METHOD OF CHEMICAL HEAT TREATMENT OF ARTICLES OF TOOL STEEL Russian patent published in 1994 - IPC

FIELD: mechanical engineering. SUBSTANCE: chemical heat treatment of articles of tool steel comprises heating up to process temperature in endothermic-base atmosphere with ammonia addition, holding at this temperature in atmosphere containing nitrogen, and article cooling. Heating up to process temperature is performed in two stages. First, the article is heated up to 480 - 500 C temperature in endothermic gas, and then it is heated up to 560 - 580 C in gas mixture of 50 per cent of nitrogen, and 50 per cent of endothermic gas. Holding at this temperature and this mixture content is carried out during 0.5 - 1.0 h. Then holding is performed at the same temperature and in gas mixture of 25 per cent of ammonia and 75 per cent of nitrogen. Then the article is cooled down to 480 - 500 C in mixture of 10 per cent of ammonia, and 90 per cent of nitrogen. The article is hold at this temperature and in nitrogen atmosphere for 1.5 to 2.0 h. EFFECT: tool steel of improved properties. 1 dwg