Abstract
For three usual mild steels of tensile strengths 35, 42 and 49 kg/mm2 and two high tensile steels of tensile strengths 51 and 54kg/mm2, differed from the steels in the former reports 1-4, the non-notch bending test and tensile test were performed. Then the results of these tests were considered relating to the continuous cooling transformation diagram of each steel. The summary is as follows;
(1) According to the non-notch bending tests of the steels as received, the steel which has a higher tensile strength, has generally the larger absorbed energy. All angles bended by impact and slow bending were 180°, and the every specimen was not fractured.
(2) For the steels KS (49kg/mm2), YD (51kg/mm2) and YE (54kg/mm2), the bended angle becomes smaller in cases of specimens cooled with shorter cooling time than about Cf. For the steel SS (42kg/mm2), the bended angle becomes smaller below about Cp' critical cooling time (about 2 sec) already.
(3) Comparison of the cooling times at which the bended angle, the reduction of area and the elongation begin to lower is generally as follows. That of bended angle is shortest, that of reduction of area is intermediate and that of elongation is longest.
(4) It was understood from the relation between the chemical anlyses and results of the non-notch bending tests on steels that the carbon content is desired to be lower to than about 0.13%.
