摘要:
将C-Mn钢加热至800℃保温60 s后, 随即快速冷却至300℃进行过时效处理以模拟连续退火工艺, 最终获得铁素体和马氏体双相组织, 然后进行预应变和烘烤处理以测量其BH2值。研究了预应变、烘烤温度和烘烤时间对780 MPa级冷轧双相钢微观组织演变和烘烤硬化性能的影响。结果表明, 在0~2%范围内, BH2值随预应变增加而明显提高;在2%~%范围内, BH2值随预应变增加而降低;预应变为2%时, BH2值达到最大值51 MPa。在140~300℃范围内, 随着烘烤温度提高, 在铁素体中形成的Cottrell气团和碳化物, 以及马氏体中析出的碳化物数量增加, 双相钢的烘烤硬化性能明显提高;烘烤温度为300℃时, BH2值达到最大值102 MPa。在5~240 min范围内, 随烘烤时间的延长, 促进了Cottrell气团的形成和碳化物的析出, BH2值逐渐增加。
Abstract:
In a typical process,C-Mn steel was annealed at 800 ℃ for 60 s,and then cooled rapidly to 300℃ to carry out the over-aging treatment.The ferrite-martensite microstructure was obtained after the simulated continuous annealing process. After pre-straining and baking,the specimens were used to measure the BH2 values.The influences of pre-strain,baking temperature and baking time on the microstructure evolution and bake-hardening behavior of the 780 MPa cold rolled dual-phase steel were investigated.It was found out that the BH value apparently increased with an increase of pre-strain in the range from 0% to 2%; however,increasing pre-strain from 2% to 8% led to a decrease in the BH2 value.And the maximum of BH2 value at the pre-straining of 2% is 51 MPa. Furthermore,the BH2 value enhanced due to increaseing amount of Cottrell atmosphere in the ferrite grain interior and carbide in both of ferrite and martensite phases with increasing the baking temperature.The BH2 value reached a maximum of 102 MPa at the baking temperature of 300 ℃.Moreover,with an increase in the baking time from 5 to 240 min,the BH2 value enhanced gradually due to the Cottrell atmosphere formation and carbide precipitation in the ferrite.
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