Development of a 780MPa Ferritic Hot Rolled High Strength Steel with Superior Stretch-Flangeability
This paper deals with the laboratory study of a fully ferritic hot rolled high strength steel with nano-sized precipitation in the ferrite grain interior,having tensile strength of 780MPa grade with excellent stretch flangeability.The ultimate tensile strength and fractured elongation of specimen reach above 780MPa and 20%,respectively.Of special interest is the high mean hole expansion ratio (HER) exceeding 80%,implying an excellent stretch flangeability of the present steel.The excellent combination of high strength and high HER is strongly dependent on the microstructure.Mainly two types of precipitates have been observed with transmission electron microscope (TEM).The nearly spherical precipitates of 4±1nm with planar interface are located at the ferrite grain interiors,which are suggested to be formed during austenite to ferrite transformation,i.e.,interphase precipitation.Random precipitation was also observed in the ferrite grains with size of approximately 4nm.It is believed that grain refinement and precipitation strengthening are main factors contributing to the high strength of steel sheet.The single phase ferrite microstructure with nanoscale precipitates in ferrite grain interiors offers a good balance between high strength and stretch flangeability.
interphase precipitation nano-sized precipitation ferritic steel stretch-flangeability HER TEM
WANG Huanrong WANG Wei HUANG Rui YANG Ana LIU Junliang
Baosteel Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China
国际会议
成都
英文
354-358
2016-11-16（万方平台首次上网日期，不代表论文的发表时间）