正火及高温回火对低合金高强度铸钢组织与性能的影响  

Effects of normalizing and high temperature temper on microstructure and properties of a high-strength low-alloy (HSLA) cast steel

作　　者：雷勇[1] 许晓嫦[1] 李良[1] 张奇[1] 赵凤晓[1] 徐浩浩[1] 

机构地区：[1]中南大学材料科学与工程学院,长沙410083

出　　处：《粉末冶金材料科学与工程》2013年第2期241-249,共9页Materials Science and Engineering of Powder Metallurgy

基　　金：长沙市科技计划资助项目(K1207019-11)

摘　　要：针对铸钢材料在恶劣环境（重载、低温等）下具有高强度、良好的低温冲击韧性和焊接性的使用要求，设计了1种低碳（w（C）为0．11％），含Ni、Mo的低合金高强度铸钢，重点研究该铸钢经880℃正火＋520-650℃回火后的组织与力学性能。结果表明：实验铸钢经正火＋回火处理后，由铸态粗大的亚共析组织转变为细小的铁素体＋回火贝氏体，铸钢的综合力学性能显著提高；铁素体＋贝氏体的混合组织具有高回火稳定性，与添加的Cr、Mo、V等合金元素有关；少量合金元素V在回火过程中形成弥散的（Ti,V）（C，N）析出相，起到析出强化作用；在580℃回火时，δb=590MPa，δ0．2=470MPa，伸长率为26％，断面收缩率为70％，尤其是冲击功Aku（室温）与Aku（-40℃）分别达到150J和110J，室温及低温冲击断口均存在大量的韧窝和撕裂棱，断裂机制为韧性断裂。可见，实验铸钢表现出良好的综合性能匹配，能满足材料在苛刻条件下的使用要求。According to the requirements for high strength, better toughness at low temperatures and weldability of cast steel in harsh environments, a low-carbon （0.11%） nickel and molybdenum-containing high strength low alloying （HSLA） cast steel was designed. The microstructure and properties of cast steel normalized at 880 ℃ and tempered at 520-650℃ were studied. Microstructure characterization was conducted by optical microscopy, transmission electron microscopy and scanning electron microscopy. The experimental results show that, the coarse sub-eutectoid structure of novel HSLA cast steel changes to a fine polygonal ferrite and tempering bainite structure after normalized at 880 ℃ and tempered at 580 ℃; the better temper stability of the novel steel is related to the additive elements ofCr. Mo and V; a small amount of V forms （TIN） and （C, N） phases which play a role of strengthening; the cast steel tempered at 580 ℃ exhibits ab of 590 MPa, a0.2 of 470 MPa, percentage elongatin （A） of 26% and reduction （Z） of 70%, especially room temperature and -40 ℃ Charpy U-Notch （CUN） impact energy are of 150 and 110 J, respectively. Upon fracture morphology analysis, vast dimples and tearing edges are found in both of impact fractures, demonstrating the fracture mechanism is ductile fracture. Therefore, the samples show excellent comprehensive properties and match to fulfil the operating requirements of materials under rigorous conditions.

关 键 词：低合金高强度铸钢 合金设计 力学性能 微观组织 低温冲击韧性 

分 类 号：TG142.1[一般工业技术—材料科学与工程]