WO1999008012A1 - Composite metal powder for sintered bearings, and sintered oil-retaining bearing - Google Patents

Abstract

Composite metal powder for sintered bearings, prepared by coating surface layers of particles of iron powder with 10 wt.% to less than 30 wt.% of copper based on the iron powder so that the particle size of the coated iron powder is at most 80 meshes, the content of the powder of at most 350 meshes is at most 30 %, and the specific surface area of the powder is 450-750 cm2/g according to the subsieve sizer method. This metal powder can provide an oil-retaining bearing for motors, which is capable of providing a low gas-permeability without decreasing the oil content and which has a low and constant coefficient of friction, a high corrosion resistance, a high adaptability and a high durability, readily at a low cost.

Description

 ― Description Composite metal powder for sintered bearings and sintered oil-impregnated bearings Technical field

 INDUSTRIAL APPLICABILITY The present invention provides simple and low-cost bearings for motors, etc., and provides low air permeability without lowering the oil content, low friction and constant flatness, high corrosion resistance, and high conformability. Excellent and durable oil-impregnated bearings Related to composite metal powder for sintered bearings and sintered oil-impregnated bearings. Background art

 Japanese Patent Publication No. 55-38019 discloses a sintered body for bearings using copper-coated iron powder, and it has been proposed to use iron powder coated with 30-60% copper. Japanese Unexamined Patent Publication (Kokai) No. 3-166303 discloses a method in which a foil-like powder made of a metal which is the same as the coating layer or which is alloyed is added.

In addition, in Japanese Patent Publication No. Hei 7-54 126, it is necessary to lower the air permeability in order to improve the characteristics of sintered oil-impregnated bearings. In addition, Japanese Patent Application Laid-Open No. Hei 08-208336 discloses a bearing material made of copper-coated iron powder, which has an oil content of 18% by volume or more and a gas permeability of 30 Darcy (30X). 10—Hem ² ) It is proposed to use iron powder coated with 30 to 60% by weight of copper and to sinter in a shimomo atmosphere to adsorb zinc. ing.

The above-mentioned Japanese Patent Publication No. 55-38019 requires that 30% or more of copper be covered, so that a large amount of expensive copper is required, which inevitably leads to an increase in cost and an overlay. There is a disadvantage that the sliding performance as a bearing is inferior because the copper layer to be formed is too thick and the underlayer effect of iron particles cannot be sufficiently obtained. In the case of JP-A-3-1663 03, the same as the coating layer is used. Is an alloy-added foil-like powder made of metal, so that the steps are complicated and there is a disadvantage that stable characteristics cannot be obtained. In particular, these materials lack the consideration of the air permeability required for high-performance bearing materials, and the hydraulic oil escapes from the oil holes in the bearing sliding surface even after the familiarization is completed, making it ideal for sintered oil-impregnated bearings. However, there is a disadvantage that it is difficult to obtain a sliding state close to fluid lubrication. It is Japanese Patent Publication No. 7-514126 that mentions the suppression of the air permeability as described above. However, this powder is expensive because a copper-graphite composite powder is added. This has the disadvantage of reducing the strength of the sintered body. Further, the above-mentioned Japanese Patent Application Laid-Open No. 8-208336 requires a step of using 30 to 60% copper-coated iron powder and sintering in a zinc atmosphere to adsorb zinc. Even if the characteristics are excellent, the required amount of copper is high, and sintering in a zinc atmosphere is required, so the number of steps is increased, and in any case, it must be expensive. Disclosure of the invention

 The present invention has been studied to solve the problems in the prior art as described above, and has used a composite metal powder coated with copper in an amount of 10% by weight or more and less than 30% by weight with respect to iron powder, By setting the specific surface area of the composite metal powder to a specific range, and setting the air permeability of the compacted sintered body of the composite metal powder to a specific range, and setting the oil content to a specific state, it is preferable at a relatively low cost. It succeeded in obtaining bearing performance.

That is, according to the present invention, by covering 10% or more of copper with respect to the iron powder, the peripheral surface of the iron powder is completely covered, thereby improving the corrosion resistance and improving the adaptability to the shaft material and the like. By reducing the amount of copper to less than 30%, low cost properties can be ensured, and the underlying effect of the coated iron particles can be appropriately obtained to ensure stable sliding performance as a bearing. . Although not particularly specified as a method of coating iron powder with copper, the method of electroless plating is used. However, the copper coating layer is porous, has a large specific surface area, and has characteristics such as low air permeability in a powder state.

 Since the particle size of the copper-coated iron powder is 80 mesh or less and 350 mesh or less is 30% or less, no special raw material powder is required, and general powder metallurgy iron is used. The above-mentioned copper-coated iron powder can be easily obtained by using the powder, and there is no difficulty in filling the mold, etc., and the molding operation is simple, and the product can be obtained at low cost.

In addition, by setting the specific surface area of the composite metal powder as described above to 450 cm ² / g or more by a subsizer / sizer method, the air permeability as the composite metal powder is reduced, and molding is performed while maintaining this characteristic. By sintering, a bearing with high oil content and strength and low air permeability can be obtained. When the upper limit of the specific surface area is 750 cm ² / g according to the sub-sizer / sizer method, the mold can be easily filled at the time of compacting and can be easily molded.

Furthermore properly hold the oil amount at the time of the bearing by the air permeability of the powder sintered compact 3 X 1 0 one ^{1 1} cm ² or more, yet the 3 0 X 1 0 - ^{1 1} ^ ² or less This prevents unequal escape of hydraulic pressure and ensures favorable lubrication to the shaft surface and the associated bearing action.

 By setting the oil content to 15% or more, appropriate durability of the bearing is ensured, and by setting the oil content to 28% or less, the strength of the bearing is ensured and the durability is appropriately adjusted. To win. Further, it is also possible to add a solid lubricant or a low melting point metal such as tin in the present invention. Further, the present invention facilitates sintering by adding 0.1 or 2 wt% of either or both of tin and lead as a low melting point metal, and appropriately improves conformability during bearing. be able to.

In addition, according to the present invention, the friction coefficient during sliding of the bearing is further reduced by adding one or more of graphite, molybdenum disulfide, and boron nitride as a solid lubricant. Temperature rise Lower. BEST MODE FOR CARRYING OUT THE INVENTION

 (Example 1)

 The specific embodiment of the present invention as described above will be described together with its comparative example. First, the iron powder used by the inventors of the present invention has a copper coating amount of 20 \ ¥ 1%. Which has a specific surface area of 573 cm and is formed into a cylindrical green compact having an inner diameter of 6 mm, an outer diameter of 12 mm, and a height of 4 mm in both the examples and comparative examples. Sintering was carried out at 100,000 for 30 minutes in a decomposition gas.

 The obtained sintered body was subjected to ordinary sizing and oil immersion treatment to form a bearing body having an oil content of 20% by volume, and these were subjected to a bearing test under the following conditions.

 Shaft material: S 4 5 C raw material

Load: 0.8 1 N / thigh ² , 1.63 N / ram ² , 3.26 N / mni ²

 Sliding speed: 5 2.9 m / rai n

 Impregnating oil: Mineral oil 3 2 est

The comparative examples to the above-mentioned examples of the present invention are as follows. _C Comparative Example 1. 20 weight of 100 mesh and specific surface area of 295 cm ² / g

 % Copper-coated iron powder, a bearing sample was prepared under the same conditions as in Example 1, and a bearing test was performed under the same conditions.

 Comparative Example 2. A reduced iron powder of —100 mesh and an electrolytic copper powder of —150 mesh were mixed at a weight ratio of 8: 2, and a bearing sample was prepared under the same conditions as in the example. A bearing test was performed under the same conditions as in the example.

The results of bearing tests on the material of the present invention and the comparative material as described above show the amount of wear and the rise in bearing temperature (difference from room temperature) as shown in Table 1 below. The measurement results show the average value of each of the three samples, but the one according to the example of the present invention has a lower temperature rise than Comparative Examples 1 and 2, and has excellent both abrasion resistance and sliding characteristics. This was sufficiently confirmed.

なお上記し-たような本発明の実施例と比較例 1、 2のものについての 含油率、 圧環強度、 硬度および通気度をそれぞれ求めた結果は次の表 2 に示す如くであって、 含油率、 強度、 ロックゥ エル硬さがほぼ同等で ある。 また、 比較例 2は通気度も実施例よりやや高い程度である。 すな わち、 実施例の軸受は 3 0 X 1 0—n cra²以下の通気度と銅被覆鉄の両方 の特性を共に備えることにより、 本発明の優れた特性が得られることが 理解される。

The results of oil content, radial crushing strength, hardness and air permeability of each of the above-described examples of the present invention and those of Comparative Examples 1 and 2 are shown in Table 2 below. The ratio, strength and rock-well hardness are almost the same. Further, the air permeability of the comparative example 2 is slightly higher than that of the example. In other words, it is understood that the bearings of the examples have both the air permeability of 30 × 10−n cra ² or less and the characteristics of both copper-coated iron and thus the excellent characteristics of the present invention. You.

Oil content Radius strength Hardness Air permeability

(vol¾) (stroke (X 10 " ⁿ cm ² ) Example 1 2 1. 1 3.45 7 4 1 0.0 Comparative Example 1 2 0.8 .3 3 7 2 5 1.0 Comparative Example 2 2 0. 0 3. 1 7 1 1 2.8 Example 2 2 0. 2 4. 5 4 8 3 2 0. 1 Example 3 2 1.3 3. 9 2 8 1 1 0.3 Example 4 2 0.3 ¾ 1 5 7 1 7.3 Example 5 2 0.7 2. 4 1 6 6 3.5 (Example 2)

 A sintered body having the same shape as that of Example 1 was produced by adding 1.0% by weight of tin powder to the powder of Example 1 as described above. The bearing characteristics of this are also shown in Table 1 above, and the oil content, strength, hardness and air permeability are also shown in Table 2 above.

 (Example 3)

Similarly, 1.8 wt% of tin powder was added to the powder of Example 1, and a sintered body having the same shape was sintered at a sintering temperature of 860 ° C under the same conditions as in Example 1 described above. _c However, the bearing characteristics and oil content of this product are as shown in Tables 1 and 2 above.

 (Example 4)

 0.5 wt% of graphite powder was added to the powder of Example 1, and a sintered body having the same shape was produced under the same conditions as in Example 1. The bearing characteristics and oil content of this product are also shown in Tables 1 and 2 above.

 (Example 5)

 A sintered body having the same shape was produced under the same conditions as in Example 1 except that 1.0% of the graphite powder was added to the powder of Example 1 and the sintering temperature was set at 860 ° C. The bearing characteristics and oil content of this product were also as shown in Tables 1 and 2 above. Industrial applicability

 As described above, according to the present invention, a sintered oil-impregnated bearing can be obtained simply and at low cost, and has little friction and excellent conformability, reduces air permeability without reducing oil content, and reduces wear. A bearing excellent in durability can be provided appropriately.

Claims

- The scope of the claims 1. Iron powder is coated with copper in an amount of 1 Owt% or more and less than 3 Owt%, is 80 mesh or less, and 350 mesh or less is 30% or less. 4 5 0 cm ² / g or more 7 5 0 cm ² / g complex metal powder for sintered bearing which is characterized in that less is at Subsystem part 'sizer of the Act. 2. A sintered body having a gas permeability of 3 to 30 × 10—Hem ^{2 obtained} by compacting and sintering the composite metal powder for a sintered bearing according to claim 1; The oil-impregnated sintered bearing is characterized in that the oil content is 15-28% by volume.  3. The sintered oil-impregnated bearing according to claim 2, wherein 0.1 to 2% by weight of a low melting point metal is added.  4. The sintered oil-impregnated bearing according to claim 2, wherein 0.1 to 1 wt% of a solid lubricant is added.  5. The sintered oil-impregnated bearing according to claim 3, wherein 0.1 to 1 wt% of a solid lubricant is added.