Repair welding has caused crack initiation in the upper Treiber roll in the steel works plant mill at Železara in Smederevo. The upper and lower Treiber rolls serve the purpose of folding and directing rolled metal strips, supplied by the output rollers to the coiling mandrel. The parent material of the upper Treiber roll is S235JO. Unsuccessful welding resulted in a series of further activities to remove cracks. In addition, the cracks are identified on the Treiber roll for easier designation and monitoring while machining. Hardness tests have been performed on specific locations within the welded hard layer. After machining and removal of the whole welded layer with defects, it is determined that the welding activities contributed to the occurrence of a number of cracks in the parent material, which did not exist prior to surfacing. Hence, steps that need to be taken in order to eliminate these cracks in the parent material are suggested at the end of this paper.
Keywords: repair welding, cracks, preheating, machining, human error