Effect of Chemical Composition and Heat Treatment upon Impact Toughness of High Tensile Mn-Si Steels. (Report 1)

Abstract

V-notch Charpy impact tests were performed of 30 ship steel plates which were rolled into 12 or 20mm in thickness from the top and bottom of nine production heats of weldable high strength manganesesilicon steels.
The results of tests may be summarized as follows :
(1) The yield ration was generally 65 percents. However, steels M3 and M6 showed higher ratio of 75% which was comparable to that of German HSB steel.
(2) The notch toughness of test steels in as rolled condition was inferior to that of the current killed ship steels and approximately equal to that of rimmed steels. However, the notch toughness was improved remarkably by normalizing the test steels, and was then superior to that of killed steels.
(3) The notch toughness was almost constant in a range, 0.3 to 0.6%, of silicon content.
(4) The notch toughness of test steels was affected more remarkably by ferrite grain size of distribution of carbide, than by chemical composition.