Investigation of skew piercing and upsetting effect on wheel steel mechanical properties

Abstract

Abstract The article states the results of the investigation of the skew piercing effect on the wheel steel mechanical properties. The comparative analysis is based on the comparison of mechanical properties of wheel steel samples manufactured by upsetting and heat treatment of the initial cast billets (option 1) and samples preliminarily pierced using the skew rolling mill with the extrusion ratio of µ ≈ 1.49 and feed angle of 12°, upset and heat treated (option 2). The values of elongation/contraction ratios of the samples made from solid workpieces are in the range 13.8–15/28–32%, and of hollow workpieces 14.2–15.8/26–32.9%. Strength properties of the wheel steel (for 1 and 2 variants) meet the requirements. The greatest differences in the properties of wheel steel of both variants were obtained during toughness tests. Toughness value of the wheel steel samples obtained by piercing, upsetting and subsequent heat treatment is ∼2.5 times higher in both tangential and radial directions than the toughness of samples obtained only by upsetting and heat treatment. It is shown that piercing of workpieces in a screw rolling mill increases the toughness without reducing the strength properties, which may be due to intense shear deformations causing the processing of the cast macrostructure and the formation of a spiral-shaped grain structure.