Anisotrope Maßänderungen bei der Wärmebehandlung ledeburitischer Chrom-Werkzeugstähle

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 blindhardened 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 semi-finished 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 characterised by dilatometer measurements.

“…The steelmaking procedures casting and hot forming can lead to distortion of steel parts [2,3]. Segregations are formed by casting and modified by hot forming.…”

Section: Introductionmentioning

confidence: 99%

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

Prinz

Rentsch

2012

“…It is known for long that segregations are one of these parameters and can lead to distortion of steel parts [2,3]. Continuous casted hypoeutectoid steels like case hardening steels generally reveal segregations due to physical reasons, whereby the forming of the segregation are directly connected to the plant type of the continuous caster, and could be reduced by casting technologies like electromagnetic stirring or soft reduction.…”

Section: Introductionmentioning

confidence: 99%

Characterization of segregations and microstructure and their influence on distortion of low alloy SAE 5120 steel

Prinz

Hunkel

Clausen

et al. 2009

Investigations within the SFB 570 "Distortion Engineering" showed that shafts produced of the low alloy steel SAE 5120 (EN 20MnCr5) changed curvature into a preferred direction after blank hardening. The changes of curvature could be correlated with a macroscopic structure, which was visible in the metallographic cross section of the hardened shafts. Due to a quantitative description of the orientation of the square structure within the metallographic cross section it could be shown that the changes of the orientation of the structure were similar to the changes of the preferred direction of the curvature of the blank hardened shafts.Metallographic structures in different sections became visible because of differences of the local corrosion behavior. Such differences cause in varieties of the local chemical composition or grain size. Therefore the local chemical analysis was characterized by means of EPMA measurements with highest resolution. Further the grain size was described by quantitative image analysis of the former austenite grain boundaries. Additionally, characteristic areas of the metallographic cross section were investigated by FEM measurements due to the fact that the grain size could be affected by elemental precipitations.The laminar EPMA-measurements (mapping) at blank hardened shafts of the element distributions concerning the substantial alloying elements C, Mn and Cr showed a square structure in the element distribution. Best reproduction of the square structure within the metallographic cross section could be reached by moving averages of the highly resoluted mappings and their standard deviations.Different distributions of the former austenite grain boundary were found within characteristic areas of the metallographic cross section. FEM measurements seem to point on the fact that differences of the former austenite grain size distributions could cause in varieties of the character and distribution of elemental precipitations.

Werkstoffeigenschaften eines neuen, warmverformbaren ledeburitischen Stahles mit 12% Chrom und 3% Kohlenstoff

Staska

Kulmburg

1973