JPS6346139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sintered alloy, and the present invention relates to a method for producing a sintered alloy, which is produced by producing a sintered alloy that has excellent strength and toughness, as well as excellent properties in terms of coefficient of friction and other bearing functions, using relatively low molding pressure and sintering. The purpose is to provide a method that can be produced industrially advantageously depending on the temperature.

Various sintered alloys have been known for use as bearing materials and other materials, but they can be roughly divided into copper-based and iron-based.
Sn, Cu-Sn-C, Cu-Sn-Pb-C alloys, etc.
In addition, iron-based materials include Fe-C, Fe-Pb-C, Fe-Cu, Fe
-Cu-C alloys and the like have been variously proposed and put into practical use. However, in such conventional products, iron-based products have higher hardness than copper-based products, do not necessarily conform well to shaft materials, etc., and are inferior in corrosion resistance. Copper-based materials have the advantage of having excellent physical properties, allowing for thin walls, and being relatively inexpensive. Copper-based materials have a symmetrical relationship with respect to these properties.

In other words, it is natural that the sintered alloy used in this type of bearing should be one that has excellent performance in terms of conformability to the shaft material, corrosion resistance, mechanical strength, etc., as described above, and has been conventionally used. Various studies have been conducted to obtain various sintered alloys, but since the above-mentioned characteristics are technically contradictory, a product that effectively satisfies them has not yet been obtained. Therefore, it is generally believed that copper-based sintered alloys should be used primarily for oil-impregnated bearings, and iron-based sintered alloys should be used for mechanical parts.

The present invention was devised after repeated studies in view of the above-mentioned circumstances.
This proposal proposes sintering a green compact made by molding a mixture of bronze powder containing bronze powder in a vaporized Zn gas atmosphere. Add a solid lubricant such as

That is, to further explain the present invention, based on the technical concept as described above, the present inventor has developed an iron,
As a result of detailed studies on various sintered alloys using copper, tin, etc., we found that when copper, tin, or zinc are combined as single substances, and when they are used as an alloy of bronze, I discovered that they behave differently. The bronze casting, which is one of the copper-based alloys used in the present invention, is generally Cu: 79 ~ as specified in JISH5111.
It has a composition of 90%, Sn: 2-11%, Zn: 1-12%, and also contains a small amount of Pb, etc., and as bronze powder for sintering, Cu and Sn are Those exceeding the above range are subject to the 1974 law
Although it is specified in JISB1581 and is commercially available, even if the percentage range of each component varies within this range, different properties can be obtained. Even so, the melting point is lower than that of copper alone. However, when iron, copper, and tin powders are blended as described above, Sn has a relatively low melting point of about 230℃, while Cu has a relatively low melting point of 1083℃ and Fe has a melting point of 1083℃.
Each has a high melting point of 1539℃, and even if these three types of metal powder are mixed and molded and sintered, reverse segregation of Sn occurs, so-called tin sweat is generated, and the Sn content is high and the δ phase is formed. However, once the Cu and Sn are alloyed, it becomes difficult to form a hard phase with a large amount of copper, resulting in a lack of compatibility with shaft materials, etc., which is desirable as a bearing material. In the case of the resulting bronze powder, even if Fe powder is used, it is not only sintered at a temperature considerably lower than the approximately 1000°C generally used for Fe-based sintered metals. During crystallization, a part of the bronze component eutectics with iron to form a bronze-iron alloy composition, and in particular, this bronze-iron alloy composition has been recognized to have a tendency to coat the surface of iron particles. Even when a large amount of iron powder is mixed, the color and feel are similar to that of a simple copper-based sintered alloy, and the composition is uniform, and the sintered product does not show the inevitable segregation that occurs in iron-copper sintered products. Obtain the bond.
It is clear that a composition with a uniform, non-segregating Fe particle surface coated with a bronze-iron alloy exhibits sufficient corrosion resistance. The material coated with the bronze alloy has a mechanical strength equivalent to or higher than that of conventional iron-based sintered alloys, and the bronze coating layer also provides good conformability to shaft materials, etc.

Regarding the blending ratio of the Fe powder and the above-mentioned copper-based bronze powder, the content of the bronze powder can be within the range of 10 to 85%. That is, to put this more specifically, if the bronze powder content is less than 10%, it becomes similar to a mere iron-based sintered body and a sufficient alloy layer with bronze cannot be obtained, as mentioned above. It is difficult to properly obtain the characteristics of the present invention. On the other hand, if the content of bronze powder is 85% or more, it will be difficult to obtain the core effect of Fe particles as described above, and the mechanical strength etc. will be close to that of copper-based sintered alloy. In particular, when a bronze powder with a high Sn content is used, there is a tendency for a hard phase as so-called hard spots to appear, which also makes it difficult to achieve the object of the present invention.

Powder compaction of the above-mentioned mixture of iron powder and bronze powder can be carried out appropriately by any conventionally known compaction technology, and by sintering the mixture, A product having the above-mentioned characteristics can be obtained. However, in the present invention, it is possible to concretely carry out such powder compacting and then sintering with a relatively low compacting force, and to obtain sufficient mechanical strength. In order to increase the mechanical strength of this type of sintered alloy body, it is necessary to increase the pressure and sintering temperature during powder compaction. This not only reduces the workability of the powder compaction mechanism and increases operating costs, but also increases wear and tear on the molding die. Moreover, even if the mechanical strength is increased by high-pressure forming, the porosity, which is an inherent characteristic of this type of sintered metal body, will be largely lost, and the oil content will be reduced when used as an oil-impregnated bearing. . Of course, the required amount of mixed powder as a raw material must also be large. The present invention provides a preferable solution to this relationship, and makes it possible to obtain a product with high strength even with a comparatively low compaction. That is, for this reason, when sintering the powder compact as described above in a reducing or non-oxidizing atmosphere, Zn or ZnO may be arranged in the upper layer of the compact, or placed in a separate container and heated together.
We propose a sintering process in a Zn gas atmosphere, whereby the evaporated Zn gas is absorbed into the compacted powder structure and alloyed. Also, by doing so, it is possible to appropriately prevent the Zn contained in the copper-based alloy powder from being diffused during sintering. In this way, the mechanical strength of the Zn-absorbed product is increased even if it has a relatively low density, and compacting of a relatively low-density powder compact can be performed easily and smoothly. It is clear that wear and tear on the mold can be reduced. Furthermore, since the porosity is increased, the properties of this type of sintered alloy are sufficiently ensured, the oil content etc. are also increased, and the amount of raw material powder required to obtain a product of a predetermined size is reduced.

The sintering temperature may generally be 1000° C. or lower, which is generally lower than the sintering temperature used to obtain the above-mentioned iron-based or copper-based sintered alloys. As mentioned above, it is sufficient to form a Zn atmosphere using Zn or ZnO at temperatures above 700°C.
Even within the above range, even if you adjust the sintering temperature depending on the amount of bronze powder mixed, the sintering temperature is 700.
A temperature suitable for each case is selected within the range of ~1000°C. To be more specific, for example, if the bronze powder is 10% (iron powder is 90%), 950
℃, and this bronze powder accounts for 85% (iron powder accounts for 15%).
%), adopting a temperature of about 800°C is the reason why the above-mentioned characteristics of the present invention can be effectively exhibited, and in the case of an intermediate composition relationship between them, the sintering temperature should be adjusted according to the degree. Adjust the temperature and operate.

Graphite and other solid lubricants are blended in an amount of 3% or less, which facilitates compaction and further improves the performance of the resulting product. Specific embodiments according to the present invention will be described below.

Example 1 Cu: 81.0~87.0%, Sn: 4.0~6.0%, Zn: 4.0~
100% of bronze powder obtained by melting and then spraying a bronze casting consisting of 7.0% Pb and impurities.
Prepare iron powder of ~350 mesh and iron powder of 150 to 250 mesh, and use a mixture of these materials in equal amounts to make a bearing material with an outer diameter of 10 mm, an inner diameter of 4 mm, and a height of 8 mm. The compacting pressure is about 2500
It was molded under a pressure of Kg/cm ² to obtain a molded body having a density of approximately 6.0 g/cm ³ , which was sintered in a reducing atmosphere at 850°C.

Separately, as mentioned above, when the mixed powder containing equal amounts of bronze powder and iron powder is compacted into a bearing material of the same size, the compacting pressure is also about 2500 kg/cm ²
The compacted compact obtained under the same density is then sintered in a reducing atmosphere at 850°C under the condition that Zn is placed thereon, that is, under this temperature condition, the Zn By sintering in a diffused Zn gas atmosphere, a sintered body with approximately 4.0% Zn absorbed into the compacted structure was obtained. The density of this material is 6.2 g/ ^cm3 , and the results of measuring its mechanical strength (radial crushing strength) show that it is 14-15% superior in strength compared to the above-mentioned material that does not use the Zn gas atmosphere. It has been found that it is possible to secure the desired mechanical strength even if the density is considerably low. The sintering time was about 30 minutes in all cases.

The results of measuring the composition of the obtained sintered metal bodies indicate that those simply sintered in a reducing atmosphere are
Fe: 50.2%, Cu: 43.4%, Sn: 2.8%, Zn: 2.3%
On the other hand, those sintered in a reducing Zn atmosphere with Zn powder had Fe: 48.2%, Cu: 41.8%,
It contained Sn: 2.7% and Zn: 6.2%, and the Zn content was increased by about 4%.

Example 2 Using the same bronze powder and iron powder as in Example 1, a mixture of 50% bronze powder, 49% iron powder, and 1% graphite powder was subjected to standard powder compaction as in Example 1. The compacting pressure was lower than that of about 2100 kg/cm ² . The density of the former is 6.0 g/cm ³ and the density of the latter is 5.8 g/cm ³ .

In addition, these green compacts were sintered in a reducing atmosphere without using Zn gas, and the latter was sintered under a relatively low compaction pressure as in Example 1.
The material was sintered in a reducing atmosphere containing Zn gas diffused using The processing conditions such as sintering temperature and time are all the same as in Example 1.

Also, the composition of the product obtained in this way was measured and found that the former product sintered simply in a reducing atmosphere had Fe: 49.4%, Cu: 43.7%, Sn: 2.8%, and Zn:
2.3%, whereas the latter sintered in a reducing Zn atmosphere had Fe: 47.4%, Cu: 41.9%,
Sn: 2.7%, Zn: 6.3%, and as in Example 1, the Zn content was increased.

Furthermore, the results of testing and measuring the bearing performance of Examples 1 and 2 impregnated with turbine oil-based lubricating oil, respectively, showed that the bearing performance was lower than that of conventional copper-based bearing materials at a load of 15 kg/kg. ^cm2 or more,
It was confirmed that the bearing performance was favorable at a PV value of 1000 or more, and of course it was known to be better than iron-based bearings in all areas. The results of examining and measuring the mechanical strength (radial crushing strength), temperature rise, and friction coefficient of variously adjusted materials (volume %) are summarized as shown in the attached drawings. Figure 1 shows that even if a compact is formed using a low compacting pressure and has a relatively low porosity, it exhibits mechanical strength equivalent to or higher than that obtained by compacting at a high compacting pressure. As shown in Figure B in
For example, it is understood that a material with a lower porosity of about 3.5 to 5% has a similar radial crushing strength. It is obvious that this can increase the oil content in the sintered metal body, improve its lubrication performance, and improve its durability. Moreover, it is clear that the sintering process in the zinc vaporization atmosphere of the present invention generally shows a tendency to lower the temperature rise and the friction coefficient during operation, for example, the temperature rise at the same PV value. is 1 to 5°C lower, and the coefficient of friction is also reduced, which can be said to further improve the characteristics of a sintered body using copper-based alloy powder.

Example 3 50% bronze powder of Cu: 90%, Sn: 10%, 50% Fe powder
After compacting the mixture at approximately 2200 kg/cm ² , the mixture was buried in ZnO powder and sintered at 850° C. for 30 minutes in a reducing atmosphere.

The composition of the obtained sintered body was Fe: 46.1%,
Cu: 41.3%, Sn: 4.6%, Zn: 7.9%.

Example 4 For the same 10% bronze powder as in Example 3, Fe
After a mixture of 90% powder was pressure-molded at approximately 2400 kg/cm ² , it was buried in ZnO powder and sintered at 950°C for 30 minutes in a reducing atmosphere.

The results of measuring the component composition of the obtained sintered body were: Fe: 86.1%, Cu: 8.6%, Sn: 0.9%,
Zn: 41%.

Example 5 The same 85% bronze powder as in Example 3 and 15% iron powder.
% of the mixture was pressure-molded at approximately 2100Kg/ ^cm2 , and this compacted powder was embedded in ZnO powder.
A sintering process was performed at 800°C for 30 minutes.

The composition of the obtained sintered body is Fe:
13.7%, Cu: 71.0%, Sn: 7.9%, and Zn: 7.2%.

The bearing performance of the bearings of Examples 3 to 5 as described above was impregnated with the same turbine oil-based lubricating oil as in Examples 1 and 2. FIG. 2 shows the same thing as FIG. 1 together with 1.
Except for Example 4, which contained 90% Fe powder, the friction coefficient was further reduced compared to Example 1, and the temperature rise was about 2 to 3°C lower. In terms of radial crushing strength, Examples 3 and 5 are similar to Example 1 when the porosity is the same, and Example 4 shows a value about 10 kg/mm ² higher, which makes it difficult to absorb NH ₃ decomposed gas. It is better than the pure iron type that is used and sintered at 1000℃ for 30 minutes.

The results of measuring the bearing performance of these Examples 3 to 5 impregnated with turbine oil in the same way as Examples 1 and 2 are shown together with the above Example 1 and the above pure iron type. As shown in Fig. 2, Examples 3 and 5 have excellent friction coefficients even in the region of load 15 kg/cm ² or less, and the temperature rise is generally low in Examples 3 to 5. . Furthermore, the radial crushing strength of Example 4 is very excellent.

According to the present invention as explained above, by sintering a press-formed body made of a mixture of bronze alloy powder mainly composed of Cu and containing Sn, it has good conformability to shaft materials, etc. It is possible to obtain a product with high mechanical strength and excellent corrosion resistance, and in addition, by using a Zn gas atmosphere during the above sintering, it is preferable even if it is a compacted compact with a relatively low density. By incorporating Zn into the bronze alloy powder, it is possible to obtain strength, and even when Zn is contained in the bronze, dispersion during sintering can be avoided, thereby advantageously producing a sintered body having the desired strength. This invention has the advantage of improving bearing performance by increasing the amount of lubricating oil impregnated into the sintered body, and is industrially very effective.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and Figure 1 shows the relationship between porosity, radial crushing strength, friction coefficient, and temperature rise for Examples 1 and 2 in which iron powder was mixed with bronze powder. Figure 2 shows the relationships between porosity, radial crushing strength, friction coefficient, and temperature rise for Examples 3 to 5 of the present invention, as well as Example 1 and pure iron-based sintered metals. This is a diagram. Furthermore, in FIGS. 1 and 2, the outlined measurement points indicate the case of simple reducing atmosphere sintering, and the solid measurement points indicate the case of sintering according to the present invention using Zn gas.

Claims (1)

[Scope of Claims] 1. Vaporization of a press-molded compact made by adding and mixing 15 to 90 wt parts of iron powder to 10 to 85 wt parts of bronze powder containing 79% or more of Cu and 11% or less of Sn. A method for producing a sintered alloy, characterized by sintering at 700 to 1000°C in a Zn gas atmosphere. 2 Arrange Zn or ZnO on the upper layer of a green compact or put them together in a container in a reducing or non-oxidizing atmosphere.
The method for producing a sintered alloy according to claim 1, wherein a Zn gas atmosphere is formed and sintered by heating to 700 to 1000°C.