Cast Steel Research Articles

Influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags for casting of high-Ti steel

In the current study, the influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags was discussed through the measurement of viscosity-temperature relationship, melting temperature, crystallization temperature, crystallization rate and phases, and Raman spectrum. With the substitution of SiO2 by TiO2 in slags from 0 % to 12 %, the viscosity at 1300 °C, the melting temperature and break temperature decreased and then increased, while those of slags with the substitution of CaO by BaO from 4 % to 16 % decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, crystallization phases gradually changed from cuspidine (Ca4Si2F2O7) to perovskite (CaTiO3), the initial and complete crystallization temperatures had the tendency to increase from 918 °C to 1260 °C and from 857 °C to 1139 °C, respectively, and the overall crystallization ability of slags increased. With the substitution of CaO by BaO from 4 % to 16 %, the initial and complete crystallization temperature of these slags decreased, and the overall crystalline ability decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, structural units changed from the simple units to complex units, but the transition was opposite with the substitution from 10 % to 12 %, which was related to the transition of TiO2 from basic oxide to amphoteric oxide. With the substitution of CaO by BaO from 4 % to 16 %, the degree of polymerization and the viscosity of theses slags decreased, which was related to the supplement of more active O2− ion from BaO. Hence, the excessive substitution of SiO2 by TiO2 under the steel-slag reaction would cause the increase of the slag viscosity and crystallization ability, while the substitution of CaO by BaO could weaken the variation of slag viscosity and crystallization ability.

Suppressing interfacial reactions and burn-on defects in sand casted 13Cr9Mo1VNb steel castings. Part I: a novel MgO-chromite hybrid material

Addressing the significant issues of sand burn-on defects and interfacial reaction in sand casted 13Cr9Mo1VNb steel castings, which notably compromise the quality of the steel castings, remains a persistent challenge. The interfacial behaviors between the novel mixed sands and the steel grade were investigated under various sands. The sintering behavior of the sands was also studied without liquid steel at various holding time. In the absence of the influence of molten steel, sintering of mixed chromite-MgO does not undergo solid-solid reaction, with no detected presence of liquid phase and 2MgO·SiO2. The mixed sands undergo sintering reactions upon contact with molten steel, yet no liquid phase is detected. This is primarily attributed to the chemical reaction between MgO and the liquid phase, resulting in the formation of forsterite, leading to the near-complete liquid phase consumption. Magnesia grains can suppress the liquid phase sintering of chromite by 13Cr9Mo1VNb, thus weakening its sintering performance. The presence of 2MgO·SiO2, which exhibits excellent resistance to slag (liquid phase) and steel liquid corrosion, impedes the rising of the liquid phase. Consequently, this reduces the thickness of the adhesive layer and suppresses metal penetration. The production of 2MgO·SiO2 diminishes with the escalation of MgO addition, which increases adhesive thickness and metal penetration as the magnesia content rises. Within the scope of this study, the incorporation of 20 % MgO is suggested to mitigate burn-on defects, which may represent an advantageous selection.

Agglomeration behaviors of different types of complex TiN inclusions in high titanium wear resistant steel

Large-sized titanium-containing inclusion clusters seriously affect the continuous casting and performance of high titanium wear-resistant steel. In the current work, thermodynamic calculations were firstly conducted to predict the formation of various complex TiN inclusions, viz, TiOx-TiN, Al2O3–TiN and LaAlO3–TiN. Based on that, laboratory-scale experiments were designed to prepare samples containing a single type of complex TiN inclusions. The agglomeration characterizes of different complex inclusions were compared by combing in-situ observation based on confocal laser scanning microscopy and Newtonian motion equation. Furthermore, the Kralchevsky-Paunov model was used to study the influences of density and size on the agglomeration behavior of complex TiN inclusions. The result shows that the attractive force between TiOx-TiN complex inclusions increases from 1.93 × 10−18 to 4.34 × 10−17 N, while it was 3.41 × 10−17 to 5.12 × 10−16 N for Al2O3–TiN complex inclusions and 6.42 × 10−18 to 1.14 × 10−16 N for LaAlO3–TiN inclusions. Based on the experimental results and theoretical calculation, the agglomeration tendency of Al2O3–TiN is the strongest due to the considered size and compared to the TiOx-TiN inclusions, the stronger agglomeration tendency of LaAlO3–TiN ones can be attributed to their higher density.

An in-situ investigation on the microstructure and viscosity characteristic of mold flux during slag-metal reaction process

The slag-metal reaction during the continuous casting of high Al steel changes the molten slag structure from silicon-oxygen to silicon-oxygen-aluminum network structure, greatly affecting the viscosity properties of mold flux. In order to reveal the internal mechanism of the viscosity change during slag-metal reaction, the molecular dynamics simulation was employed to monitor the microstructure evolution characteristics of molten slag under different Al2O3/SiO2. The results showed that Q3Al decrease from 25.48% to 22.26%, Q4Al and Q5Al increase from 68.82% and 1.70% to 71.26% and 2.88%, respectively with an increase of Al2O3/SiO2 from 0.1 to 1.2. The [AlO4]5- tetrahedral structure changed from low coordination to high coordination structure, the degree of polymerization increased, and the viscosity increased. The viscosity calculated by molecular dynamics is in good agreement with the experimental measurement. Finally, A dynamic link model between structural transformation and viscosity was innovatively established.

Advanced Lightweight Structural Materials for Automobiles: Properties, Manipulation, and Perspective

The key drivers for automotive manufacturers to develop vehicles with decreased weight are the growing requirements for improved fuel efficiency. This endeavor not only tackles the issues related to fuel efficiency but also aligns with the objectives of enhanced recyclability and overall performance of the vehicle, encompassing factors like driving efficiency, braking characteristics, and collision safety. Herein, a successful strategy entails investigating and utilizing lightweight materials with superior performance as substitutes for conventional automotive materials such as cast iron and steel. This article provides a thorough analysis of the lightweight materials that are currently being researched and available for use in the production of next-generation cars. These materials include composites, light alloys, high-strength steel, and other innovative materials. The review covers all aspects of the life cycle of automotive materials, examining their mechanical and physical characteristics, production processes, characterization strategies, and their uses. Both the merits and limitations of these materials are analyzed, leading to a nuanced understanding of suitable scenarios for their application. In anticipation of future challenges, the study suggests that advancements in versatile materials or enhancements in manufacturing and treatment techniques hold promise for overcoming potential obstacles, ultimately facilitating the creation of more capable, safer, durable, and environmentally friendly vehicles.

Field monitoring and modelling of sediment transport, hydraulics and hydroabrasion at Sediment Bypass Tunnels

Sediment Bypass Tunnels (SBTs) are proven to be an effective measure to reduce or even stop reservoir sedimentation by bypassing sediment laden flows around reservoir dams to the downstream river reach. They are mostly used in Switzerland, Japan, and Taiwan. However, hydraulic and sedimentological operating conditions and the resistance of the invert materials against hydroabrasive erosion affect their cost-effectiveness. Hydroabrasion is a pressing issue at SBTs, other hydraulic structures and steep bedrock rivers exposed to high sediment transport rates under supercritical flow conditions. The present study was therefore conducted to address this issue by aiming at improving knowledge on abrasion mechanics and calibrating a mechanistic saltation abrasion model enhanced by Demiral-Yüzügüllü (2021). To this end, the abrasion resistance of fourteen different invert materials installed at Solis, Pfaffensprung and Runcahez SBTs in Switzerland was quantified by annual 3D laser scanning and the hydraulic conditions and sediment transport rates were regularly monitored between 2017 and 2021. The analysis of invert scans and hydraulic conditions revealed that Prandtl’s first and second kinds of secondary currents occurring in the bends and straight sections of the SBTs, respectively, and the observed abrasion patterns were strongly interrelated. The tested potassium aluminate cement and steel fibre concretes, granite, cast basalt and steel plates had better abrasion resistance against impact of sediment-laden flows compared to other materials. Sediment mineralogical composition i.e., bulk hardness relative to the invert material properties significantly affected hydroabrasion. The enhanced abrasion prediction model was calibrated with the present data and a quasi-constant abrasion coefficient of kv = (4.8 ± 2.2) × 104 was obtained. The enhanced model is well-suited for both laboratory and field scales. The present findings will contribute to the sustainable utilization and operational safety of hydraulic structures, optimization of SBT and reservoir operations regarding bypassing efficiency and reservoir lifetime and modelling of bedrock river erosion.

Irregular initial solidification by mold thermal monitoring in the continuous casting of steels: A review

Irregular initial solidification by mold thermal monitoring in the continuous casting of steels: A review

A new hybrid local radial basis function collocation method for 2.5D thermo-mechanical modelling of continuous casting of steel

This study presents a new strong-form meshless method to solve the thermo-mechanical problem of the solidification process in the continuous casting of steel. A two-dimensional slice that travels in the casting direction is modelled in the Lagrangian system. The newly developed mechanical model is one-way coupled to the thermal model, where the heat flux due to the mould, sprays, rolls and radiation are imposed to solve heat transfer in the strand. The resulting temperature and metallostatic pressure govern the Norton-Hoff visco-plastic model used for computing shrinkage of the solid shell and induced residual stresses. The results are used to estimate critical areas susceptible to hot-tearing formation. The mechanical model uses a generalised plane strain assumption that includes linear strains perpendicular to the slice and enables the computation of the straightening of the strand. The thermo-mechanical model is spatially discretised with a local radial basis function collocation method (LRBFCM). The mechanical part includes a new hybrid method that combines LRBFCM with finite differences for increased stability. The presented work shows how the developed model is used to assess the impact of casting velocity on the solid shell shrinkage and the probability of hot-tearing occurrence in the continuous casting of square billets.

Visualization of inclusions in a water model for continuous casting of steel

With the water model, we experimentally confirmed the possibility of using a suspension to imitate the molten casting powder (slag) at the upper edge of the melt during the continuous casting of steel. The project requires that the slag particles do not leave the suspension layer during operation or that they return to it from the molten steel. It turns out that this is possible if the selected suspension particles mimic sufficiently large inclusions in the real system. The imitation of slag particles in a real system with suspension particles in water model is ensured by the equal terminal flotation velocities of both. Among the discussed polyethylene and cork particles, only cork particles, with a size of 0.2 mm to 0.5 mm, and a density of around 400 kg/m3, meet this condition. It was shown that the presented methodology could be used to estimate the proper position of the submerged entry nozzle.

The durability increasing of high-wear cast parts of mining and processing equipment

The analysis of the operation of rapidly wearing parts of the ore-grinding equipment was carried out. It has been established that unloading grates and ladles are fast-wearing parts of layered fracture mills and determine their downtime between repairs. The possibility of improving the mechanical properties of medium-carbon steel 40HL due to the reduction of harmful impurities is shown. The effects of modification with aluminum, vanadium, calcium, and rare earth metals on structural formation, mechanical, and operational properties of steel are investigated. It was established that the complex modification of cast steel 40HL (0.04…0.1% vanadium, 0.15% silicon calcium and 0.15% rare earth metals) allows to significantly increase its mechanical properties and wear resistance. The separate and joint influence of aluminum, vanadium, calcium and rare metals on the austenite grain size and hardening of steel was studied. The proposed modification technology makes it possible to obtain a fine grain, through-hardening of castings and ensure reliable and long-lasting operation of ball mills.

Research on the Seismic Performance-Based Design of Cast Steel Joints Based on the Capacity Spectrum Method

Research on the Seismic Performance-Based Design of Cast Steel Joints Based on the Capacity Spectrum Method

Insulating refractories based on rice husk ashes functionalized by flame-sprayed alumina coatings for steel ingot casting

This study investigates a new insulating refractory material based on rice husk ashes (RHA) for its application in the steel ingot casting process. The excellent insulating properties of this material may improve heat- and energy balance during ingot casting. A flame-sprayed alumina coating is applied to provide chemical inertness of the substrate material against the steel melt. The refractoriness, oxidation resistance, phase evolution and thermal expansion of four different grades of RHA materials and phase evolution and thermal expansion of flame-sprayed alumina coatings are studied. The refractoriness of the RHA materials increased with increasing silica content, showing sufficient refractoriness up to 1600°C for SiO2>94wt%. Immersion tests with composite materials made from RHA substrate and a flame-sprayed alumina coating were successfully performed in a steel casting simulator. No deformation of the substrate material nor spalling of the flame-sprayed alumina coating was observed despite an immersion without preheating.

Ultrasonic wave propagation analyses in centrifugally cast stainless steel using solidification grain structure models

Several components of nuclear power plants are made from cast austenitic stainless steel (CASS) because of its high corrosion resistance and strength. CASS that is centrifugally fabricated in a rotating mold is used in primary coolant piping. In-service inspection based on ultrasonic testing (UT) has to be conducted for primary coolant piping in accordance with fitness-for-service codes. However, a high-accuracy evaluation of flaws in CASS components through UT is difficult because the ultrasonic waves are scattered and attenuated by the coarse grains, and the ultrasonic beam is distorted by the anisotropy resulting from the grain orientations. Some works have attempted to improve UT capability for CASS components. For more improvement, it is essential to understand how ultrasonic waves propagate in the solidification structure of CASS. Numerical simulations are a useful and reasonable way for this purpose. The simulation model should account for a three-dimensional grain structure. In this study, we prepared three different models of solidification structures for centrifugally CASS, and we fed these structures into an explicit finite element model to simulate the propagation of ultrasonic waves. Afterward, we compared the simulated wave propagations with those measured by a laser Doppler vibrometer to determine an appropriate model that showed good agreement between the simulated and experimental results.

ДІАГНОСТИЧНИЙ МЕТОД КОНТРОЛЮ МЕХАНІЗМУ КОЛИВАНЬ КРИСТАЛІЗАТОРУ МАШИНИ БЕЗПЕРЕРВНОГО ЛИТТЯ ЗАГОТОВОК

Diagnostic devices for monitoring the oscillation mechanism of the mold can increase the stability of steel casting on a continuous caster. The amplitude of crystallizer oscillations is expressed as a sum of harmonic oscillations with different frequencies and is described by the Fourier transform. Wear of the crystallizer sleeves occurs in the lower part. Constant diagnostic monitoring of the state of the crystallizer swing mechanism will increase the durability of copper sleeves. Recommendations for increasing the durability of copper sleeves are provided.

Composite castings based on ferrous alloys reinforced by ceramic spatial structure

A method is presented for manufacturing composite castings that are reinforced by ceramic preforms that have a porous spatial structure. The ceramic preforms were made from oxide ceramic in the form of ZrO2 and Al2O3. Composite castings were produced using the pressure-less infiltration method of ceramic preforms with cast steel (CS) and high-chromium cast iron (HCCI). A chemical analysis indicated the positive role of Cr, which promoted a physiochemical interaction between the matrix and the phase reinforcement. The hardness of each of the composite zones was higher by at least 150–350 HV0.1 as compared to the base alloys. The presence of the ceramic phase in the microstructure of the composite zones resulted in improved wear resistance of up to 20%.

A mathematical mould model for transient infiltration and lubrication behaviour of slag in a steel continuous casting process

The transient infiltration and lubrication behaviour of slag during continuous casting of steel is important for billet quality. A two-dimensional coupled mathematical mould model was developed to investigate these phenomena. The accuracy of the model was verified by comparing the calculated slag consumption with measurements by the plant. The results show that the liquid slag is consumed from the middle and late period of positive strip time to the next early period of positive strip time, including the entire negative strip time. The maximum downward infiltration velocity and positive pressure in the slag channel is at the middle of the negative strip time. Increasing the positive pressure of the slag channel is conducive to lubrication. The shear stresses acting on the shell surface and at the mould side were determined by the lubrication slag consumption and total slag consumption, respectively, and gradually decreased with increasing slag consumption. The negative strip time was lengthened to increase the slag consumption and prolong the time near the maximum downward shear stress, so as to be conducive to the demould.

Wear Behaviors of the Surface of Duplex Cast Steel after the Burnishing Process.

Duplex steel and cast steels have a wide range of applications in many industrial sectors, for example, oil extraction, printing, petrochemical industry, energy-exhaust gases desulphurization systems, seawater desalination plants, and the shipbuilding industry. The machine elements can be produced with different techniques, which determine the operational properties. A material with the same chemical composition made as a casting will have worse mechanical properties than, for example, a forged element. This depends on the microstructure, its fragmentation and its morphology. However, the costs of casting are lower than, for example, forging, and, in addition, not all shapes obtainable in the casting process can be made using metal-plastic working methods. This article presents research results concerning the influence of the burnishing process on the properties of the duplex cast steel surface layer. The purpose of the research was to verify the impact of static pressure roller burnishing (SPRB) parameters on the wear of the surface layer of duplex cast steel. The subject of the research was cast steel in the GX2CrNiMoN22-5-3 grade-according to PN-EN 10283:2019-that was burnished using 15 variants of technological parameters. Then, the samples were subjected to surface wear tests using the INSTRON 8874 device. On the basis of the observed wear appearances, the acting wear mechanisms are defined and evaluated according their contribution to the wear behavior. Detailed information about the wear phenomena will help industries to minimize their maintenance losses related to surface wear. The possibility of shaping surface properties by mechanical burnishing is part of the current direction of surface engineering development. This technology, combined with a high-potential material such as duplex cast steel, makes it possible to increase wear resistance.

Stress-strain state of ceramic shell mold during formation of spherical steel casting in it. Part 1

Stress-strain state of ceramic shell mold during formation of spherical steel casting in it. Part 1

Iron and Steel Castings and Core Production Results from Finer Grades of Chromite Sand in Shell Applications

Iron and Steel Castings and Core Production Results from Finer Grades of Chromite Sand in Shell Applications

Development of geometry-driven quantitative prediction for shrinkage porosity in T-junction of steel sand castings

Shrinkage porosity poses a significant challenge in metal casting processes, impacting both productivity and energy efficiency, especially when dealing with components that are not accepted or reprocessed. Addressing this issue requires proactive measures, and predictive techniques play a crucial role in minimizing its occurrence. Among these methods, the Criterion Function stands out as a valuable empirical model extensively explored in the literature. By intricately linking solidification processes to the development of shrinkage porosity, the Criterion Function leverages key process parameters, including thermal gradient, molten metal velocity during solidification, and cooling rate, to offer predictive insights into the location and presence of porosity. However, a criterion function is needed that also considers the effect of geometric variations as well as the size of the defect (shrinkage porosity). In this study, a casting with three T-joints was taken as a benchmark shape to develop a geometry-based quantitative prediction model for plain carbon steel castings. Real experimental results were combined with solidification simulation results to produce reliable data, which were then used to extrapolate the results. The developed quantitative prediction model, which includes the effect of geometric changes, has been validated and proven effective in predicting shrinkage porosity.