JPH04124248A - Sintered alloy for oilless bearing and its production - Google Patents

Abstract

PURPOSE:To improve durability and conformability to a shaft material by mixing bronze powder, graphitic carbon, etc., with iron powder in a specific ratio, compacting the resulting powdered raw material mixture, and then sintering the resulting green compact at a temp. in a specific range. CONSTITUTION:A mixture is prepared by mixing 92-97%, by weight, of iron powder, 2-5% of bronze powder, 0.3-5% of graphitic carbon, and 1.2% of MnS and/or FeS. This powdered raw material is compacted and the resulting green compact is sintered at 850-<1000 deg.C, by which a sintered alloy for oilless bearing can be obtained. Because this sintered alloy is reduced in temp. rise at the time of rotating the shaft material, it is free from seizure even under very severe conditions of rotation and causes no damage to the shaft material. Further, wear loss can be minimized and superior durability can be provided, and stable bearing property can be maintained over a long period.

Description

Detailed Description of the Invention Object of the Invention The present invention relates to a sintered alloy for oil-impregnated bearings and a method for producing the same, which has excellent wear resistance, reduces the rise in bearing temperature during motor rotation, and prevents wear and tear on the rotating shaft. It is an object of the present invention to provide a Fe-based sintered alloy for oil-impregnated bearings that has good conformability without causing any damage, and a preferable method for producing the same.

(Industrial Application Field) Sintered alloys and their manufacturing technology used as bearing materials in household and various industrial equipment that are driven under certain loads, such as washing machines and stirring or mixing equipment.

(Prior art) It goes without saying that it is desirable for bearing materials to have excellent heat abrasion resistance, low temperature rise during use, and low cost, and various studies have been conducted to obtain such bearing materials. Although they have been overlapped, it is not easy to satisfy these characteristics together.

That is, as mentioned above, in order to mass-produce bearing materials for equipment that has a certain load, it is essential to use sintered metal, and such sintered metal is impregnated with oil to obtain lubricity. Furthermore, in order to obtain wear resistance, iron-based materials are used in which 20% or less of alloying elements such as Cu and Pb are added together with a solid lubricant such as graphite.

(Problem B to be solved by the invention) However, in recent years, household or industrial equipment as described above is increasingly being used under harsh conditions. For example, in household washing machines, in addition to the traditional two-tub type, fully automatic models have recently become widespread, and as the throughput increases, they are used under harsher conditions, and motor bearings, etc. They are now exposed to harsh conditions.

For this reason, the temperature rise during use becomes large, the wear becomes large, and the durability becomes poor. Furthermore, as described above, materials to which a large amount of alloying elements such as Cu or PB are added are inevitably expensive and are not necessarily desirable in terms of compatibility.

"Structure of the Invention" (Means for Solving the Problems) The present invention was developed after consideration to solve the problems in the prior art as described above, and is as follows.

(11Fe: 92-97wt%, Cu: 1.5-5
．． 0 wt%, Sn: 0.1 to 1.3 wt%, and 0.3 to 5 wt% of C as free carbon or cementite, with the remainder being unavoidable impurities and having a porosity of 12 to 25 volume%. A sintered alloy for oil-impregnated bearings, characterized by having a tissue structure.

(2) Fe: 92 to 97 wt%, Cu: 1.
5 to 5.0 wt%, Sn: 0.1 to 1.3 wt%, 0.3 to 5 wt% of C as free carbon or cementite, and 0.25 wt% of either MnS or FeS or both. A sintered alloy for an oil-impregnated bearing, characterized in that the sintered alloy contains ~1.2 wt%, the remainder being unavoidable impurities, and has a sintered structure with a porosity of 12 to 25% by volume.

(3) 92-97-t% iron powder, 2-5 t% bronze powder, 0.3-5 wt% graphitic carbon, and 1.2 wt% of one or two of MnS or FeS. A method for producing a sintered alloy for oil-impregnated bearings, which comprises compacting raw material powder and sintering it at 850°C or more and less than 1000°C.

(Function) The composition of the product according to the present invention described above is explained in terms of -t% (hereinafter simply referred to as %) as follows.

Fe: 92-97%.

Fe constitutes the main component of the sintered alloy of the present invention, and by setting it to 92% or more, appropriate strength can be obtained and low cost can be ensured. In addition, by setting the upper limit to 97%, appropriate amounts of other Cu, Sn, and free carbon or C as cementite can be contained, thereby achieving wear resistance, reducing temperature rise during bearing operation, and achieving preferable stain resistance for rotating shafts. .

CLI: 1.5-5.0%, Su: 0.1-1.3%.

In the present invention, Cu is required to be contained together with Su, preferably as an alloy thereof, and reduces the coefficient of friction in an alloy body based on Fe, suppresses temperature rise during bearing operation, and damages the shaft material. A product with less than 1.5% Cu, 5nlJ<0
．． If the amount is less than 1%, these effects will be poor. On the other hand, Cu is 5%
If Sr+ exceeds 1.3%, it becomes expensive and the material becomes brittle. Dimensional accuracy must be satisfied in oil-impregnated bearings that require high dimensional accuracy. (Cracks occur during the sizing process.) This makes it difficult to manufacture suitable products.

C:O as free carbon or cementite, 3-5%
.

This free carbon or C in the form of cementite provides lubricity and has the effect of reducing wear. If it is less than 0.3%, this effect is insufficient, while if it exceeds 5%, it may deteriorate strength and wear resistance. to degrade.

Porosity = 12-25% by volume.

If the porosity in the sintered structure is less than 12% by volume, an appropriate oil content cannot be obtained when manufactured as an oil-impregnated bearing. On the other hand, if it exceeds 25% by volume, the strength as a sintered alloy body will be insufficient, so this is set as the upper limit.

MnS or FeS: 0.25-1.2%.

By containing one or both of MnS and FeS, when it rubs against the shaft material, fine abrasion powder is generated and welding is prevented, and damage to the shaft material is avoided to ensure stable rotation. Close. If it is less than 0.25%, these effects are insufficient, while if it exceeds 1.2%, there is a tendency to weaken the sintered alloy structure, so this is set as the upper limit.

During production, by using raw material powder mixed at a ratio of 92 to 97% iron powder, 2 to 5% bronze powder, and 0.3 to 5% graphitic carbon, Fe, Cu, Sn, and C as described above can be produced.
A sintered body having a specific composition is obtained.

Sintering temperature: 850 to less than 1000°C.

If the temperature is lower than 850°C, proper sintering cannot be obtained even under the conditions described above using bronze powder. - On the other hand, at a sintering temperature of 1000℃ or higher, sintering progresses too much due to the influence of the added Cu-Sn alloy, resulting in large deformation, and the amount of cementite, which is a hard structure, increases, resulting in higher strength and hardness. , the elongation decreases, and as a result, the shape cannot be corrected completely during sizing performed to ensure the high dimensional accuracy required for the bearing, making it impossible to obtain the desired bearing dimensions.

Therefore, in order to manufacture the sintered oil-impregnated bearing according to the present invention, sintering at a temperature of less than 1000° C. is required, especially from the viewpoint of dimensional accuracy.

It should be noted that during powder compaction, mixing a small amount of a vaporizable lubricant such as zinc stearate facilitates compaction and is also advantageous for forming a porous structure after sintering.

(Embodiment) To explain a specific embodiment of the present invention, the present inventors have discovered that the diameter is 20 mm as shown in FIG. 1 of the attached drawings.
Both ends of the crane sphere 1 are notched end surfaces 2.2, and the thickness between these notched end surfaces 2.2 is 14 m, and a bearing hole with a diameter of 1011 is made by penetrating the center of both notched end surfaces 2.2. 3
In manufacturing the bearing body 10 which has been penetrated, iron powder of 80 mesos or less, various bronze powders and graphite powders containing 5 to 25% Sn and the remainder Cu, and zinc stearate as a molding lubricant are used. The raw material powders shown in Table 1 below were arranged and mixed evenly.

The particle sizes of bronze powder, graphite powder, and zinc stearate are as follows.

Bronze powder Graphite powder less than 80 mesh
100 mesh or less Zinc stearate 20
0 mesh or less Table (parts by weight) Using each raw material powder in Table 1 above, the bearing body shown in Figure 1 was obtained by compacting, sintering, and sizing. The rates are shown in Table 2 below.

In Table 1 and Table 1.2, as a comparative example, 94.5 parts of iron powder of 80 mesh or less, 1.5 parts of Cu powder, 4.0 parts of lead powder, and stearic acid were added. Mixed with 0.5 part of zinc and compacted at 1050℃
Comparative material 1 was obtained by sintering the bearing body with an oil content of 24.4% by volume, which is the same as that shown in FIG. Furthermore, 95.5 parts of the same iron powder, 2 parts of electrolytic copper powder, 2.5 parts of graphite powder, and 0 parts of zinc stearate.
．． Comparative material 2 was prepared by blending 5 parts of the same and powder molding, sintering and sizing at 1000°C to obtain a bearing body with an oil content of 19.3% by volume and the same shape and dimensions.

Regarding the bearing body of the present invention and the comparative material obtained as described above, each was impregnated with turbine oil #83, and the bearing hole was made of 345C raw material with a diameter of 9.990 mm and a shaft surface roughness of 0.8 S~. Insert the shaft material of 1.68, load 15
A rotary bearing performance test was conducted for 500 hours at a rotational speed of 180 Orpm under a load condition of 500 kg. The average wear amount of the inner diameter of each of the five samples is as shown in Table 3 below.

In Table 1, all of the products according to the present invention have a diameter of 5 μm or less, especially Mn.
It was confirmed that those containing S or FeS and having a grade of 8 or below had a wear amount of less than 3 μm, had excellent durability, and had excellent conformability to the shaft material. On the other hand, about 80% of Comparative Material 1 developed seizing after 30 to 40 hours, and could not withstand the harsh test or usage conditions mentioned above. It is data. As shown in Table 3, the amount of wear of Comparative Material 2 is approximately 10 times that of the material of the present invention.

In addition, the results of measuring the temperature rise of the bearing during the above-mentioned test are summarized in Table 4, and in all of the bearings according to the present invention, a significant temperature decrease was observed after 1 hour, and after 5 hours. In general, the temperature increase value is less than half of that of Comparative Material 1, but a significant temperature decrease can be ensured especially in the floors 8 to 10 and the rooms 12 to 14.

"Effect of the invention" As explained above, according to the present invention, Fe is 92%
Since this is a sintered alloy for bearings made mainly of iron powder, it is clear that the product can be obtained at low cost.Moreover, the temperature rise during rotation of the shaft material is small, so there is no risk of seizure even under fairly severe rotation conditions. To maintain stable and excellent bearing performance over a long period of time, with no damage to the shaft material and good compatibility with the shaft material, minimal wear and excellent durability. This invention has great industrial effects because it allows for the advantageous production and provision of a sintered material for oil-impregnated bearings.

[Brief explanation of drawings]

The drawings illustrate the technical content of the present invention, and FIG. 1 is a sectional view of a bearing body in an embodiment of the present invention. However, in FIG. 1, 1 is a bearing sphere, 2 is a notched end surface,
3 indicates a bearing hole. Flood 1 diagram φ20 (ball) 1～---

Claims (3)

[Claims] (1) Fe: 92-97wt%, Cu: 1.5-5.0
wt%, Sn: 0.1 to 1.3 wt%, free carbon or C as cementite, 0.3 to 5 wt%, the remainder being unavoidable impurities, and a sintered material with a porosity of 12 to 25% by volume. A sintered alloy for oil-impregnated bearings, characterized by having a tissue structure. (2) Fe: 92-97wt%, Cu: 1.5-5.0
wt%, Sn: 0.1 to 1.3 wt%, C as free carbon or cementite, 0.3 to 5 wt%, and either or both of MnS and FeS, 0.25 to 1.2 wt%. %, the remainder being unavoidable impurities, and having a sintered structure with a porosity of 12 to 25% by volume. (3) Raw material powder containing 92 to 97 wt% of iron powder, 2 to 5 wt% of bronze powder, 0.3 to 5 wt% of graphitic carbon, and 1.2 wt% of one or both of MnS or FeS is pressed. A method for producing a sintered alloy for oil-impregnated bearings, which comprises powder-forming and then sintering at a temperature of 850°C or higher and lower than 1000°C.