![]() ![]() Today, a major proportion of all ferrous PM parts are based on Fe–Cu–C usually prepared through the mixing route. This reactivity of PM compacts is the main reason why the traditional alloy elements for sintered steels have been those with fairly low oxygen affinity, which means low stability of the oxides. This plays a much more critical role for sintered steels as compared to IM grades since in PM the temperatures are lower (and thus less favourable for carbothermal reduction of oxides), and the specific surface is much higher, enhancing the reactivity towards the environment, in particular the sintering atmosphere. MN ELEMENT FREEThe main problem usually associated with Mn in powder metallurgy (PM) is its high oxygen affinity, the Gibbs free energy of formation for the most stable oxide MnO being more negative than that of Cr 2O 3 and only slightly less than that of SiO 2. In sintered steels, in contrast, Mn has been used rarely, although its benefits have been recognised very early, in particular by Andrej Šalak who thoroughly studied Mn alloying of sintered steels for decades, starting in the 1970s (e.g. In this class of steels, Mn is in fact indispensable as alloy element. A unique class of Mn steels are the so-called Hadfield steels, grades with high Mn and C levels, typically 12%Mn and 1.2%C, which are rather soft as-quenched but present excellent work hardening capability while retaining toughness. dual phase, transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels used, e.g. ![]() Mn is also contained by many modern steel grades, such as e.g. In that respect, Mn is the most effective of the common alloy elements for steels. The reasons for the widespread use of Mn in steel metallurgy – in part also for cast iron – are its low price, its hardening effect in the ferrite lattice and its high Grossmann factor, which significantly improves the hardenability. Manganese is a very common alloy element in steels produced by ingot metallurgy (IM) – in fact so common that steel grades containing up to 0.4% of Mn are still regarded as ‘unalloyed’. ![]()
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