Abstract
As the cause of red-shortness, it is wellknown that copper metal freed from steel in oxidation penetrates into grain boundary and makes bending cracks on the surface of the steel at high temperatures. In our research of the low carbon steel containing copper content below 0.4% and ordinary commercial steel, we have found the fact that such low copper content is not serious factor, but heating in the strong oxidizing atomsphere is the main factor of the surface cracking; i. e. the oxidation red shortness. Over 1200°C the red shortness of the steel (on an Oelsen bending test machine) recovers and surface cracking diminishes. This suggests the existence of the temperature range of oxygen hot shortness and the authors ascertained the temperature range of the shortness both in hot bending test and hot impact test. Other factors such as sulphur are alsot conside red and heating in te atomsphere of hydrogen or mere prevention of strong oxidation surely makes less cracks.
The surface cracks of the steel containing 0.10.4% copper at the temperature range 900°1200°C may be attributed to the oxygen inclusion of the steel.
