Effect of alloying elements on strain hardening exponent of ferritic stainless steel.

Abstract

The effects of alloying elements on the strain hardening exponent, n-value, of ferritic stainless steels have been investigated to assess important factors for improvement of the stretchability. The results have shown that the n-value is determined substantially by the chemical composition. The major requirements to improve the n-value are as follows:1) lowering of Cr content2) reduction of C and N contents as well as addition of Ti about 10 times that of (C+N)3) elimination of the substitutional minor elements, such as P, Si, and Al.The substitutional elements affect the n-value through their effects on the flow stress and the work-hardening rate. The elements can be grouped into two types: Type Si (Si, Ti, Al, Mn, and Cr) and Type P (P). The elements of Type Si are found to raise the flow stress and the work-hardening rate in accordance with the difference of atomic size. In the case of P, interaction between precipitates of phosphide and dislocations mainly determines the work-hardening behavior, when the P content is more than about 0.03wt%.