Microstructure of 316 LN stainless steel(ss),including the as-received material and samples processed by solution anneal treatment and stress relief treatment after forging,was characterized by Vickers hardness(HV) te...Microstructure of 316 LN stainless steel(ss),including the as-received material and samples processed by solution anneal treatment and stress relief treatment after forging,was characterized by Vickers hardness(HV) testing and electron back scattering diffraction(EBSD).The oxide film formed on samples after immersion in borated and lithiated water at 583.15 K was investigated by scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS).Results showed that the grain size of samples was largely reduced after forging.Higher fraction of coincidence site lattice(CSL) boundaries and lower residual strain were observed in samples with either solution anneal treatment or stress relief treatment.The proportion of CSL boundaries was largely enhanced by solution anneal treatment after forging,due to the recrystallization occurring during solution anneal treatment.The oxide film grown on 316 LNss with solution anneal treatment after forging exhibited more strong protectiveness,as compared to the oxide film grown on samples with stress relief treatment after forging and the oxide film grown on asreceived samples without forging.The mechanisms of oxidation were then discussed.展开更多
Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE we...Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE were discussed. The results showed that with increasing content of RE, the wear rate of cast steel reduced at first and then increased. By adding 0.05% （mass fraction） RE, the cast hot-forging die steel with optimum thermal wear resistance was obtained, which was better than that of H13 and 3Cr2WSV. The large amount of coarse inclusions, （RE）2O2S, resulted from excessive RE, which obviously deteriorated thermal wear resistance. The mechanism of thermal wear of the modified cast die steel is oxidation wear and oxide fatigue delamination. The wear debris are lumps of Fe2O3 and Fe3O4.展开更多
The microstructure models were integrated into finite element（FE）code,and a three-dimensional（3D）FE analysis on the entire hot forging processes of 300 M steel large components was performed to predict the distrib...The microstructure models were integrated into finite element（FE）code,and a three-dimensional（3D）FE analysis on the entire hot forging processes of 300 M steel large components was performed to predict the distributions of effective strain,temperature field and austenite grain size.The simulated results show that the finest grains distribute in the maximum effective strain region because large strain induces the occurrence of dynamic recrystallization.However,coarse macro-grains appear in the minimum effective strain region.Then,300 M steel forging test was performed to validate the results of FE simulation,and microstructure observations and quantitative analysis were implemented.The average relative difference between the calculated and experimental austenite grain size is 7.56%,implying that the present microstructure models are reasonable and can be used to analyze the hot forging processes of 300 M steel.展开更多
Non-quenched and tempered (NQT) steels have been applied for auto forging products at the aim of lower cost since 1980’s in China.Without quenching and tempering processes,the cost of heat treatment was greatly decre...Non-quenched and tempered (NQT) steels have been applied for auto forging products at the aim of lower cost since 1980’s in China.Without quenching and tempering processes,the cost of heat treatment was greatly decreased,so they are widely applied in car forgings such as crankshaft,connecting rod.Recently,with the aim of improving performance and reducing production cost,new technologies,such as:reductions of microalloyed elements,microstructure refining,and mechanical properties forecast have been developed in China auto industry.The designation,processing,properties prediction and microstructure of auto components have been controlled comprehensively.With the development of new technologies,NQT steel gradually began to be applied to product important parts,and replace Quenching and Tempering (QT) steels.Both steel makers and end product users are expressed their desire to share benefits of technological innovation.The technologies will have a huge developing space and very bright developing prospects in motor parts industry in future.展开更多
Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique ...Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.展开更多
The fatigue behavior of cemented carbide die under service load in the multistage cold forging of steel was investigated. It was found that the fatigue cracks do not initiate at the stress concentration position and t...The fatigue behavior of cemented carbide die under service load in the multistage cold forging of steel was investigated. It was found that the fatigue cracks do not initiate at the stress concentration position and the crack initiation position can be classified to three types. The crack initiation position can be predicted by FEM only when the plastic deformation of the die is considered.展开更多
基金supported by the National Science and Technology Major Project(No.2011ZX06004-009)
文摘Microstructure of 316 LN stainless steel(ss),including the as-received material and samples processed by solution anneal treatment and stress relief treatment after forging,was characterized by Vickers hardness(HV) testing and electron back scattering diffraction(EBSD).The oxide film formed on samples after immersion in borated and lithiated water at 583.15 K was investigated by scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS).Results showed that the grain size of samples was largely reduced after forging.Higher fraction of coincidence site lattice(CSL) boundaries and lower residual strain were observed in samples with either solution anneal treatment or stress relief treatment.The proportion of CSL boundaries was largely enhanced by solution anneal treatment after forging,due to the recrystallization occurring during solution anneal treatment.The oxide film grown on 316 LNss with solution anneal treatment after forging exhibited more strong protectiveness,as compared to the oxide film grown on samples with stress relief treatment after forging and the oxide film grown on asreceived samples without forging.The mechanisms of oxidation were then discussed.
基金Project supported by the Itemof Early-TermKey Technology of Industrialization ,Plan Committee of China (1999317) 863project of China (2002AA331180)
文摘Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE were discussed. The results showed that with increasing content of RE, the wear rate of cast steel reduced at first and then increased. By adding 0.05% （mass fraction） RE, the cast hot-forging die steel with optimum thermal wear resistance was obtained, which was better than that of H13 and 3Cr2WSV. The large amount of coarse inclusions, （RE）2O2S, resulted from excessive RE, which obviously deteriorated thermal wear resistance. The mechanism of thermal wear of the modified cast die steel is oxidation wear and oxide fatigue delamination. The wear debris are lumps of Fe2O3 and Fe3O4.
基金Item Sponsored by National Natural Science Foundation of China(51575446)Natural Science Basis Research Plan in Shaanxi Province of China(2016JQ5070)
文摘The microstructure models were integrated into finite element（FE）code,and a three-dimensional（3D）FE analysis on the entire hot forging processes of 300 M steel large components was performed to predict the distributions of effective strain,temperature field and austenite grain size.The simulated results show that the finest grains distribute in the maximum effective strain region because large strain induces the occurrence of dynamic recrystallization.However,coarse macro-grains appear in the minimum effective strain region.Then,300 M steel forging test was performed to validate the results of FE simulation,and microstructure observations and quantitative analysis were implemented.The average relative difference between the calculated and experimental austenite grain size is 7.56%,implying that the present microstructure models are reasonable and can be used to analyze the hot forging processes of 300 M steel.
文摘Non-quenched and tempered (NQT) steels have been applied for auto forging products at the aim of lower cost since 1980’s in China.Without quenching and tempering processes,the cost of heat treatment was greatly decreased,so they are widely applied in car forgings such as crankshaft,connecting rod.Recently,with the aim of improving performance and reducing production cost,new technologies,such as:reductions of microalloyed elements,microstructure refining,and mechanical properties forecast have been developed in China auto industry.The designation,processing,properties prediction and microstructure of auto components have been controlled comprehensively.With the development of new technologies,NQT steel gradually began to be applied to product important parts,and replace Quenching and Tempering (QT) steels.Both steel makers and end product users are expressed their desire to share benefits of technological innovation.The technologies will have a huge developing space and very bright developing prospects in motor parts industry in future.
文摘Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.
文摘The fatigue behavior of cemented carbide die under service load in the multistage cold forging of steel was investigated. It was found that the fatigue cracks do not initiate at the stress concentration position and the crack initiation position can be classified to three types. The crack initiation position can be predicted by FEM only when the plastic deformation of the die is considered.
