1977 Volume 46 Issue 5 Pages 279-285
The dissolution phenomena of MC type carbides in HAZ of SUS 321 and SUS 347, which were the commencements of knife line attack phenomena in these steels, were quantitatively and theoretically considered.
In this report, as the first step to make clear these phenomena, the dissolution phenomenon of Nb(C, N) in SUS 347 under isothermal heat treatment was analyzed theoretically on the basis of diffusion controlled model of Nb.
In order to obtain (∂C/∂r)r=R in a theoretical equation, the sperical approximation which was reported by Zener, was adopted.
By comparing theoretical values with experimental results, the validity of this model was discussed. The results obtained in this report are as follows;
(1)Two different theoretical equations were derived. One is derived on the assumption of the radius of Nb(C, N) being uniform, and the other is derived by considering the distribution of radius of Nb(C, N)
(2)Comparing theretical values with experimental results, the validity of the theoretical equation derived by considering the distribution of radius of Nb(C, N) was proved.
(3)The fact that the obtained n value in Johnson-Mehl's equation is about 3/2 concerning the dissolution phenomenon of Nb(C, N) in SUS 347 supports diffusion controlled reaction model proposed in this report.
