1976 Volume 45 Issue 8 Pages 641-648
The attempts was conducted to develop the testing procedure which provided a quantitative assessment of lamellar tearing susceptibility on the basis of its occurrence mechanism. Several lamellar tearing tests, in which the constant strain test proposed by authers was included, were carried out on different types of Al-killed steels, and the physical meanings of their criteria were discussed.
Using the constant strain test, the critical strain levels which need to the decohesion cracking and hydrogen-induced one from non-metallic inclusions are determined respectively, and the causes of lamellar tearing will be able to be clearified for individual plate. The value of reduction of area in a through-thickness tensile test will be considered to have comparatively good correlation with the cracking from MnS inclusions, whereas the value will not correlate with the lamellar tearing when it is induced from oxide inclusions at the sub-surface of plate.
The difference between the susceptibility to root crack in a roll direction and that in a through-thickness direction was apt to increase with the rise of the lamellar tearing susceptibility.
Microanalyses by EPMA showed that the inclusions playing a significant role for the cracking were found to be sulfide for Al-killed steels with more than 0.01 %S, alumina for those with less than the level.