The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated ...The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.展开更多
The microstructure characteristics and properties(especially hole expansion property)of 800 MPa hot-rolled complex phase steel with different coiling temperatures were studied.The microstructure consisted of polygonal...The microstructure characteristics and properties(especially hole expansion property)of 800 MPa hot-rolled complex phase steel with different coiling temperatures were studied.The microstructure consisted of polygonal ferrite and precipitates when the steel was coiled at 550℃,and when the steel was coiled between 460–520℃,the microstructure was composed of granular bainite and martensite and austenite(M/A)islands.The morphology of the crack was analyzed by scanning electron microscopy,and the in situ scanning electron microscope tensile test was used to find out the fracture mechanism and deformation behavior of the steel with different coiling temperatures.When the steel was coiled at 550℃,the cracks initiated at the ferrite grain boundary and propagated through the grains or along the grain boundaries.When the steel was coiled at 520℃,the cracks first initiated at the junction of ferrite and M/A island and then propagated through the grains.The steel coiled at 520℃ has quite good mechanical properties and relatively high hole expansion ratio.展开更多
The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy （HSLA） steel, complex phase steel and martensite steel were studied in the laborat...The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy （HSLA） steel, complex phase steel and martensite steel were studied in the laboratory. And S700MC and MP1200 ultra-high strength steels were trial produced at the 1 880 mm hot-rolling line of Baosteel. Compared with conventional hot-rolled high strength products,the idea that water is alloy was applied in the newly developed hot-rolled ultra-high strength steel. By the use of the economical composition design and controlled cooling after hot-rolling effectively,ultra-high strength steel of different steel grades can be obtained.展开更多
基金The authors gratefully acknowledge the support from the Key Research and Development Plan of Shandong Province(No.2019TSLH0103)the New Energy Automobile Material Production and Application Demonstration Platform Project(No.TC180A6MR-1)Guangxi Innovation-Driven Development Special Fund Project(No.AA18242012).
文摘The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.
基金This work was supported by the Foundation of China Electric Power Research Institute(No.51601174).
文摘The microstructure characteristics and properties(especially hole expansion property)of 800 MPa hot-rolled complex phase steel with different coiling temperatures were studied.The microstructure consisted of polygonal ferrite and precipitates when the steel was coiled at 550℃,and when the steel was coiled between 460–520℃,the microstructure was composed of granular bainite and martensite and austenite(M/A)islands.The morphology of the crack was analyzed by scanning electron microscopy,and the in situ scanning electron microscope tensile test was used to find out the fracture mechanism and deformation behavior of the steel with different coiling temperatures.When the steel was coiled at 550℃,the cracks initiated at the ferrite grain boundary and propagated through the grains or along the grain boundaries.When the steel was coiled at 520℃,the cracks first initiated at the junction of ferrite and M/A island and then propagated through the grains.The steel coiled at 520℃ has quite good mechanical properties and relatively high hole expansion ratio.
文摘The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy （HSLA） steel, complex phase steel and martensite steel were studied in the laboratory. And S700MC and MP1200 ultra-high strength steels were trial produced at the 1 880 mm hot-rolling line of Baosteel. Compared with conventional hot-rolled high strength products,the idea that water is alloy was applied in the newly developed hot-rolled ultra-high strength steel. By the use of the economical composition design and controlled cooling after hot-rolling effectively,ultra-high strength steel of different steel grades can be obtained.
