碳含量对热成形用钢组织和性能的影响初探
发布时间：2018-10-21 15:20
【摘要】：当今汽车节能减排和提高安全性能问题日益突出，强度级别在1500MPa以上的热成形用钢已经在减轻车身重量和提高汽车安全性能方面表现出巨大的优势，其在未来汽车车身零件中的应用潜力也毋庸置疑。为了研究和开发新一代具有自主知识产权的高性能超高强度热成形用钢，满足国内市场的需求，本文设计了四种不同碳含量的热成形用钢新钢种，，对设计的热成形用钢进行基础性研究工作，为开发新型具有自主知识产权的热成形用钢提供必要的基础数据和设计原则。 本文采用热膨胀法和热分析法对四种热成形用钢实验钢连续冷却转变规律进行了分析研究，得到了四种实验钢的CCT曲线，观察了不同冷却速率下转变的微观组织。研究结果表明：增加碳含量，能够有效的提高热成形用钢的奥氏体稳定性，铁素体析出温度、珠光体转变温度、贝氏体转变温度和马氏体转变温度下降；同时增加碳含量提高了热成形用钢的淬透性，CCT曲线向右下方移动。对于碳含量为0.35%的热成形用钢，当以20°C/s的冷却速率冷却到室温，就可获得100%马氏体组织。此外，碳含量的增加还可以提高热成形用钢冷却转变后组织的显微硬度。 最后本文研究了四种实验钢的力学性能，研究结果发现：碳含量较低的两种实验钢经淬火后得到100%马氏体组织的抗拉强度低于1500MPa；而碳含量较高的两种实验钢100%马氏体组织的试样拉伸时出现脆性断裂。针对这两种碳含量较高的实验钢，我们采用马氏体、贝氏体或马氏体、贝氏体、少量铁素体的复合组织来代替100%马氏体组织，从而使得试样在淬火后拥有高强度和一定的塑性。
[Abstract]:Nowadays, the problems of energy saving and emission reduction and improving safety performance of automobile are becoming more and more prominent. Hot forming steel with strength grade above 1500MPa has shown great advantages in reducing body weight and improving vehicle safety performance. Its application potential in the future car body parts is beyond doubt. In order to study and develop a new generation of high performance ultra-high strength hot forming steels with independent intellectual property rights to meet the needs of the domestic market, four new types of hot forming steels with different carbon content are designed in this paper. The basic research work of hot forming steel is carried out in order to provide the necessary basic data and design principles for the development of new hot forming steel with independent intellectual property rights. In this paper, the continuous cooling transformation of four experimental steels for hot forming was studied by means of thermal expansion method and thermal analysis method. The CCT curves of four experimental steels were obtained, and the microstructure of the transformation at different cooling rates was observed. The results show that the austenite stability, ferrite precipitation temperature, pearlite transformation temperature, bainite transformation temperature and martensite transformation temperature of hot forming steel can be improved effectively by increasing carbon content. At the same time, the hardenability of hot forming steel was improved by increasing carbon content, and the CCT curve moved to the lower right. For hot forming steel with 0.35% carbon content, 100% martensite structure can be obtained when cooling rate is 20 掳C / s to room temperature. In addition, the increase of carbon content can also improve the microstructure microhardness of hot forming steel after cooling transformation. Finally, the mechanical properties of four kinds of experimental steels are studied. The results show that the tensile strength of 100% martensite microstructure of two experimental steels with low carbon content is less than 1500 MPA after quenching. The brittle fracture occurred in the specimens of 100% martensite microstructure of two experimental steels with higher carbon content. For these two kinds of experimental steels with high carbon content, the composite structure of martensite, bainite or martensite, bainite, and a small amount of ferrite is used to replace the 100% martensite structure, which makes the specimen have high strength and certain plasticity after quenching.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TG142.1
本文编号：2285509
[Abstract]:Nowadays, the problems of energy saving and emission reduction and improving safety performance of automobile are becoming more and more prominent. Hot forming steel with strength grade above 1500MPa has shown great advantages in reducing body weight and improving vehicle safety performance. Its application potential in the future car body parts is beyond doubt. In order to study and develop a new generation of high performance ultra-high strength hot forming steels with independent intellectual property rights to meet the needs of the domestic market, four new types of hot forming steels with different carbon content are designed in this paper. The basic research work of hot forming steel is carried out in order to provide the necessary basic data and design principles for the development of new hot forming steel with independent intellectual property rights. In this paper, the continuous cooling transformation of four experimental steels for hot forming was studied by means of thermal expansion method and thermal analysis method. The CCT curves of four experimental steels were obtained, and the microstructure of the transformation at different cooling rates was observed. The results show that the austenite stability, ferrite precipitation temperature, pearlite transformation temperature, bainite transformation temperature and martensite transformation temperature of hot forming steel can be improved effectively by increasing carbon content. At the same time, the hardenability of hot forming steel was improved by increasing carbon content, and the CCT curve moved to the lower right. For hot forming steel with 0.35% carbon content, 100% martensite structure can be obtained when cooling rate is 20 掳C / s to room temperature. In addition, the increase of carbon content can also improve the microstructure microhardness of hot forming steel after cooling transformation. Finally, the mechanical properties of four kinds of experimental steels are studied. The results show that the tensile strength of 100% martensite microstructure of two experimental steels with low carbon content is less than 1500 MPA after quenching. The brittle fracture occurred in the specimens of 100% martensite microstructure of two experimental steels with higher carbon content. For these two kinds of experimental steels with high carbon content, the composite structure of martensite, bainite or martensite, bainite, and a small amount of ferrite is used to replace the 100% martensite structure, which makes the specimen have high strength and certain plasticity after quenching.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TG142.1
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