The conventional middle and high carbon spring steels have some drawbacks in properties, production and application. In order to meet the demands of rapid development of automobile, a new low and middle carbon spring ...The conventional middle and high carbon spring steels have some drawbacks in properties, production and application. In order to meet the demands of rapid development of automobile, a new low and middle carbon spring steel 35Si2CrMnVB, C0.34, Sil.66, MnO.80, CrO.67, V0.13, B0.001, P0.011, S0.014 wt.%, has been developed. Comparison between the new spring steel 35Si2CrMnVB and the conventional spring steel 60Si2MnA, C0.61, Si 1.75, MnO.76, P0.021, S0.018 wt.%, shows that the new spring steel has not only high strength, good ductility, good comprehensive mechanical properties, but also low decarbonization tendency, sufficient hardenability and high elastic sag resistance, etc.. The microstructure change in quenched steel caused by the decreasing of carbon contents is detected through metallographic observation, the new low and middle carbon spring steel 35Si2CrMnVB after quenching is composed of almost lath martensite with high dislocation density and only a little martensite with twin structure. It is testified that to develop low carbon spring steel with more excellent properties for automobile is feasible.展开更多
The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensiti...The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.展开更多
Room temperature tensile tests were carried on the hot-rolled state ultra-low carbon and low alloy cabainite and martensite steels which were get by different finishing temperatures and different cooling methods.We us...Room temperature tensile tests were carried on the hot-rolled state ultra-low carbon and low alloy cabainite and martensite steels which were get by different finishing temperatures and different cooling methods.We used the Scanning Electron Microscopy (SEM),Electron Backscattered Diffraction (EBSD) and X-Ray Diffractometer (XRD) to identify the metallographic structure and analyse the precipitated phase.The inherent mechanism of high strength of ultra-low carbon and low alloy bainite and martensite steels was discussed,and the analysis indicated that the reinforcement of ultra-low carbon and low alloy bainite and martensite steels was mainly produced by the superposition of the dislocation strengthening,solution strengthening and grain refinement strengthening.展开更多
基金supports from the Natural Science Foundation of Jiangxi Province,P.R.China under contracts No.0250024.
文摘The conventional middle and high carbon spring steels have some drawbacks in properties, production and application. In order to meet the demands of rapid development of automobile, a new low and middle carbon spring steel 35Si2CrMnVB, C0.34, Sil.66, MnO.80, CrO.67, V0.13, B0.001, P0.011, S0.014 wt.%, has been developed. Comparison between the new spring steel 35Si2CrMnVB and the conventional spring steel 60Si2MnA, C0.61, Si 1.75, MnO.76, P0.021, S0.018 wt.%, shows that the new spring steel has not only high strength, good ductility, good comprehensive mechanical properties, but also low decarbonization tendency, sufficient hardenability and high elastic sag resistance, etc.. The microstructure change in quenched steel caused by the decreasing of carbon contents is detected through metallographic observation, the new low and middle carbon spring steel 35Si2CrMnVB after quenching is composed of almost lath martensite with high dislocation density and only a little martensite with twin structure. It is testified that to develop low carbon spring steel with more excellent properties for automobile is feasible.
基金performed within the VINN Excellence Center Hero-m,financed by VINNOVA,the Swedish Governmental Agency for Innovation Systems,Swedish Industry,KTH Royal Institute of Technology
文摘The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.
文摘Room temperature tensile tests were carried on the hot-rolled state ultra-low carbon and low alloy cabainite and martensite steels which were get by different finishing temperatures and different cooling methods.We used the Scanning Electron Microscopy (SEM),Electron Backscattered Diffraction (EBSD) and X-Ray Diffractometer (XRD) to identify the metallographic structure and analyse the precipitated phase.The inherent mechanism of high strength of ultra-low carbon and low alloy bainite and martensite steels was discussed,and the analysis indicated that the reinforcement of ultra-low carbon and low alloy bainite and martensite steels was mainly produced by the superposition of the dislocation strengthening,solution strengthening and grain refinement strengthening.
