This study aims to investigate the effect of the 1-step quenching and partitioning （Q＆P） process on the microstructure and the resulting Vicker＇ s hardness of 0.3C-1.5Si-1.5Mn steel by using in-situ dilatometry ,o...This study aims to investigate the effect of the 1-step quenching and partitioning （Q＆P） process on the microstructure and the resulting Vicker＇ s hardness of 0.3C-1.5Si-1.5Mn steel by using in-situ dilatometry ,optical microscopy （ OM ）, scanning electron microscopy （ SEM ）, X-ray diffractometry （ XRD ）, and Vicker ＇ s hardness measurement. Systematic analyses indicate that the microstructure of the specimens quenched and partitioned at 150℃ ,200 ℃ ,250℃ ,and 300℃ mainly comprises lath martensite and retained austenite. The dilatometry curve of the specimen partitioned at 150℃ is presumably ascribed to the formation of isothermal martensite. In the early stages of partitioning at 200℃,the nearly unchanged dilatation curve is closely related to the synergistic effect of isothermal martensite formation and transitional epsilon carbide precipitation. In the later stages of partitioning at 200 ℃ ,the slight increase in the dilatation curve is due to the continuous isothermal martensite formation. With further increase in partitioning temperature to 250℃, the dilatation increases gradually up to 3600 s, which is related to carbon partitioning and lower bainite formation. Partitioning at a higher temperature of 300 ℃ causes a rapid increase in the dilatation curve during the initial stages, which subsequently levels off upon prolonging the partitioning time. This is mainly attributed to the rapid diffusion of carbon from athermal martensite to retained austenite and continuous formation of lower bainite.展开更多
This paper studies the chemical composition, tensile properties, inclusions, metallogrophic structure, and other such parameters to identify the causes of cracking during the bending of high-strength steel. The result...This paper studies the chemical composition, tensile properties, inclusions, metallogrophic structure, and other such parameters to identify the causes of cracking during the bending of high-strength steel. The results show that the major causes of cracking are the original transverse cracks or holes on the surface of the slab and the presence of scales rolled into the cracks or holes. Cold fracturing from such defects is rare, and can be eleminated by enhancing the control of the steelmaking process and by mechanical clean-up of the surface cracks and holes in the slab.展开更多
文摘This study aims to investigate the effect of the 1-step quenching and partitioning （Q＆P） process on the microstructure and the resulting Vicker＇ s hardness of 0.3C-1.5Si-1.5Mn steel by using in-situ dilatometry ,optical microscopy （ OM ）, scanning electron microscopy （ SEM ）, X-ray diffractometry （ XRD ）, and Vicker ＇ s hardness measurement. Systematic analyses indicate that the microstructure of the specimens quenched and partitioned at 150℃ ,200 ℃ ,250℃ ,and 300℃ mainly comprises lath martensite and retained austenite. The dilatometry curve of the specimen partitioned at 150℃ is presumably ascribed to the formation of isothermal martensite. In the early stages of partitioning at 200℃,the nearly unchanged dilatation curve is closely related to the synergistic effect of isothermal martensite formation and transitional epsilon carbide precipitation. In the later stages of partitioning at 200 ℃ ,the slight increase in the dilatation curve is due to the continuous isothermal martensite formation. With further increase in partitioning temperature to 250℃, the dilatation increases gradually up to 3600 s, which is related to carbon partitioning and lower bainite formation. Partitioning at a higher temperature of 300 ℃ causes a rapid increase in the dilatation curve during the initial stages, which subsequently levels off upon prolonging the partitioning time. This is mainly attributed to the rapid diffusion of carbon from athermal martensite to retained austenite and continuous formation of lower bainite.
文摘This paper studies the chemical composition, tensile properties, inclusions, metallogrophic structure, and other such parameters to identify the causes of cracking during the bending of high-strength steel. The results show that the major causes of cracking are the original transverse cracks or holes on the surface of the slab and the presence of scales rolled into the cracks or holes. Cold fracturing from such defects is rare, and can be eleminated by enhancing the control of the steelmaking process and by mechanical clean-up of the surface cracks and holes in the slab.
