Effect of Various Alloying Elements on Notch-Sensitivity of 2%-Mn High-Strength Steel

Study on the low-manganese high-strength steel-I

Abstract

The authors studied upon the influence of various alloying elements on notch-sensitivity of low-manganese high-strength steel, standard composition of 0.28% C, 2.00% Mn, 0.5% Cr and 0.3% Mo, mainly by V-notch Charpy impact test at -40°C. The notch-sensitivity of this steels for sorbitic structure were improved both by increasing of Mo contents and small amount of V additions. On the other hand, for martensitic structure, it was found that notch-sensitivity could be improved by many other elements additions. Results obtained were as follows:
(1) Increasing of C contentof this steel gave remarkable harm to notch-sensitivity than any other element. Therefore, it was recommended to decrease C content as low as possible.
(2) Si and Cr, both increased notch-sensitivity as their content for sorbitic structure was increased, but the improving effects of impact value at 300°C tempered range were recognized.
(3) Mo-free steel was remarkably notch-sensitive and therefore Mo addition was always necessary in this steel. Addition of 0.5% Mo were the most adequate to improve of notch-sensitivity but when its contents was increased to 1%, the sensitivity was a again increased.
(4) W and Ti additions were not effective in sorbitic structure, but a little effective in low tempering-temperature range. Especially, Ti-B additions were effective in a low tempering-temperature range.
(5) V addition was effective in both sorbitic and martensitic structure. In the former, the small amount of addition to 0.05% was effective, while in the later, 0.2% was adequate.
(6) Cu addition was not effective under any conditions.