Molybdenum alloying in high-performance flat-rolled steel grades

Abstract

Considerable progress in developing flat-rolled steel grades has been made by the Chinese steel industry over the recent two decades. The increasing demand for high-performance products to be used in infrastructural projects as well as in production of consumer and capital goods has been driving this development until today. The installation of state-of-the-art steel making and rolling facilities has provided the possibility of processing the most advanced steel grades. The production of high-performance steel grades relies on specific alloying elements of which molybdenum is one of the most powerful. China is nearly self-sufficient in molybdenum supplies. This paper highlights the potential and advantages of molybdenum alloying over the entire range of flat-rolled steel products. Specific aspects of steel property improvement with respect to particular applications are indicated.

Effect of Annealing Process on Microstructure, Texture, and Mechanical Properties of a Fe-Si-Cr-Mo-C Deep Drawing Dual-Phase Steel

“…Mo and Cr could be used to partially replace C and Mn for sufficient hardening ability, since they help retard the formation of pearlite or bainite and thus keep a sufficient amount of martensite as well as help enhance the solute-hardening effect. Mo addition is more effective than Cr and Mn to obtain the required volume fraction of martensite and higher mechanical strength [36,42,43]. Silicon promotes ferrite transformation and has a negligible solubility in cementite, thus suppressing the precipitation of cementite [44][45][46].…”

Effect of Quenching Strategy and Nb-Mo Additions on Phase Transformations and Quenchability of High-Strength Boron Steels

“…Although cooling rates above 100°C/s could be reached through current cooling facilities, the effective cooling rate for thicker gauges at the plate core is considerably lower and so ensuring full martensitic structures throughout the thickness becomes challenging. 6 Therefore, depending on rolling conditions and the alloy concept, there may be a risk of forming undesirable soft phases such as ferrite and bainite. Furthermore, residence time in the cooling device may be excessively long in the case of thicker gauges, lowering the output of the rolling mill.…”

“…Besides the direct effects of molybdenum, the combination of Nb and Mo leads to pronounced synergetic effects, while Mo significantly contributes to austenite pancaking by solute drag during hot rolling. This effect is even greater in combination with niobium, as the martensitic substructures are formed in the previously pancaked austenite grains, 6 , 19,20 combining drag and straininduced precipitation mechanisms. Molybdenum also delays precipitation of niobium during austenite conditioning, making a higher amount of solute niobium available for precipitation during tempering treatment.…”

Role of Vanadium Carbide in Hydrogen Embrittlement of Press-Hardened Steels: Strategy From 1500 to 2000 MPa

“…The strength of martensite can be controlled by varying the carbon content of the steel (Krauss, 1999). Hence, 34MnB5 steel, which contains 0.34 wt% of carbon for higher strength, has been developed into 2000 MPa PHS (Uranga et al, 2020). However, stronger steel is more susceptible to hydrogen embrittlement (HE) (Bhadeshia, 2016).…”

“…For example, semicoherent TiC acts as a reversible trapping site and incoherent TiC acts as an irreversible trapping site (Wei and Tsuzaki, 2006). In the first commercialized 34MnB5 PHS, combined microalloying of niobium and molybdenum contributes to microstructural refinement and shows benefits for reducing susceptibility to HE (Uranga et al, 2020;Mohrbacher and Senuma, 2020). Actually, many studies have shown that nanocarbides can enhance the resistance to HE (Zhang et al, 2011;Kim et al, 2018;Zhang et al, 2015;Zhang et al, 2020;Lin et al, 2018).…”