Experimental investigation concerning the development of distortion potential during the production of 20MnCr5

Investigations within the SFB 570 „Distortion Engineering” showed that properties of the low alloyed 20MnCr5 (SAE 5120) had an influence on distortion. The changes of curvature of blind-hardened shafts could be correlated to a macroscopic structure, which was visible at micrographs of cross-sections. The development of lined structures and the macroscopic structure was observed by metallographic methods at cast material, hot-rolled material and an intermediate step of the hot forming process. The lined structure within the semifinished material was measured by EPMA measurements with highest resolution. The contents of the alloying elements Mn and Cr could be correlated to the development of the lined structure, the carbon content fluctuated in a higher frequency. To determine the differences of phase transformations, two different homogenous materials were produced by spray-forming: one with the maximum content of the alloying element Mn, Cr and C concerning the EPMA measured values, and a second with the minimum measured Mn, Cr and C content. The material was hot formed to a diameter of 25 mm after spray-forming and characterized by dilatometer measurements.