1958 Volume 27 Issue 4 Pages 201-206
In this report, the high tensile steel "Wel-ten 55" containing 0.13% C, 0.48% Si and 1.40% Mn was used for the investigation. The authors constructed separately the continuous cooling transformation diagrams of same steel with one method using the Sato's apparatus for quenching test and with other method using the new apparatus. The both continuous cooling transformation diagrams were compared each other, and the critical cooling times Cz', Cf', Cp' and Ce' nearly agreed respectively each other. However there were considerable differences between the both transformation beginning curves to intermediate structure or them to martensite. In the case used Sato's apparatus for quenching test, those curves exist in the lower temperature side. This is considered to be due to the reason that a γ-type bar was used for the temperature indicator in the Sato's apparatus and a certain delay in cooling rate of a specimen, being due to transformation, was neglected. In the new apparatus, the temperature-measurement is correct since the temperature of the specimen is measured directly. The following matter was also confirmed as well as in Report 3: the continuous cooling transformation diagram in case of rapid heating maximum temperature 1300-1400°C is very useful for supposition of the structure and hardness in the heat-affected zone, in the neighbourhbourhood of fusion line, by welding.
