Mechanical properties and fracture toughness of rail steels and thermite welds at low temperature

• Published in: International journal of minerals, metallurgy and materials Vol. 19; no. 5; pp. 409 - 420
• Main Authors: Wang, Yuan-qing, Zhou, Hui, Shi, Yong-jiu, Feng, Bao-rui
• Format: Journal Article
• Language: English
• Published: Springer Berlin Heidelberg University of Science and Technology Beijing 01.05.2012; Springer Nature B.V; Key Labotatory of Civil Engineering Safety and Durability of China Education Ministry, Beijing 100084, China; Department of Civil Engineering,Tsinghua University, Beijing 100084, China%Department of Civil Engineering,Tsinghua University, Beijing 100084, China
• Subjects: Brittle fracture; Ceramics; Characterization and Evaluation of Materials; Charpy impact test; Chemistry and Materials Science; Cold regions; Cold welding; Composites; Corrosion and Coatings; Ductility; Ductility tests; Elongation; Fracture mechanics; Fracture surfaces; Fracture toughness; Glass; Heat treating; Impact strength; Low temperature; Materials Science; Mechanical properties; Metallic Materials; Natural Materials; Plane strain; Rail steels; Railroads; Rails (railroad); Railway construction; Railway engineering; Railways; Reduction of area; Steel; Surfaces and Interfaces; Tensile tests; Thermites; Thin Films; Tribology; Welded joints; 低温; 力学性能; 扫描电子显微镜; 断裂韧性; 焊缝; 钢轨钢; 铝热焊; 青藏铁路; welds; brittle fracture; fracture toughness; rails; mechanical properties; low temperature properties
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-012-0572-8

Brittle fracture occurs frequently in rails and thermite welded joints, which intimidates the security and reliability of railway ser- vice. Railways in cold regions, such as Qinghai-Tibet Railway, make the problem of brittle fi＇acture in rails even worse. A series of tests such as uniaxial tensile tests, Charpy impact tests, and three-point bending tests were carried out at low temperature to investigate the mechanical properties and fracture toughness of U71Mn and U75V rail steels and their thermite welds. Fracture micromechanisms were analyzed by scanning electron microscopy （SEM） on the fracture surfaces of the tested specimens. The ductility indices （percentage elongation aider frac- ture and percentage reduction of area） and the toughness indices （Charpy impact energy Ak and plane-strain fracture toughness Kic） of the two kinds of rail steels and the corresponding thermite welds all decrease as the temperature decreases. The thermite welds are more critical to fracture than the rail steel base metals, as indicated by a higher yield-to-ultimate ratio and a much lower Charpy impact energy. U71Mn rail steel is relatively higher in toughness than U75V, as demonstrated by larger Ak and Klc values. Therefore, U71Mn rail steel and the corresponding thermite weld are recommended in railway construction and maintenance in cold regions.