JP2008291316A - Method for manufacturing slide bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for bonding different materials in the manufacture of a slide bearing that employs a bearing material made from an Al-Sn alloy containing no environmental pollutants, which shows a high degree of freedom in a size and a shape, reduces the number of parts, the number of steps and a cost, and shortens the delivery time. <P>SOLUTION: This method for manufacturing the slide bearing that employs the bearing material made from the Al-Sn alloy includes adopting a HIP (hot isostatic pressing) process, and using stainless steel for a base material of a back metal or making nickel exist in the interface between the slide bearing and the base material of the back metal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a plain bearing composed of a relatively soft bearing material and a back metal base material usually made of carbon steel.

  Typical examples of the slide bearing as a mechanical element used in any product having a drive unit include a journal bearing that supports a rotating shaft with a rotating surface and a thrust bearing that supports the shaft in the axial direction.

  A bearing that supports the rotating shaft by a surface and performs relative movement of the slide is particularly called a “slide bearing”, and is distinguished from a “rolling bearing” using a point contact ball.

  FIG. 1 shows a typical form of a journal bearing in (a) and a typical form of a thrust bearing in (b). In each of (a) and (b), a cross section along the line XX with the cross section of the shaft is shown.

  In general, a plain bearing is composed of a relatively soft bearing material 1 and a back metal base material 2, and an iron alloy having general versatility and rigidity, usually carbon steel or mild steel, is often used for the back metal.

  In recent years, as a bearing material 1 of such a sliding bearing, an Al alloy, which is a lighter material, is used instead of a lead (Pb) -based or tin (Sn) -based white metal or a Cu alloy containing Pb. I came.

  This is because the load conditions such as the load and the speed on the bearing are increased, including the reduction of the environmental load inherent in Pb, and there are conditions that cannot be endured in terms of material.

  As this bearing material, the contained Pb and Sn have indispensable characteristics as a slide bearing, such as foreign matter burying property and conformability, and they are a combination in which they do not dissolve, and they do not dissolve in the bearing material. By dispersing in, the characteristics as a soft material in the bearing material can be expressed more.

  For example, a bearing alloy called A40 made of Al-40 wt% Sn-1 wt% Cu is well known as an Al alloy containing Sn. This alloy contains 40% by weight of Sn as a second phase which does not dissolve in an Al alloy matrix containing 1% by weight of Cu.

  By the way, in such a bearing material, a bearing material including a second phase that does not dissolve a large amount of soft material in a Cu or Al alloy base material has been conventionally used in a powder sintering method or a strip pressure welding. It is manufactured by the method or the manufacturing method which combined these. (See Patent Documents 1 to 3)

  However, in the case of journal bearings, the powder sintering method and strip pressure welding method require bending to produce the bearing, so the plate thickness is thin enough to allow the back metal base material to be bent. Limited to ferrous alloys such as carbon steel or mild steel. Therefore, in the case of a bearing that requires rigidity or a large-sized bearing, it is necessary to separately manufacture a container for housing the bearing with a hard iron alloy having rigidity, and install it at the bearing position.

  In the production of bearings by the conventional powder rolling method and strip plate pressure welding method, the bearing material 1 and the back metal base material 2 can be bent, and it is essential to select both dimensions and materials. It is self-evident that the characteristics are also limited.

  In the case of the journal bearing shown in (a), the bearing material 1 having a thin backing metal base material 2 manufactured by bending in the conventional method is entirely made of a different backing metal reinforcing material having a shape and size having higher rigidity. In this case as well, there is a disadvantage inherent to the manufacturing method in that an increase in the number of parts and the number of processes is unavoidable, which is disadvantageous in terms of cost and delivery time.

  Further, in the thrust bearing shown in (b) that supports the load of the rotating shaft from the axial direction, which is another form of the slide bearing, the back metal base material 2 is thick and cannot be bent, so that it is manufactured differently from the journal bearing according to the conventional method. The process was adopted, and it was complicated in terms of quality and process control. In other words, journal bearings could be manufactured efficiently on a continuous production line, but thrust bearings could only be produced discontinuously on a production line different from conventional ones, and different management methods and production conditions were adopted. It was also disadvantageous in terms of costs and delivery time in terms of what had to be done.

Also, in bearings obtained by powder sintering or strip pressure welding, thermal stress occurs due to the difference in thermal expansion between the bearing material and the back metal base material, and a fragile reaction layer is formed. Or there was a risk of low quality bearings.
Japanese Patent No. 3195042 JP 2004-76039 A JP 2002-38230 A

  An object of the present invention is to eliminate the above-mentioned drawbacks of a bearing obtained by a powder sintering method or a band plate pressure welding method of a conventional bearing which is a bearing material containing a large amount of a soft material as a second phase that does not dissolve in a solid solution. .

  Specifically, in a bearing obtained by a powder sintering method or a strip pressure welding method, the generation of thermal stress at the joint interface between the bearing material and the back metal base material is reduced, and a fragile reaction layer at the joint interface is reduced. By preventing the formation, it is to stably obtain a highly reliable bearing.

  In the present invention, in FIG. 1, in the production of the bearing by the conventional powder rolling method and the strip pressure welding method, the bearing material 1 and the back metal base material 2 can be bent. It is essential for both, and, of course, it is obvious that the product characteristics are also limited, and the HIP method that can be integrally manufactured in a so-called near net shape, which is a shape and size closer to the product, is suitable. Based on the recognition.

  The present invention uses a base material containing a large amount of a soft material as a second phase that does not form a solid solution as a bearing material, and is suitable for manufacturing a bearing having a complicated shape and a complex shape or near net shape product. A diffusion bonding method using a hot isostatic pressing method is applied.

  The bearing obtained by applying the diffusion bonding method by the HIP method is integrated with the steel, which is the backing metal base material, by interfacial bonding, whereby heat due to the difference in thermal expansion coefficient at the bonding interface is obtained. The formation of a fragile reaction layer at the joint interface can be suppressed by reducing the generation of stress and by using at least a part of the steel as the backing metal base on the bearing material side as stainless steel.

  In particular, in the manufacture of a sliding bearing using an Al-Sn alloy bearing material that is lighter and softer than a sliding bearing using a Cu alloy as a bearing material and does not contain environmental load components, Due to the formation of Al-Fe-based intermetallic compounds by the reaction of and the difference in coefficient of thermal expansion, the degree of freedom in dimensions and shape is high, and it is advantageous in terms of cost and delivery, including the omission of the number of parts and processes. It is necessary to obtain a different material joining method.

  Al-Sn alloy bearing materials, Al and Sn, which are the main components, have the property of being easily oxidized and deteriorated even at low temperatures, so it is necessary to manufacture them in a vacuum atmosphere, at least in a non-oxidizing atmosphere that does not oxidize. On the other hand, since the HIP process is performed in a clean state in which the raw material is stored in a vacuum vessel, there is no oxidative deterioration due to the atmosphere.

In the case of Al alloy, the thermal expansion coefficient difference with respect to steel is considerably larger than that of Cu alloy (about 24 × 10 ^{−6 for} aluminum, about 16 × 10 ^{−6 for} copper, and about 12 × 10 ^{−6 for} steel), Further, there is a problem that Al and iron (Fe) which is a main component of steel easily react to generate an Al—Fe-based intermetallic compound.

  For example, an excessive difference in the coefficient of thermal expansion between the Al alloy and steel constituting the bonding interface causes interface peeling due to excessive thermal stress generated in the cooling process after the interface bonding, and the thermal stress at the bonding interface is relaxed. It becomes necessary.

  In addition, Al-Fe intermetallic compounds generated at the bonding interface are inherently brittle, so they have the basic property of being easily broken by the thermal stress generated at the bonding interface, producing excessive intermetallic compounds. May cause interfacial delamination with the generation of thermal stress.

  Thus, when manufacturing a plain bearing using an Al—Sn alloy as a bearing material in the HIP method, a measure to suppress the generation of thermal stress at the joint interface as much as possible and to reduce the amount of intermetallic compound generated as much as possible. Will be needed.

  That is, in the case of Al alloy, since the HIP holding temperature, which is a bonding temperature, is lower than that of Cu alloy, it is predicted that the influence due to the difference in characteristics from the carbon steel that is a normal backing metal base material is slightly reduced.

Therefore, in order to minimize the occurrence of thermal stress, at least the difference in the thermal expansion coefficient at the joint interface is reduced, so that stainless steel, which has a thermal expansion coefficient close to that of the Al—Sn alloy, is used as the back metal (the thermal expansion coefficient is about 14 to 16 × 10 ⁻⁶ ) or nickel (thermal expansion coefficient is about 13 × 10 ⁻⁶ ) as an interface layer is very effective.

  That is, in the manufacture of a sliding bearing using an Al—Sn alloy as a bearing material in the HIP method of the present invention, an austenitic stainless steel containing at least a part of an austenitic structure is adopted as a back metal base material, or nickel is used as an interface layer. As an intermediary, there is an effect in both thermal stress relaxation and interface reaction suppression at the bonding interface.

  The Al—Sn bearing material itself is a conventionally known bearing alloy, and does not include environmental contamination components such as Pb, and can simultaneously achieve softening and weight reduction of the sliding bearing. However, when an Al—Sn alloy containing a large amount of tin that functions as a lubricant is manufactured from a molten material such as an ingot, it causes coarsening and segregation due to tin having a melting point lower than that of aluminum as a parent phase. Therefore, since a uniform structure and characteristics cannot be obtained, it is necessary to use a powder form.

  As a powder production method, a gas atomization method is suitable as an atomization method conventionally used.

  The back metal base material, which is another major bearing component, is made of stainless steel or at least part of the interface on the back metal base side for thermal stress relaxation and interface reaction control, or nickel intervenes in the interface. Let

  For example, as an example where stainless steel is used at least near the interface on the back metal base material side, the most basic and simple example is to use stainless steel for the entire back metal base material, which is most advantageous in terms of manufacturing cost and delivery time. is there. Of course, it is possible to use a two-layer clad material in which the interface side serving as the bonding interface is stainless steel, but the price is also expensive, and it is not easy to obtain in the market based on the specification of a predetermined size range.

As the material of the stainless steel, the most versatile austenitic stainless steel is preferable from the range of the coefficient of thermal expansion. In other words, SUS304 and SUS316 as a representative example, austenitic stainless steel contains moderate Ni, has a high thermal expansion coefficient among stainless steels, and sets a smaller difference in interfacial reactivity and thermal expansion coefficient with the Al-Sn alloy. it can. Ferritic stainless steel such as SUS430 does not contain Ni and has a relatively low coefficient of thermal expansion (about 9 × 10 ⁻⁶ ), and martensitic stainless steel such as SUS410 has a low thermal expansion coefficient. Therefore, arc welding is difficult, and it is not suitable for the present invention. Of course, precipitation hardening stainless steel SUS630 and duplex stainless steel SUS329 having Ni and having an austenite structure at least in part are also applicable.

As another method, interposing nickel (Ni) at the interface is evaluated from the viewpoint of suppressing the interfacial reaction between Al—Fe rather than the coefficient of thermal expansion (about 13 × 10 ⁻⁶ ). Of course, an intermetallic compound exists between Al-Ni, but it is relatively advantageous in that it is slower in growth than the Al-Fe system or is a less brittle intermetallic compound.

  Electroplating is a preferred example of a method for interposing nickel at the interface. The characteristics required of the plating layer as the intervening layer may be pure Ni containing inevitable impurities, and if the average thickness is 10 μm or more, the reaction is effective, and even if it is thick, it is easy to peel off after plating. However, the disadvantage is that the plating time becomes higher due to the longer processing time.

  In the present invention, the apparatus used for the HIP may be any apparatus that can perform heating and pressurization simultaneously or individually, and the processed product can be vacuum-sealed in a container and loaded with a predetermined isotropic pressure by pressurized argon or nitrogen gas. What is necessary is just to have a function.

  If the HIP method used in the present invention is used, powder sintering and diffusion bonding can be performed at the same time.

  Powder sintering method by applying diffusion bonding method by HIP method to manufacture bearings made of Cu-Pb, Al-Sn alloy-based bearing material made of base material containing second phase that does not dissolve soft material as solid phase Compared with the band plate pressure welding method, the degree of freedom in dimensions and shape is increased, and the number of parts and the number of processes can be omitted.

  Moreover, by applying the diffusion bonding method by the HIP method, the generation of thermal stress is reduced, and the formation of a fragile reaction layer at the bonding interface is prevented. Is achieved. In particular, it is suitable for manufacturing a bearing using an Al—Sn alloy containing no environmental load component as a bearing material.

  In the case of the HIP method, powder sintering and diffusion bonding can be performed at the same time.

  Because journal bearings and thrust bearings can be used in common for HIP devices, the same management method and manufacturing conditions can be used, and batch processing can be performed within the limited capacity regardless of size and shape. This is also advantageous.

  Hereinafter, one of the embodiments of the present invention has an Al—Sn alloy bearing material that contains 40% by weight of Sn as a second phase that does not form a solid solution in an Al alloy matrix containing 1% by weight of Cu. An embodiment will be described in which the present invention is applied to a journal bearing that supports a load of a rotating shaft in a ring shape from the radial direction.

  In the HIP method, a processed product is vacuum-sealed in a container for processing, but in the present invention, the back metal base material is used as a container for HIP processing.

  FIG. 2 uses the backing metal base material 2 as a container in the journal bearing (A) and the thrust bearing (B) shown in FIG.

  That is, in the case of the journal bearing (A), the bearing material 1 can take the form of a welded structure container made up of the back metal base material 2, the lid 3 constituting the storage container, and the inner tube 4. As the form of welding, TIG welding can be adopted in the case of arc welding, and electron beam welding (EBW) can be adopted as the special welding. However, considering that the atmosphere control in the case of HIP processing is also performed at the same time, the electron beam can be used. Welding is particularly suitable.

  In the case of a thrust bearing (b), the bearing material 1 is set in a recess formed on the outer surface of the back metal base material 2, and the outer peripheral surface thereof is sealed with a lid 3. The bearing material 1 is covered with the back metal base material 2. The container is formed in a vacuum-sealed form.

Thus, by using the back metal base material 2 as a structural member of a storage container in which the bearing material 1 is vacuum-sealed, the container structure is simplified, and the manufacturing cost and the process are advantageous.

  Table 1 shows representative examples of the composition of the bearing material, the back metal base material, and the inner pipe of the slide bearing shown in FIG.

  In the table, A40 is generally an Al—Sn alloy as a bearing material, and is a material common to journal bearings and thrust bearings containing Sn as much as 40% by weight.

STKM 13A is a carbon steel pipe for machine structure, and in the case of a journal bearing, it is a material that becomes the inner pipe 4 shown in FIG. The backing metal base material of the journal bearing is usually carbon steel S45C, and in the case of the thrust bearing, carbon steel S25C, and the stainless steel SUS304 is partially used in the journal bearing for thermal stress relaxation and interface reaction suppression according to the present invention. The effect was obtained. Further, in FIG. 2, a carbon steel S25C equivalent or mild steel plate is used for the lid 3 constituting the container, and a mild steel plate is also used for the lid 3 of the thrust bearing.

  Table 2 shows the holding temperature as HIP processing conditions, including the above A40 as the bearing material of the sliding bearing, various materials as the back metal base material, and those having various platings on the surface of the back metal base material. The holding pressure and holding time were 500 ° C., 98 MPa and 90 minutes, respectively.

  In the table, no. 1 to No. No. 5 is a journal bearing. 6 to No. 8 is a thrust bearing.

  Among journal bearings, No. 1 to No. 4 shows a case where the back metal base material is S45C and various plating layers interposed at the interface are changed.

  In the case of no plating or electroless Ni—P plating, as a result of the inspection by the ultrasonic flaw detection test (UT) immediately after the HIP treatment, a defect was found at a part of the bonding interface and failed. In addition, in both cases of Cu (copper) and Ni plating by electroplating, no defect was found at the joint interface, and the UT inspection passed.

  And the whole back metal base material made the austenitic stainless steel SUS304 No .. In the case of 5, no defect was found at the bonding interface, the UT inspection passed, and it was found that the bonding interface had an appropriate bonding strength.

  No. 6 is a case of a thrust bearing without plating, but as a result of the UT inspection immediately after the HIP processing, a defect was found in a part of the joining interface and it was rejected.

  No. 7 and no. In the case of the thrust bearing shown in FIG. 8, Cu and Ni plating as an interface intervening layer was carried out. However, no defect was found in the joint interface, and the UT inspection passed.

  As a method for quantitatively evaluating the soundness at the joint interface, the shear strength at the joint interface was measured. As shown in FIG. 3, (b) as a journal bearing, (b) as a thrust test piece of a thrust bearing, and (b) in the case of (b), the diameter portion is adjusted to the product dimensions, the total length is 15 mm, the flange thickness is 5 mm, In this case, a plurality of test pieces having a back metal base material diameter of 25 mm and a bearing material diameter of 15 mm were collected in accordance with the product length.

In the case of (a) shown in FIG. 4, the mechanism is configured by a receiving jig and a pushing jig, and a load is applied so as to be pushed out in the direction of the rotation axis. Using a test jig with a mechanism that shifts the base metal part parallel to the interface, the maximum load load (kgf) is divided by the joint area (mm ² ) while loading the load with an Amsler universal testing machine. The shear strength (kgf / mm ² ) was determined and shown in Table 3. In the figure, (a) is a journal bearing and (b) is a thrust bearing.

In addition, the thickness of the intermetallic compound generated at the interface from the microstructure observation observed in the microstructure observation piece collected from the vicinity of the position where the shear specimen was taken was observed by observing the specimen after the test. The composition of the compound was also determined by measurement and EDX (energy dispersive X-ray spectroscopy) analysis.

No. 1-No. In the case of the journal bearing shown by No. 3, the non-plating, Ni-P plating and Cu plating have a low and unstable bonding strength of 5 kgf / mm ² or less, both of which are intermetallic compounds formed at the bonding interface It was destroyed within.

And No. In the case of the Ni plating shown in FIG. 4, the shear strength was a stable joint strength of 5 to 6 kgf / mm ^2, and it was broken at the interface partially including A40.

Furthermore, when the entire back metal base material was SUS304, the shear strength further increased to ⁶ to 7 kgf / mm ^2, and it was also broken at the interface including a part of A40.

In addition, No. corresponding to the thrust bearing. 6 to No. In the case of No. 8 and in the case of Cu plating, the bonding strength was as low as 5 kgf / mm ² or less, but in the case of Ni plating, the bonding strength was stable with a shear strength of 5 to 6 kgf / mm ^2. It was broken at the interface partly including A40.

  That is, both journal bearings and thrust bearings are No. 4, no. 5 and no. As shown in Fig. 8, it is confirmed that the back metal base material is stainless steel, or Ni is interposed in the joint interface, so that it can pass the UT inspection and manufacture a plain bearing with a joint interface having a considerable joint strength. did it.

The typical form and cross-sectional shape of the journal bearing and thrust bearing which can apply this invention are shown. The container form of a journal bearing and a thrust bearing is shown by a cross section. The shape of the shear test piece used in the Example is shown. The test jig | tool for the shear test used in the Example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Al-Sn alloy bearing material 2 Back metal base material 3 Cap of storage container for HIP processing 4 Inner tube of storage container for HIP processing

Claims (5)

  A manufacturing method of a slide bearing in which a soft material that does not dissolve in an alloy base material of Cu or Al is used as a bearing material containing a second phase and a steel base material is used as a back metal base material and a diffusion bonding method using the HIP method is applied.   The manufacturing method of the sliding bearing of Claim 1 which made the back metal base material the austenitic stainless steel.   The manufacturing method of the sliding bearing of Claim 1 which provided the intervening layer which has Ni or Ni as a main component between a bearing material and a back metal base material.   The method for manufacturing a sliding bearing according to claim 1, wherein the bearing material is an Al—Sn alloy.   2. The method of manufacturing a plain bearing according to claim 1, wherein the backing metal base material is a bearing material storage container for processing by the HIP method.

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