Process Analysis and Experiment of Precise Control of Nitrogen Content in Pressure Smelting of Mn18Cr18N

The precise control of nitrogen content of high nitrogen stainless steel is the key control factor of production. Taking Mn18Cr18N high nitrogen steel as an example， this paper studies the relationship between steel composition， temperature， nitrogen pressure and nitrogen content control in pressure induction melting process by using metallurgical principle， factage thermodynamic software and thermal state experiment and detection analysis methods.The results show that the reliability of the "composition temperature pressure" relationship equation based on the theoretical data is high， and the theoretical and predicted values of nitrogen pressure in the three heats experiment are in good agreement with the actual control values. The thermal experiment finds that when the contents of Mn and Cr remain unchanged， increasing the nitrogen partial pressure can increase the N content in the ingot， but when the nitrogen reaches about 1%， the effect of increasing the nitrogen content by increasing the nitrogen partial pressure decreases.When the content of Mn or Cr is low， the nitrogen content can be increased by increasing the nitrogen partial pressure. Reducing the content of C and Si in steel is beneficial to the alloying and stable control of high nitrogen content in steel. It is advisable to control the melting temperature of the pressure furnace at 1 500-1 550 ℃ and the nitrogen pressure at 0.225-0.325 MPa when the nitrogen content in Mn18Cr19N steel is necessary to be controlled ≥ 0.8%.