An original 600MPa high aluminum dual phase steel had been successfully developed in this paper.The microstructure analysis showed that the microstructures of the steel mainly consist of ferrite and 16% martensite whi...An original 600MPa high aluminum dual phase steel had been successfully developed in this paper.The microstructure analysis showed that the microstructures of the steel mainly consist of ferrite and 16% martensite which distributed around the ferrite grain boundaries.TEM analysis demonstrated that there exist lots of high density dislocations in ferrite as well as an obvious twin-structure and some ribbon structures in martensite.The tensile test and the bake-hardening test showed that the steel delivers an excellent mechanical properties of R p0.2 =350-390MPa,R m =620-660MPa,R p0.2 /R m =0.55-0.65,A 80mm =25-29%,n=0.18-0.21 and an excellent bake-hardening property of BH 2 =50-60MPa as well as an excellent of work-hardening (WH) property of WH=120MPa。The spot-welding test showed that this dual phase steel has a good welding adaptability.Own to the excellent formability,the steel has been successfully used in the production of some auto parts.展开更多
Hot rolling, cold rolling and continuous annealing processes of Ti bearing and Ti＋ Nb stabilized ultra-low-carbon bake hardened steels were experimentally studied. The microstructure and texture evolution, as well as...Hot rolling, cold rolling and continuous annealing processes of Ti bearing and Ti＋ Nb stabilized ultra-low-carbon bake hardened steels were experimentally studied. The microstructure and texture evolution, as well as the morphology, size and distribution of second phase precipitates during hot rolling, cold rolling and continuous annealing were also analyzed. The results showed that the size of NbC precipitates in Ti＋Nb stabilized ultra-low-carbon bake hardened steel was smaller than that of TiC precipitates in Ti bearing ultra-low-carbon bake hardened steel, which made the average grain size of Ti＋ Nb stabilized ultra-low-carbon bake hardened steel finer than that of Ti bearing ultra-low-carbon bake hardened steel; for the yield strength, the former was higher than the latter; but for the r value which reflects the deep-drawing performance, the former was lower than the latter.展开更多
After 2% predeformation,the baking treatment with different schedule was carried out for low silicon TRIP steel sheet with niobium.The effects of baking temperature and time on microstructures and mechanical propertie...After 2% predeformation,the baking treatment with different schedule was carried out for low silicon TRIP steel sheet with niobium.The effects of baking temperature and time on microstructures and mechanical properties were investigated.The results showed that with increasing the baking temperature and time,the volume fraction of retained austenite decreases,and the volume fraction of tempered martensite increases; as baking temperature ranges from 80 ℃ to 170 ℃,the bake-hardening（BH）value increases obviously,while from 170 ℃ to 230 ℃,the variation of BH value is very slight; as baking time ranges from 2 min to 20 min,the BH value increases significantly,while the BH value decreases when baking time exceeds 20 min.So that when the baking temperature is 170 ℃ and the baking time is 20 min,the low silicon TRIP steel sheet exhibits good bake-hardening behavior,and the highest BH value is above 70 MPa.展开更多
文摘An original 600MPa high aluminum dual phase steel had been successfully developed in this paper.The microstructure analysis showed that the microstructures of the steel mainly consist of ferrite and 16% martensite which distributed around the ferrite grain boundaries.TEM analysis demonstrated that there exist lots of high density dislocations in ferrite as well as an obvious twin-structure and some ribbon structures in martensite.The tensile test and the bake-hardening test showed that the steel delivers an excellent mechanical properties of R p0.2 =350-390MPa,R m =620-660MPa,R p0.2 /R m =0.55-0.65,A 80mm =25-29%,n=0.18-0.21 and an excellent bake-hardening property of BH 2 =50-60MPa as well as an excellent of work-hardening (WH) property of WH=120MPa。The spot-welding test showed that this dual phase steel has a good welding adaptability.Own to the excellent formability,the steel has been successfully used in the production of some auto parts.
基金Item Sponsored by National Science and Technology Support 11th Five-Year Plan of China(2006BAE03A13)
文摘Hot rolling, cold rolling and continuous annealing processes of Ti bearing and Ti＋ Nb stabilized ultra-low-carbon bake hardened steels were experimentally studied. The microstructure and texture evolution, as well as the morphology, size and distribution of second phase precipitates during hot rolling, cold rolling and continuous annealing were also analyzed. The results showed that the size of NbC precipitates in Ti＋Nb stabilized ultra-low-carbon bake hardened steel was smaller than that of TiC precipitates in Ti bearing ultra-low-carbon bake hardened steel, which made the average grain size of Ti＋ Nb stabilized ultra-low-carbon bake hardened steel finer than that of Ti bearing ultra-low-carbon bake hardened steel; for the yield strength, the former was higher than the latter; but for the r value which reflects the deep-drawing performance, the former was lower than the latter.
基金Item Sponsored by National Natural Science Foundation of China(50527402)
文摘After 2% predeformation,the baking treatment with different schedule was carried out for low silicon TRIP steel sheet with niobium.The effects of baking temperature and time on microstructures and mechanical properties were investigated.The results showed that with increasing the baking temperature and time,the volume fraction of retained austenite decreases,and the volume fraction of tempered martensite increases; as baking temperature ranges from 80 ℃ to 170 ℃,the bake-hardening（BH）value increases obviously,while from 170 ℃ to 230 ℃,the variation of BH value is very slight; as baking time ranges from 2 min to 20 min,the BH value increases significantly,while the BH value decreases when baking time exceeds 20 min.So that when the baking temperature is 170 ℃ and the baking time is 20 min,the low silicon TRIP steel sheet exhibits good bake-hardening behavior,and the highest BH value is above 70 MPa.
