Investigation of the effect of the temperature process on din DIN 41Cr4 and 30MnB4 steels

In this study, the mechanical, morphological and crystallographic properties of 41Cr4 and 30MnB4 low alloy steels were compared after different tempering processes. Samples prepared from DIN 41Cr4 and 30MnB4 steels were produced in a 4-station horizontal cold forming machine. Both materials were annealed and homogenized at 860 oC in a continuous heat treatment furnace, then cooled in oil. Afterwards, tempering process was applied at different temperatures. Phase structures, morphological formations and mechanical properties of each temperature value were determined. The samples, whose heat treatment processes were completed, were made suitable for X-ray analysis by cutting disc-shaped pieces with wire erosion. Determination of phase structures by X-ray analysis was performed with X-ray diffractometer device. The peaks were indexed using the resulting reflections. After the heat treatments, metallographic samples were prepared by taking sections from the samples. Microstructures of polished and metal microscope samples were examined by scanning electron microscope (SEM). The elemental composition of the phases was determined by EDS examinations. In order to determine the mechanical properties, tensile tests were performed on five test rods for each different tempering process. Rockwell-C and Vickers hardness measurements of the samples were taken. As a result, the usability of the cheaper 30MnB4 steel as an alternative to DIN 41Cr4 and DIN 42CrMo4 steels, which are widely used in wheel bolt production, was investigated. The hardness, mechanical and metallographic properties between the two materials were compared by changing the tempering temperatures. The aim of this thesis is to reduce foreign dependency relatively by using 30MnB4 steel more widely in the production of 10.9 quality class bolts defined in the standards and to contribute to export by producing a more economical product without sacrificing quality. Thus, by replacing the wheel bolt and bolt production, which has a large market share in our country, with a cheaper material, an alternative material that will contribute to the economy in this area annually is presented.