Since nitrogen has been found to be an element which improves strength, nitrogen has been added to many austenitic heat-resistant stainless steels. However, this has a shortcoming in that ductility is lost. In the present study, ultra-high nitrogen stainless steel (UHNSS) of 20Cr-10Ni-0.7N (wt%) was prepared by a high-pressure melting method and the mechanical properties at elevated temperatures were investigated. High elongations were obtained on the occurrence of superplasticity of cold-rolled UHNSS at 1073 to 1273 K at low strain rates of the order of 10 -4 sec -1. The superplasticity was related to the precipitation of fine chromium nitrides which was promoted by cold rolling.
High N-20Cr-10Ni stainless steels in the range of 0.25-0.7"/•N were melted by a high pressure induction furnace. These molten metals were deoxidized and desulfurized by calcium after pre-deoxidation by aluminum. It But if calcium can be added under a higher pressure than the vapor pressure to prevent its boiling and in an inert gas atmosphere to protect its oxidation, it will work as a strong deoxidizer and desulfurizer, and the calcium addition will become an economically cheap method, since it saves the refining time.In the present study, we produced high N-20Cr-lONi stainless steels with nitrogen contents up to 0.8 wto/o by a high pressure induction furnace, and investigated the effectiveness of calcium addition for the deoxidation and desulfurization in the process.
2.Experimental Method Fig. I
The present study deals with the characteristics of the heat storage vessel packed with rectangular phase change materials by numerical analysis , The latent heat storage 皿 aterials . i皿 the vessel are heated by utilizing the natura1 convection of the heat transfer medium , which 且ow the interval of the latent heat storage materials . The interval of rectangular latent heat storage materials is greatly related to natural convection of the heat transfer medium . Numerical results revealed temperature pro 丘les and flow patterns of the heat transfer medium affected the heat storage characteristics .
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