| 摘要 |
PURPOSE:To obtain a product of good quality at a low cost while contriving efficient nitridation and making a treating time shorter, in performing solid- phase nitridation inside an oven, by controlling an initial nitriding speed, and replacing in-oven gas after the attainment of a specified nitriding ratio to enhance the nitriding speed. CONSTITUTION:A truck 2 on which a powdery raw material 1 such as pure metal or ferroalloy, e.g. ferrosilicon, is laminately piled up is introduced into a vacuum oven 3, said oven 3 is hermetically sealed, and a rotary pump 6 and a mechanical booster pump 7 are driven to perform exhaustion. Then, the interior of the oven 3 is heated up to a temp. necessary for nitriding treatment with a graphite heater 5, and N2 gas is introduced through an inlet opening 9 while closing a valve 8 to start nitridation. Hereon, the nitridation is performed while controlling an initial nitriding speed. When said nitriding ratio reaches 35-45%, the in-oven gas is exhausted. Thereafter, N2 gas is reintroduced to enhance the speed of nitriding reaction, and then the nitridation is completed. |
