淬火工艺对500MPa级热轧态海工钢组织与力学性能的影响  

Effect of quenching process on microstructure and properties of a 500 MPa grade hot-rolled offshore engineering steel

作　　者：脱臣德 高擎[1] 张勇伟[1] 史术华 冯赞[1] Tuo Chende;Gao Qing;Zhang Yongwei;Shi Shuhua;Feng Zan(Hunan Valin Xiangtan Iron&Steel Co.,Ltd.,Xiangtan Hunan 411101,China)

机构地区：[1]湖南华菱湘潭钢铁有限公司,湖南湘潭411101

出　　处：《金属热处理》2025年第1期110-118,共9页Heat Treatment of Metals

摘　　要：为研究500 MPa级海工钢组织和低温韧性的主要影响因素,采用淬火+回火工艺探究淬火温度对热轧态试验钢组织和力学性能的影响,同时明确裂纹在不同显微组织中的扩展机制。结果表明:亚温淬火(800℃和850℃)时,显微组织以铁素体和马氏体为主,随着淬火温度升高,组织中铁素体体积分数降低。高温淬火(910~1010℃)后显微组织完全由板条状马氏体组成,板条尺寸随淬火温度升高而增加,进而导致试验钢的强度升高,低温韧性和均匀延伸率降低。试验钢获得最优强韧性的热处理工艺为910~960℃淬火+500℃回火。试验钢中的裂纹大多起源于回火组织中软硬相界面处,其在铁素体晶粒和马氏体板条边界沿直线扩展,终止于原始奥氏体晶界处。组织中大角度晶界比例的提高有助于试验钢低温韧性的提升。In order to study the main factors affecting the microstructure and low temperature toughness of a 500 MPa grade offshore engineering steel,quenching and tempering process was carried out to explore the effect of quenching temperature on microstructure and mechanical properties of the as-hot-rolled tested steel,and to identify the propagation mechanism of cracks in different microstructure.The results show that the microstructure is dominated by ferrite and martensite after subcritical quenching at 800 ℃ and 850 ℃,and with the increase of quenching temperature,the volume fraction of ferrite decreases.After higher temperature quenching at 910-1010 ℃,the microstructure is completely composed of lath martensite,and the size of martensitic lath increases with the increase of quenching temperature,resulting in the increases of strength,and the decrease of low temperature toughness and uniform elongation.The best heat treatment process for the tested steel to obtain the best strength and toughness is quenching at 910-960 ℃ and tempering at 500 ℃.Most of the cracks in the tested steel originate at the interface of the soft and hard phases in the tempered microstructure,propagate in straight line along the interface between ferrite grains and martensitic laths,and end at the prior austenite grain boundary.The increase of the proportion of large angle grain boundary is helpful to improve the low temperature toughness of the tested steel.

关 键 词：海工钢 淬火 强韧性 裂纹 

分 类 号：TG156.4[金属学及工艺—热处理]