Large-sized precipitates are fatal to the thermal fatigue of H13 hot work die steel.Different amounts of Ti and/or rare earth(RE)were added in H13 steel during electroslag remelting to improve the element segregation ...Large-sized precipitates are fatal to the thermal fatigue of H13 hot work die steel.Different amounts of Ti and/or rare earth(RE)were added in H13 steel during electroslag remelting to improve the element segregation and refine the large-sized precipitates.The results show that as Ti content increases from 0.0032 to 0.057 wt.%,the segregation of Cr,Mo and V becomes more severe.V-rich M(C,N)carbides are shorter,and their branches are denser in 3D observation.Moreover,the number density of V-rich M(C,N)carbides with a size less than 2μm increases and that with other sizes decreases.In addition,Ti-rich MN nitrides with the size greater than 4μm increases significantly at high Ti content.When RE content increases from 0.0051 to 0.036 wt.%,the segregation of main alloying elements is first weakened and then aggravated.Compared with that in RE-free H13 steel,V-rich M(C,N)carbides are less developed in 3D observation,and the change in number density is similar to that of Ti-modified alloys.After composite modification of 0.024 wt.%Ti and 0.011 wt.%RE,the segregation of alloying element and V-rich M(C,N)carbides are not significantly improved.展开更多
Large-size primary MC carbides can significantly reduce the performance of M2 high-speed steel.To better control the morphology and size of primary MC carbides,the effect of melting rate on microsegregation and primar...Large-size primary MC carbides can significantly reduce the performance of M2 high-speed steel.To better control the morphology and size of primary MC carbides,the effect of melting rate on microsegregation and primary MC carbides of M2 steel during electroslag remelting was investigated.When the melting rate is decreased from 2 kg·min^(-1) to 0.8 kg·min^(-1),the columnar dendrites are gradually coarsened,and the extent of segregation of Mo and V is alleviated,while the segregation of Cr becomes severe.At 2 kg·min^(-1),the number of primary MC carbides per unit area with the sizes in the range of 2 μm to 6 μm accounts for about 75% of all MC carbides,while the carbides are mainly concentrated on the size larger than 8 μm at 0.8 kg·min^(-1).Thermodynamic calculations based on the Clyne-Kurz (simplified to C-K) model shows that MC carbide can be precipitated in the final solidification stage and a smaller secondary dendrite arm spacing caused by higher melting rate (2 kg·min^(-1) in this experiment) facilitates the refinement of primary MC carbides.展开更多
基金The authors wish to express thanks to the National Natural Science Foundation of China(No.51904087)the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(No.E2019202482)+1 种基金the Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2019-20)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200).
文摘Large-sized precipitates are fatal to the thermal fatigue of H13 hot work die steel.Different amounts of Ti and/or rare earth(RE)were added in H13 steel during electroslag remelting to improve the element segregation and refine the large-sized precipitates.The results show that as Ti content increases from 0.0032 to 0.057 wt.%,the segregation of Cr,Mo and V becomes more severe.V-rich M(C,N)carbides are shorter,and their branches are denser in 3D observation.Moreover,the number density of V-rich M(C,N)carbides with a size less than 2μm increases and that with other sizes decreases.In addition,Ti-rich MN nitrides with the size greater than 4μm increases significantly at high Ti content.When RE content increases from 0.0051 to 0.036 wt.%,the segregation of main alloying elements is first weakened and then aggravated.Compared with that in RE-free H13 steel,V-rich M(C,N)carbides are less developed in 3D observation,and the change in number density is similar to that of Ti-modified alloys.After composite modification of 0.024 wt.%Ti and 0.011 wt.%RE,the segregation of alloying element and V-rich M(C,N)carbides are not significantly improved.
基金financially supported by the National Natural Science Foundation of China(No.51904087)the Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2019-20)+2 种基金the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(No.E2019202482)Tianjin Science and Technology Project(No.18YFZCGX00220)。
文摘Large-size primary MC carbides can significantly reduce the performance of M2 high-speed steel.To better control the morphology and size of primary MC carbides,the effect of melting rate on microsegregation and primary MC carbides of M2 steel during electroslag remelting was investigated.When the melting rate is decreased from 2 kg·min^(-1) to 0.8 kg·min^(-1),the columnar dendrites are gradually coarsened,and the extent of segregation of Mo and V is alleviated,while the segregation of Cr becomes severe.At 2 kg·min^(-1),the number of primary MC carbides per unit area with the sizes in the range of 2 μm to 6 μm accounts for about 75% of all MC carbides,while the carbides are mainly concentrated on the size larger than 8 μm at 0.8 kg·min^(-1).Thermodynamic calculations based on the Clyne-Kurz (simplified to C-K) model shows that MC carbide can be precipitated in the final solidification stage and a smaller secondary dendrite arm spacing caused by higher melting rate (2 kg·min^(-1) in this experiment) facilitates the refinement of primary MC carbides.
