Effect of Grain Size and Boron on Resistance to Secondary Working Embrittlement of High-purity Ferritic Stainless Cold-rolled Steel Sheet

The effbct of gmin size and boron on the resistance to the secondary working embrittlement of high-purity ferritic stainless cold-rolled steel sheet is investigated and analyzed. The mechanism for improving the resistance to the secondary working embrittlement by adding boron to high-purity ferritic stainless steel sheet is studied from the standpoint of the behavior of the segregated boron. The results obtained are as follows. (1) The secondary working embrittlement in Ti stabilized low C, N ferritic stainless steel sheet occures by the interganular fracture. (2) Refining the grain size improves the resistance to the embrittlement, but it remarkably deteriorates the deep drawing property. (3) Adding boron improves the resistance to the embrittlemnt, with ensuring the deep drawing property. (4) The morphology of fracture in the secondary working embrittlement changes from the intergranular fracture to the cleavage fracture by adding boron. (5) It is considered that the improvement of the resistance to the working embrittlement is due to strengthening the grain boundary by the segregated boron to the grain boundary instead of carbon. This agrees with the results obtained in the interstitial-atom free steel sheets.