| 摘要 |
<p>Sintred bearing metal is made by a powder metallurgical process from a mixture comprising at least 50 per cent Cu (60-325 mesh) and 0.25 to 15 per cent of hard particles of aluminium oxide. The remaining metallic ingredient may be Zn up to 45 per cent, Ni up to 49 per cent, Pb up to 30 per cent, Al up to 15 per cent or Fe from 1 to 11 per cent, or, when there is more than 70 per cent Cu, it may be Su up to 18 per cent. The mixture may also contain 1 to 3 per cent Si, small quantities of Mn, Be, Co and P, up to 6.5 per cent finely divided graphite (80 mesh or finer) and 0.3 to 2 per cent of a die lubricant comprising powdered zinc stearate or stearic acid. The aluminium oxide may be in the form of fused alumina, "Turkish emery," corrundum or tabular corundum, and may be in the form of 100 to 600 mesh powder. The mixture may be briquetted at a pressure of 20,000 to 120,000 pounds per square inch and then sintered in an inert atmosphere for 4 to 120 minutes at a temperature of 1300 to 1950 DEG F. The inert atmosphere may comprise H, a mixture of N and H or methane dissociated NH3, a mixture of 20 per cent CO, 3 per cent H, and 77 per cent N, or a mixture of 1.5 per cent CO, 1.5 per cent H, and 97 per cent N. After sintering, the product may be subjected to a solution heating for 1 to 8 hours at 600 to 1400 DEG F., in an inert atmosphere, or to an initial heating for 5 hours at 1400 DEG F. in an inert atmosphere, a water or oil quench, and to a second heating for 5 hours at 600 DEG F. Instead of briquetting under high pressure before sintering, the powder may be loosely filled into a mould and may contain a relatively small amount of one ingredient (e.g. Sn) having a lower melting point than the Cu. Alternatively, before sintering, the powder may be spread on a steel backing strip having a thin electroplated metal as its surface. The sintered metal may be used for piston pin bushings, cam shaft bushings, balancer shaft bushings and thrust washers.</p> |
