高温回火对SA533B钢力学性能及微观组织的影响

Effect of high temperature tempering on mechanical properties and microstructure of SA533B steel

为研究高温回火对SA533B(0.15C-1.39Mn-0.28Si-0.50Mo-0.59Ni-Fe,wt%)钢力学性能及微观组织的影响,采用拉伸试验、夏比V型缺口冲击试验检验了钢板在660~720℃回火60 min后的力学性能,膨胀试验测定相变点,用SEM、TEM表征了不同状态下的微观组织。结果表明:SA533B钢的Ac_1、Ac_3、Ms、Mf点分别为630、816、446和280℃,在910℃水淬后的组织为板条马氏体。回火温度范围可以选择在660~710℃。当回火温度低于710℃时,由于组织仍然保持着铁素体板条形貌,并且板条总体的尺寸较小,整体强度与韧性仍然匹配较好。当回火温度高于710℃时,回火过程中形成大量富碳奥氏体,冷却过程中可转变为孪晶马氏体,强度显著提高,韧性剧烈降低。

In order to investigate the effect of high temperature tempering on mechanical properties and microstructure of SA533 B steel（ 0. 15C-1. 39Mn-0. 28Si-0. 50Mo-0. 59Ni-Fe,wt%）,the mechanical properties of the steel tempered at 660-720 ℃ for 60 min were tested by tension and Charpy V-notch impact tester,and transformation points were determined by dilation experiment,and microstructures under various heat treatment conditions were characterized by SEM and TEM. The results show that the Ac_1,Ac_3,Ms and Mf points of the steel are630,816,446,and 280 ℃,respectively. The microstructure water quenched at 910 ℃ is lath martensite. Tempering temperature range can be chosen at 660-710 ℃. When tempering temperature is lower than 710 ℃,the good combination of strength and toughness is attributed to the fine ferrite microstructure with lath morphology,when tempering temperature is above 710 ℃,a lot of C-rich austenite forms during tempering,then transforms to twin martensite during cooling,as a result,strength substantially increases while toughness sharply reduces.