I am working on an experimental project in-which I use an induction furnace to melt duplex stainless steel and Nitrogen-containing ferrochromium to increase the Nitrogen in my material.
1-How I should add N-containing ferrochromium to melt?
2-Should I add it in ladle or in furnace?Is it necessary to give some time to melt between adding N-containing ferrochromium and pouring melt to mold? If yes, how much?
3-In-which temperature should I add the ferrochromium?
Nitrogen introduce in liquid state of the metal all the alloying element also introduced in liquid face of the metal.nitrogen is the strong austenite former.a number of factors influence the solubility of Nitrogen in the Iron Alloy composition the crystal structure ,temperature and the pressure of the gaseous nitrogen in the atmosphere above the alloy.Addition of Cr,Mn & Mo to liquid steel increase the Nitogen solubilty. While the addition of Ni,C, Si & Cu decrease it.
Plasma nitriding is used to increase the surface hardness, by nitrogen diffusion into the crystal lattice, and to improve wear resistance. In this study, DSS samples were plasma nitrided at temperatures between 350 °C and 500 °C for 240 minutes under an atmosphere of 75% N2 + 25% H2 . Aparent diffusion coefficients, activation energy and pre-exponential constant were calculates using the first law of Fick for each material phase, austenite and ferrite. Nitrogen diffusion in both phases appears to be similar. The layer thickness on the alpha phase is greater than in the gama phase. Nevertheless, the difference on the layer thickness in both of the phases is small. From these results, it was proposed a model of nitrogen diffusion into a two-phase stainless steel to explain the morphology of the interface between the layer and the substrate.
Research MATERIAL SELECTION FOR NITROGEN BASED FERTILIZERS PLANTS
In the liquid state only. You can try mixing with argon. Partial pressure will dictate solubility
Adding high-nitrogen ferrochromium is a good way to obtain the steel. However, you should calculate how much it should be added to the melt otherwise you may get a double phase steel , for instance sigma phase and austenite.
Pressurizing the melt is also good approach since nitrogen solubiity is a direct function of the nitrogen partial pressure. At 1560 C the nitrogen solubility may be as high as 0.08%. Optimal time of saturation is about 1 hr. Further saturation gives only negligible increase in nitrogen content.
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