Tempering and Intercritical Annealing of Air‐Hardening 4 wt% Medium Manganese Steels

Abstract

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.

Air-Hardening Die-Forged Con-Rods—Achievable Mechanical Properties of Bainitic and Martensitic Concepts

“…The additional annealing at 450 °C for 2 h leads to an improvement of the yield ratio (from 0.63 to 0.71) and to an increase of the impact toughness. Both changes can be attributed to the coarsening of existing carbides, the resulting depletion of the matrix by carbon and the relaxation of the martensitic microstructure, as previously reported for alloys cast on the laboratory scale [24]. The progression of force-displacement curves of the bainitic grades (Figure 12) demonstrates that both materials fracture completely brittle.…”

Alloying and Processing of Medium Manganese Steels for Forging Applications

“…This significantly increases ductility and toughness, while strength remains unchanged. Exceeding the optimum intercritical annealing temperature leads to a volume fraction increase and morphology change of austenite, which forms a coarse network [2].…”

Effect of Manganese on the Strength–Toughness Relationship of Low-Carbon Copper and Nickel-Containing Hull Steel

“…Currently, much of the research in Mn steel focuses on enhancing its strength and plasticity [ 17 , 18 , 19 , 20 , 21 , 22 ]. However, studies examining low-temperature toughness, particularly the impact of RA phase transformation on toughness, are relatively scarce.…”