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In this study, a Ni-reduced austenitic stainless TRIP/TWIP steel with < 5 vol.% δ-ferrite was investigated before and after plasma arc welding and gas tungsten arc welding. The 4-mm-thick hot-rolled sheet was produced as hot-rolled heavy plate on an industrial scale and manufactured as longitudinally welded pipes without filler metal. Microstructural characterization was done using light optical microscope and scanning electron microscope with electron backscatter diffraction (EBSD). The microstructure consisted of non-recrystallized austenite with a small amount of δ-ferrite. The welds exhibited skeletal and lacy δ-ferrite morphologies. ε-martensite and α´-martensite were found in the weld seam after pipe expansion. Further, the mechanical properties were evaluated using tensile test. The results showed a tensile strength of 823 MPa with a uniform elongation of 69% at room temperature. The change of hardness in the weld seam was studied for welded pipe, welded expanded pipe and welded, post-weld heat-treated (PWHT) pipe with Vickers hardness testing. The lowest hardness was achieved after PWHT. The corrosion resistance tests were conducted in chloride containing environment. The results showed that the susceptibility to pitting corrosion increased with the degree of deformation. Furthermore, the weld metal and heat-affected zone exhibited local attack whereas the base metal seemed unaffected. [ABSTRACT FROM AUTHOR]

The influence of V2O5 on the phosphorus partition between liquid crude steel and heterogenous basic oxygen furnace (BOF) slag with CaO/SiO2 = 4.2 was investigated at a temperature of 1600 °C in a middle frequency induction furnace. Thereby the phosphorus transfer from "steel to slag" as well as from "slag to steel" was studied over a holding time of 60 minutes. The measured results were shown as phosphorus partition and phosphorus capacity and compared with the experimental values from the literature. It was found that V2O5 in highly basic BOF slags decreases phosphorus partition and phosphorus capacity. In addition, the resulting slags were investigated using a scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

The vaporization of vanadium pentoxide from CaO-SiO2-VOx ternary slags using different gas treatment regimens and parallel vacuum gas extirpation to treat V-bearing slags at 1873 K has been developed in the present study. The novelty of the present study is to monitor the effect of parallel alumina dissolution on the vaporization phenomenon. Vanadium pentoxide has high vapor pressure at the temperatures over 1500 K. When CaO-SiO2-VOx ternary slags, kept in dense alumina crucibles, are injected with oxygen, V2O5 gas bubbles are formed which are forced out by using vacuum extirpation. The vanadium pentoxide could be then collected in the exhaust gases. The mechanism of the process phenomenon is described as the formation of V2O5 gas phase resulting from the oxidation of the lower-valent oxides present in the slag. This gas phase would form microbubbles in the molten slag bulk phase due to low surface tension between the gas phase and the slag, thereby increasing the contact surface. At the same time, the crucible material would dissolve in the slag causing an increase in the slag viscosity. Due to the high slag viscosity of the bulk slag, these microbubbles formed would have difficulty in coalescing and reaching the slag surface. The escaping of the bubbles into the gas phase is enabled by the vacuum extirpation. [ABSTRACT FROM AUTHOR]

Manganese is an important metal for steelmaking. Data on the density of the metal are scarce and show considerable scatter. Present work reports the density of the liquid manganese in the range of 1535 K to 1836 K estimated for the first time with the use of the maximum bubble pressure technique. The obtained density of the manganese is marginally higher than previously reported in the literature. [ABSTRACT FROM AUTHOR]

By time-of-flight (TOF) neutron diffraction experiments, the influence of segregation-induced microstructure bands of austenite (γ) and martensite (α′) phases on the partitioning of stress and strain between these phases was investigated. Initially, tensile specimens of a Co-added stainless steel were heat treated by quenching and partitioning (Q&P) processing. Tensile specimens were subsequently loaded at 350 °C parallel to the length of the bands within the apparent elastic limit of the phase mixture. Lattice parameters in both axial and transverse directions were simultaneously measured for both phases. The observation of a lattice expansion for the γ phase in the transverse direction indicated a constraint on the free transverse straining of γ arising from the banded microstructure. The lateral contraction of α′ imposed an interphase tensile microstress in the transverse direction of the γ phase. The multiaxial stress state developed in the γ phase resulted in a large deviation from the level of plastic strain expected for uniaxial loading of single phase γ. Since segregation-induced banded microstructures commonly occur in many engineering alloys, the analysis of stress and strain partitioning with the present Q&P steel can be used to interpret the observations made for further engineering alloys with two-phase microstructures. [ABSTRACT FROM AUTHOR]

Thermo-physical properties of the liquid metals and alloys play an essential role in modeling and controlling metallurgical processes. In particular, surface tension of metals has a strong impact on wetting various surfaces. Boron is added in numerous iron-based alloys as micro-alloying component. In existing literature, there is no general agreement with the effect of boron on the surface tension. The present study focuses on investigations of boron micro-alloying on the surface tension of iron and CrMnNi alloys by the maximum bubble pressure method (MBP). In contrast to other techniques, maximum bubble pressure technique is less affected by the evaporation of surface-active elements and the purity of the atmosphere around the sample. Measurement of the surface tension was accomplished before and after in situ addition of boron to the molten metal phase. Samples were molten in ZrO2 and Al2O3 crucibles and yttria-PSZ capillaries were used for the experiments. Measurements were carried out at 1550 °C in argon atmosphere and argon as bubbles formation media. Results of the experiments indicate a minor effect of boron on the surface tension of liquid iron. Effect of boron on the surface tension of steels is discussed in the context of other surface-active elements present. [ABSTRACT FROM AUTHOR]

Tempering reactions in the martensite phase of Fe-13Cr-0.47C (mass pct) stainless steel and its Si- and Mn-added modifications were studied by correlative dilatometry and magnetic measurements. Tempering for 5 minutes was performed at sequentially higher temperatures up to 923 K (650 °C). Classical tempering reactions including the segregation of C atoms at defects, precipitation of M3C and Cr-rich carbides, and austenite decomposition were clearly identified. The formation of M3C carbides was partially and entirely suppressed by Mn and Si additions, respectively. Compared to low-alloy steels, the decomposition of retained austenite in stainless steels was delayed to temperatures above 823 K (550 °C). The latter occurred concurrently with the formation of Cr-rich carbides in the martensite. In addition, non-classical tempering reactions such as the partial dissolution of C clusters at temperatures above 573 K (300 °C) and the short-range diffusion of substitutional elements including Cr and Mn to C clusters and M3C carbides in the temperature range of 673 K to 823 K (400 °C to 550 °C) were identified based on the associated increase in the magnetization. [ABSTRACT FROM AUTHOR]

The detrimental effect of nonmetallic inclusions (NMIs) in steels on, e.g., fatigue lifetime is well known. In order to increase the durability and safety of materials and components, inclusion control and a deep understanding of inclusion formation are essential. The present study examines the formation of inclusions as well as their content, type, morphology, and size distribution for different batches of the steel alloy 18CrNiMo7-6 (AISI 4317), which was processed with various refractory crucible materials. To this end, extensive metallographic investigations were carried out including fracture surface analyses, metallographic sections, and the chemical extraction of inclusions. Scanning electron microscopy supported by energy-dispersive X-ray spectroscopy was used alongside electron backscatter diffraction for the qualitative and quantitative analysis of the NMIs. Oxide contents were found to have a significant effect on sulfide precipitation behavior, and had a strong impact on the resulting sizes and numbers of inclusions. The formation and growth of sulfides and oxide-sulfides featuring different morphologies is discussed on the basis of these experimental results. [ABSTRACT FROM AUTHOR]

The influence of chemical composition, temperature, and pressure on the nitrogen solubility of various high alloy stainless steel grades, namely Fe-14Cr-(0.17-7.77)Mn-6Ni-0.5Si-0.03C [wt pct], Fe-15Cr-3Mn-4Ni-0.5Si-0.1C [wt pct], and Fe-19Cr-3Mn-4Ni-0.5Si-0.15C [wt pct], was studied in the melt. The temperature-dependent N-solubility was determined using an empirical approach proposed by Wada and Pehlke. The thus calculated N-concentrations overestimate the actual N-solubility of all the studied Fe-Cr-Mn-Ni-Si-C steel melts at a given temperature and pressure. Consequently, the calculation model has to be modified by Si and C because both elements are not recognized in the original equation. The addition of the 1st and 2nd order interaction parameters for Si and C to the model by Wada and Pehlke allows a precise estimation of the temperature-dependent nitrogen solubility in the liquid steel bath, and fits very well with the measured nitrogen concentrations during processing of the steels. Moreover, the N-solubility enhancing effect of Cr- and Mn-additions has been demonstrated. [ABSTRACT FROM AUTHOR]

Tempering reactions in ternary Fe-2M-0.7C steels (M=Cr, Ni, Mn, Mo, and Si) were studied by correlative dilatometry and magnetic measurements at room temperature. Magnetic measurements were conducted after tempering at progressively higher temperatures. Based on the magnitude of demagnetization in the temperature range associated with the tempering stage I contraction, Mn- and Si-added steels formed the largest and smallest fractions of transition carbides, respectively. Estimation of the magnetization of paraequilibrium cementite indicated that Cr, Mn, and Mo reduced the magnetization while Ni increased it. In the presence of Si, the decomposition of retained austenite and cementite formation were shifted to higher temperatures. At temperatures above approximately 723 K (450 °C), the enrichment of cementite with Mn and Cr significantly reduced the total magnetization. In the Mo-added steel, on the other hand, the magnetization slightly increased implying the formation of ferromagnetic Mo-rich carbides. For the Ni- and Si-added steels, the magnetization remained almost constant indicating minimal redistribution of Ni and Si subsequent to the formation of cementite. The possibility of analyzing the latter redistribution is one of the main advantages of sequential tempering and magnetic measurements at room temperature compared to in situ thermomagnetic measurements. [ABSTRACT FROM AUTHOR]

The dissolution of Cr-rich carbides formed in the martensitic constituent of a 13 pct Cr stainless steel was studied by dilatometry and correlative electron channeling contrast examinations. The dissolution of carbides subsequent to the martensite reversion to austenite was associated with a net volume expansion which in turn increased the dilatometry-based apparent coefficient of thermal expansion (CTE) during continuous heating. The effects of carbides fraction and size on the CTE variations during carbides dissolution are discussed. [ABSTRACT FROM AUTHOR]

Age-hardening of homogenized and cold-rolled invar-based Sn alloys results in the development of continuously-formed (CP) and discontinuously-formed (DP) Ni3Sn2 precipitates. In situ investigation of the DP reaction front (RF) velocity (V) revealed a nonsteady-state behavior upon early aging stages followed by a constant V after prolonged aging. The reason for the initial nonsteady-state behavior was experimentally studied and attributed to the reduction of matrix Sn-supersaturation ahead of the DP RF as a result of the simultaneous CP coarsening (in homogenized specimen) or the CP increased volume fraction (in cold-rolled specimen). A similar trend of V variation in the homogenized specimen was obtained after the modification of the original Hornbogen model for the nonsteady-state DP growth kinetics. In general, variations of the transformed matrix fraction via the DP reaction suggest the faster kinetics of this reaction in cold-rolled specimen as compared to the homogenized one due to the existence of more nucleation sites induced by the cold deformation. [ABSTRACT FROM AUTHOR]

Today, MgO-C bricks are widely used in steel industry due to their excellent resistance to slag corrosion and thermal shock increased particularly by the carbon content. The presence of carbon makes these bricks very susceptible to oxidation, leading to a reduction of the strength and to the penetration of metal and/or slag. The aim of this paper is to investigate the processes of carbon oxidation of MgO-C commercial bricks containing 7 and 14 pct C by both isothermal and non-isothermal methods. The results show that carbon oxidation of the samples is limited by diffusion through the pores only. If the carbon content does not have a greater influence on the oxidation process at lower temperatures, then at higher temperatures the weight loss increases with increasing carbon content. Both types of commercial bricks oxidize directly in a lower temperature range and indirectly at higher temperatures. That means that the indirect oxidation does not exist alone, but is initiated by direct oxidation of carbon. Activation energy and diffusion coefficient for different bricks have been determined and compared with literature data. The results of the investigation of the non-isothermal carbon oxidation show that for one and the same final thermal state of the refractory the carbon oxidation can be essentially minimised by choosing specific heating-up rates. [ABSTRACT FROM AUTHOR]

The melting of steel scrap in high temperature liquid iron melt is investigated by conducting cold model experiments of the melting of ice sample of different geometries and sizes in an argon-stirred vessel containing water. The melting process of ice samples is observed using a high-speed camera. Design of experiments is based on similarity criteria. The relationships between non-dimensional groups related to heat transfer (Nu, Re, Pr, and Gr) are derived for different experimental conditions. The results are compared with those reported in the literature. The heat transfer coefficient is estimated as a function of mixing power and is found to be in good agreement with the calculated values obtained by using reported relationships in literature. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]