含铌低硅TRIP钢板烘烤硬化行为分析

Bake-hardening behavior of low silicon TRIP steel with niobium

模拟汽车板的烘烤工艺,研究了预变形量、烘烤温度和烘烤时间等对含铌低硅TRIP钢板组织和性能的影响,探讨了TRIP钢的烘烤硬化机理。结果表明,当预变形量小于4%时,烘烤硬化值随预变形量增大而增加,预变形量大于4%时反而降低了烘烤硬化效应;当烘烤温度低于170℃时,随烘烤温度的上升,烘烤硬化值明显增加,当烘烤温度高于170℃时,烘烤温度对烘烤硬化值影响不大;当烘烤时间在20min以内时,随烘烤时间的延长,烘烤硬化值显著增加,烘烤时间超过20min时,烘烤硬化值随烘烤时间的延长反而有所降低。通过对TRIP钢的烘烤硬化机理分析,建立了烘烤硬化值变化模型:ΔYBH=ΔYγ+ΔYb+ΔYγc+ΔYdp+ΔYc,其中沉淀析出碳氮化物数量和Cottrell气团数目变化引起的ΔYdp+ΔYc对烘烤硬化值变化影响相对显著。

In order to simulate baking process of automobile steel sheet ,baking treatment experiments at different pre-strains ,temperatures and times were carried out on low silicon TRIP steel with Nb . T he variation of the microstructures and bake-hardening values of the experimental steel during bak-ing treatment was investigated ,and the bake-hardening mechanism of TRIP steel was discussed .A model of variation of the bake-hardening value was built as follows :ΔYBH = ΔYγ + ΔYb+ ΔYγc+ΔYdp+ ΔYc ,in which effects of ΔYdp and ΔYc on the variation of the bake-hardening value (ΔYBH) are relatively strong ,which are the yield strength variations caused by the amount of carbide precipi-tation and Cottrell atmosphere .