Preventing Crack Formation at the Vicinity of the Fusion Zone in the Welding of Crane Rail Steel by Preheating Treatment

Abstract

The effect of preheating temperature on crack formation, microstructure and mechanical properties of overhead crane rail steel joint by the use of shielded metal arc welding was investigated. The rail material was high carbon pearlitic rail steel. Applications of such steels require high strength and hardness at the welding zone so that the required wear resistance is obtained. However, due to the high carbon content, microstructure in the welding zone usually undergoes undesirable changes including formation of a brittle zone adjacent to fusion boundary in the rail. Welding of the rail steel with E9018-G, E11018-M, and Railroad (E12016-G) electrodes was performed without preheating and with preheating at 150, 250, and 325°C. Microstructural and mechanical properties of the weld metals and heat affected zones were investigated. Results revealed that for all the fillers, increasing preheating temperature results in decreasing the brittle zone width and prevents formation of the crack. Besides, the results showed that for the rails welded by E12016-G and E11018-M electrodes, by increasing the preheating temperature, the amounts of martensite–austenite islands and acicular ferrite decreased, and mechanical properties including impact energy significantly improved. Based on the results, an optimum preheating temperature and welding electrode are suggested.