This paper offers systematic analysis and in-depth research on the surface rust problem of cold-rolled bell-type annealing strip products.The defect characteristics,occurrence rules,generation mechanism,and influencin...This paper offers systematic analysis and in-depth research on the surface rust problem of cold-rolled bell-type annealing strip products.The defect characteristics,occurrence rules,generation mechanism,and influencing factors of surface rust are presented.This research employed a cold-rolled bell-type furnace annealing unit in a coastal steel factory as an example and conducted production process tests,on-site production tests,scanning electron microscopy,energy spectrum analysis,MINITAB statistical analysis,etc.Moreover,six significant influencing factors and their rules were studied:the cooling time of the final cooling table,the storage time of the intermediate storage,the temperature setting of the intermediate storage,the temperature of leveling liquid,the purging pressure of leveling machine,and the dust in the environment.展开更多
Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend ...Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.展开更多
In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation si...In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. （111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of （111} advantageous texture components in the annealing texture increases from 55vo1% to 65vo1%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.展开更多
Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pan...Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction （RD） and normal direction （ND） of sheets （dr/dn）. A mathematical model （ r = e^0.345（dn^1/2-dr^1/2） ） was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production （CSP）. It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.展开更多
Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were ...Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 ~C and various annealing time. The A1/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some 8 phases were detected close to the interface after anneal treating for 3 h and 8 phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of 8 phase due to diffusion annealing, the interface hardness was reduced.展开更多
文摘This paper offers systematic analysis and in-depth research on the surface rust problem of cold-rolled bell-type annealing strip products.The defect characteristics,occurrence rules,generation mechanism,and influencing factors of surface rust are presented.This research employed a cold-rolled bell-type furnace annealing unit in a coastal steel factory as an example and conducted production process tests,on-site production tests,scanning electron microscopy,energy spectrum analysis,MINITAB statistical analysis,etc.Moreover,six significant influencing factors and their rules were studied:the cooling time of the final cooling table,the storage time of the intermediate storage,the temperature setting of the intermediate storage,the temperature of leveling liquid,the purging pressure of leveling machine,and the dust in the environment.
文摘Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.
文摘In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. （111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of （111} advantageous texture components in the annealing texture increases from 55vo1% to 65vo1%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.
文摘Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction （RD） and normal direction （ND） of sheets （dr/dn）. A mathematical model （ r = e^0.345（dn^1/2-dr^1/2） ） was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production （CSP）. It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.
文摘Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 ~C and various annealing time. The A1/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some 8 phases were detected close to the interface after anneal treating for 3 h and 8 phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of 8 phase due to diffusion annealing, the interface hardness was reduced.
