JP2001303217A - Fe BASED SINTERED ALLOY BEARING EXCELLENT IN SEIZURE RESISTANCE AND CRACKING RESISTANCE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Fe based sintered alloy bearing exhibiting excellent seizure resistance with a rotary shaft as a corresponding member under the high load-high speed driving condition and also improved in cracking resistance by its high toughness. SOLUTION: This Fe based sintered alloy bearing is composed of an Fe series sintered alloy having a composition containing, by mass, 18 to 25% Cu, 1 to 3% C and 0.1 to 5% CaF2, and the balance Fe with inevitable impurities and a structure in which Cu, CaF2 and free graphite are dispersedly distributed into a base essentially consisting of pearlite and bainite and also having a porosity of <=9%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention exhibits excellent seizure resistance with a rotating shaft as a mating material, particularly under high load and high speed operation conditions, and also has improved crack resistance due to the high toughness provided. The present invention relates to an Fe-based sintered alloy bearing.

[0002]

2. Description of the Related Art Conventionally, various driving devices generally use various sintered alloy bearings as a support member for a rotating shaft as a mating member. One type of the sintered alloy bearing is mass%.
(Hereinafter,% relating to the composition indicates mass%), Cu: 1
8 to 25%, C: 1 to 3%, the balance being composed of Fe and inevitable impurities, and a structure in which Cu and free graphite are dispersed and distributed in a base material mainly composed of pearlite and bainite. Fe-based sintered alloy bearings having a porosity of 9% or less are known.

[0003]

On the other hand, in recent years, high performance and high output of a driving device are remarkable, and there is a strong demand for reduction in size and weight. The rotation of the shaft tends to be faster and the load on the rotating shaft tends to be higher.
In the case of sintered sintered alloy bearings, seizure is likely to occur under high load and high speed operation conditions, and cracks are likely to occur due to lack of toughness if the thickness is reduced for the purpose of miniaturization and weight reduction. It is.

[0004]

Therefore, the present inventor has paid particular attention to the above-mentioned conventional Fe-based sintered alloy bearing, and has conducted research to improve seizure resistance and crack resistance thereof.
Calcium fluoride (hereinafter, referred to as CaF ₂ ) is added to the Fe-based sintered alloy constituting the above-mentioned conventional Fe-based sintered alloy bearing in an amount of 0.1%.
When contained at a ratio of 1 to 5%, this CaF ₂ is dispersed and distributed in the base material to significantly improve the seizure resistance, and also finely disperses and distributes Cu in the base material. Research has been carried out to suppress as much as possible so that as much Cu as possible is dispersed and distributed in the substrate, thereby improving toughness and preventing cracking even when the thickness is reduced.

The present invention has been made on the basis of the above-mentioned research results, and it has been found that Cu: 18 to 25% and C: 1 to 3
%, CaF ₂ : 0.1 to 5%, and the balance is composed of Fe and unavoidable impurities, and a structure in which Cu, CaF ₂ and free graphite are dispersed and distributed in a base material mainly composed of pearlite and bainite. And a Fe-based sintered alloy bearing having excellent seizure resistance and cracking resistance, comprising an Fe-based sintered alloy having a porosity of 9% or less.

Next, the reason why the composition and porosity of the Fe-based sintered alloy constituting the Fe-based sintered alloy bearing of the present invention are limited as described above will be described. (A) Cu content The Cu component is an indispensable component for enabling liquid phase sintering and thereby ensuring a predetermined strength.
The action of aF ₂ suppresses solid solution in the base material and disperses and distributes in the base material in a finely divided state to improve toughness, that is, an effect of improving crack resistance. If the desired effect is not obtained, the wear will rapidly progress if the content exceeds 25%, so that the content is 18 to 25%, preferably 19 to 2%.
It was determined to be 1%.

(B) C content The C component forms pearlite and bainite of the base material, and further improves the wear resistance by forming cementite, and also contributes to the improvement of lubricity by dispersing and distributing as free graphite in the base material. If the content is less than 1%, the desired effect cannot be obtained in the above-mentioned effect, while if the content exceeds 3%, the aggressiveness of the opponent increases, so that the content is reduced. 1-3%, preferably 1.5-2.5%.

(C) CaF ₂ content The CaF ₂ component is dispersed and distributed in the matrix as described above, and remarkably improves the seizure resistance particularly under high-load and high-speed operation conditions. Has an effect of promoting the distribution of dispersion on the substrate and contributing to the miniaturization of the material. However, if the content is less than 0.1%, the desired effect cannot be obtained in the above-mentioned effect. If the amount exceeds 5%, the toughness rapidly decreases, and it becomes impossible to secure the desired excellent crack resistance, so that the content is 0.1 to 5%.
Preferably, it is set to 2 to 4%.

(D) Porosity When the porosity exceeds 9%, the strength and toughness rapidly decrease, and cracks easily occur under high load and high surface pressure. Therefore, the porosity is preferably 9% or less. Has been determined to be 7% or less.

[0010]

Next, the present invention will be described in more detail with reference to examples. Atomized iron powder, electrolytic copper powder, CaF ₂ powder, and carbon powder having a predetermined average particle size in the range of 40 to 200 μm were prepared as raw material powders, and these raw material powders were blended in the composition shown in Table 1. Then, 0.4% of zinc stearate was added as a lubricant to the mixture, and the mixture was mixed by a V-type mixer for 30 minutes. Then, the mixture was pressed into a green compact at a predetermined pressure in the range of 196 to 588 MPa. Is sintered at a predetermined temperature in the range of 1,090 to 1,150 ° C. for 30 minutes in an ammonia decomposition gas atmosphere, and the porosity shown in Table 1 and the composition shown in Table 1 are substantially the same. Are composed of Fe-based sintered alloys having the same composition.
The sintered alloy bearings 1 to 8 of the present invention and the conventional sintered alloy bearings 1 to 6 having the dimensions of 8 mm × inner diameter: 8 mm × width: 8 mm were manufactured, respectively.

With respect to the various sintered alloy bearings obtained as a result, the structure of the Fe-based sintered alloy constituting the sintered alloy bearing was observed with an optical microscope (200 × and 400 ×). No. 8 to No. 8 each show a structure in which a Cu phase, a CaF ₂ phase and a free graphite phase are dispersed and distributed in a base material in which a pearlite phase and a bainite phase are mainly contained and a cementite phase is present. ~ 6
Shows a structure in which a Cu phase and a free graphite phase are dispersed and distributed in a matrix mainly composed of a pearlite phase and a bainite phase, and a cementite phase is present. A coarse state was observed.

Next, with respect to the above various sintered alloy bearings, in order to evaluate the seizure resistance, a block size: length: 40 mm × width: 10 mm × thickness:
10 mm, Block material: SCM420 quenched and tempered heat-treated material, Bearing rotation speed: 600 r. p. m. A block-on-ring test was performed under the condition that the load applied to the bearing via the block horizontally arranged on the upper side in contact with the outer peripheral surface of the bearing was increased by 19.6 N every 2 minutes. The load (seizing load) at the time when seizure occurred on the bearing was measured. The impact value and crushing strength of the various sintered alloy bearings were measured for the purpose of evaluating the crack resistance (toughness). Further, for the purpose of evaluating the wear resistance of these various sintered alloy bearings under high load and high speed operation conditions, a radial type abrasion tester shown in a schematic front view in FIG. Bearing 1 for 2
The material of the rotating shaft 3 is JIS S45C, the clearance between the bearing 2 and the rotating shaft 3 is 25 μm, and is added to the rotating shaft 3 via the bearing 2, the support jig 1, and the ball bearing 4. Load (W): 98 N, number of rotations of the rotating shaft 3: 1200 r. p. m. , Operation time: 1 hour, a wear test was performed, the maximum wear depth on the bearing inner peripheral surface after the test was measured, and the wear state was observed.

[0013]

[Table 1]

[0014]

As shown in Table 1, all of the sintered alloy bearings 1 to 8 of the present invention show much higher seizure load, impact value and crushing strength than the conventional sintered alloy bearings 1 to 6. ,
These results are clearly shown in the wear test under the high-load and high-speed operation conditions described above, and the sintered alloy bearings 1 to 8 of the present invention.
Exhibits superior seizure resistance and cracking resistance (toughness) as compared to conventional sintered alloy bearings 1 to 6 and exhibits excellent wear resistance, whereas conventional sintered alloy bearings 1 to 6 In this case, seizure and cracking phenomena appear, and it is clear that this causes the wear to be further accelerated. As described above, the Fe-based sintered alloy bearing of the present invention has excellent seizure resistance and crack resistance (toughness) and exhibits excellent wear resistance under high load and high speed operation conditions. The present invention can satisfactorily cope with high performance and high output of the drive device, and further downsizing and weight reduction.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a radial type wear tester.

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Claims (1)

[Claims] 1. A mass% of Cu: 18 to 25%, C: 1 to 3%, and calcium fluoride: 0.1 to 5%, with the balance being Fe
Having a structure in which Cu, calcium fluoride, and free graphite are dispersed and distributed in a base material mainly composed of pearlite and bainite, and
An Fe-based sintered alloy bearing having excellent seizure resistance and cracking resistance, comprising an Fe-based sintered alloy having a porosity of not more than 0.1%.