The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformat...The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.展开更多
The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain...The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain size,the quantity,and the character of distribution of nonmetallic inclusions in the railroad frogs.The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area.After the modifying mixture was introduced into the melt,either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types,or simultaneously the microtwins and wafers of ε-martensite,were present in each grain.展开更多
X-ray diffraction profiles of various deformed steel 1Cr18Ni9 through stepped scanning were obtained.By profile analysis,some structure parameters such as effective domain size D_(eff), dislocation density in domain,d...X-ray diffraction profiles of various deformed steel 1Cr18Ni9 through stepped scanning were obtained.By profile analysis,some structure parameters such as effective domain size D_(eff), dislocation density in domain,distribution parameterand bulk stored energy densiy (E/V),etc.,were obtained.The results were compared with those of TEM observation.The true domain sizes D_e are comparable,but the minimum and characteristics of width of stack- ing fault are different.This may be resulted from the large fluctuation in width of stacking fault.展开更多
Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of ...Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength, flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.展开更多
An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treat...An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treatment processes. The result shows that with decreasing prior austenite grain size, both the packet size and block width decrease, while the lath width has virtually no change. Accordingly, both strength and toughness increase, while total elongation decreases. The yield strength has a Hall Petch type relationship with the prior austenite grain size, packet size and block width, and the block width may be regarded as a key factor influencing strength. On the other hand, the ductile to brittle transition temperature （DBTT） is found to be more related lo the packet size, which may be considered as a dominant factor influencing toughness.展开更多
The microstructure of 40Cr steel sample and its surface is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the superplasticity is studied under isothermal superplastic compressive def...The microstructure of 40Cr steel sample and its surface is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the superplasticity is studied under isothermal superplastic compressive deformation condition. The experimental results indicate that the stress-strain curves are shown to take place obvious superplastic flow characteristic at the temperature of 750-770℃ and at the initial strain rate of (1.7-5.0)×10-4 s-1. Its strain rate sensitivity is 0.30-0.38, the steady superplastic flow stress is 60-70MPa, the superplastic flow activation energy is 198-217kJ/mol, and it is close to α-Fe grain boundary self-diffusion activation energy. The super-plastic compressive constitute equations of this steel are correspondingly set up. Due to the finer microstructure of high frequency hardening, it appears bigger strain rate sensitivity value, smaller the steady superplastic flow stress and the superplastic flow activation energy, so it has better superplastic deformation capability.展开更多
The roof steel structure of group C project of Zibo cultural center is composed of steel truss,welded H-shaped steel and large-diameter steel pipe embedded parts.The construction of embedded parts of inclined cylinder...The roof steel structure of group C project of Zibo cultural center is composed of steel truss,welded H-shaped steel and large-diameter steel pipe embedded parts.The construction of embedded parts of inclined cylinder overhanging steel structure is difficult.The stair square tube ladder beam requires precise angles and radians,complex processing,and construction site setting out is difficult.A three-dimensional visual building information model has been established for this projects which includes several aspects which are as follows:the development of the post anchor construction technology of large steel sleeve embedded parts with inclined cylinders based on Building Information Modeling(BIM)technology,multi discipline synthesis and collision optimization,the net height optimization of electromechanical pipelines,fine reinforcement management,BIM virtual construction template.Through this planning,14908 pipeline collisions,including 236 major collisions have been eliminated.BIM is used in handling and solving problems with the construction unit and the supervision company.This greatly improves the project work efficiency and saves meeting time.Through optimization of electromechanical line collision and secondary masonry layout,more than RMB 9 million has been saved in terms of personnel and materials,effectively reducing material losses,saving manpower,and significantly improving the implementation efficiency of the project.Based on the on-site simulation,the project planning scheme of the enterprise was adjusted,efficient work allocation with less idle time were ensured,and the correct utilization of project funds and time were ensured.The original extensive annual control and monthly control have been dynamically and accurately controlled to realize the dynamic understanding of the profits and losses of the project,and effectively reduce the occurrence of non-ideal situations.展开更多
文摘The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.
基金partly supported by the Russian Foundation for basic Researches(No.16-48-700198)the Tomsk State University competitiveness improvement programme
文摘The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain size,the quantity,and the character of distribution of nonmetallic inclusions in the railroad frogs.The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area.After the modifying mixture was introduced into the melt,either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types,or simultaneously the microtwins and wafers of ε-martensite,were present in each grain.
文摘X-ray diffraction profiles of various deformed steel 1Cr18Ni9 through stepped scanning were obtained.By profile analysis,some structure parameters such as effective domain size D_(eff), dislocation density in domain,distribution parameterand bulk stored energy densiy (E/V),etc.,were obtained.The results were compared with those of TEM observation.The true domain sizes D_e are comparable,but the minimum and characteristics of width of stack- ing fault are different.This may be resulted from the large fluctuation in width of stacking fault.
文摘Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength, flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.
文摘An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treatment processes. The result shows that with decreasing prior austenite grain size, both the packet size and block width decrease, while the lath width has virtually no change. Accordingly, both strength and toughness increase, while total elongation decreases. The yield strength has a Hall Petch type relationship with the prior austenite grain size, packet size and block width, and the block width may be regarded as a key factor influencing strength. On the other hand, the ductile to brittle transition temperature （DBTT） is found to be more related lo the packet size, which may be considered as a dominant factor influencing toughness.
基金supported by State Key Laboratory of New Nonferrous Metal Materials Natural Science Foundation of He'nan Province,China(No.984040900)Natural Science Foundation of the Education Department of He'nan Province,China(No.2003430211).
文摘The microstructure of 40Cr steel sample and its surface is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the superplasticity is studied under isothermal superplastic compressive deformation condition. The experimental results indicate that the stress-strain curves are shown to take place obvious superplastic flow characteristic at the temperature of 750-770℃ and at the initial strain rate of (1.7-5.0)×10-4 s-1. Its strain rate sensitivity is 0.30-0.38, the steady superplastic flow stress is 60-70MPa, the superplastic flow activation energy is 198-217kJ/mol, and it is close to α-Fe grain boundary self-diffusion activation energy. The super-plastic compressive constitute equations of this steel are correspondingly set up. Due to the finer microstructure of high frequency hardening, it appears bigger strain rate sensitivity value, smaller the steady superplastic flow stress and the superplastic flow activation energy, so it has better superplastic deformation capability.
文摘The roof steel structure of group C project of Zibo cultural center is composed of steel truss,welded H-shaped steel and large-diameter steel pipe embedded parts.The construction of embedded parts of inclined cylinder overhanging steel structure is difficult.The stair square tube ladder beam requires precise angles and radians,complex processing,and construction site setting out is difficult.A three-dimensional visual building information model has been established for this projects which includes several aspects which are as follows:the development of the post anchor construction technology of large steel sleeve embedded parts with inclined cylinders based on Building Information Modeling(BIM)technology,multi discipline synthesis and collision optimization,the net height optimization of electromechanical pipelines,fine reinforcement management,BIM virtual construction template.Through this planning,14908 pipeline collisions,including 236 major collisions have been eliminated.BIM is used in handling and solving problems with the construction unit and the supervision company.This greatly improves the project work efficiency and saves meeting time.Through optimization of electromechanical line collision and secondary masonry layout,more than RMB 9 million has been saved in terms of personnel and materials,effectively reducing material losses,saving manpower,and significantly improving the implementation efficiency of the project.Based on the on-site simulation,the project planning scheme of the enterprise was adjusted,efficient work allocation with less idle time were ensured,and the correct utilization of project funds and time were ensured.The original extensive annual control and monthly control have been dynamically and accurately controlled to realize the dynamic understanding of the profits and losses of the project,and effectively reduce the occurrence of non-ideal situations.
