Flexible manufacturing technology for ultra-low-carbon bake hardening (BH)steels with different solute carbon contents in the range of (6-16)× 10^-4 wt.%was systematically studied.The effects of soaking temperatu...Flexible manufacturing technology for ultra-low-carbon bake hardening (BH)steels with different solute carbon contents in the range of (6-16)× 10^-4 wt.%was systematically studied.The effects of soaking temperature,cooling rate and aging time on solute carbon content were explored.The bake hardening value in a continuous galvanizing line with an over-aging section was investigated.Optimal manufacturing parameters were calculated using the design of experiment to obtain the best and most flexible process parameters.Results indicate a relationship among carbon content,soaking temperature and cooling rate.When solute carbon is 9 × 10^-6,cooling rate is 50 ℃/s,the soaking temperature is 745 ℃,and BH value is 45 MPa,the requirements of an automobile factory can be met.展开更多
Grain growth kinetics of austenite in a hypoeutectoid steel（containing carbon of 0.35%）at 920 ℃ and in a hypereutectoid steel（containing carbon of 1%）at 980 ℃ for holding time ranging from 1 h to 6 h was investi...Grain growth kinetics of austenite in a hypoeutectoid steel（containing carbon of 0.35%）at 920 ℃ and in a hypereutectoid steel（containing carbon of 1%）at 980 ℃ for holding time ranging from 1 h to 6 h was investigated.The hypoeutectoid steel exhibited normal grain growth without solute drag hindrance with a time exponent（0.51）close to the theoretical value（0.5）.However,the grain growth of austenite in the hypereutectoid steel held up to 3 h was extremely slow,characterizing by a low value of time exponent（0.08）.Thereafter,a breakaway occurred and the grain growth in the hypereutectoid steel held from 3 h to 6 h progressed normally with a time exponent（0.52）close to the theoretical value（0.5）.展开更多
Specimens of two different kinds of bake hardening steels （BH-Mn and BH-P） were prepared and treated with different annealing processes （water quenching and overaging）. A novel technique of three dimensional atom ...Specimens of two different kinds of bake hardening steels （BH-Mn and BH-P） were prepared and treated with different annealing processes （water quenching and overaging）. A novel technique of three dimensional atom probe was used to investigate solute distributions in these steels. The results indicate that C concentration decreases, whereas V increases during overaging in both bake hardening steels. The conclusion that no vanadium carbides pre- cipitate during the overaging is therefore originally obtained by microanalysis in bake hardening steels. Moreover, bake hardening values of all the specimens were tested by tensile experiments with 2 0/~ pre-deformation. However, those of overaged specimens were further measured with higher levels of pre-deformation because no bake hardening phenomenon was present at 2% pre-deformation. As the pre-deformation increases from 2% to 6% and 8%, both overaged steels show bake hardening values, and the value data are almost the same.展开更多
基金the financial support by National Natural Science Foundation of China (Grant No. U1460101).
文摘Flexible manufacturing technology for ultra-low-carbon bake hardening (BH)steels with different solute carbon contents in the range of (6-16)× 10^-4 wt.%was systematically studied.The effects of soaking temperature,cooling rate and aging time on solute carbon content were explored.The bake hardening value in a continuous galvanizing line with an over-aging section was investigated.Optimal manufacturing parameters were calculated using the design of experiment to obtain the best and most flexible process parameters.Results indicate a relationship among carbon content,soaking temperature and cooling rate.When solute carbon is 9 × 10^-6,cooling rate is 50 ℃/s,the soaking temperature is 745 ℃,and BH value is 45 MPa,the requirements of an automobile factory can be met.
文摘Grain growth kinetics of austenite in a hypoeutectoid steel（containing carbon of 0.35%）at 920 ℃ and in a hypereutectoid steel（containing carbon of 1%）at 980 ℃ for holding time ranging from 1 h to 6 h was investigated.The hypoeutectoid steel exhibited normal grain growth without solute drag hindrance with a time exponent（0.51）close to the theoretical value（0.5）.However,the grain growth of austenite in the hypereutectoid steel held up to 3 h was extremely slow,characterizing by a low value of time exponent（0.08）.Thereafter,a breakaway occurred and the grain growth in the hypereutectoid steel held from 3 h to 6 h progressed normally with a time exponent（0.52）close to the theoretical value（0.5）.
基金sponsored by National Natural Science Foundation of China(50934011,50971137)National Basic Research Program of China(2010CB630802)
文摘Specimens of two different kinds of bake hardening steels （BH-Mn and BH-P） were prepared and treated with different annealing processes （water quenching and overaging）. A novel technique of three dimensional atom probe was used to investigate solute distributions in these steels. The results indicate that C concentration decreases, whereas V increases during overaging in both bake hardening steels. The conclusion that no vanadium carbides pre- cipitate during the overaging is therefore originally obtained by microanalysis in bake hardening steels. Moreover, bake hardening values of all the specimens were tested by tensile experiments with 2 0/~ pre-deformation. However, those of overaged specimens were further measured with higher levels of pre-deformation because no bake hardening phenomenon was present at 2% pre-deformation. As the pre-deformation increases from 2% to 6% and 8%, both overaged steels show bake hardening values, and the value data are almost the same.
