Acceleration of diffusional transformation in a high-carbon steel layer composed of a sandwich-like clad steel sheet

Abstract

The thermomechanical interactions between two different regions with different carbon contents during cooling from the austenite single phase condition was studied with a sandwich-like clad sheet. The clad steel with a layered structure where a 0.65%C high-carbon steel sheet was sandwiched by 0.05%C low-carbon steel sheets was prepared. The benefit of this clad structure for this study is that any fraction of the composed layers can be fabricated artificially with the constant carbon content in both component layers. In the experiments, the clad sheets were prepared by plain strain compression at 900 °C for welding, followed by gas quenching. The microstructural observation revealed that the fraction of the martensite structure in the high-carbon steel layer decreased and, alternatively, a pearlite structure evolved as the fraction of the low-carbon steel layers was increased; whereas the low-carbon steel layers showed ferrite and pearlite structures with any construction of the clad steel. Consequently, the hardness of the high-carbon steel layer decreased in the sheet with the higher fraction of low-carbon steel layers. The reason for this change is due to both the elastic strain and the plastic deformation of the high-carbon steel layer induced by phase transformation in the low-carbon layers.