抄録
A study was made of the effect of controlled rolling on austenite to ferrite or bainite decomposition, and also on the resultant mechanical properties. Several laboratory heats of 0.05C-1.9Mn-0.25Mo-0.06Nb steel were used with emphasis on the role of austenite forming elements such as carbon and manganese and that of ferrite forming elements such as silicon, molybdenum and vanadium. Controlled rolling were carried out after heating slabs at temperatures of 1100°C and 920°C.
The results can be summarized as follows.
1) Fine duplex microstructures of ferrite plus bainite, or ferrite plus martensite, were obtained by controlled rolling, resulting in an excellent combination of toughness and tensile strength above 70kg/mmmm2.
2) By applying controlled rolling, the austenite to ferrite transformation was accelerated, while the austenite to bainite transformation was shifted to lower temperature range. Thus, the separation of the above two transformations was accompanied by the increased volume fraction of ferrite, and by the decreased volume fraction of martensite or bainite. However, the obtained hardness was increased.
3) Similar separation of the transformations could also be achieved by increasing silicon content.
