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Advanced engineering materials 2201931 (2023). doi:10.1002/adem.202201931, Published by Deutsche Gesellschaft für Materialkunde, Frankfurt, M.

Berg- und hüttenmännische Monatshefte : BHM 167(11), 534-537 (2022). doi:10.1007/s00501-022-01288-2, Published by Springer, Wien

A new quenching and tempering steel is presented and compared with reference alloys 42CrMo4 and AISI 4140. Through the substitution of chromium (− 0.7 wt.-%) by manganese (+ 1.3 wt.-%) high hardness could be guaranteed by reduced alloying costs. Hardness gradients are shown in the Jominy-test for the reference alloys, while the new alloy shows nearly a constant hardness of 600 HV10. The inductive hardenability was tested using a dilatometer. The new alloy shows a hardness of 780 HV which is 60 HV10 higher than the reference alloys. The critical cooling rate was reduced from 19 K/s for the reference alloys to 9 K/s for the new alloy.

In material development processes, the question if a new alloy is more sustainable than the existing one becomes increasingly significant. Existing studies on metals and alloys show that their composition can make a difference regarding the environmental impact. In this case study, a recently developed air hardening forging steel is used to produce a U-bolt as an example component in automotive engineering. The production process is analyzed regarding the environmental performance and compared with the standard quench and tempering steels 42CrMo4 and 33MnCrB5-2. The analysis is based on results from applying the method of Life Cycle Assessment. First, the production process and the alterations on material, product, and process level are defined. The resulting process flows were quantified and attributed with the environmental impacts covering Carbon Footprint, Cumulative Energy Demand, and Material Footprint as they represent best the resource-, energy- and thus carbon-intensive steel industry. The results show that the development of the air hardening forging steel leads to a higher environmental impact compared to the reference alloys when the material level is considered. Otherwise, the new steel allows changes in manufacturing process, which is why an additional assessment on process level was conducted. It is seen that the air hardening forging steel has environmental savings as it enables skipping a heat treatment process. Superior material characteristics enable the application of lightweight design principles, which further increases the potential environmental savings. The present work shows that the question of the environmental impact does not end with analyzing the raw material only. Rather, the entire manufacturing process of a product must be considered. The case study also shows methodological questions regarding the specification of steel for alloying elements, processes in the metalworking industry and the data availability and quality in Life Cycle Assessment.

Steel research international 2200623 (2022). doi:10.1002/srin.202200623, Published by Wiley-VCH-Verl., Weinheim

Steel research international 2000592 (2021). doi:10.1002/srin.202000592, Published by Wiley-VCH-Verl., Weinheim

Steel research international 92(11), 2100180 (2021). doi:10.1002/srin.202100180, The mechanical properties after tempering and intercritical annealing of medium manganese steels with 4 wt% Mn for forging applications are presented. After forging with subsequent air cooling, heat treatments were performed, specifically tempering from 250 and 450 ��C and intercritical annealing between 600 and 675 ��C. Tensile properties, Charpy V-notch impact toughness, and hardness were determined and compared with microstructural features characterized by metallography and synchrotron measurements, leading to the classification of six different heat treatment stages for medium manganese steels. Furthermore, the effects of different alloying additions (boron 0.0016���0.0057 wt%, molybdenum 0.2 wt%, and aluminum 0.5 wt%) are discussed with respect to the mechanical properties. It is shown that boron increases the impact toughness more effectively in the tempering regime, while the molybdenum alloyed samples exhibit higher toughness after intercritical annealing. Most of the materials and heat treatment states follow the inverse relationship between toughness and strength, while the aluminum alloyed samples show a superior toughness after tempering., Published by Wiley-VCH-Verl., Weinheim

Steel research international (2020). doi:10.1002/srin.202000172, Published by Wiley-VCH-Verl., Weinheim

Physical Metallurgy of High Manganese Steels / Special Issue Editors: Wolfgang Bleck, Christian Haase; Basel : MDPI, Metals 134-143 (2019)., Published by MDPI, Basel

A new alloy design for air-hardening forging steels has been investigated. Five laboratory melts with C contents between 0.15 and 0.19 wt.−% and a Mn content of 4 wt.−% distinguished by their Al (0.03/0.50), Ti (-/0.02), B (-/0.005), Mo (-/0.20) contents have been laboratory casted and forged into rectangular blocks with a cross section of 60 x 60 mm. After air cooling the tensile test properties, the Charpy toughness and the fatigue properties have been determined and compared to a Q+T steel as reference material. While the static mechanical properties are comparable to the reference grade, a small decrease in toughness and a significant increase in fatigue strength have been obtained. These findings are discussed with respect to the role of the individual alloying elements and their impact on microstructure and precipitation state.

In this study, Fe‐Cr‐C and Fe‐Cr‐W‐C alloys are characterized using atom probe tomography. The alloys have been heat treated at 1070 °C for 30 min and subsequently at 780 °C for various time periods. Carbide formation is observed at each state. Cr‐C precipitates smaller than 5 nm in radius for short heat treatment times and larger than 50 nm for heat‐treatment times greater than 1000 s are observed. It is found that the phase interface moves during the first time period at an almost constant speed. Later on the velocity of the phase interface decreases. Furthermore, kinetic assumptions for carbide growth from a previous theoretical study have been verified. As expected, a decrease of the microhardness with increasing aging time is detected which is caused by martensite tempering. The aim of this study is to measure the change in chemical compositions across phase interfaces between matrix and precipitates to obtain a better understanding of the precipitation process.