Failure during fabrication of clamps of Mn-alloyed steel for springs in heavy vehicles. (January 2020) - Tavares, S.S.M.
Highlights: Brittle failure of U-bolt of SAE 1552 steel occurred during fabrication by bending. The hot rolled steel has low total and uniform elongation. The microstructure consisted of peartlite, ferrite and some granular bainite. The ductility could be much improved by previous quenching and tempering at 600 °C. Abstract: Clamps or "U" bolts for springs in heavy trucks made of SAE 1552 C-Mn steel presented cracks during the fabrication process by flattening and bending. The cracks initiated in the external face of curves bended, where the tensile stress was maximum. The surface of cracking showed a large portion of brittle fracture by cleavage. The microstructure consisted of fine pearlite (major part), pro-eutectoid ferrite and traces of bainite. The bar used to fabricate the clamps were probably hot rolled and air cooled, resulting in a material with only 1.3% of uniform deformation in the tensile test. This study shows that the bars should have been quenched and tempered at around 600 °C, in order to provide higher workability to the flattening and bending processes, and improve mechanical properties for service.