Bubbles Separation Research Of Cr12N In High Pressure Solidification Process

As a new kind of engineering materials, high nitrogen steel has very good mechanical properties,corrosion resistance, etc. While, there are many problems should be solved to make it to be industrial production. Such as how to aid a lager mount of nitrogen into steel in melting process, and how to make sure that the high nitrogen content can not precipitate in solidification process. In current condition, high nitrogen stainless steel is easily to separate in the process of solidification. So it is important to research the precipitation behavior of bubbles in the solidification process of high nitrogen steel.It has been more than ten years of Hebei United University to research on high nitrogen steel.Now it can produce the austenitic stainless steel with nitrogen content higher than 1% and the ferrite stainless steel with nitrogen content higher than 0.3%. Now the phenomena that melting ingot segregation and bubble precipitation are serious in the solidification process without phase control pressure.Theoretical analysis and experimental research are used to analysis the bubbles precipitation behavior on Cr12 N steel in the solidification process of high pressure. From the analysis of segregation in melting process, the results showed that nitrogen is easily enrich in solidification front in the process of solidify. The separate of bubbles is easy because of the element enrichment. In high pressure, the bubble is easy to be squeezed out among the dendrite, and this reduces the chance of bubbles in it. At the end of solidification, the nitrogen balance solidification pressure is the largest.When setting the balance of the minimum pressure greater than the nitrogen partial pressure finally.Qualified ingot can be get in the solidification process.Combining the theoretical analysis results show that the solidification process need higher nitrogen pressure. We have made the experiment that melting pressure at 0.3 MPa, solidification pressure at 0.8 MPa, 1.0 MPa, 1.6 MPa and smelting pressure at 0.6 MPa, solidification pressure at 1.0MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa. The experimental results show that the quality of ingot improve significantly with the increase of solidification pressure. It is concluded that the solidification pressure is higher, the number of bubbles is less. The increasing pressure is not conducive to the nucleation of bubbles. Calculating and testing the solidification pressure model with the experimental results. The ingot is very good by the smelting pressure at 0.3 MPa and solidification pressure at 1.6 MPa.