Modification of non-metallic inclusions with rare-earth metals in 50CrMoV13-1 steel

Abstract

The potential use of the rare-earth metals in clean steel production was investigated. Reactions between the non-metallic inclusions and the rare-earth metals were investigated in a cold-work tool-steel grade (50CrMoV13-1). A rare-earth metal alloy misch metal (Ce, La, Nd, Pr) was used for the inclusion modification. Aluminium oxide non-metallic inclusions that have a negative effect on the mechanical properties usually occur in the investigated steel. The experimental melts were made in a vacuum induction furnace with different rare-earth metal additions (50, 150, 340, 950 and 2900) ppm. The laboratory cast ingots were hot forged and analysed with light and electron microscopy. It was found that misch metal additions influence the size, composition and type of the non-metallic inclusions in the steel. Most importantly, very small inclusions are formed at lower rare-earth metal additions (up to 340 ppm), but at high additions large non-metallic inclusions are formed (2900 ppm).

Evaluation of different alloying concepts to trace non-metallic inclusions by adding rare earths on a laboratory scale

“…In addition, REEs start interacting with aluminium oxides on the interface, whereby REE-containing complex inclusions occur [19,20]. As mentioned by Šuler et al [21], REEs are not best suited for following the modification steps of inclusions because they also interact and influence the morphology, size, number and distribution of NMIs. The addition of rare earths lowers the melting point of inclusions, resulting in modified liquid-type inclusions at production temperatures, similar to the classical Ca-treatment [21][22][23][24].…”

Modification of Alumina Inclusions in SWRS82B Steel by Adding Rare Earth Cerium

“…There are many thermodynamic studies on the treatment of alumina inclusions with rare earth in molten steel [19][20][21][22][23][24][25][26][27]. However, limited works are focused on the rare earth treatment of high-carbon steel.…”

Nitrogen and nitride non-metallic inclusions in steel

“…The presence of elements like aluminium, calcium, silicon, manganese, rare-earth metals, magnesium and zirconium has a profound effect on the non-metallic inclusion formation and related size, number, chemistry and morphology. [8][9][10][11][12][13] Nitrogen, on the other hand, is often an overseen factor in the prediction of the non-metallic content. Specialized test methods cover a number of recognized procedures for determining the non-metallic inclusion content of steel, these methods are primarily intended for rating oxide and sulphide inclusions.…”