Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid st...Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.展开更多
This paper explained the mechanism of carbon pickup byultra-low-carbon steels during continuous casting and indicated that the major cause of carbon pickup is the contact of the molten steel with the enriched-carbon l...This paper explained the mechanism of carbon pickup byultra-low-carbon steels during continuous casting and indicated that the major cause of carbon pickup is the contact of the molten steel with the enriched-carbon layer of the powder. Forming of the enriched-carbon layer is due to the existing of “carbon core”. Accordingly, the measures to reduce the carbon content and amount of the enriched-carbon layer were investigated. A kind of new powder has been developed and successfully used to minimize the carbon pickup by ultra-low carbon steels during continuous casting.展开更多
According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring ene...According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.展开更多
The hot deformation behavior of an ultralow-carbon microalloyed steel was investigated using an MMS-200 thermal simulation test machine in a temperature range of 1073-1373 K and strain rate range of 0.01-10 s-1.The re...The hot deformation behavior of an ultralow-carbon microalloyed steel was investigated using an MMS-200 thermal simulation test machine in a temperature range of 1073-1373 K and strain rate range of 0.01-10 s-1.The results show that the flow stress decreases with increasing deformation temperature or decreasing strain rate.The strain-compensated constitutive model based on the Arrhenius equation for this steel was established using the true stress-strain data obtained from a hot compression test.Furthermore,a new constitutive model based on the Z-parameter was proposed for this steel.The predictive ability of two constitutive models was compared with statistical measures.The results indicate the new constitutive model based on the Z-parameter can more accurately predict the flow stress of an ultralow-carbon microalloyed steel during hot deformation.The dynamic recrystallization(DRX)nucleation mechanism at different deformation temperatures was observed and analyzed by transmission electron microscopy(TEM),and strain-induced grain boundary migration was observed at 1373 K/0.01 s^-1.展开更多
The relationship of the P and C grain boundary segregation and its effect on bake hardening behavior were investigated in ultra-low carbon bake hardening (ULC-BH)steel with and without P addition annealed at 810 ℃ fo...The relationship of the P and C grain boundary segregation and its effect on bake hardening behavior were investigated in ultra-low carbon bake hardening (ULC-BH)steel with and without P addition annealed at 810 ℃ for various time using electron probe micro-analyzer,electroh backscattered diffraction,and three-dimensional atomic probe techniques.Results revealed that P addition and annealing duration considerably affected the bake hardening behavior of experimental steel. The BH value of ULC-BH steel without P addition is lower than that with P addition within a short annealing time,and the difference in the BH value gradually decreases as the annealing duration is prolonged.P segregation is dominant in terms of a high P bulk content in steels with P addition at the expense of C segregation during annealing.By contrast,opposite effects are observed in low carbon bake hardening steel.The high residual solute C content in steel with P addition is due to P segregation at the grain boundary.Site competition is mainly responsible for the lower BH value in ULC-BH steel without P addition than that with P addition.As the annealing time is further extended,C segregation begins at grain boundary despite the delayed P segregation,leading to a gradual decrease in the solute concentration in the matrix of steels with P addition.C and P segregations reach the equilibrium as the annealing time increases to 60 min at 810 ℃ in the two steel samples.Theoretical calculations reveal that the residual solute C concentration in the matrix decreases to zero,and this finding is consistent with the change trend of the bake hardening value.Hence,the C segregation at grain boundary. adversely influences the bake hardening property of ULC-BH steel.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financially supported by the Fundamental Research Funds for the Central Universities (No. FRF-TP-16-079A1)the National Science Foundation for Young Scientists of China (No. 51704021)+1 种基金the Joint Funds of National Natural Science Foundation of China (No. U1560203)supported by Beijing Key Laboratory of Special Melting and Preparation of High-end Metal Materials
文摘Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.
文摘This paper explained the mechanism of carbon pickup byultra-low-carbon steels during continuous casting and indicated that the major cause of carbon pickup is the contact of the molten steel with the enriched-carbon layer of the powder. Forming of the enriched-carbon layer is due to the existing of “carbon core”. Accordingly, the measures to reduce the carbon content and amount of the enriched-carbon layer were investigated. A kind of new powder has been developed and successfully used to minimize the carbon pickup by ultra-low carbon steels during continuous casting.
文摘According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.
基金Funded by the Fundamental Research Funds for the Central Universities(Nos.HEUCFP201731 and HEUCFP201719)the"One Three Five"Equipment Pre-research National Defense Science and Technology Key Laboratory Fund(No.KZ42180125)。
文摘The hot deformation behavior of an ultralow-carbon microalloyed steel was investigated using an MMS-200 thermal simulation test machine in a temperature range of 1073-1373 K and strain rate range of 0.01-10 s-1.The results show that the flow stress decreases with increasing deformation temperature or decreasing strain rate.The strain-compensated constitutive model based on the Arrhenius equation for this steel was established using the true stress-strain data obtained from a hot compression test.Furthermore,a new constitutive model based on the Z-parameter was proposed for this steel.The predictive ability of two constitutive models was compared with statistical measures.The results indicate the new constitutive model based on the Z-parameter can more accurately predict the flow stress of an ultralow-carbon microalloyed steel during hot deformation.The dynamic recrystallization(DRX)nucleation mechanism at different deformation temperatures was observed and analyzed by transmission electron microscopy(TEM),and strain-induced grain boundary migration was observed at 1373 K/0.01 s^-1.
基金the National Natural Science Foundation of China (Nos.51874114 and 51501052)the Youth Talent Support Program of Hebei Province (No.BJ2017056).
文摘The relationship of the P and C grain boundary segregation and its effect on bake hardening behavior were investigated in ultra-low carbon bake hardening (ULC-BH)steel with and without P addition annealed at 810 ℃ for various time using electron probe micro-analyzer,electroh backscattered diffraction,and three-dimensional atomic probe techniques.Results revealed that P addition and annealing duration considerably affected the bake hardening behavior of experimental steel. The BH value of ULC-BH steel without P addition is lower than that with P addition within a short annealing time,and the difference in the BH value gradually decreases as the annealing duration is prolonged.P segregation is dominant in terms of a high P bulk content in steels with P addition at the expense of C segregation during annealing.By contrast,opposite effects are observed in low carbon bake hardening steel.The high residual solute C content in steel with P addition is due to P segregation at the grain boundary.Site competition is mainly responsible for the lower BH value in ULC-BH steel without P addition than that with P addition.As the annealing time is further extended,C segregation begins at grain boundary despite the delayed P segregation,leading to a gradual decrease in the solute concentration in the matrix of steels with P addition.C and P segregations reach the equilibrium as the annealing time increases to 60 min at 810 ℃ in the two steel samples.Theoretical calculations reveal that the residual solute C concentration in the matrix decreases to zero,and this finding is consistent with the change trend of the bake hardening value.Hence,the C segregation at grain boundary. adversely influences the bake hardening property of ULC-BH steel.
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.
