摘要
采用力学性能测试、金相组织观察、透射电镜以及扫描电镜观察,研究奥氏体化工艺对超深井用V150油套管强韧性的影响。研究结果表明:较高的奥氏体化温度可提高合金元素在奥氏体中的溶解度,但过高的奥氏体化温度会使奥氏体晶粒粗大,导致塑性、韧性下降,890℃为实验钢较优的常规奥氏体化温度;奥氏体化30 min后,实验钢成分和组织分布趋于均匀,油套管的强韧性指标匹配达到最好,保温时间超过45 min后,晶粒开始长大,导致冲击性能有所下降;亚温淬火形成铁素体和贝氏体、马氏体、残余奥氏体的混合组织,可得到超高强度钢希望获得的B/M复相组织,B/M组织中贝氏体能够分割马氏体基体,阻止裂纹扩展,残余奥氏体膜分割马氏体板条,使实验钢在保持足够强度的同时得到很高的韧性;实验钢在800℃亚温淬火后于640℃回火,强度和韧度均到达了V150油套管的目标要求,能够满足条件苛刻的超深井作业需求。
The effects of different austenitizing processes on the strength and toughness of V150 grade oil casing steel were investigated.Mechanical tests were used to evaluate the impact toughness and tensile properties of the steel.The microstructures were analyzed by optical microscope(OM),scanning electron microscope(SEM) and transmission electron microscope(TEM).The results show that high austenitizing temperature can enhance the solubility of alloy elements in austenite,but overhigh austenitizing temperature can make the austenite grain coarser,which results in the decrease of plasticity and toughness.According to the experimental results,890 ℃ is the appropriate conventional austenitizing temperature for the experimental steel.When the steel is austenitized at 890 ℃ for 30 min,microstructure distributes uniformly,and a good combination of strength and toughness can be obtained.When the holding time is longer than 45 min,impact energy begins to decrease due to the growth of grains.Mixed microstructure including ferrite,bainite,martensite,and retained austenite can be obtained by subcritical quenching process.Bainite-martensite(B/M) dual phase structure is a kind of expected microstructure for ultra-high strength steel.This is because bainite in the B/M dual phase structure can cut martensite matrix and retard crack propagation.In addition,retained austenite film in matrix can cut martensite lath,which can make the experimental steel obtain a good toughness while keeping a high strength.When the experimental steel is subcritical-quenched at 800 ℃ and then tempered at 640 ℃,both the strength and toughness can meet the requirement of V150 grade oil casing,which indicating that the steel can be used in the severe service environment.
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2013年第9期3625-3633,共9页
Journal of Central South University:Science and Technology
基金
湖南省重大科技专项(2008FJ1003)
关键词
油套管
V150钢
奥氏体化
组织
强韧性
oil casing
V150 grade steel
austenitizing
microstructure
strength and toughness
