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Friction stir processing (FSP) is a surface treatment technology that can eliminate casting defects locally by refining microstructures, thereby improving the mechanical properties of material.
Welding of super bainitic and triplex structure steels was studied using AWS A5.5 E11018-M and AWS A5.4 E312-17 electrodes. The existence of martensitic structure at the heat affected zone encourages the occurrence of cold cracking at the HAZ in welding of both super bainitic and triplex steels. Using E312-17 electrode renders the occurrence of cold cracks at the heat affected zone of these steels. The tensile strength of welded joints using E11018-M electrode is higher than that of the pure weld metal of E11018-M electrode. This could be attributed to the dilution of weld metal from the base metal especially carbon content. The V– notch impact test results using E312-17 electrode were slightly higher than that obtained using E11018-M electrode. This could be attributed to the occurrence of cold cracks using E11018-M electrode in addition to the tough austenitic weld metal using E312-17 electrode.
In the present work, the effect of welding procedure on weldability of conventional high manganese steel compared with the recent developed ladle treated one. This research aims at disclosing the microstructure, hardness, impact toughness and tensile strength of the welded joints. The optical micrograph of the conventional high manganese steel welded joint without cooling between passes shows that the heat affected zone (HAZ) has a high density of carbides formed at the grain boundaries. However, cooling between passes using compressed air resulted in a decrease in the density of carbides formed at the grain boundaries of the HAZ. In the ladle treatment samples, the microstructure shows an increase the density of the eutectic phase of the HAZ as a result of welding without cooling. On the other hand, application of cooling using compressed air between passes results in a low density of the eutectic phase in the HAZ.
Application of cooling between deposited passes resulted in a significant improvement of the impact toughness of weldment in both conventional and ladle treated samples of high manganese steel. The result obtained by SEM observation shows the reduction of both carbides at the grain boundaries in HAZ of conventional high manganese steel and the eutectic phase in HAZ of ladle treated one.
