Sulfur Segregation Research Articles

Study on separation of 6–0 mm low rank high sulfur lignite by FGX dry separation bed

ABSTRACT Coal is an essential primary energy for the national economy and people’s livelihood. In recent years, with the rapid growth of the consumption of high-quality coal resources, Lignite with a low degree of metamorphism has been extensively exploited and utilized. In this paper, desulfurization and ash reduction treatment of 6–0 mm fine-grade low-grade high-sulfur Lignite was carried out using a FGX dry separation bed (FGX FGX compound dry separation bed). The migration and distribution of differentiated density particles in the bed under the action of cascade air flow were mainly studied, and the influence of vibration intensity (amplitude and frequency) on the separation effect of fine-grade low-grade high-sulfur Lignite was explored. At the same time, the material distribution characteristics of each section in the direction of the discharge edge of the bed were systematically analyzed, the material distribution area of the bed was determined, the optimal operating parameters (A = 2.8 mm, f = 26 Hz, V = 2.29 m/s) were obtained, and the sorting test was carried out under the optimal parameter conditions. The test results show that when the vibration frequency f = 26 Hz, the sulfur segregation degree of bedding materials reaches the maximum Ss = 0.36, and the sulfur content of materials in I, II, and III regions is 0.85%, 5.47%, and 18.78%, respectively. The stratification effect of bedding materials is the best. When A = 2.8 mm, the material sulfur segregation reaches the minimum value of Ss = 0.28, and the average sulfur content of materials in I, II, and III regions is 0.78%, 5.46% and 18.27%, the material is stratified according to density. When the airflow rate is 2.55 m/s. The stratification effect of bed material is best according to density. The clean coal yield is 69.87%, and the sulfur content is 0.98%. The gangue yield is 30.13%, and the sulfur content is 18.66%. The Ep value of energy deviation is 0.11 g/cm3, which realizes high precision dry desulfurization and upgrading fine-grade, low-grade, and high sulfur lignite.

The high temperature creep and fracture behavior of Inconel 718 produced by additive manufacturing

High-temperature creep tests of additively manufactured (AM) and wrought nickel alloy 718 (IN718) were conducted at 650 °C and 704 °C at stresses ranging from 316 to 819 MPa. The AM alloy had a greater creep strength than the wrought alloy at nearly all testing conditions due to increased volume fractions of γ” in the matrix and carbides at grain boundaries; however, the creep rupture ductility of the AM material was significantly reduced at all testing conditions. Secondary ion mass spectrometry (SIMS) revealed that sulfur segregation, resulting from a lack of Mg in the AM alloy, is the most plausible explanation for the observed ductility loss in AM IN718. Overall, this work focuses on understanding and defining the mechanism of embrittlement in AM IN718.

Superior oxidation resistance of a Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy at 1100–1300 °C

We report a study on the oxidation behavior of Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy co-doped with reactive elements (RE) Y and Hf at 1100–1300 °C. The highly stable eutectic microstructure of γ’/β phases within this alloy contributes to a low coefficient of thermal expansion, thus a low residual stress in the Al2O3 scale. The spinel with a low thickness is formed at the top of Al2O3 scale at 1100 °C due to the low Al diffusion coefficient of γ’-phase and low aspect ratio of β-phase in maze-like eutectic region. As the oxidation temperature increases, the oxidation products transition to exclusive Al2O3 at 1200 °C and 1300 °C, facilitated by the increased Al diffusion coefficient. The Al2O3 scale exhibits a dominated columnar grain microstructure at 1100–1300 °C, suggesting that the inward O diffusion plays more critical role than Al diffusion and thus leads to the low oxidation rate. Besides, the segregation of S to scale/metal interface is inhibited by the uniform RE distribution in the alloy resulting from the fine eutectic microstructure in the alloy. Overall, this alloy exhibits low residual stress in the oxide scale, slow oxidation rate, and the lack of interfacial sulfur segregation, thus contributing to its superior oxidation resistance. The strong oxidation resistance of Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy makes it a potential candidate for advanced oxidation-resistant alloy or coating applications.

Magnetron Sputtering as a Microstructural Screening Tool for Laser Additive Manufacturing: Study on Ni Superalloys

In this work, magnetron sputtering coupled with a heat treatment is demonstrated as a route to obtain surrogate microstructures comparable to those achieved by laser‐based additive manufacturing (AM) for Ni superalloys. Furthermore, this technique is shown to be a novel and efficient way of screening elemental additions with high compositional resolution for AM, without the need for designing and characterizing custom‐atomized powders. Herein, Inconel 718 films are sputtered from both arc‐melted and AM targets to capture any compositional changes and to develop a comprehensive methodology. Films are characterized via electron microscopy techniques to establish similarities between sputtered plus heat‐treated films and bulk AM Inconel 718 microstructures reported in literature. Since Inconel 718 is susceptible to high‐temperature S embrittlement, films were then co‐sputtered with small amounts of Zr or Hf, which are found to facilitate sulfur segregation via nano secondary ion mass spectrometry analysis. Overall, this work highlights how magnetron sputtering plus heat treatment can be leveraged to rapidly screen novel AM microstructures, thereby accelerating the development and deployment of AM materials.

Room temperature magnetron sputtering and laser annealing of ultrathin amorphous sulfur-rich MoSx films

Room temperature magnetron sputtering of an ultra-thin transition-metal dichalcogenide amorphous precursor and subsequent laser annealing-induced phase transformations were investigated for the synthesis of polycrystalline 2H-MoS2 semiconducting thin films. Radio frequency magnetron sputtering of a MoS3.6 target was used to produce amorphous precursors with S to Mo ratios greater than 2:1 on thermally annealed SiO2 substrates, glass, indium tin oxide coated glass, and amorphous boron-oxy-nitride. The influence of working pressure on the MoS2 and MoS3 interatomic bonding arrangements in amorphous MoSx films was explored with x-ray photoelectron spectroscopy. A 248 nm pulsed laser was used for annealing 1 cm2 sized areas of the amorphous precursor in an ambient atmosphere at fluences of 100–450 mJ for 1, 5, and 10 pulses to form a crystalline 2H-MoS2 phase. The role of laser fluence and substrate choice on phase transformation from the amorphous precursor to the 2H phase, as well as the competition between oxidation, elemental sulfur segregation, and ablation is discussed. Hall effect measurements confirmed p-type behavior of the produced semiconducting films and established mobility and charge carrier density characteristics of the laser-annealed films. The feasibility of scalable processing by combining sputtering from sulfur-rich targets and laser annealing for production of p-type 2H-MoS2 ultrathin films on various substrates is presented.

Hot Ductility Evolution Mechanism of Titanium‐Bearing Microalloyed Steels

Titanium‐bearing (Ti‐bearing) microalloyed steels have high strength and toughness by grain refinement effect of carbonitride precipitates. However, they can induce surface cracks of continuous casting slab when the Ti alloyed content is high. A microalloyed steel with Ti content (0.10–0.15 wt%) is carried out by thermalmechanical simulator over 600–1350 °C to analyze hot ductility evolution mechanism. Fracture surface morphology, phase transition, and behavior of precipitates of the tensile samples are investigated by experimental detection and thermodynamic calculation. The ductility–temperature curves show that the third brittle temperature range is 600–890 °C, which is mainly attributed to the thin proeutectoid ferrite film and precipitated titanium carbonitride particles, widening the embrittlement temperature ranges through of steel. In addition, the tensile samples at 890–1350 °C have good hot ductility, indicating the dynamic recrystallization of deformed austenite can trigger grain boundaries migration away from cracks and avoid the side effect of the Ti (C,N) particles on hot ductility. The first brittle temperature range of 1350 °C‐melting point is mainly ascribed to the partial melting of the grain boundaries with element segregation of sulfur and phosphorus, and microporosity loose among dendrites.

Morphological, compositional and phase evolutions in sulfur-rich W-S targets during magnetron sputtering

A sulfur-rich WS2.7 target was manufactured via ball milling of sulfur and tungsten-disulfide powders, followed by sintering. The target morphology, composition, and phase changes induced by sputtering processes were investigated by a number of analytical methods and compared to a stoichiometric WS2 target used as a control. Radio frequency magnetron sputtering of the WS2.7 target was conducted with progressively increasing time intervals, from a few minutes to several hours, where the target was intermittently removed for characterization. Selective sputtering of sulfur within both the control WS2 and the sulfur-rich WS2.7 targets yielded sulfur depletion over the extended sputtering time. Depressions on the target surface formed from the selective sputtering of sulfur, where at the base of these regions developed growth of metallic tungsten dendrites and additional unbonded sulfur segregation over sputtering time. A catalytically enhanced WS2 phase decomposition mechanism was proposed based on detailed analysis of phases and oxidation states from site specific spectroscopic and x-ray diffraction analysis. The observed phenomenological process exemplifies the need for monitoring and maintenance of sulfur-rich sputtered targets in their use for thin film growth.

In situ annealing studies on the microstructural evolution of a macro defect free electroformed nanocrystalline Ni-Co sheet metal and its relation to tensile properties

The effect of annealing at temperatures between 200 – 400 °C on the microstructural evolution and tensile properties of a recently developed macro defect free electroformed nanocrystalline Ni-32at%Co free-standing sheet metal was investigated. The tensile strength of the materials exhibited an extrinsic Hall-Petch (HP) to inverse Hall-Petch (IHP) transition due to grain growth. In situ transmission electron microscopy (TEM) annealing revealed for the first time that at lower annealing temperatures, in addition to reordering of atoms at grain boundaries, grain rotation and grain recovery were also found to be mechanisms for grain boundary relaxation (GBR). Combined, these mechanisms contribute to the increase in ultimate tensile strength (UTS) observed in the IHP regime of the Ni-32at%Co alloy. TEM energy dispersive X-ray spectroscopy (EDX) and in situ synchrotron X-ray diffraction (XRD) annealing analyses showed that the drop in UTS and ductility in the HP regime after annealing at higher temperatures was associated with the onset of abnormal grain growth and sulfur impurity segregation to random high angle boundaries. Atom probe tomography (APT) further showed that there is no sulfur impurity segregation in the electroformed material before annealing. Increasing in annealing temperature led therefore to a transition from ductile to brittle fracture manifested as a change in dimple to mixed and eventually to faceted brittle fracture surfaces at 400 °C.

Corrosion Mechanisms of 304L NAG in Boiling 9M HNO3 Containing Cr (VI) Ions

In this research, the mechanisms of end-grain corrosion of 304L NAG tubes in boiling 9M HNO3-containing Cr (VI) ions are reported to sustainably manage the corrosion of nuclear fuel reprocessing plant components. Specific heat treatments were applied to as-received specimens to produce phosphorus and/or sulphur intergranular segregation. End-grain corrosion on heat-treated specimens and the effect of a Cr (VI) concentration on a 304L NAG tube (as-received) were investigated. It has been reported that an increase in Cr (VI) ions leads to the acceleration of end-grain corrosion due to high electrochemical potential. After systematic heat treatments on the 304L NAG specimens, it is concluded that the primary causes of heat-induced end-grain corrosion are phosphorus or sulphur segregation to the grain boundaries. The key findings of this research are highly significant in terms of understanding the corrosion mechanisms and controlling the end-grain corrosion of NAG steel in boiling HNO3 environments. This research will help to sustainably reduce power plant maintenance costs and will have a significant impact on the delivery of long-term, clean, secure, and tenable energy.

Characterization of precipitation, evolution, and growth of MnS inclusions in medium/high manganese steel during solidification process

MnS as a main manganese-containing inclusion in medium/high manganese steel, which can be determined to the mechanical properties of steel. However, the precipitation and evolution mechanism of MnS in medium/high manganese steel is still unclear due to the special solidification properties and element segregation behavior. Hence, the effects of sulfur content, manganese content and cooling rate on the precipitation, evolution, and growth behavior of MnS inclusions in medium/high manganese are various experimentally characterized and thermodynamically elucidated in the present work. The results of 2D and 3D observation indicated that the morphology of MnS in medium manganese steel were transformed from globular and spindle-like (type I MnS) into large-sized rods (type II MnS) and dendritic (type D MnS), when sulfur content was increased from 78 ppm to 1578 ppm. Particularly, the spatial distribution and structure of MnS inclusions are elaborated in detail through X-ray micro-CT observations, which are discussed by defining the quantitative topography parameters and statistical analysis. Based on in situ CSLM observations, MnS precipitation path in high sulfur medium manganese steel was monitored as L → (L + δ + MnS) → (δ + MnS) → (δ + γ + MnS) → (γ + MnS) → (α + γ + MnS) → (α+MnS). Simultaneously, the Scheil-solidification calculations demonstrated that MnS is precipitated at the interdendritic region where the solid-liquid states are coexisted, which is caused by the segregation of sulfur and manganese. Moreover, increasing sulfur content generates the earlier precipitation, and leads to the significant increase in the number and size of MnS inclusions. Besides, the increase of manganese content promotes the transition of MnS from globular to polyhedral shape, which is attributed to the dissociative eutectic reaction of MnS formation preferentially takes place earlier in case of high manganese steel. It is also found that the decreasing of cooling rate and increasing the manganese content tends to increase the number and size of MnS inclusions, which is resulted from the long growth times of high manganese steel induced by large solid-liquid temperature differences. This work provides a systematic understanding of the precipitation and evolution of MnS inclusions in medium/high manganese steel.

Effect of Mo and Cr on S-Induced Intergranular Fracture in γ-Fe

S is a common corrosion medium for austenitic stainless steels. The severe intergranular fracture of austenitic stainless steels occurs in sulfur environments. In this paper, the permeation of S at different atomic positions for three symmetric tilt grain boundary types, i.e., Σ5(210), Σ5(310), and Σ9(114) have been computed using first-principles calculations. S has the strongest segregation tendency in the Σ5(210) grain boundary. A high content of S at the grain boundary indicates harm to the grain boundary. Sulfur segregation in the grain boundaries can weaken the strength of the metallic bond. When Mo and Cr are present at the Σ5(210) grain boundary, the sulfur-induced embrittlement is inhibited. With increased S concentration at the grain boundary, the coexistence of Mo and Cr can suppress the intergranular fracture of S on the grain boundary. The reason why high-Mo stainless steel has excellent sulfur-induced intergranular corrosion resistance is explained at the atomic level.

Diffusionless α′ to γ transformation and its effect on hot ductility in a high-nickel steel

The role of diffusionless α′ to γ transformation on the microstructure evolution and hot ductility of high-nickel steel is investigated. In-situ Auger electron spectroscopy fracture test reveals the correlation of ductility loss and sulfur segregation at the grain boundary. The α′ to γ transformation start temperature is measured by heating the initial α′-martensite at various rates. The transformation temperature remains constant when the heating rate is higher than 15 °C/s. Despite the α′ to γ phase transformation, the diffusionlessly transformed specimen shows a similar γ grain size with the initial prior γ grain size. The γ grain size decreases dramatically after the continuous annealing of the transformed specimen. The temperature-dependent recrystallization behavior and corresponding hot-ductility are evaluated. The improved hot ductility is achieved by active recrystallization at 900–1100 °C. Due to the late recrystallization behavior, the improvement of hot ductility is limited after annealing at 800 °C. The origin of hot ductility loss and enhancement depending on the thermal cycles is discussed by sulfur segregation at the grain boundary and recrystallization behavior after diffusionless transformation.

An in-situ ToF-LEIS and AES study of near-surface modifications of the composition of EUROFER97 induced by thermal annealing

Surface segregation and diffusion of W, Ta, Cr, O and S after thermal annealing of EUROFER97 were studied in-situ. The sample was prepared by polishing, annealing up to 300°C and 3 keV Ar sputtering. In-situ measurements with time-of-flight low energy ion scattering using 8 keV Ne ions and Auger electron spectroscopy were carried out close to room temperature after each annealing, in sequence, to 425°C, 675°C, 400°C, 675°C, 900°C, and 925°C. Surface segregation/diffusion of chromium and tungsten and/or tantalum can be observed in the ion scattering spectra. The segregation of sulfur was clearly observed in Auger electron spectroscopy. The energy converted time-of-flight low-energy ion scattering spectrum after the first annealing to 675°C was compared to Monte-Carlo simulations using the TRBS code. The most compatible simulation indicates a layer enriched in W + Ta of 1 ± 0.3 nm featuring 0.0276 combined relative concentration of tungsten and tantalum to total metal content which is considerably higher than the bulk value of 0.0042.

Sulfur segregation and inclusion modification in steel using magnesium addition

In order to investigate the effect of magnesium treatment on the distribution and segregation of sulfides in carbon high-sulfur free-cutting steel in industrial tests, scanning electron microscope, energy dispersive spectrometer, electrolysis device, and other characterization methods are used to examine the sulfide morphology in the steel continuous casting billet. The sulfide type, spatial distribution and three-dimensional morphology of the slab in the casting slab are analyzed, and the law of sulfur segregation is calculated and summarized using the diffusion growth model. The results of the study showed that the area of cluster-like sulfides before and after magnesium modification decreased by 6.4%, the area of chain-like sulfides reduced by 6.6%, and the area of single-type sulfides increased by 12.7%. In the magnesium modified steel, a fine composite sulfide with MgO·Al2O3 as the core is formed, which provides a heterogeneous nucleation site for the later precipitated MnS, enhancing the shape and size of the sulfide. The sulfide segregation index was reduced from 1.30 to 1.04 before and after magnesium modification, and the sulfur concentration was 1.56 times the original precipitation when the middle position of the slab was entirely cemented. The macroscopic shrinkage cavity on the surface of the cast slab is minimized after magnesium treatment, which enhances sulfide dispersion and segregation dramatically.

Study on MnS Inclusion Aggregation along Continuous Casting Slab Thickness of Medium Carbon Structural Steel

Precipitation of MnS inclusions in steel affects the mechanical properties of the material significantly. The evolution of MnS inclusions along the continuous casting slab thickness and its influencing factors has not been clearly established and comprehensively studied. In this paper, solidification macrostructure, sulfur segregation and MnS inclusions in the continuous casting slab of medium carbon structural steel 45# were studied by various methods, including the metallographic observations, elemental analysis, scanning electron microscope (SEM) with Energy Dispersive Spectrometer (EDS) observation, automatic particle analysis, and thermodynamic calculations. The 2D/3D morphologies of MnS inclusions suggest that the sulfides turn from globular to rodlike, and further to dendritic shape along the slab thickness progressively. Furthermore, it was found that MnS inclusions are remarkably aggregated in the columnar crystals and the equiaxed crystals mixed zone, where the sulfides have the largest average diameter of 6.35 μm and the second maximum area fraction of 0.025% along the slab thickness. In order to reveal the mechanism of this phenomenon, the precipitation temperature of MnS inclusion in the 45# steel was clarified by thermodynamic calculation and experimental observation, and the quantitative relationships among the distribution of sulfur content, secondary dendrite arm spacing (SDAS), and precipitation area fraction of MnS inclusions were discussed. Moreover, the inclusion size was numerically predicted to compare with the measured value. The results indicate that the large SDAS, high sulfur content and low cooling rate accounting for the large-size aggregated MnS inclusions in the mixed zone. Unfortunately, the dendritic MnS inclusions, even if the average diameter exceeds 52 μm, can act as the nucleation sites for ferrites, and the distribution of the sulfides promotes uneven microstructure in the steel.

Chloride stress corrosion cracking of a non-standard, ‘Borderline’ Chromium-Manganese stainless steel – Problems of counterfeits and substandard materials

Nonstandard chromium-manganese (stainless) steels are gaining popularity nowadays, but data for them are inadequate as the majority of literature is on the ‘pedigrees’ such as the standard 200 series and 300 series steels. This paper begins with a brief overview of the counterfeit problems of such steels. It then presents the slow-strain-rate test results of a chromium-manganese ‘borderline’ stainless steel in room-temperature air, 60 °C NaCl and 60 °C distilled water (the lower-bound temperature for chloride stress corrosion cracking in austenitic stainless steels). At low strain rates (10-6 s−1), grain-boundary segregation of phosphorus and sulphur (especially the latter) can cause intergranular cracking in air and in 60 °C distilled water. In 60 °C NaCl, manganese sulphides may serve as the initiation sites of transgranular cracking. Many producers of nonstandard chromium-manganese (stainless) steels lack impurity control technologies, and so users must be vigilant of this issue. The fracture mode of the ‘borderline’ stainless steel is strain-rate dependent, changing from being mainly intergranular to being transgranular and dimpled as the strain rate goes up. The reason behind this is unclear, but a plausible suggestion is given in this paper.

Two‐stage magmatism and mineralization of Tulaergen nickel‐copper deposit in eastern Tianshan, North‐west China: Evidence from bulk rock geochemistry and in situ mineral chemistry

The Tulaergen magmatic Ni–Cu deposit is related to mafic‐ultramafic rocks of the Central Asian Orogenic Belt. The ore‐host rocks are lherzolite and websterite and the major ore types are net‐textured and sparsely disseminated ores. The disseminated ores host high‐Fo (82–85) olivine and hornblende with low‐Al contents, high‐rare earth element (REE) abundances and negative Eu anomalies. The net‐textured mineralized lherzolite contains low‐Fo (74–82) olivine and high‐Al hornblende, the latter characterized by low REE concentrations and no Eu anomaly. The contrasting composition of olivine and hornblende suggests two stages of magmatism. In situ analysis of pentlandite, chalcopyrite and pyrrhotite shows that platinum‐group elements contents in sulphides are low. Contrasting Ni, Co, Se, Ag, Cd, and Pb contents in sulphides from net‐textured and in disseminated ores also supports two pulses of magmas, each with a distinct chemical composition. High‐Mg basaltic magma characterized the first stage, followed by a second‐stage less basic magma with a high H2O content. Whole‐rock Sr and Nd isotopic signatures suggest that about 4–6% crustal materials were added to the depleted mantle source. The fractional crystallization of olivine and crustal contamination play important roles in sulphur segregation at Tulaergen based on sulphur content at sulphide saturation modelling. Injection of magma enriched in H2O further enhanced sulphide aggregation and deposit forming. It is proposed that two pulses of magma injections occurred at the Tulaergen deposit, with the products of the first pulse settling at the base, and of the second one with dense mineralization laying at the top of the deposit.

The creep and fracture properties of additively manufactured inconel 625

High temperature creep tests of additively manufactured (AM) nickel-based superalloy 625 (IN625) and wrought IN625 were conducted at 650 ˚C and 800 ˚C over the stress range of 65 MPa to 658 MPa. Thermal treatments were conducted for both AM and wrought IN625 samples prior to creep testing: either solution heat-treated or hot isostatically pressed and, additionally, long-term cyclic heat-treatments (LHT) at 650 ˚C for 6 months and 1 year. AM IN625 showed equal or even higher creep strength than wrought IN625 for all heat treatments. However, AM IN625 exhibited poor ductility compared to wrought IN625 under all creep testing conditions, and the ductility decreased after the LHT. Both AM and wrought IN625 obtained some additional strength after the LHT. The amount of extra strength in the alloys was generally proportional to the matrix volume fraction of γ’’ phase (650 ˚C) and δ phase (800 ˚C). The creep analysis suggests that dislocation climb is the rate controlling mechanism for creep. Atomic probe tomography revealed that oxygen content at the grain boundaries of creep-deformed AM IN625 was too small to cause any embrittlement. Nano-secondary ion mass spectrometer analysis found strong sulfur segregation at Al2O3/matrix interfaces. Fracture is intergranular where Al2O3 (that forms as a result of oxygen absorption by the powder particles before additive manufacturing) is sometimes located. Cracking can occur from these interfaces and repeated sulfur diffusion to the crack tip was the foremost possibility to explain the poor ductility of AM IN625 within the temperature range tested.

Origins of a Low-Sulfur Superalloy Al2O3 Scale Adhesion Map

Low-sulfur single-crystal Ni-base superalloys have demonstrated excellent cyclic oxidation resistance due to improved Al2O3 scale adhesion. This derives from preventing deleterious interfacial sulfur segregation that occurs at common ppm levels of S impurity. Multiple hydrogen-annealing desulfurization treatments were employed to produce a continuum of levels demonstrating this oxidative transition, using 1 h cyclic oxidation at 1100 °C for 500 h to 1000 h. The sulfur content was determined by glow discharge mass spectrometry. The complete gravimetric database of 25 samples is revealed and correlated with sulfur content. Maximum adhesion (i.e., no weight loss) was achieved at ≤ 0.3 ppmw S, significant spallation (20–30 mg/cm2) above 2 ppmw, with transitional behavior between 0.3 and 2 ppmw S. A map suggested that adhesion was enabled when the total sulfur reservoir was less than one S atom per Ni interface atom. Equilibrium models further suggest that segregation may be minimized (~1% at 0.2 ppmw bulk), regardless of section thickness. 1st order adhesion effects have thus been demonstrated for PWA 1480 having no Y, Zr, or Hf reactive element dopants and no possibility of confounding reactive element effects. The results are compared with 2nd generation PWA 1484, Rene’N5, N6, and CMSX-4® SLS, all having Hf dopants.

Chemical composition influence on element segregation and properties of steel strip manufactured by strip casting route

The article presents the results of the chemical composition influence on element segregation and properties of steel strip manufactured by strip casting route. It is shown that in the transition from the slab production with a thickness of 220 mm to slabs with a thickness of 1.2 mm, the thickness of the segregated diffusion layer in the case of the continuous strip casting process is 4.1 - 12.4 times less than in the case of traditional continuous casting. The carbon, nitrogen, copper, tin, phosphorus and sulfur segregation percentage in the continuous strip casting process is 1.7 - 5.1 times less than in traditional continuous casting. A method is proposed for calculating the element segregation based on the equality of the segregation level in traditional and strip continuous casting. It has been established that the content of elements in steels during two-roll continuous casting can be increased for impurities such as S, O, N, P, H from a minimum of 3 for P to a maximum of 497% for S. For residual elements such as Pb, Bi, Sn, Cu, Sb, Zn, As minimum increase from 1.1 for Zn to maximum 401% for Pb. The content of such alloying elements as B, Se, Al, Te, Ca, Mg, Ce, C, La, Nb, Ti, Mn, Ni, Si can be increased from a minimum of 1.1 for Si and Mn to a maximum of 675% for B. The time and rate of cooling of a 20-ton coil of steel strip are calculated, which are, respectively, 13.7 hours and 0.0051 oC/s. Such cooling conditions create the prerequisites for the precipitation of chromium carbides and an increase in the tendency of steel to intergranular corrosion. It was found that for eliminate this problem, it is necessary to increase the cooling time with water after rolling to a strip temperature from 300 to 400 oC.