Low Temperature Sensitization of Type 304 Stainless Steel Available to Purchase

It has been shown that Type 304 stainless steel may be sensitized at temperatures below the normal isothermal sensitization range. A necessary prerequisite for this phenomenon is a heat treatment capable of forming chromium carbide nuclei. The combination of the nucleating and subsequent low temperature heat treatments has been termed low temperature sensitization (LTS). Reversing the order of the heat treatments does not produce sensitization. LTS has been experimentally quantified using the acid copper sulfate test (A262E). The experimental results show that the rate limiting process in LTS obeys an exponential temperature dependence which is consistent with a diffusion controlled chromium depletion model for LTS. The practical significance of LTS is difficult to establish due to the excessive environmental conditions inherent in A262E. However, the times and temperatures involved in LTS may be within many industrial services ranges for Type 304 stainless steel. LTS may also be of value as an enhanced screening test for the presence of carbides, and as a tool for the study of diffusion in stainless steel.