Ti微合金化700MPa级汽车大梁钢的研究

通过实验，采用低成本Ti微合金元素进行强化，获得了抗拉强度745～760MPa，下屈服强度640～655MPa，伸长率为23. 0%～23. 5%的热轧钢板。同时，通过调整热轧工艺，获得了终冷温度与热轧板强度的关系。此外，研究了轧制过程不同阶段析出相的种类、分布以及析出量的变化情况。结果表明，钢板屈服强度、抗拉强度与其终冷温度基本呈线性关系，随终冷温度的降低，屈服强度和抗拉强度均明显提高。析出相的定量分析结果表明，在粗轧结束时，Ti的析出率接近50%，在精轧结束时，Ti的析出率接近60%。在700℃等温卷取后，Ti的析出率超过95%。降低卷取温度到650、600℃时，Ti的析出率分别降低到87. 5%、75. 2%。如果700℃终冷后采用空冷方式冷却，Ti的析出率最低，降低到只有63. 3%，与精轧结束时析出量相近。

Study on Ti Micro-alloyed 700MPa High Strength Automobile-beam Steel

Under low COSt production routine, high strength steels only with Ti strengthening micro alloying el- ement were obtained in this paper using middling hot rolling apparatus, and the hot rolled steel plate had the tensile strength of 745 ~760MPa, lower yield strength of 640~ 655MPa, and elongation rate of 23.0% 23.5%. By adjusting the hot rolling process, the relationship between the final cooling temperature and the strength of hot-rolled plates was obtained. In addition, the types, distribution and amounts variation of the precipitates at different hot rolling stages were investigated. Results showed that both the yield strength and tensile strength showed a linear relationship with the final cooling temperature. Decreasing of final cooling temperature, the yield strength and tensile strength of plate were significantly improved. Quantitative phase a- nalysis results of precipitates in steels showed that at the end of rough rolling stage, the precipitation rate of Ti was close to 50%, while close to 60M at the end of finishing roiling stage. After isothermal coiling simulation at temperature of 700 ℃, Ti precipitation rate was more than 95 %. If reducing the coiling temperature to 650 ℃ or 600 ℃, Ti precipitation rate were reduced to 87.5% or 75.2M accordingly. If using air cooling mode in- stead of isothermal coiling process after final cooling at 700℃, the precipitation rate of Ti was reduced to the lowest value of 63.3 %. This precipitation rate was very close to that at end of finishing rolling stage.