| 摘要 |
1482489 Permanent magnet material MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 11 July 1975 [11 July 1974] 29320/75 Heading C7A [Also in Division B3] A method of making an anisotropic permanent magnet comprises extruding a lubricated, polycrystalline body of Mn-Al-C alloy at 530‹-830‹C through a converging die. The constituents of the alloy are present in the range:- Mn 68À0% to 73À0% C (<SP>1</SP>/ 10 Mn - 6À6) to (<SP>1</SP>/ 3 Mn - 22À2)% Al the remainder There may also be impurities and additives in addition. The semi-angle ½ of the die is preferably in the range 2À5 degrees to 30 degrees and optimum magnetic properties for the alloy are obtained within the range 5 degrees - 20 degrees. Prior to extrusion an alloy billet is heated to 1150‹C for two hours, cooled at a rate of 500‹C/ min and tempered at 550‹C for 30 minutes. Alternatively it may be cooled at 10 degrees - 15 per minute, held at 830‹C for 15 minutes and quenched. The lubricant may be a copper-graphiteglass composite. In another method the billet is held at 1050‹C for one hour and then cooled at about 400‹C/min. The lubricant in this case is colloidal graphite. The die may converge in one plane only and be of constant width in a plane normal to the maximum taper, Figs. 2 and 3 (not shown), or the amount of taper may vary, Fig. 4 (not shown) and there may be a non-tapered portion II, Fig. 1, with any configuration of die. |
