微合金钢等温过程中带状组织演变规律研究

Study on Banded Structures Evolution of Microalloyed Steel during Isothermal Holding Process

采用热模拟试验机、金相显微镜和扫描电镜研究了微合金钢在等温过程中的带状组织演变规律,并对其形成机理进行了分析。结果表明:试样在650~700℃等温时,带状组织为铁素体/马氏体。在550~600℃等温时,带状组织为针状铁素体/马氏体,且随着等温温度的下降,针状铁素体的体积分数不断升高。Mn的带状偏析是导致该等温期间不完全转变现象的根本原因。当等温温度降到450℃时,组织全部为针状铁素体,带状组织基本消失。

The evolution of banded structures of microalloyed steel during isothermal holding process was studied by thermal simulation test machine,optical microscope and scanning electron microscope,and its formation mechanism was analyzed.The results show that the banded structure is ferrite/martensite at 650-700℃.At 550-600℃,the banded structure is acicular ferrite/martensite,and the volume fraction of acicular ferrite increases with the decrease of holding temperature.Mn segregation is the main reason for the incomplete transformation.When the isothermal temperature drops to 450℃,the microstructure is all acicular ferrite,and the banded structure almost disappears.