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This study received financial support from the Department of Education of the Basque Government for the Research Group program IT1507-22. The research was financed from the funds of the Scientific Discipline Council for Mechanical Engineering: M/KOPM/FD-20/IM-5/013/2022.
Skew rolling is a manufacturing process in which two or three rolls are used to reduce the diameter or modify the shape of
a cylindrical workpiece, which is used to manufacture mechanical components such as shafts, rods or balls. Hot conditions
are used to overcome limitations related to material ductility, residual stress and machine capacity. In this paper, the warm
skew rolling (WSR) process of 42CrMo4 rods is modeled by the finite element method. The effects of forming parameters,
namely initial temperature and roll rotational velocity, on the material strain rate, thermal properties, microstructure and
hardness were analyzed. Simulation results were validated by experimental process data, while hardness tests and SEM-EBSD
microscopy were used to assess mechanical properties and microstructure, respectively. The WSR resulting microstructure
is different from the normalized ferritic–pearlitic initial one. The degree of spheroidization (DoS) of cementite increases
with temperature. The maximum DoS of 86.5% occurs at the initial temperature of 750 °C, leading to the highest material
softening. Rolling from lower temperatures favors grain fragmentation and the achievement of incomplete spheroidization,
which, in combination with the highest proportion of high-angle boundaries, contributes to a higher hardness of the rods with
respect to those rolled at higher temperatures. The highest reduction in hardness takes place at 750 °C and 30 rpm, leading
to 209.4 HV1 (30.7% reduction) and 194.1 HV1 (35.7% reduction) in the near-surface and internal regions, respectively.
The driving factor is the transformation of cementite precipitates into a spheroidal form characterized by the greatest degree
of dispersion.
