超高强贝氏体钢的回火组织与力学性能  

Tempering microstructure and mechanical properties of an ultra high strength bainitic steel

作　　者：万德成[1] 蔡庆伍[1] 余伟[1] 董长征[1] 

机构地区：[1]北京科技大学冶金工程研究院,北京100083

出　　处：《材料热处理学报》2013年第5期143-148,共6页Transactions of Materials and Heat Treatment

摘　　要：观察并研究了250～600℃区间回火对超高强贝氏体钢组织与力学性能的影响。结果表明:随回火温度升高,抗拉强度不断降低,屈服强度先升高后降低,伸长率和冲击功则呈先升高后降低然后再升高变化规律。250～350℃回火,残留奥氏体分解速率缓慢,抑制了板条合并粗化,组织为板条贝氏体+稳定膜状残留奥氏体,析出相粒子尺寸细小,具有良好的强度和塑韧性。特别是在350℃回火时,板条内部有ε碳化物析出,以及位错移动所形成的位错胞状亚结构细化了晶粒,使其具有最佳强韧配合。450℃回火,残留奥氏体大量分解导致组织内部出现链状分布的渗碳体,引起回火脆性。600℃回火,残留奥氏体几乎全部分解,部分区域发生再结晶,塑性和韧性提高而强度明显降低,析出物明显粗化。力学性能的非单调变化归因于钢在回火过程中,既包括板条贝氏体和位错亚结构的回复、再结晶软化过程,也包括残留奥氏体分解与析出相的强化机制。Mechanical properties and microstructure evolution of an ultra high strength bainitic steel after tempering treatment in the range of 250-600 ℃ were investigated. The results show that with increasing tempering temperature the tensile strength continuously decreases, the yield strength increases at first and then decreases while the elongation and impact energy exhibit a variation of increase-decrease- increase. When tempered at 250-350 ℃ , the retained austenite decomposes slowly which inhibits the merging of the adjacent laths of bainite to form a single larger one, the precipitated phase particles are very fine, the strength and toughness of the experiment steel are both excellent. When tempered at 350 ℃ , e-carbide precipitation is found in the bainite lath and cell substructure is formed because of the movement of dislocations, which are beneficial to the mechanical properties of experimental steel. A large amount of retained austenite in the steel decomposes and chain-like distributed cementite can be observed when tempered at 450 ℃ , the toughness of the steel decreases and has a temper brittleness. The amount of retained austenite is closed to zero, meanwhile reerystallization oceurrs at part laths when tempered at 600 ℃ , plasticity and toughness of the experimental steel improve but the strength decreases significantly, the size of precipitated phase particles becomes bigger. The mechanical properties of the experimental steel change non-monotonically with tempering temperature because of two aspects： recovery and recrystallization softening processes of bainite laths and dislocation substructure; strengthening mechanism due to the decomposition of retained austenite and precipitation of dispersed particles.

关 键 词：超高强钢 贝氏体 回火 组织 力学性能 

分 类 号：TG142.2[一般工业技术—材料科学与工程]