JPH03113118A - Bearing ring and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a bearing ring whose tracking surface is hard to be damaged, being excellent is heat resistance, and can be manufactured with a low cost by providing intermediate layers whose compositions are different from one other between the ring like tracking surface made of ceramic and an anti- tracking surface made of heat resistant steel. CONSTITUTION:Parts on the side of a rolling body 3, that is, track surfaces, of inner and outer rings 1, 2 are made of ceramic and anti-tracking sides are made of heat resistant steel. An intermediate layer therebetween is formed by sintering a ring like multilayer green consisting of mixture powder of heat- resistant steel and ceramic having different mixture ratio continuously or stepwise, in non-oxidation atomosphere. Generation of damage on the tracking surface is prevented due to ceramic, high toughness is obtained due to heat- resistant steel. Concentration of thermal strain on an interface of between metal and ceramic is prevented due to the intermediate layer. The products are obtained with a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bearing ring used in a mechanical element exposed to high temperatures for a long period of time, such as in a jet engine, gas turbine, or steel manufacturing equipment, and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Bearing races are the main elements constituting a bearing used to transmit loads between relatively interlocking objects while allowing large displacements or rotations, and are composed of an outer ring and an inner ring.

Bearing races are required to have high strength so that they do not deform even when large loads are applied to them, and high hardness so that their raceway surfaces do not peel off even when they repeatedly come into contact with rolling elements.

For this reason, SUJ steel specified in JIS G4805 and structural alloy steel specified in JIS G4052 are currently used as bearing materials after being carburized or induction hardened. However, these materials have the disadvantage that they do not function satisfactorily as a bearing used in a high-temperature atmosphere.

Therefore, JIS SKH4 steel and AMS M2O steel are used as high-temperature bearing materials in such a high-temperature atmosphere. However, since these materials contain large amounts of alloying elements, they not only have many manufacturing problems such as segregation and precipitation/retention of giant carbides, but also have a maximum usable temperature limit of 500°C. .

On the other hand, in order to fundamentally solve these problems, bearings using ceramics have recently been developed (NS
K Technical Journal
No.

646 (1986) 15).

However, although ceramics have extremely high hardness and excellent heat resistance, they have the disadvantage of extremely poor ductility and are difficult to process. Therefore, there is a risk that fine scratches left during manufacturing and assembly or small peelings that occur during use will immediately lead to destruction of the entire bearing ring. In particular, thermal shock and thermal stress often act on bearings used at high temperatures, which poses a major problem in the practical application of ceramic bearings.

As a countermeasure against this problem, a method has been proposed in which the bearing ring body is made of heat-resistant steel and the surface other than the fitting part is coated with ceramics by TD treatment (see Japanese Patent Application Laid-open No. 61-92320). Because it is thin (6 μm).

10 to 15 μm) There is a restriction that it cannot be applied to high surface pressure bearings.

Another method is to use a ceramic ring on the raceway side.
It is conceivable to use a heat-resistant steel ring on the opposite raceway surface side and shrink-fit them, but this method has the disadvantage that the resistance to heat load is significantly reduced because the coefficients of thermal expansion are different between the two rings.

Problems to be Solved by the Invention As mentioned above, conventional bearing rings are basically made of a single material, so it is difficult to achieve the contradictory functions of high strength/hardness and toughness/ductility at high temperatures. It is.

As a countermeasure against this, this idea uses ceramics with heat resistance and high hardness on the raceway side, heat-resistant steel with excellent heat resistance, toughness, and ductility on the opposite raceway side, and uses composite materials. As a result, the high-temperature bearing raceway does not deform even when used for long periods at high temperatures of 500°C or higher, has excellent durability against damage such as raceway surface peeling, and does not cause brittle fracture like ceramics. The purpose of this paper is to propose a method of manufacturing this bearing ring at low cost.

Means to Solve the Problems In recent years, progress has been made in the development of new materials in which the composition of the material is continuously changed to eliminate interfaces and reduce thermal stress.

For example, like the body of a spacecraft, the temperature difference between the inside and outside surfaces is 10
For components with temperatures exceeding 00℃, ceramics are placed on the high temperature side and metals are placed on the low temperature side, and the microelements (components, density, voids, etc.) that make up the ceramic-metal space are continuously controlled to alleviate thermal stress. (
Journal of the Japan Institute of Metals Vol. 51 No. 6 (19g?) 525-5
29).

This invention basically develops this idea, and in addition to relaxing the thermal stress of a metal-ceramic bonded body to a high-temperature member,
The high hardness of ceramics and the excellent ductility of metals,
This effectively utilizes the toughness function.

That is, the present invention provides a bearing raceway in which the raceway surface is made of ceramics, the counter-raceway surface is made of heat-resistant steel, and an intermediate layer whose composition is changed continuously or stepwise is interposed between the ceramics and the heat-resistant steel. The gist is the circle.

In addition, as for its manufacturing method, between a ring-shaped raceway surface made essentially of ceramics and a ring-shaped counter-raceway surface made of heat-resistant steel, heat-resistant steel is mixed continuously or in stages with different mixing ratios. The gist is a method in which a ring-shaped green made of a mixed powder of powder and ceramic powder is inserted to form a preformed product, and this preformed product is sintered in a non-oxidizing atmosphere. A plate-shaped green made of a mixed powder of heat-resistant steel powder and ceramic powder with different mixing ratios is interposed continuously or stepwise between the plate-shaped green made of heat-resistant steel and a plate-shaped green made of heat-resistant steel to form a plate-shaped multilayer green. The gist is a method in which a plate-like multilayer green is formed into a ring shape and then sintered in a non-oxidizing atmosphere.

The reason why ceramics are used for the working raceway surface is that the decrease in hardness at high temperatures (below 500° C.) is extremely small compared to metals, and damage is difficult to occur even when high surface pressure is repeatedly applied.

Heat-resistant steel is used for the anti-raceway surface at high temperatures (750℃ or less).
This is because there is little decrease in strength even in the case of ceramics, and it has significantly higher ductility and toughness than ceramics.

The reason for constructing an intermediate layer between the raceway surface made of ceramics and the opposite raceway surface made of heat-resistant steel, which changes continuously or in stages, is due to the difference in coefficient of thermal expansion at the interface between metal and ceramics. This is to avoid the presence of such an interface since thermal strain concentrates and peeling easily occurs due to temperature fluctuations (thermal shock and thermal fatigue).

A thermal spraying method and a sintering method can be used to continuously or stepwise change the composition between ceramics and heat-resistant steel.

Although thermal spraying is suitable for manufacturing simple ring-shaped members, machining is required for bearings with uneven parts such as bearing rings.゛The intermediate layer is made of a mixed powder of heat-resistant steel powder and ceramic powder prepared in advance with different mixing ratios, for example, 0.1 to 0.211I1.
1, and stack 4 to 5 layers in the order of mixing ratio to form a ring, or continuously or stepwise change the mixing ratio while supplying heat-resistant copper powder and ceramic powder to the plate shape. Create a multi-layer green.

The mixing ratio of heat-resistant steel powder and ceramic powder is changed continuously or stepwise. For example, from the heat-resistant steel side, which is the anti-raceway surface, the mixing ratio of ceramic powder to heat-resistant steel powder is 20 vo1%, 40 vo1%, and 60 vo1.
%, 80 vo1%, and finally the raceway surface is made substantially of ceramics.

However, it is preferable to gradually increase the mixing ratio of the ceramic powder to the heat-resistant steel powder rather than to increase it rapidly.

In addition, the bearing ring of this invention is finally manufactured by sintering, but this sintering is performed in a non-oxidizing atmosphere, such as an inert gas atmosphere, or in a vacuum. is most preferable.

In addition, the sintering temperature and time may vary slightly depending on the type of sintering atmosphere, etc., but as described in the examples below,
Conditions of about 50° C. for 1 hr are sufficient.

Embodiment FIG. 1 is a schematic diagram showing an example of a bearing to which the present invention is applied, and FIG. 2 is an explanatory diagram showing a procedure for manufacturing a bearing raceway by a sintering method as an example of the manufacturing method of the present invention. , Figure (A) shows the case of the inner ring, and Figure (B) shows the case of the outer ring.

In Figure 1, (1) is the inner ring, (2) is the outer ring, and (3)
is a rolling element.

When manufacturing the inner ring (1) using the sintering method, as shown in Figure 2 (A), a ring-shaped raceway surface (1) made of ceramic is used.
-1) and a ring-shaped anti-orbital surface made of heat-resistant steel (1-2
) and a plate-shaped green made of a mixed powder of heat-resistant steel powder and ceramic powder, the plate-shaped green with a high ceramic mixture ratio is formed into a ring shape so that it faces the raceway surface to form an intermediate layer (
1-3) and assemble them together to form a preformed product (1-3).
-4), and this preformed product (1-4) is sintered in a non-oxidizing atmosphere.

In addition, as shown in Figure 2 CB), the outer ring (2) has a ring-shaped raceway surface (2-1) made of ceramics and a ring-shaped anti-raceway surface (2-2) made of heat-resistant steel. Among the plate-shaped greens made of a mixed powder of heat-resistant steel powder and ceramic powder, the plate-shaped green with a high ceramic mixture ratio is formed into a ring shape so that it faces the raceway surface side, and an intermediate layer (2-3) is formed.
These are stacked and assembled to form a preform (2-4), and this preform is sintered in a non-oxidizing atmosphere.

Next, the results of a crush test of the bearing ring according to the present invention will be explained.

The specimens used in the test are shown below.

Specimen A: Single ceramic (SiiN+) Specimen B: Single heat-resistant steel (IN-100) Specimen C: Ceramic (SisN4) ring on the raceway side and heat-resistant steel (IN loo) ring on the opposite raceway side. Shrink-fitted specimen D: 100% 5is from raceway side to counter-raceway side
N*/80%5isN++20%lN-100/60%
5isN4+40%lN-100/40%5isN4+
60%lN-100/20%5fsN++80%lN-
The specimens of the present invention, in which 1007100%IN~100 and 5 layers of green were stacked and sintered, were single-row deep groove ball bearings #6204,
After preforming, it was sintered in a vacuum at 1250°C, and then only the raceway surface was finish polished. Specimen C was obtained by sintering the ring under the same conditions, polishing the fitting surface and raceway surface, and shrink-fitting the ring. Wax was used as the binder.

These were subjected to a crush test using the method shown in FIG. 3, and the results shown in FIG. 4 were obtained. In Figure 3, (10) is the specimen, (11)
is the base, (12) is the hydraulic cam, (13) is the displacement gauge, and (4) is the high temperature tank.

From FIG. 4, it can be seen that specimen A suffered brittle fracture under a low load, while specimen B fractured after being significantly deformed.

Specimen D (product of the present invention) had the second largest amount of deformation after Specimen B, and it is recognized that the defects of ceramic bearings have been significantly improved.

In addition, Table 1 shows the actual transfer fatigue test results at 700℃, and only specimen B (IN-100) was 8.5×10
While delamination occurred on the raceway surface in the 5i
Specimens A, C, and D, which are sN+, are all 2×107
No damage occurred at times. From this result, it was confirmed that the product of the present invention has the same level of transfer fatigue strength as a ceramic bearing.

Further, the thermal fatigue test results are shown in Table 2. In the test, a 0.1 mm pre-crack was introduced into the raceway surface of the specimen, the specimen was kept in a furnace at 700° C. for 5 minutes, and then cooled with jet air, and this process was repeated.

From Table 2, 5isN4 of specimens A and C1 are 2 and 5, respectively.
X 10", 1.L Ta.

Effects of the Invention As is clear from the above examples, the bearing ring according to the present invention has a high-temperature transfer fatigue strength equivalent to that of a ceramic bearing, a crushing strength close to that of a metal material, and is durable even at high temperatures of 500°C or higher. It is highly reliable and safe to use.

In addition, although composite materials generally cost more than a single material, this invention method basically only adds a composite process to the manufacturing method of ceramic bearings, so the cost increase can be minimized. It can be suppressed and there is no particular problem economically.

[Brief explanation of drawings]

FIG. 1 is a schematic view showing an example of a bearing to which the present invention is applied, and FIG. A) shows the case of the inner ring, and Figure (B) shows the case of the outer ring. FIG. 3 is a schematic diagram showing a crushing test method in an embodiment of the present invention, and FIG. 4 is a diagram showing the results of the same crushing test. 10...Specimen 11...Base 12...Hydraulic cam 13...Displacement meter 14...
・High temperature bath

Claims (1)

[Scope of Claims] 1 The raceway surface is made of ceramic, the counter-raceway surface is made of heat-resistant steel, and an intermediate layer whose composition is changed continuously or stepwise is interposed between the ceramic and the heat-resistant steel. A bearing ring characterized by: 2 Between the ring-shaped raceway surface substantially made of ceramics and the ring-shaped counter-raceway surface made of heat-resistant steel, a mixed powder of heat-resistant steel powder and ceramic powder with varying mixing ratios is continuously or stepwise. A method for producing a bearing raceway, which comprises inserting a ring-shaped green material to form a preform, and sintering the preform in a non-oxidizing atmosphere. 3 Between the plate-shaped green substantially made of ceramics and the plate-shaped green made of heat-resistant steel, a plate-shaped green made of a mixed powder of heat-resistant steel powder and ceramic powder with different mixing ratios is continuously or stepwise added. 1. A method for manufacturing a bearing raceway ring, which comprises interposing the plate-like multilayer green to form a plate-like multilayer green, forming the plate-like multilayer green into a ring shape, and then sintering the plate-like multilayer green in a non-oxidizing atmosphere.