Glass forming ability and soft-magnetic properties of Fe-based glassy alloys developed using high phosphorous pig Iron

Glass forming ability (GFA) and soft-magnetic behaviour of melt-spun Fe69C5.5P11.5Mn0.4Si2.3Cr1.8Mo1B8.5 (alloy 2) and Fe68C9P12Mn1Si3Nb2B5, (alloy 3) alloys prepared using high phosphorous pig iron (h-PI, Fe80C14P2.2Mn0.4Si3.4) has been studied. The glass formation, thermo-physical and soft-magnetic properties of the alloys were analyzed for different quenching rates by varying wheel speed as 23, 26, 33, 39 and 43 m/s. The simultaneous incorporation of alloying elements (Cr, Mo, Nb) and metalloids (C, B, P, Si) transforms h-PI to complete glassy alloy, even at low quenching rates. The melt quenching rate influences the thermal parameters and Curie temperature of glassy ribbons in an opposite way. Amongst all, FeCPMnSiCrMoB glassy alloy show superior combination of higher glass transition temperature of 788 K, super cooled region of 34 K, glass Curie temperature of 552 K, coercivity less than 13 A/m and maximum saturation magnetization of 1.1 T. In addition, the annealing treatment at 758 K improves magnetic softness (1.7 A/m) of the alloy by relaxation of quenched-in stresses. The comparison of developed glassy alloy with similar Fe-glassy alloys and SENNTIX type alloys show best combination of thermo-physical and magnetic properties. The glassy alloy prepared using blast furnace high phosphorous pig iron can be used for uniformly gapped soft-magnetic cores

Investigation on Mold Flux Melting and Consumption During Continuous Casting of Liquid Steel

Mold powders play an integral role in maintaining the stability and efficiency of the continuous casting process as they (1) provide lubrication, (2) control heat transfer, (3) absorb nonmetallic inclusions, and (4) prevent reoxidation of liquid steel during continuous casting of liquid steels. Much of the previous investigations are focused on the characterization of mold powders to understand the physicochemical aspects of the continuous casting process. However, limited attention has been given to analyzing the melting behavior of mold powder, which is necessitated for the proper functioning of the caster. An experimental technique akin to the industrial practice has been adopted in this investigation to study the melting behavior of the mold powder. A realistic nondimensional correlation is proposed considering the various casting parameters (casting speed, mold oscillation frequency, and stroke, negative strip time, and cross-sectional area of mold), the mold powder melting, and the consumption rate based on the adopted experimental and theoretical methods for real-time application

High-Temperature Simulation of Continuous Casting Mould Phenomena

The present investigation describes experimental simulation methods to evaluate the performance of mould powder during the continuous casting of peritectic steel. The dip mould simulator method developed in this investigation will take into account the actual mould powder along with the steel to be cast and certain casting parameters (casting speed, oscillation frequency and stroke) to evaluate the suitability of casting steel in the continuous caster. Another experimental technique akin to industrial practice has also been designed and proposed to study the melting behaviour of mould powder. Melting rate determined in this study for peritectic grade flux is in agreement with the theoretical melting rate estimated using a method proposed by K.C. Mills. The cast structure obtained from the dip mould simulator possesses oscillation marks and other features (slag infiltration) akin to the industry practice

Compositional optimization of high induction (> 1.7T) FeCo-based nanocomposite alloys with enhancement of thermo-physical and magnetic properties

The substitution of Fe with Co and B with Si is investigated in a series of high induction Fe84B13Nb2Cu1 amorphous alloys. The as-quenched melt-spun alloys are structurally amorphous in wheel side and a mild crystallites alongwith amorphous phase in air side. The alloy with 35 at% Co addition depicts improved thermal stability, saturation induction and coercivity, and the optimal combination of soft magnetic properties is achieved for an extended annealing temperature range. The additional 10 at% Si deteriorates soft magnetic properties

Effect of compositional elements and processing routes on structural and thermal response in Fe-based metallic glasses

The effect of varying thickness on structure and thermal properties is investigated in Fe-B-Nb and Fe-B-Si-Nb glassy alloy systems with the addition of different Nb and Co content, respectively. Accordingly,four alloys with the nominal compositions of Fe76-xB18Nb6+x (x = 0, 2) and (Fe1-yCoy)72B12Si12Nb4 (y = 0,0.5) are processed in the forms of ribbon and rod. All alloys of ribbons represent amorphous structure,while those of rods explain the crystalline structure with the exception of heteromorphous structure for Co added alloy. The Nb addition causes about same glass transition temperature (Tg) but increases crystallization onset (Tx), resulting in a wider supercooled liquid region (deltaTx =Tx-Tg). Moreover, Nb also improves glass forming ability (GFA) with more free volume generation and higher structural relaxation exothermic heat (delta H0). The Co addition also improves free volume generation and higher delta H0 for ribbon, but lower amount free volume generation in bulk alloys (rod) than ribbon

The Role of Slag Carryover on the Non-metallic Inclusion Evolution and Magnetic Behavior in Electrical Steel

In the present investigation, a set of high-temperature experimentations were carried out to improve the understanding of the influence of slag carryover (SCO) on non-metallic inclusion evolution during the production of high silicon electrical steels for functional applications. It was observed that the liquid steel treated with synthetic slag and lime resulted in the formation of CaO-based complex oxide, sulfide, and nitride inclusions in the matrix. Whereas the top slag (synthetic slag and lime) contaminated with carryover slag transforms the complex oxide inclusions to Mn free oxy-sulfide inclusions in the high Si steel. Further, the high-silicon steel evaluated for magnetic property confirms the detrimental magnetic behavior of the steel treated using the top slag with the excess amount of SCO (10 kg/t). The increase in coercivity is due to a higher fraction of sub-micron inclusions in the steel matrix. The industry implications of the present findings are highlighted in the light of the evolution of Goss texture in high silicon steel during downstream processing. The evolution of detrimental inclusions in functional grade (electrical) steels due to the presence of SCO call for stringent process control during the upstream processing of liquid steel to maintain the desired magnetic properties. © 2022, The Minerals, Metals & Materials Society and ASM International

Impact of Pre-formed Martensite on the Electromagnetic Properties and Martensitic Transformation Kinetics of Uniaxially Tensile Loaded 304 Stainless Steel

The investigation addresses the influence of tensile deformation on the magnetic properties of 304SS samples in their as-received state as well as those with martensite content of 12 and 17%. Non-destructive electromagnetic techniques like magnetic Barkhausen emission (MBE) and magnetic hysteresis loop have been used to measure variation in MBE voltage and coercivity, respectively, during plastic deformation through tensile loading. As both the techniques use surface probe, the present investigation will be useful for in situ evaluation of structural components. With progressive plastic deformation, those measurements revealed different stages of deformation indicated by change in MBE signal and magnetic coercivity. The stages of magnetoelastic response, strain-induced martensitic transformation, dislocation pile-ups and formation of voids reflected different patterns of magnetic Barkhausen emission and magnetic coercivity variation with progressive straining of austenitic stainless steel samples. The changes in true strain with variation in martensite content along gauge length of fractured samples have been analyzed with respect to martensite transformation kinetics. Mathematical fitting methodology has been adopted to distinguish as-received and pre-strained martensitic transformation characteristics. In situ magnetic NDE and associated martensitic transformation parameters may be useful for structural health monitoring of in-service components

Magnetostriction of Fe-rich FeSiB(P)NbCu amorphous and nanocrystalline soft-magnetic alloys

The compositional effect of magneto-elastic and magnetostriction properties of Fe-rich Fe81B15-xPxSi2Nb1Cu1 (ii) Fe(82)B(14-x)PxSi(2)Nb(1)Cu(1) and (iii) Fe83B13-xPxSi2Nb1Cu1 (x = 0, 4, 8) amorphous and annealed nanocrystalline alloy ribbons were investigated. The present study adds knowledge to the limited magnetostriction literature available for Fe-rich nanocrystalline alloys by systematically varying the Fe and P content. A combination of Becker-Kersten and small angle magnetization rotation (SAMR) techniques has been employed for the magnetostriction (lambda s) evaluation. Both the as-quenched and nanocrystalline ribbons exhibit large positive magnetostriction and show strong compositional dependence to the P content. In the as-quenched condition, 4 at% P addition shows maximum magneto-elastic response and magnetostriction constant, with Fe81B11P4Si2Nb1Cu1 alloy exhibiting a maximum of + 52 ppm and P-free Fe83B13Si2Nb1Cu1 alloy exhibiting a minimum of + 27 ppm. In the nanocrystalline state, a slight reduction of magnetostriction is seen for all alloys, with a maximum of + 32 ppm (4 at% P) and a minimum of + 22 ppm (P-free) in Fe83 at% alloys. The unusual large magnetostriction of optimally annealed samples is attributed to the relatively low crystal volume fraction (30-45%) of nano-crystalline ribbons. The lowest magnetostriction of Fe83B13Si2Nb1Cu1 alloy in both as-quenched and annealed state is explained based on ribbon structural heterogeneity consisting of crystal nuclei and textured alpha-Fe surface crystallization. The study reveals a contradictory response of magneto-crystal anisotropy (grain size reduction) and magneto-elastic anisotropy to the P addition and ribbon structural heterogeneity. The study discusses the implications of the large magneto-elastic anisotropy associated with Fe-rich nanocrystalline ribbons and the way forward for improving their magnetic softness. (C) 2023 Elsevier B.V. All rights reserved

Evaluation of Microstructural and Mechanical Behaviours of Tempered 2.25Cr-1Mo Steel Through Electromagnetic Characterization

The effect of tempering treatment has been investigated on water quenched P22 steel with the chemical composition of 0.13C, 0.24Si, 0.47Mn, 0.012P, 0.005S, 2.19Cr, 0.93Mo and balance Fe (all in wt%) within the temperature ranges of 650–900 °C. The microstructural, mechanical and magnetic properties of as-quenched and tempered steels have been investigated through optical and scanning electron microscopy, hardness and universal tensile testing, electromagnetic sensor (Magstar), respectively. The water quenched sample consists of fine martensitic structure with a hardness of 381 HV. With the progress of tempering, the martensite becomes coarse till 800 °C, decreasing the hardness of steel samples. The tempering at 700 °C results in martensite coarsening and precipitation of rod and globular shaped carbides; while a fraction of globular carbide is observed to increase in the matrix after 750 °C of tempering. Beyond 800 °C, the ferrite and bainite phases gradually form by replacing martensite, and the ferrite structure is prevalent after 900 °C. Due to microstructural changes, the magnetic properties are also affected as a function of tempering temperature. The coarsening of martensite causes the decrease in coercivity with increasing tempering temperature, leading to magnetic softening

Rapidly quenched magnetic materials for functional and sensor applications

Rapidly quenched (RQ) amorphous / nanostructured materials have been addressed in relation to their properties targeted towards potential applications. Quenching techniques like melt spinning and in-water quenching for production of these materials in the form of ribbons and microwires production respectively have been addressed. CoFe-based microwires exhibited interesting giant magneto-impedance (GMI) behviour and was used in development of GMI sensor for detection of carburization in austenitic stainless steel. Efforts have been laid on the production of Fe-based magnetostrictive amorphous ribbons and their potential use in magnetostrictive sensor (MsS) for generation of guided waves for detection of defects in pipes. Compositional tailoring has also been carried out in amorphous / nanostructured ribbons to raise the saturation magnetization beyond 1.6 Tesla. Some of these ribbons have also been found to manifest interesting electromagnetic interference shielding effectiveness (EMI SE) properties