Industrial processing, microstructures and mechanical properties of Fe–(2–4)Mn (–0.85Mo)–(0.3–0.7)C sintered steels

Abstract

The potential of PM Mn steels has been established yield, tensile and bend strengths of 499, 637 and in laboratory experiments. This paper deals with 1280 MPa, respectively, with impact energy of 18 J, and sintering of Fe-(2-4)Mn-(0•3/0•7)C, also with 0•85%Mo tensile and bend strains of 1•17 and 1•57%, were achieved addition, in an industrial pusher furnace at 1180°C in an for the Fe-2Mn-0•85Mo-0•5C alloy, marginally superior atmosphere of 25% hydrogen plus 75% nitrogen, to Fe-2Mn-0•7C. For the sinter hardened Fe-4Mn-0•3C obtained from a cryogenic liquid, giving an inlet dew-alloy yield, tensile and bend strengths were 570, 664 and point of −55°C. Tensile, bend (including fatigue) and 1263 MPa, respectively, at an acceptable impact energy miniature Charpy specimens were sintered in flowing of 14 J, with tensile and bend strains of 0•52% and 1•8%. gases and in semiclosed containers with a getter of ferro-Many of the results compare favourably with the requiremanganese, carbon and alumina. The quenched and tem-ments of MPIF standard 35. Mn is a more effective pered state was investigated, as was sinter hardening strengthening agent than either Ni or Cu, or their combi-(cooling rate of 55 K min−1), simulated for comparison nation, though generally at reduced plasticity. with slow cooling at 10 K min−1. As there was no forma-PM/1086 tion of oxide networks at the combination of sintering temperature and dewpoint, in accordance with the Dr Dudrova ´(

Influence of Geometry and Cooling Rate on Properties of Sinter-Hardened Steels

“…Sinter-hardening is a widely used, well-known process [6], aiming to enhance mechanical properties of sintered components, also when made up of modified alloy powder mixes [7], combining sintering and hardening in the same heat treatment. In order to get high performance components it is possible to work on the hardening of the material, increasing the cooling rate after sintering and getting a hardened part.…”

The Sintering Behaviour of Fe-Mn-C Powder System, Correlation between Thermodynamics and Sintering Process, Manganese Distribution and Microstructure Composition, Effect of Alloying Mode

“…Recent studies of brittleness of admixed with manganese PM steels studied by complex of advanced microscopy and spectroscopy techniques (high-resolution scanning electron microscopy (HR SEM), energy dispersive X-ray analysis (EDX), Auger spectroscopy and X-ray photoelectron spectroscopy (XPS)) clearly indicate that the brittleness of material containing admixed manganese is caused by the weakness of grain boundaries within the base matrix particles around the manganese carrier residuals (Hryha, 2007;Hryha et al, 2008;. Completely brittle behaviour associated with predominantly inter-granular type of failure caused by the oxide phase at grain boundaries was also assumed in previous works by Dudrova (Dudrova et al, 2004;Dudrova et al, 2005). Inter-granular type of failure starts to be observed in the admixed materials above ~1000ºC, see Fig.12, caused by the presence of very thin manganese oxide layer, formed due to diffusion of condensed manganese from the iron particle surface inside the particles along the grain boundaries and its further oxidation there.…”

“…Detrimental effect of pores, filled with slag, after manganese source due to its evaporation was emphasized by Dudrova (Dudrova et al, 2004) and Danninger (Danninger et al, 2005). Due to angular shape of such pores with inclusions they act as strong crack-initiation sites.…”

“…The main obstacle for industrial application of admixed manganese PM steels is high brittleness of sintered components. Several hypotheses have been proposed, connected with brittleness caused by microstructure heterogeneity, size of manganese carrier particles, their residue and their oxidation (Dudrova et al, 2004;Dudrova et al, 2005;Danninger et al, 2005;Cias et al, 2003).…”

“…The easiest way to introduce manganese is by admixing of ferromanganese powder that is cheap and widely available on the market in different grades. This approach was firstly proposes around 30 years ago and have been scrutinized thoroughly from different perspectives Cias et al, 1999;Šalak et al, 2001;Dudrova et al, 2004;Danninger et al, 2005;Cias&Wronski, 2008, Hryha, 2007. The first thing that has to be considered when dealing with admixed with manganese systems is high affinity of manganese to oxygen, implying possibility of considerable oxidation during component processing due to high activity of manganese in admixed elemental powder.…”