To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by ...To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.展开更多
In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary elec...In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.展开更多
This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynam...This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.展开更多
基金supported by Specific Research Project of Guangxi for Research Bases and Talents(Grant No.GuiKe AD19245145)Natural Science Foundation of Guangxi Province(Grant No.2018GXNSFBA281106).
文摘To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.
基金supported by the National Natural Science Foundation of China(No.51801219)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193)+1 种基金the Scientific Research Project of China Three Gorges Corporation(No.JD-YJ-05006)the National Key Research and Development Program of China(No.2017YFB0702302)。
文摘In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.
文摘This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.
