Several 35CrMo4 and 38MnV7 steels with different additions of Ti and V were manufactured by electroslag remelting. The influence of the alloying and microalloying elements on phase transformation at different cooling ...Several 35CrMo4 and 38MnV7 steels with different additions of Ti and V were manufactured by electroslag remelting. The influence of the alloying and microalloying elements on phase transformation at different cooling rates was studied and the continuous cooling transformation diagrams were plotted. In order to optimize the heat treatment and improve the mechanical properties, the range of cooling rates leading to a fully bainitic microstructure （without ferrite, pearlite and especially without martensite） was determined. Bainite and martensite transformation start temperatures （Bs, Ms） were also established and compared with the values predicted by empirical equations. The important role of precipitates （especially V carbonitride particles） on final microstructure and mechanical properties was assessed.展开更多
The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray d...The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray diffraction,expansion method,and so on.Under equilibrium conditions,the main carbonitrides are MX,M7C3,and M23C6 types.The measured Ac1,Ac3,start temperature of martensitic transformation,and M7C3 transformation temperatures are 811,855,324,and 1100 ℃,respectively.Bainite appears at cooling rates ranging from 0.5 to 5 ℃/s and ferrite forms at grain boundaries at a cooling rate lower than 0.5 ℃/s.Finally,the effects of adding N and lowering the C content on workability and mechanical properties of common 8％Cr steel were discussed.展开更多
The influence of cooling rate on the microstructure and mechanical properties of two new ultrahigh-strength steels(UHSSs)with different levels of C,Cr and Ni has been evaluated for the as-cooled and untempered conditi...The influence of cooling rate on the microstructure and mechanical properties of two new ultrahigh-strength steels(UHSSs)with different levels of C,Cr and Ni has been evaluated for the as-cooled and untempered condition.One UHSS had higher contents of C and Cr,while the other one had a higher Ni content.On the basis of dilatation curves,microstructures,macrohardness and microhardness,continuous cooling transformation diagrams were constructed as a guide to heat treatment possibilities.Cooling rates(CRs)of 60,1 and 0.01°C/s were selected for more detailed investigations.Microstructural characterization was made by laser scanning confocal microscopy,field emission scanning electron microscopy combined with electron backscatter diffraction,electron probe microanalysis and X-ray diffraction.Mechanical properties were characterized using macrohardness,tensile and Charpy V-notch impact tests.UHSS with the higher C and Cr contents showed lower transformation temperatures and slower bainite formation kinetics than that with the higher Ni content.Higher cooling rates led to lower volume fractions and carbon contents of retained austenite together with finer prior austenite grain size,as well as effective final grain size and lath size.These changes were accompanied by higher yield and tensile strengths.The best combinations of strength and toughness were obtained with martensitic microstructures and by avoiding the formation of granular bainite accompanied by proeutectoid carbides at low CR.For the cooling rates studied,UHSS with the higher C and Cr contents showed the higher hardness and strength but at the cost of toughness.展开更多
采用DIL805L型膨胀仪研究了弹簧钢52Cr Mo V4连续冷却相变组织变化规律,分析了合金元素和冷却速度对CCT曲线、相变组织和显微硬度的影响。结果表明:Cr、Mo、V、Mn等元素的加入使得弹簧钢52Cr Mo V4珠光体和贝氏体转变曲线完全分离,可以...采用DIL805L型膨胀仪研究了弹簧钢52Cr Mo V4连续冷却相变组织变化规律,分析了合金元素和冷却速度对CCT曲线、相变组织和显微硬度的影响。结果表明:Cr、Mo、V、Mn等元素的加入使得弹簧钢52Cr Mo V4珠光体和贝氏体转变曲线完全分离,可以在较宽的冷却速度范围内得到马氏体+贝氏体组织,当冷却速度大于等于5℃/s时,连续冷却转变获得单一的马氏体组织。冷却速度增加,促使了连续冷却转变后的组织细化,显微硬度增大。展开更多
基金the financial support of Spanish Ministry of Economy and Competitiveness through the project ref.MAT2011-29039-C02-02
文摘Several 35CrMo4 and 38MnV7 steels with different additions of Ti and V were manufactured by electroslag remelting. The influence of the alloying and microalloying elements on phase transformation at different cooling rates was studied and the continuous cooling transformation diagrams were plotted. In order to optimize the heat treatment and improve the mechanical properties, the range of cooling rates leading to a fully bainitic microstructure （without ferrite, pearlite and especially without martensite） was determined. Bainite and martensite transformation start temperatures （Bs, Ms） were also established and compared with the values predicted by empirical equations. The important role of precipitates （especially V carbonitride particles） on final microstructure and mechanical properties was assessed.
基金Sponsored by the Natural Science Foundation of Hebei Province for Distinguished Young Scholars(Grant No.E2011203131)the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(Grant No.E2013203110)
文摘The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray diffraction,expansion method,and so on.Under equilibrium conditions,the main carbonitrides are MX,M7C3,and M23C6 types.The measured Ac1,Ac3,start temperature of martensitic transformation,and M7C3 transformation temperatures are 811,855,324,and 1100 ℃,respectively.Bainite appears at cooling rates ranging from 0.5 to 5 ℃/s and ferrite forms at grain boundaries at a cooling rate lower than 0.5 ℃/s.Finally,the effects of adding N and lowering the C content on workability and mechanical properties of common 8％Cr steel were discussed.
文摘The influence of cooling rate on the microstructure and mechanical properties of two new ultrahigh-strength steels(UHSSs)with different levels of C,Cr and Ni has been evaluated for the as-cooled and untempered condition.One UHSS had higher contents of C and Cr,while the other one had a higher Ni content.On the basis of dilatation curves,microstructures,macrohardness and microhardness,continuous cooling transformation diagrams were constructed as a guide to heat treatment possibilities.Cooling rates(CRs)of 60,1 and 0.01°C/s were selected for more detailed investigations.Microstructural characterization was made by laser scanning confocal microscopy,field emission scanning electron microscopy combined with electron backscatter diffraction,electron probe microanalysis and X-ray diffraction.Mechanical properties were characterized using macrohardness,tensile and Charpy V-notch impact tests.UHSS with the higher C and Cr contents showed lower transformation temperatures and slower bainite formation kinetics than that with the higher Ni content.Higher cooling rates led to lower volume fractions and carbon contents of retained austenite together with finer prior austenite grain size,as well as effective final grain size and lath size.These changes were accompanied by higher yield and tensile strengths.The best combinations of strength and toughness were obtained with martensitic microstructures and by avoiding the formation of granular bainite accompanied by proeutectoid carbides at low CR.For the cooling rates studied,UHSS with the higher C and Cr contents showed the higher hardness and strength but at the cost of toughness.
文摘采用DIL805L型膨胀仪研究了弹簧钢52Cr Mo V4连续冷却相变组织变化规律,分析了合金元素和冷却速度对CCT曲线、相变组织和显微硬度的影响。结果表明:Cr、Mo、V、Mn等元素的加入使得弹簧钢52Cr Mo V4珠光体和贝氏体转变曲线完全分离,可以在较宽的冷却速度范围内得到马氏体+贝氏体组织,当冷却速度大于等于5℃/s时,连续冷却转变获得单一的马氏体组织。冷却速度增加,促使了连续冷却转变后的组织细化,显微硬度增大。
