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The research was financed in the framework of the project: New metal forming technique for producing flanged hollow parts for the mining industry, No. LIDER/1/0003/L-9/17/NCBR/2018. Total cost of the Project: 1197000 PLN. The project is financed by the National Centre for Research and Development under the 9th edition of the LIDER.
For decades, steel has been a crucial structural material. Mainly low-alloy steel grade 42CrMo4 is utilized for
manufacturing forgings. This paper investigates the microstructure and hardness development of the 42CrMo4
steel hollow component with an outer flange. The component has been formed via cold forging in combination
with extrusion and upsetting technologies. Prior to forming, the workpiece was annealed to obtain hardness at the
level of 181±9 HV0.3. The FEM analysis reveals the areas that undergo higher stress and strain. The flow lines
macrostructure and microstructure of hollow parts were investigated using light optical microscopy (LOM) and
scanning electron microscopy (SEM) equipped with EDS. Vickers hardness allows identifying the work hardening
of the crucial element areas. The microstructure consists of ferrite matrix and semispherical carbides. Laboratory
studies confirm appropriate flow lines arrangement, which corresponds well to those shown by FEM computer
simulations. The highest hardness at the level of 293±7 HV0.3 was identified in the flange area, where the material
shows a higher distribution of effective strain revealed by FEM. Cold metal forming results in work-hardening of
the steel. The work hardening ranges up to 1.62 of the initial 42CrMo4 steel hardness. The metal forming process
did not affect the microstructural uniformity of the flanged hollow part. The final outer flange component presents
high quality and is free from plastic deformation nonuniformities.
