Patent GB-674056-A (GB)
Title: Manufacture of self-lubricating metallic bodies by sintering metallic powders
IPC: B22F3/26
Filed: 1948-11-16
Abstract: 674,056. Powder metallurgy; making bearings &c. WILLIAMS, W. P. (Soc. Edras). Nov. 16, 1948, No. 29754/48. Classes 83 (ii) and 83 (iv). [Also in Groups V, XXIV and XXXIV] A method for the manufacture of selflubricating bodies, such as bearings, or brake or clutch linings, comprises moulding substantially to the shape desired for the body, a metal powder whose grains have a globular structure, sintering said powder at a temperature sufficiently high to obtain cohesion between the grains whilst retaining their globular structure, impregnating the resulting porous body with a lubricant, and compressing the body to obtain a reduction of the dimensions of the pores in the body. The powder may be obtained by the method of Specification 654,803, [Group II]. The compression is carried out by pressing, hammering, shotting &c. to produce a body such as shown in Fig. 6, the lubricant 5 surrounding the grains 4. A bearing, Fig. 1, comprises a ring 1 of steel, cast iron, bronze &c. into which is forced a steel or bronze sleeve 2 having a self-lubricating liner 3. The liner 3 is obtained by covering the sleeve 2 with a powder of copper-lead alloy and grain-size 10-300Á. to a thickness of <SP>1</SP>/ 10 - <SP>3</SP>/ 10  mms. The powder is treated, prior to painting on the sleeve 2, by passing it through a 10 per cent camphor in alcohol solution which causes the powder to be adhesive. The whole is then sintered at 850‹ C. and the liner 3 impregnated with oil and sized at 1000 kgs./cm<SP>2</SP>. An oil reservoir 10 in the ring 1 feeds the liner. Axial bearings, Fig. 4, are also described. As an alternative to coating the powder with camphor, the liner 3 may be formed by using a jig 15, Fig. 7, of aluminium or chromium-plated copper. The inner surface of the sleeve 2 is prepared by coating it by painting &c. with a tin-bronze powder and heating it at 920‹ C. The space between the jig 15 and sleeve 2 is filled with a 30 per cent Pb 70 per cent Cu alloy and pre-sintered at 400‹ C. The whole is then removed, sintered at 850‹ C., impregnated, and bored to final dimensions. In a modified construction the porous liner is formed on a steel strip 18a and clamped between bearing halves 20, 21. Alternatively, the strip and liner are formed as a continuous length and afterwards cut to length, the sintering taking place in a tunnel-type furnace with lateral guides to control the liner-width. The liner is then rolled to size. Porous metal masses may also be filled with resins or synthetic plastics. Carbon - base plastics or plastics containing silicon can be used, the filled mass then being shaped by pressing or hammering. As an example, an 80 per cent Cu, 12 per cent Sn, 8 per cent Pb alloy of grain size 1-300Á is sintered in a reducing atmosphere at 860-920‹ C. It is then impregnated with a resin, such as that manufactured under the Registered Trade Mark " Bakelite," dissolved in alcohol. The alcohol is then evaporated in air and then in a stove at 50‹ C. before the mass is compressed at 1-5 tons/cm<SP>z</SP>. It is finally heated at 170‹ C. The resulting material may be used as a brake lining.