The aging embrittlement of 30Cr2Ni4MoV steel during service at high temperature has been attributed to the segregation of Si and Mn at grain boundary(GB).We report an alternative mechanism of aging embrittlement of 30...The aging embrittlement of 30Cr2Ni4MoV steel during service at high temperature has been attributed to the segregation of Si and Mn at grain boundary(GB).We report an alternative mechanism of aging embrittlement of 30Cr2Ni4MoV steel.Using atom probe tomography,it is found that the quenched and tempered(QT)30Cr2Ni4MoV steel has already contained obvious Si and Mn segregations at GB,which means that the Si and Mn segregations at GB are not sufficient to induce aging embrittlement.It is discovered for the first time in aged 30Cr2Ni4MoV there newly precipitate many G-phases along GB,and Si and Mn segregations at GB of QT30Cr2Ni4MoV steel are the main reason for the precipitation of G-phase.The hard and brittle G-phase helps to promote crack initiation during impact deformation.Subsequently,the cracks can rapidly propagate along GB due to the distribution of G-phase and the segregation of Si and Mn along the GB,which leads to intergranular cracking and low impact energy as for aged 30Cr2Ni4MoV steel.展开更多
The optimal composition of a CaO-SiO_(2)-Al_(2)O_(3)-MgO slag in the ladle furnace refining process was investigated to precisely control the contents of[0]and[Si]and improve the cleanliness of 30Cr2Ni4MoV steel.The i...The optimal composition of a CaO-SiO_(2)-Al_(2)O_(3)-MgO slag in the ladle furnace refining process was investigated to precisely control the contents of[0]and[Si]and improve the cleanliness of 30Cr2Ni4MoV steel.The iso-[O]lines and iso-[Si] lines of the equilibrium between the CaO-SiO_(2)-Al_(2)O_(3)-MgO refining slag and 30Cr2Ni4MoV steel at 1873 K were calculated by the thermodynamic software FactSage 7.3,and the activities of SiO_(2),Al_(2)O_(3)and CaO in the refining slag were discussed to achieve the optimal composition range of the refining slag.Finally,combined with high-temperature"slag-steel"equilibrium experiments,the effects of different refining slags on the oxygen contents,chemical composi-tions,quantities and sizes of inclusions in steels were studied,and then the thermody namic formation mechanism of MgAl_(2)O_(4) inclusions in 30Cr2Ni4MoV steel was discussed.The results showed that the contents of dissolved[O]nd[Si]in steel can be controlled below 10 × 10^(-6)and 0.05%.respectively;when the slag basicity is above 7.the CaO/Al_(2)O_(3)ratio is above I.and the mass fraction of SiO_(2)in the slag docs not cxcced 7%.The chemical composition of the slag has a great influence on the removal and composition of inclusions.The assessed stability phase diagrams of MgO.Al_(2)O_(3)and MgOAl_(2)O_(3) inclusion formation in the Fe-Al-Mg-O system calculated by FactSage 7.3 show good agreement with the experimental results.展开更多
In order to perform numerical simulation of forging and determine the hot deformation processing parameters for 30Cr2Ni4MoV steel, the compressive deformation behaviors of 30Cr2Ni4MoV steel were investigated at the te...In order to perform numerical simulation of forging and determine the hot deformation processing parameters for 30Cr2Ni4MoV steel, the compressive deformation behaviors of 30Cr2Ni4MoV steel were investigated at the temperatures from 970 to 1270 ℃ and strain rates from 0. 001 to 0.1 s-1 on a Gleeble-3500 thermo-mechanical simulator. The flow stress constitutive equations of the work hardening-dynamical recovery period and dynamical recrystallization period were established for 30Cr2Ni4MoV steel. The stress-strain curves of 30Cr2Ni4MoV steel predicted by the proposed model well agreed with experimental results, which confirmed that the proposed equations can be used to determine the hot deformation processing parameters for 30Cr2Ni4MoV steel.展开更多
基金supported by the Youth Innovation Promotion Association CAS(No.Y2021059)the LingChuang Research Project of China National Nuclear Corporation,the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA28040200)+1 种基金the Liaoning Unveiling and Commanding Program(2022JH1/10400017)the Innovation Foundation of Institute of Metal Research,CAS(No.2022-PY13).
文摘The aging embrittlement of 30Cr2Ni4MoV steel during service at high temperature has been attributed to the segregation of Si and Mn at grain boundary(GB).We report an alternative mechanism of aging embrittlement of 30Cr2Ni4MoV steel.Using atom probe tomography,it is found that the quenched and tempered(QT)30Cr2Ni4MoV steel has already contained obvious Si and Mn segregations at GB,which means that the Si and Mn segregations at GB are not sufficient to induce aging embrittlement.It is discovered for the first time in aged 30Cr2Ni4MoV there newly precipitate many G-phases along GB,and Si and Mn segregations at GB of QT30Cr2Ni4MoV steel are the main reason for the precipitation of G-phase.The hard and brittle G-phase helps to promote crack initiation during impact deformation.Subsequently,the cracks can rapidly propagate along GB due to the distribution of G-phase and the segregation of Si and Mn along the GB,which leads to intergranular cracking and low impact energy as for aged 30Cr2Ni4MoV steel.
基金supported by the National Natural ScienceFoundation of China(Grant Nos.51774217,52074198 and51604201).
文摘The optimal composition of a CaO-SiO_(2)-Al_(2)O_(3)-MgO slag in the ladle furnace refining process was investigated to precisely control the contents of[0]and[Si]and improve the cleanliness of 30Cr2Ni4MoV steel.The iso-[O]lines and iso-[Si] lines of the equilibrium between the CaO-SiO_(2)-Al_(2)O_(3)-MgO refining slag and 30Cr2Ni4MoV steel at 1873 K were calculated by the thermodynamic software FactSage 7.3,and the activities of SiO_(2),Al_(2)O_(3)and CaO in the refining slag were discussed to achieve the optimal composition range of the refining slag.Finally,combined with high-temperature"slag-steel"equilibrium experiments,the effects of different refining slags on the oxygen contents,chemical composi-tions,quantities and sizes of inclusions in steels were studied,and then the thermody namic formation mechanism of MgAl_(2)O_(4) inclusions in 30Cr2Ni4MoV steel was discussed.The results showed that the contents of dissolved[O]nd[Si]in steel can be controlled below 10 × 10^(-6)and 0.05%.respectively;when the slag basicity is above 7.the CaO/Al_(2)O_(3)ratio is above I.and the mass fraction of SiO_(2)in the slag docs not cxcced 7%.The chemical composition of the slag has a great influence on the removal and composition of inclusions.The assessed stability phase diagrams of MgO.Al_(2)O_(3)and MgOAl_(2)O_(3) inclusion formation in the Fe-Al-Mg-O system calculated by FactSage 7.3 show good agreement with the experimental results.
基金Item Sponsored by National Basic Research Program of China(2011CB012900)National Science and Technology Major Project of China(2012ZX04012011)China Postdoctoral Science Foundation(2013M531171)
文摘In order to perform numerical simulation of forging and determine the hot deformation processing parameters for 30Cr2Ni4MoV steel, the compressive deformation behaviors of 30Cr2Ni4MoV steel were investigated at the temperatures from 970 to 1270 ℃ and strain rates from 0. 001 to 0.1 s-1 on a Gleeble-3500 thermo-mechanical simulator. The flow stress constitutive equations of the work hardening-dynamical recovery period and dynamical recrystallization period were established for 30Cr2Ni4MoV steel. The stress-strain curves of 30Cr2Ni4MoV steel predicted by the proposed model well agreed with experimental results, which confirmed that the proposed equations can be used to determine the hot deformation processing parameters for 30Cr2Ni4MoV steel.
