Enlarging or reducing the elements in the γ phase region also expand or shrink the γ phase region in the Fe-Fe3C phase diagram, and when the content of Ni or Mn is also large, the steel can obtain a single-phase austenite structure at room temperature (such as 1Cr18Ni9 Austenitic stainless steel and ZGMn13 high manganese steel, etc.), and when Cr, Ti, Si, etc. exceed a certain content, the steel can obtain a single-phase ferrite structure at room temperature (such as 1Cr17Ti high chromium ferritic stainless steel, etc.). The effect on the critical points of the Fe-Fe3C phase diagram (points S and E). Enlarging the elements in the γ phase region reduces the eutectoid transition temperature in the Fe-Fe3C phase diagram, while reducing the elements in the γ phase region increases it, and both The eutectoid reaction is carried out in a temperature range. Almost all alloying elements reduce the carbon content of the eutectoid point (S) and the eutectic point (E), that is, the S point and E point are shifted to the left, and the effect of strong carbide forming elements is particularly strong.
Effects of alloy elements in SPA-C steel on heat treatmentThe addition of
alloying elements will affect the structural transformation of the steel during the heat treatment of
SPA-C steel. The influence of alloying elements on the phase transformation during heating. The alloying elements influence the rate of austenite formation and the size of austenite grains during heating. (1) Influence on the formation rate of austenite: Cr, Mo, W, V and other strong carbide forming elements have a high affinity for carbon, forming alloy carbides that are insoluble in austenite, which significantly slows down austenite Formation rate: Co, Ni and other non-carbide-forming elements increase the diffusion rate of carbon and accelerate the formation of austenite; alloy elements such as Al, Si, Mn have little effect on the formation rate of austenite. (2) Effect on austenite grain size: most alloying elements have the effect of preventing austenite grain growth, but the degree of influence is different. The elements that strongly hinder the growth of grains are: V, Ti, Nb, Zr, etc.; the elements that hinder the growth of grains are: W, Mn, Cr, etc.; the elements that have little effect on the growth of grains are: Si, Ni, Cu, etc.; elements that promote grain growth: Mn, P, etc.
