| 摘要 |
1,136,022. Sintered ferritic stainless steel. WARGONS A. B. Feb.22, 1966 [March 10, 1965], No.7783/66. Heading C7D. Sintered ferritic stainless steel is produced from a cast ingot of the steel having a Cr content of 20-55% which is heat-treated at 600‹ -900‹ C. to produce a brittle phase, the ingot is then crushed and the powder formed is sintered. The powder of minus 325 mesh U.S.A. standard may be poured into a mould and sintered as a loose powder e. g. to form bearings and filters with a porosity of 40-50%, or it may be pressed at 4/8 tons/sq. cm. or rolled in a metal sheath sintered and rolled to form rods, bars and wires. The powder is preferably annealed at 900‹ -1100‹ C. prior to forming and sintering at temperatures above 1000‹ C. Fe and/or Al powder may be added to the steel powder to suppress the formation of sigma phase e.g. 10% of a 50/50 Fe/Al alloy may be added. Alternatively the powder may be annealed in a nitrogen atmosphere to form surface nitrides. To inhibit grain growth an oxide layer is preferably formed on the powder during annealing or alternatively iron oxide may be added to the powder. |
