GB2075065A

GB2075065A - Method of making an aluminium based alloy bearing material

Info

Publication number: GB2075065A
Application number: GB8014476A
Authority: GB
Original assignee: Nippon Dia Clevite Co Ltd
Current assignee: Nippon Dia Clevite Co Ltd
Priority date: 1980-05-01
Filing date: 1980-05-01
Publication date: 1981-11-11
Also published as: GB2075065B

Abstract

In the manufacture of a bearing material containing an aluminium based alloy, one surface of a steel strip 1 is washed in a washing machine and roughened by a grinder 8. An aluminium based alloy powder 2'' is spread on the surface of the steel strip 1 and the aluminium based alloy and the steel strip are hot-rolled by heated rollers 5 in the ambient air to pressure-bond the aluminium based alloy to the strip to form a unitary structure. Prior to spreading the aluminum based alloy 2'', an aluminum powder 2' which enhances the bond to the steel strip 1 may first be spread on the surface of the steel strip 1. Also the strip 1 and the powder 2', 2'' may be heated by a heater 9a before the hot rolling. <IMAGE>

Description

SPECIFICATION Method of making an aluminium based alloy bearing material This invention relates to methods of making a material for bearings, by pressure bonding an aluminium based alloy powder to a steel strip, which may be of stainless steel, by means of hot rolling.

In recent years, an aluminium-bonded steel product has come into use for the fabrication of rotary, sliding and other bearings of vehicles and other machines, and a variety of methods have been proposed and employed for the manufacture of such a bearing material. However, all of these conventional manufacturing methods pose some problem or other in the pressure bonding to a steel strip of aluminium alloy powder which will ultimately form the bearing surface layer of the resulting steel-backed strip. There is a great need for a solution to these problems.

In Japanese Published Patent Application Nos.

39213/71 and 20330/64, a method is disclosed as shown in Figure 1 a of the accompanying drawings in which aluminium powder or aluminium alloy powder which will ultimately form a bearing surface (which powder will therefore be hereinafter referred to as bearing powder), is spread by a spreader 3 over the entire surface of a steel strip 1 and is then pressure-bonded thereto by heat rolling between a pair of rolls 5 in a reducing furnace 4. With this method, however, an expensive reducing furnace is needed and the pair of rolls 5 must be placed in the furnace 4, so that there are serious problems in maintenance of the apparatus and in dimensional control during rolling.

In Japanese Patent Disclosure No. 20336/77 a method is disclosed as shown in Figure 1 b in which the bearing powder 2 is spread over the steel strip 1 together with a cold-bonding powder such as aluminium base alloy or the like and the powders are pressure-bonded to the steel strip 1 by cold rolling between the pair of rolls 5 and then the resulting sheet is annealed in a furnace 4. With this method, however, the powders are pressurebonded at ambient temperature, so that in order to achieve the pressure bonding to the necessary degree (i.e. to roll the bearing powder nearly to its forging density), it is necessary to apply such a large rolling pressure as to reduce the thickness of the steel strip by about 15%. This induces a large strain in the steel strip and is likely to introduce difficulty in the subsequent working.Further, this method cannot be used with a powder which is difficult to sinter, such as an Al-Si-Cu-Pb-Sn alloy powder. After the pressure bonding, the aluminium-bonded steel strip is continuously annealed in the heating furnace 4 and is then taken up on a reel. If the annealing is insufficient, the bearing surface layer is liable to crack.

In Japanese Patent Disclosure No. 82651/74 a method is disclosed as depicted in Figure 1 C in which the bearing powder 2 is spread over the entire surface of the steel strip 1 and is heated in a furnace 4 containing an inert atmosphere.

Thereafter the strip and bearing powder are rolled between the pair of rolls 5 to pressure-bond the powder layer to the steel strip 1. This method involves the step of heating in the inert atmosphere, and hence requires expensive equipment as is the case with all of the aforesaid methods. Furthermore, a large amount of inert gas is needed and this inevitably results in the manufacturing cost being raised.

Moreover, U.S. Patents Nos. 3,104,135 and 3,093,885 disclose a bonding method as shown in Figure 1 din which a bearing metal strip 6, prefabricated by a complicated manufacturing process, is clad on to a steel strip by the pair of rolls 5. This method requires expensive apparatus, amongst other things, a continuous forging machine and a powder roll machine.

In view of the difficulties and disadvantages of the prior art described above, it is an object of this invention to provide a method of making an aluminium-bonded steel material which does not involve such expensive apparatus as an inert gas atmosphere furnace and a cladding machine, but which nevertheless ensures excellent unification of a bearing surface layer and a steel strip used as a backing material.

In accordance with the present invention, we provide a method of making an aluminium based alloy bearing material, comprising the steps of: cleaning and roughening one surface of a continuously fed steel strip; spreading a layer of an aluminium based alloy powder over the surface of the steel strip; and hot-rolling the aluminium based alloy powder and the steel strip by heated rollers situated in the ambient air to pressure-bond the powder to the strip and form a unitary structure.

Preferabiy a layer of powder consisting essentially of aluminium is spread over the surface of the strip before the layer of alloy powder is spread.

Preferably also, the strip and the layer of alloy powder, and the layer of aluminium powder when provided, are preheated before the hot rolling takes place.

An example of a method in accordance with the invention will now be described with reference to the accompanying drawings in which: Figures 1 a to 1 dare diagrams showing the conventional bearing material manufacturing methods already referred to; Figure 2 is a diagram illustrating an example of the manufacturing method in accordance with this invention; and Figures 3 to 5 are diagrammatic sections to a much larger scale through bearing materials produced by the method of the present invention and showing the microstructure of the materials.

In Figure 2 there is shown diagrammatically a side view of an arrangement of apparatus for use in carrying out the method of this invention.

Reference numeral 1 indicates a steel strip, which is unwound from a coil 1 a and is continuously fed in the direction of an arrow A. The steel strip 1 is fed first to a washing machine 7, wherein one surface of the steel strip 1 is washed, and then the surface of the steel strip 1 is ground by a grinder 8 to a required roughness. The treatments of washing and grinding by the washing machine 7 and the grinder 8 are intended to remove from the surface of the steel strip 1 oil and fats and iron oxides which prevent firm adherence of the aluminum powders to the steel strip, thereby to maintain or improve the adherence of the former to the latter. The surface roughness in this case is sufficient to be about 25 S.The steel strip 1 may be one that is usually employed as a back metal; in the present invention, a low-carbon steel containing about 0.1% of carbon is usually employed, but use can also be made of an austenite or ferrite stainless steel.

After washing and grinding the surface of the steel strip 1 as described above, a bearing powder 2" of aluminum is spread by a spreader 3 over the entire surface of the steel strip 1. The bearing powder of aluminum herein mentioned is an aluminum base alloy consisting of aluminum and some other elements which impart to the aluminum required properties of the bearing surface which will ultimately be formed. In this case, the bearing powder of aluminum forms the bearing surface layer on the steel strip, as will be described later.

In the above, it is also possible to spread by another spreader 3 an aluminum powder 2', which consists essentially of aluminum, prior to the spreading of the abovesaid bearing powder 2".

The aluminum powder 2 is to facilitate the formation of a close contact layer of the steel and the bearing powder. The aluminum powder 2' may also be added with any other components so long as the abovesaid close contact layer can be formed.

Following the spreading of the aluminum powder 2' and the bearing powder 2n, the steel strip 1 is heated by a heater 9a up to a temperature in the range of, 200 to 4000 C, and then the powders 2' and 2" are pressure-bonded by hot rolling to the steel strip 1 between a pair of rolls 5 which are heated by heaters 9b in the air up to a temperature in the range of 1 50 to 4090 C.

The above pressure bonding takes place in the air, but the aluminum powder 2' and the bearing powder 2" of the aluminum base alloy are pulverized on the steel strip 1 to achieve metallic coupling therewith, thus obtaining a bearing surface layer which firmly adheres to the steel strip 1.

The powders are heated up to such a high temperature, and when they are hot-rolled, their particles rub against one another to generate heat, by which they are heated up to an appreciably high temperature in a moment. In this case, the particles are given ductility due to heat by the hot rolling, and in spite of heating in the air, air present in the gaps between the particles is instantly driven out and an oxide film (A12O3) on the surface of each particle is readily destroyed by the rolling force by which the powders are forged; consequently, active coupling of the particles can be obtained without causing their oxidation to proceed. On top of that, only by the operation of hot rolling, the powders are sufficiently diffused into each other and their firm adherence to the steel strip can be achieved.

For the above pressure bonding, it is sufficient to perform hot rolling at such a temperature that the steel strip reaches its forging density at a reduction ratio of about 3% to about 25%. With such a rolling force being applied, sufficient adherence and sintering can be achieved only by hot rolling. Even if the adherence of the powders to the steel strip is yet insufficient, heat treatment which usually takes place after hot rolling permits sufficient diffusion of the aluminum base alloy powder into the steel strip to achieve firm coupling therebetween and, at the same time, increases the ductility of the bearing surface layer.

Further, the heating means 9a and 9b for the hot rolling may be gas, high frequency induction or like heaters; the heater 9a need not always be provided, but the combined use of the heaters 9a and 9b produces an appreciable effect on the pressure bonding of the aluminum base alloy bearing powder.

In the manner described above, the aluminum base alloy bearing powder is pressure-bonded to the steel strip to form thereon a bearing surface layer, and the resulting bearing steel strip is taken up into a coil 1 b. The bearing steel strip can be used to make bearings but may also be further heated in an air atmosphere, for example, in a heating furnace 10 at 250 to 5000C. Such heating in the air promotes diffusion of the aluminum base alloy into the steel strip to ensure firm adherence of the bearing surface layer to the steel strip, providing an excellent structure as a bearing metal.

As revealed by the foregoing description, the present invention has such advantages as follows: The present invention: (1) Performs heating and pressure bonding in the air and does not require an expensive atmosphere furnace, and hence permits reduction of the manufacturing cost and simplification of the manufacturing process; (2) Does not involve a process of pressurebonding a prefabricated bearing material sheet to the steel strip, and hence does not require any complicated manufacturing equipment; and (3) Does not require a large reduction ratio of the steel strip in the rolling process, so that the resulting bearing steel is small in work hardening and excellent in workability.

The present invention will be further described in connection with its preferred embodiments.

EXAMPLE 1 Use was made of the manufacturing equipment of Fig. 2, in which a steel strip 1 was continuously fed and its surface was washed as usual and ground to a surface roughness of about 25 S.

Then, the aluminum powder 2' was spread by the spreader 3 all over the roughened surface of the steel strip 1 and then the aluminum base alloy bearing powder was also spread by the spreader 3. The aluminum base alloy bearing powder used was an Al-Si-Cu-Pb-Sn alloy powder (Si 4%, Cu 1%, Pb 8.5% and Sn 1.5%). Then, the steel strip covered with the powders was heated by the heater 9a up to about 3500C in the air and rolled, at a reduction ratio of 10%, by the pair of rolls 5 heated up to 2500C to pressure-bond the powders to the steel strip, thereafter being taken up into the coil it.

The sectional structure of the thus obtained bearing material examined by microphotography was such a three-layered structure as shown in Fig. 3. The bearing surface layer of the bearing material firmly adhered to the steel strip and the bearing material obtained by this Example did not pose any problems in the bearing performance.

The bearing material shown in Fig. 3 is composed of the steel strip 1, a binding layer 11 and an alloy layer 12.

EXAMPLE 2 In the manufacturing equipment shown in Fig. 2, after one surface of a steel strip 1 was washed and roughened as in Example 1, an aluminum powder was spread on the roughened surface of the steel strip 1 and then an aluminum base alloy bearing powder was spread, thereafter being pressure-bonded by hot rolling to the steel strip 1 between the pair of rolls 5 heated up to 35O0C, with the reduction ratio of the steel strip being held at 12%. Thereafter, the resulting bearing material was taken up into the coil 1t and then sintered in the heating furnace 10 at 4000C for three hours. The sectional structure of this bearing material was substantiaily the same as shown in Fig. 3.

EXAMPLE 3 In the manufacturing equipment of Fig. 2, as in Example 1, after one surface of a steel strip was washed and roughened, an aluminum powder was spread on the roughened surface of the steel strip 1 and then an Al-Si-Cu alloy powder (Si 3.3% and Cu 0.6%) was spread, thereafter being heated by the heater 9a in the air up to 3000C and pressurebonded by hot rolling to the steel strip 1 between the pair of rolls 5 heated up to 2500C, with the reduction ratio of the steel strip 1 being held at 8%. The sectional structure of this bearing material was such as shown in Flg. 4, and its bearing surface layer firmly adhered to the steel strip 1.

EXAMPLE 4 In the manufacturing equipment of Fig. 2, after washing and roughening one surface of the steel strip 1 as in Example 1, an aluminum powder was spread as in Example 3 and an aluminum base alloy powder was spread, thereafter being pressure-bonded by hot rolling to the steel strip 1 between the pair of rolls 5 heated up to 4000 C, with the reduction ratio of the steel strip 1 being held at 5%. After taken up into the coil 1 t, the bearing material was heated in the heating furnace 10 at 4000C for three hours. The sectional structure of this bearing material was such as shown in Fig. 4, and its bearing surface layer firmly adhered to the steel strip 1.

EXAMPLE 5 In the manufacturing equipment of Fig. 2, after washing and roughening one surface of a steel strip 1 as in Example 1, an aluminum base alloy bearing powder consisting of 90 wt% of Al-Si alloy (Si 4%) and 10 wt% of Pb-Sn alloy (Sn 8%) was spread over the entire area of the roughened surface of the steel strip and then heated by the heater 9a, thereafter being pressure-bonded to the steel strip 1 by the pair of rolls 5 heated up to 3500C, with the reduction ratio of the steel strip 1 being held at 10%. The sectional structure of this bearing material was such as shown in Fig. 5, and its bearing surface layer firmly adhered to the steel strip.

EXAMPLE 6 In the manufacturing equipment, after one surface of a stainless steel strip 1 was washed and roughened as in Example 1, the aluminum powder 2' and the aluminum base alloy bearing powder 2" were spread on the surface of the stainless steel strip 1. In this case, the aluminum base alloy powder was the Al-Si-Cu-Pb-Sn alloy powder used in Example 1. Then, the stainless steel strip 1 and the powders spread thereon were heated by the heater 9a up to about 3500C in the air and then hot-rolled by the pair of rolls 5 heated up to about 2000C, with the reduction ratio of the stainless steel strip 1 being held at 7%. Thereafter, the resulting bearing material was taken up into the coil 1 b and heated in the heating furnace 10 at 4000C for three hours.

The sectional structure of this bearing material, examined by microphotography, was such as shown in Fig. 3, as in Example 1, and the bearing performance of this material was satisfactory.

EXAMPLE 7 In the manufacturing equipment shown in Fig. 2, after one surface of a stainless steel strip 1 was washed and roughened as in Example 1, an aluminum base alloy bearing powder 2" (Si 4%, Cu 1%, Pb 8.5% and Sn 1.5%) was spread all over the roughened surface of the stainless steel strip 1 and heated by the heater 9a in the air up to 3500C, thereafter being pressure-bonded to the stainless steel strip 1 between the pair of rolls 5 heated up to 2500C, with the reduction ratio of the stainless steel strip being held at 10%. Then, the resulting bearing material was taken up into the coil 1 b and sintered in the heating furnace at 4000C for three hours. In the sectional structure of this bearing material, the bearing surface layer firmly adhered directly to the stainless steel strip 1.

EXAMPLE 8 In the manufacturing equipment shown in Fig. 2, after one surface of a steel strip 1 was washed and roughened as in Example 1, an aluminum base alloy bearing powder 2" (Si 4%, Cu 1%, Pb 8.5% and Sn 1.5%) was spread all over the roughened surface of the steel strip 1 and heated by the heater 9a in the air up to 3500 C, thereafter being pressure-bonded to the steel strip 1 between the pair of rolls 5 heated up to 2500 C, with the reduction ratio of the steel strip being held at 10%. Then, the resulting bearing material was taken up into the coil 1 b and sintered in the heating furnace at 4000C for three hours. In the sectional structure of this bearing material, its bearing surface layer firmly adhered directly to the steel strip 1.

EXAMPLE 9 In the manufacturing equipment of Fig. 2, after washing and roughening one surface of a steel strip 1 as in Example 1, an aluminum base alloy bearing powder consisting of 90 wt% of Al-Si-Cu alloy (Si 3.3% and Cu 0.6%) and 10 wt% of Pb-Sn alloy (Sn 8%) was spread all over the roughened surface of the steel strip 1 and then heated by the heater 9a up to 3500C in the air, thereafter being pressure-bonded to the steel strip 1 between the pair of rolls 5 heated up to 3000 C, with the reduction ratio of the steel strip 1 being held at 10%. This bearing material also had such a sectional structure as shown in Fig. 5 in which its bearing surface layer firmly adhered to the steel strip.

EXAMPLE 10 In the manufacturing equipment of Fig. 2, after washing and roughening of one surface of a stainless steel strip 1 as in Example 1, an aluminum base alloy bearing powder consisting of 80 wt% of Al-Si-Cu-Pb-Sn alloy (Si 4%, Cu 1%, Pb 8.5% and Sn 1.5%) and 20 wt% of Al-Si-Cu alloy (Si 3.3% and Cu 0.6%) was spread directly all over the roughened surface of the stainless steel strip 1 and then pressure-bonded to the stainless steel strip 1 between the pair of rolls heated up to 350"C, with the reduction ratio of the stainless steel strip being held at 12%. Thereafter, the bearing material was taken up into the coil 1 b and sintered in the heating furnace 10 at 4000C for three hours. The bearing material thus obtained also had such a sectional structure as shown in Fig. 4, in which its bearing surface layer firmly adhered to the stainless steel strip 1.

As has been described in the foregoing, according to the present invention, an aluminum base alloy bearing powder is spread on a steel strip and pressure-bonded thereto by hot rolling to obtain a material for bearings. Unlike in the prior art, neither an atmosphere furnace nor a heating furnace is needed, and the entire manufacture process takes place in the air atmosphere, so that it is possible to enhance the quality of the material and reduce its manufacturing cost, permitting the fabrication of an excellent aluminum base alloy bearing material.

Claims

1. A method of making an aluminium based alloy bearing material, comprising the steps of: cleaning and roughening one surface of a continuously fed steel strip; spreading a layer of an aluminium based alloy powder over the surface of the steel strip; and hot-rolling the aluminium based alloy powder and the steel strip by heated rollers situated in the ambient air to pressure-bond the powder to the strip and form a unitary structure.

2. A method according to Claim 1, in which the steel strip is of stainless steel.

3. A method according to Claim 1 or Claim 2, in which a layer of powder consisting essentially of aluminium is spread over the surface of the strip before the layer of alloy powder is spread.

4. A method according to any one of the preceding Claims, in which the strip and the layer of alloy powder, and the layer of aluminium powder when provided, are preheated before the hot rolling takes place.

5. A method according to any one of the preceding Claims, in which the rollers are heated to a temperature of from 1500 to 4000C.

6. A method according to Claim 4 or Claim 5 when dependent on Claim 4, in which the preheating is to a temperature of from 2000C to 4000C.

7. A method according to any one of the preceding Claims, in which the hot rolling reduces the strip by an amount of from 3% to 25%.

8. A method according to any one of the preceding Claims, in which, after the hot rolling, the strip and the bonded powder layer are coiled and are then further heated in a furnace with an air atmosphere to a temperature in the range of from 250 C to 5000 C.

9. A method according to Claim 1, substantially as described with reference to Figures 2 to 5 of the accompanying drawings and in any one of Examples 1 to 1Q herein.