退火工艺对980 MPa级热镀锌双相钢组织及性能的影响

利用奥钢联热模拟试验机模拟980 MPa级双相钢连续退火镀锌过程,利用拉伸试验机、光学显微镜和扫描电镜研究连续镀锌工艺中均热温度和快冷出口温度对双相钢组织及力学性能的影响。结果表明,经热镀锌退火后,980 MPa级双相钢的微观组织为铁素体+马氏体,组织中有Nb,Ti碳氮化物析出。随着均热温度的升高,马氏体体积分数呈逐渐增加的趋势,屈服强度和屈强比不断升高。快冷出口温度从340 ℃升高到430 ℃,马氏体发生回火分解,降低了试验钢的屈服强度,同时改善了伸长率。快冷出口温度为400 ℃时,强塑积达到最大值13.9 GPa·%。当均热温度为840 ℃,快冷出口温度为460~480 ℃时,可以获得抗拉强度在980 MPa级以上的双相钢。

Effect of annealing process on microstructure and properties of 980 MPa hot dip galvanized dual-phase steel

Continuous annealing galvanizing process of 980 MPa dual-phase steel was simulated by Voestal pine thermal simulator, and the effect of soaking temperature and rapid cooling outlet temperature of continuous hot dip galvanizing process on microstructure and mechanical properties of the dual-phase steel was studied by means of tensile testing machine and optical microscope and scanning electron microscope. The results show that the microstructure of 980 MPa dual-phase steel consists of ferrite and martensite after annealing galvanizing process, and Nb, Ti carbonitrides distribute in the structure. With the increase of soaking temperature, the volume fraction of martensite increases, the yield strength and yield ratio increase. With the rapid cooling outlet temperature increasing from 340 ℃ to 430 ℃, tempering decomposition of martensite appears, which reduces the yield strength of the tested steel, but improves the elongation. When the rapid cooling outlet temperature is 400 ℃, the maximum value of the product of strength and elongation is 13.9 GPa·%. When soaked at 840 ℃ and rapid cooled at 460-480 ℃, the hot dip galvanized dual-phase steel can be obtained with the tensile strength above 980 MPa.