This is considered to be because the soft copper phase accounts for a large proportion of the structural constitution of the entire alloy. It can be seen that when the amount of Cu is 35%, the amount of bearing wear increases. Further, if the amount of Cu exceeds 30%, the dimensional change due to sintering becomes large, which is not preferable. An alloy produced by using a copper powder having a grain size of 250 mesh or less (manufactured by Fukuda Metal Foil & Powder Co., Ltd .: CE15) and a sintering temperature of 1080 ° C. and 1150
The wear characteristics of alloys produced at ℃ showed the same tendency.

[0016]

EFFECTS OF THE INVENTION The sintered alloy for oil-impregnated bearings of the present invention has a copper phase or a copper phase having good sliding conformability at the base where iron-carbon type martensite that exhibits excellent performance in high surface pressure sliding exists. The alloy phase is composed of a composite structure in which alloy particles harder than the above-mentioned martensite having good wear resistance are dispersed, and under high surface pressure, the bearing itself has excellent wear resistance and attacks against the mating material. Since the property is low, it can be used for a long time without refueling, and the effect that maintenance of the bearing element can be omitted can be obtained.

Claims (4)

[Claims] 1. The overall composition has a weight ratio of C: 0.3 to 1.5.
%, Cr: 0.1 to 1.5%, W: 0.05 to 6%, V:
0.02 to 1.8%, Cu: 7 to 30%, and the balance Fe and unavoidable impurities, and the structure of the alloy is
Cu particles or Cu alloy particles are dispersed in the iron-carbon alloy matrix containing martensite, and the composition is harder than the iron-carbon alloy matrix and has a composition by weight ratio of C: 0.6 to 1.
7%, Cr: 3-5%, W: 1-20%, V: 0.5-6
% Of Fe-based alloy particles are dispersed, and the porosity is 8 to 30%. A wear-resistant sintered alloy for oil-impregnated bearings. 2. The total composition is C: 0.3 to 1.5 by weight ratio.
%, Cr: 0.1 to 1.5%, W: 0.05 to 6%, V:
0.02 to 1.8%, Cu: 7 to 30%, Mo or Co
At least one of: 6% or less, and the balance Fe and unavoidable impurities, and the alloy structure is such that Cu particles or Cu alloy particles are dispersed in an iron-carbon alloy matrix in which martensite is present, It is harder than the iron-carbon alloy matrix and has a composition of C: 0.6 to 1.7% by weight, C
r: 3-5%, W: 1-20%, V: 0.5-6%, Mo
Or Fe containing at least one of Co: 20% or less
A wear-resistant sintered alloy for oil-impregnated bearings, wherein particles of a base alloy are dispersed in an amount of 5 to 30% by weight and a porosity is 8 to 30%. 3. The total composition is C: 0.3-1% by weight,
Mo: 2.8 to 21%, Cu: 7 to 30%, and the balance Fe and unavoidable impurities. The structure of the alloy is C in the iron-carbon alloy matrix containing martensite.
u particles or Cu alloy particles are dispersed and harder than the iron-carbon alloy matrix, and the composition is Mo: 55-by weight.
A wear-resistant sintered alloy for oil-impregnated bearings, wherein 5 to 30% by weight of particles of a Mo-Fe alloy containing 70% are dispersed and the porosity is 8 to 30%. 4. The total composition is C: 0.3-1% by weight,
Cr: 0.2-4.5%, Mo: 1-12%, Si: 0.05
.About.1.5%, Co: 2 to 22.2%, Cu: 7 to 30%, and the balance Fe and unavoidable impurities, and the structure of the alloy is in the iron-carbon alloy matrix in which martensite is present. The Cu particles or Cu alloy particles are dispersed and harder than the iron-carbon alloy matrix, and the composition is C by weight ratio.
5 to 30% by weight of particles of a Co-based alloy containing r: 5 to 15%, Mo: 20 to 40%, and Si: 1 to 5% are dispersed, and the porosity is 8 to 30%. A wear-resistant sintered alloy for oil-impregnated bearings.