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采用冷轧和退火的方法制备了不同球粒化程度的S50C钢样,比较了在同一淬回火工艺时球粒化程度对淬回火相变和力学性能的影响,检测了淬回火前后的拉伸断口形貌,并采用马氏体转变驱动力公式分析了球粒化对马氏体相变的影响。结果表明:S50C钢的球粒化程度随着退火次数的增加而提升,球粒化程度越高淬回火后的组织越均匀;相同淬火工艺下,450℃回火比400℃回火组织均匀细小,抗拉强度随着厚度规格从3.0mm减少到2.0mm,先上升后下降,而伸长率先下降后上升;球粒化程度越高断口的韧窝数量越多、越均匀,淬回火后脆性断裂趋向增强;马氏体转变驱动力公式分析表明,粒化程度增加了铁原子和碳的活度系数,促进了马氏体转变,从而提升产品的综合性能。
The S50C steel samples with different pelletization degree were prepared by cold rolling and annealing. The effects of the degree of pelletization on the phase transformation and mechanical properties of quenching and tempering during the same quenching and tempering process were compared. The tensile fracture morphology was analyzed. The influence of the granulation on the martensitic transformation was analyzed by using the martensite transformation driving force formula. The results show that the degree of pelletization of S50C steel increases with the increase of the number of annealing, and the higher the degree of pelletization, the more homogeneous the structure after quenching and tempering; under the same quenching process, the tempering at 450 ℃ is more uniform than that at 400 ℃ Small, tensile strength with the thickness of the specifications from 3.0mm to 2.0mm, first rose and then decreased, while the elongation decreased after the rise; the higher the degree of pelletizing the number of more dimple fracture, the more uniform, quenching and tempering The brittle fracture tended to be enhanced. The analysis of the martensite transformation driving force showed that the degree of granulation increased the activity coefficient of iron atoms and carbon, promoted the martensite transformation and promoted the comprehensive performance of the product.