贝氏体/马氏体复相组织对低碳合金钢强韧性的影响  

EFFECT OF BAINITE/MARTENSITE MIXED MICRO STRUCTURE ON THE STRENGTH AND TOUGH NESS OF LOW CARBON ALLOY STEELS

作　　者：刘东雨[1] 徐鸿[1] 杨昆[1] 白秉哲[2] 方鸿生[2] 

机构地区：[1]华北电力大学动力工程系,北京102206 [2]清华大学先进材料教育部重点实验室,北京100084

出　　处：《金属学报》2004年第8期882-886,共5页Acta Metallurgica Sinica

基　　金：华北电力大学博士电力科学基金;清华大学先进材料教育部重点实验室开放基金资助项目

摘　　要：对低碳Mn-Cr系和低碳Mn-Si-Cr系低合金钢采用空冷和油淬方式分别处理成贝氏体/马氏体复相组织和马氏体组织,探讨了显微组织和回火温度对钢的强韧性的影响.电镜分析表明,空冷处理的低碳Mn-Cr系和低碳Mn-Si-Cr系低合金钢中的贝氏体分别为典型贝氏体和无碳化物贝氏体.Formaster-F相变仪测定表明经空冷处理后,两种钢复相组织中的贝氏体含量均约为20％.力学性能实验表明,空冷低碳Mn-Cr系合金钢在未回火状态下就具有较高的冲击韧度.低碳Mn-Si-Cr系低合金钢油淬后的低温回火脆性开始温度约为220℃,而空冷后其低温回火脆性开始温度提高至360℃以上.示波冲击实验表明,未回火状态的空冷低碳:Mn-Cr系低合金钢和360℃回火后的空冷低碳Mn-Si-Cr系低合金钢具有较高的冲击韧度是由于在该状态下实验钢具有较高的裂纹扩展功所致.因此,空冷低碳Mn-Cr系合金钢可在未回火状态下使用,空冷低碳Mn-Si-Cr系低合金钢必须在回火后使用,经340-360℃回火后,空冷低碳Mn-Si-Cr系低合金钢具有较高的强韧性.Bainite/martensite mixed microstructure and full martensite (M) microstructure were obtained respectively by air-cooling and oil quenching the experimental steels. The effect of tempering temperature and microstructure on the strength and toughness of the steels was investigated. TEM micrograph shows that after air-cooling the microstructure of the low carbon Mn-Cr alloy steel (steel A) is typical bainite/martensite (B/M) mixed microstructure, and the microstructure of the low carbon Mn-Si-Cr alloy steel (steel B) is carbide free bainite/martensite (CFB/M) mixed microstructure. The bainite amount in mixed microstructure is about 20% by Formaster-F simulating the tensile and impact specimens cooled in air. The impact toughness of steel A with B/M is higher than that with M under as-quenched condition. The tempered martensite embrittlement onset temperature of the steel B with CFB/M is above 360 ℃, while that with M is about 220 ℃. The instrumented Charpy impact testing shows that the higher crack propagation work leads to the higher impact energy in both steels. So without tempering, the steel A with B/M can be used. The steel B with CFB/M must be tempered before using, especially after tempering under 340-360 ℃.

关 键 词：低碳合金钢 贝氏体/马氏体复相组织 强韧性 示波冲击 裂纹扩展功 

分 类 号：TG142.31[一般工业技术—材料科学与工程]