ISSN 2594-5327
59º Congresso anual — Vol. 59 , num. 1 (2004)
Título
Autoria
DOI
Downloads
Resumo
The development of high strength TRIP-aided hot rolled steel sheets was carried out by taking into account the addition of Nb and Mo and coiling conditions after hot rolling to meet the demand from automobile industry. Five kinds of 0.2%C-1.5%Si-1.5%Mn-0.01%P-0.035%Al steels with different amounts of Nb and Mo were used in this experiment. Coiling temperatures after hot rolling were varied from 300°C to 550°C with 50°C intervals, in order to study the effect of coiling temperature. The following conclusions are obtained. (1) 0.05%Nb containing steel showed higher El than Nb-free steel, regardless of the higher TS. The obtained TS and El at the best coiling temperature at 400°C were 822 MPa and 32%. Since the TS and El in Nb free steel is 762 MPa and 27% respectively under the same hot rolling condition, it is clear that the addition of Nb is effective to produce 780 MPa grade hot rolled TRIP-aided steel with excellent El. (2) The multiple addition of 0.2% Mo with 0.05% Nb resulted about by 120 MPa higher TS than Nb-Mo free steel. This result suggests that the addition of Mo with Nb is effective to produce higher TS grade hot rolled TRIP-aided steel. (3) The higher strength in Nb containing steel is mainly attributed to the precipitation of fine NbC. The NbC precipitated mainly during the coiling process. While, the higher strength in Nb and Mo containing steel is brought about by the fine precipitation of NbMoC, which precipitated during both the coiling and cooling processes. (4) Good ductility in 0.05% Nb containing steel was mainly obtained by large volume fraction and high carbon concentration of retained austenite. In addition, finely dispersed retained austenite also must be contributed to the improvement of ductility.
The development of high strength TRIP-aided hot rolled steel sheets was carried out by taking into account the addition of Nb and Mo and coiling conditions after hot rolling to meet the demand from automobile industry. Five kinds of 0.2%C-1.5%Si-1.5%Mn-0.01%P-0.035%Al steels with different amounts of Nb and Mo were used in this experiment. Coiling temperatures after hot rolling were varied from 300°C to 550°C with 50°C intervals, in order to study the effect of coiling temperature. The following conclusions are obtained. (1) 0.05%Nb containing steel showed higher El than Nb-free steel, regardless of the higher TS. The obtained TS and El at the best coiling temperature at 400°C were 822 MPa and 32%. Since the TS and El in Nb free steel is 762 MPa and 27% respectively under the same hot rolling condition, it is clear that the addition of Nb is effective to produce 780 MPa grade hot rolled TRIP-aided steel with excellent El. (2) The multiple addition of 0.2% Mo with 0.05% Nb resulted about by 120 MPa higher TS than Nb-Mo free steel. This result suggests that the addition of Mo with Nb is effective to produce higher TS grade hot rolled TRIP-aided steel. (3) The higher strength in Nb containing steel is mainly attributed to the precipitation of fine NbC. The NbC precipitated mainly during the coiling process. While, the higher strength in Nb and Mo containing steel is brought about by the fine precipitation of NbMoC, which precipitated during both the coiling and cooling processes. (4) Good ductility in 0.05% Nb containing steel was mainly obtained by large volume fraction and high carbon concentration of retained austenite. In addition, finely dispersed retained austenite also must be contributed to the improvement of ductility.
Palavras-chave
TRIP, high strength hot rolled steel sheet, Nb, Mo, coiling temperature
TRIP, high strength hot rolled steel sheet, Nb, Mo, coiling temperature
Como citar
HASHIMOTO*, SHUNICHI; IKEDA**, SHUSHI; SUGIMOTO***, KOHICHI; MIYAKE****, SYUGO.
EFFECT OF Nb AND Mo ADDITION TO 0.2%C-1.5%Si-1.5%Mn STEEL ON HOT ROLLED TRIP-AIDED STEEL SHEETS,
p. 11-25.
In: 59º Congresso anual,
São Paulo, Brasil,
2004.
ISSN: 2594-5327, DOI 10.5151/2594-5327-59-0002
