Experimental Investigation on Flame Straightening of Corrosion Resistant Structural Steel Sheet Used for Rolling Stock

Flame straightening is a common procedure used for repair work in steel components. It is based on heating a local region of the part by means of a flame torch. Due to the obstruction of the heat expansion, upsetting occurs in the work material. During cooling of the squashed zone shrinkage occurs and that is associated with tension forces which lead to the desired deformation. This process is used in railway shell manufacturing to achieve desired undulation levels of the outer shell skin material. The process of flame straightening suffers from several shortcomings that have strong impacts on the quality, safety and on the economy of railway shell construction. In this paper, a study on the oxyacetylene flame heating of 2mm thick corrosion resistant structural steel sheets (Indian Railway Standard Specification No. M 41 (IRS:M – 41)) is carried out. During heating of IRS:M41 structural steel, an exceeding of oxy acetylene pressure, torch nozzle diameter and the holding time have detrimental effects on mechanical and micro structural properties. The relationship between the micro structural features, tensile and yield strength, elongation and Vickers hardness of material at different combinations of the above parameters were analysed and results were correlated. Based on the experimental results, this study reveals the consequences of flame straightening on microstructure and mechanical properties of the work material influenced by oxy acetylene pressure, torch nozzle diameter and the holding time.