The effect of vacuum

temperature and nitride composition on nitrogen solubility in steel is analyzed and the test of adding nitrogen in alloy steel with various chemical composition (/% ： 0. 06 ~0. 36C

≤3. 23Si

≤2. 20Al

≤ 9. 00Cr) by three kinds of nitrides-silicon nitride

manganese nitride and chromium nitride in a 50 kg vacuum induction furnace is carried out. Results show that the effect of nitrogen partial pressure in gas phase on nitrogen solubility in liquid is greatest ； with containing Ti and Cr in steel the nitrogen solubility in steel and yield of nitride increase ； with increasing C content in steel the nitrogen solubility in liquid and yield of nitride decrease ； with containing definite aluminium in steel the yield of nitride obviously increases. With 40 kPa argon pressure at 1 600 ~ 1 650 ℃

the yield of silicon nitride

manganese nitride and chromium nitride being respective in silicon steel

structural steel and 9% Cr steel is respectively 25% ~ 30%

30% ~ 50% and 60% ~ 100%.