| 摘要 |
PURPOSE:To reduce the manufacturing process of an R-TM-B permanent magnet and improve the productivity, by using jointly heat treatment with hot working of low speed and high speed without processes of grinding and sintering of a casted ingot. CONSTITUTION:Rare earth metal, transition metal and boron are weighed, melted by an induction heating furnace, and casted. In order to give magnetic anisotropy to a magnet, hot working is performed. Casted ingot is cut into a suitable size, put in a carbon die, and heated at 1000 deg.C. When a desired temperature is obtained, the ingot is worked upon at a distortion speed of about 10<-1>/sec. When the working degree reaches about 60%, the distortion speed is reduced, and pressing is performed at a distortion speed of 10<-4>/sec. Then heat treatment is performed at 250 deg.C or more. That is, at first, working is performed at a comparatively large distortion speed (10<-1>-10/sec) to make mainly crystal grain fine. Then the distortion speed is reduced to 10<-4>-10<-3>/sec, and orientation of crystal is performed. As to the period to change the distortion speed, it is desirable that 20-80% of total process is worked at the high speed, and the residual process is worked at the low speed. |
