1956 Volume 42 Issue 12 Pages 1118-1122
The present report deals with a study on carbides in a high C-high Cr die steel(2.25%C, 12.03%Cr) by electrolytic isolation technique as reported before (J.I.S.I.J. 41, 1955, p 1188).
In the investigation of tempering of the die steel, a specimen (0.59% C, 4.73%Cr) named "matrix steel" was used, of which composition is similar to the matrix of the die steel at 950°C, in order to remove the interference of undissolved carbides in the quenched structure.
The results obtained were as follows:
(1) In the annealed state, carbides in the die steel are (Cr, Fe)7C3 contained 43.0%Cr, and amounted to about 26 wt %.
(2) With the rise in quenching temperature, the carbides dissolve into austenite and its contents of C and Cr come up to 0.6% and 4.4% respectively, at 950°C.
(3) The carbide precipitated in the steel by tempering at above 650°C is (Cr, Fe)7C3. But the precipitated carbide by tempering at 40-500°C shows (Fe, Cr)3C type pattern. It is expected that these two kinds of carbides coexist at 550-650°C, and carbide reaction (Fe, Cr)3C→(Cr, Fe)7C3 takes place in this tempering temperature range.