Cast Steel Research Articles

Stress Analysis of Maraging Steel Differential Gear using ANSYS

Abstract: The main purpose of this project paper is to focus on stress analysis of differential gear. For power transmitted from the engine to the rear wheels the differential gear is used. In a Vehicles, the differential gear provides equal power to all drive wheels while allowing each driving wheel to turn at a different angle and different velocity. Basically, while turning around corners, wheels of an automobile spin at differing velocity. Differential gears fails when tooth tension exceeds its safety limit. Therefore, the maximum capacity at the specified load should be determined. Gears analysis is done to minimize stress on gear teeth and prevents the gear to failure. The purpose of this project is to compare the results obtained on different materials (i.e., Maraging steel, aluminium alloy, cast steel) and achieve a suitable material for Differential Gear without any failure using ANSYS and Solid Works software.

Influence Factors of SEN Clogging of Rare‐Earth Steel Continuous Casting and Solve Ideas of Japanese Steel Enterprises

The clogging behavior of submerged entry nozzle (SEN) is the main reason restricting the continuous casting of steel, which seriously affects the application and popularization of rare‐earth (RE) steel. Through literature analysis, herein, the main influencing factors and mechanism of RE steel continuous casting immersion outlet clogging, and sorts out the main ideas and practices of relevant Japanese enterprises in solving SEN clogging in recent years, are summarized, mainly including the following: 1) optimizing SEN materials to reduce nozzle clogging reactions; 2) using Ar‐blowing SEN; 3) applying electromagnetic field to eliminate charge and inhibiting clogging reaction; and 4) and regulating the composition of molten steel to reduce the possibility of clogging, etc. The combination of these advantages and measures is a feasible way to solve the nozzle clogging of RE steel continuous casting nozzle.

Flame-sprayed alumina molten metal filters for dead-mould casting application

Ceramic foam filters are applied to remove non-metallic inclusions during steel melt filtration. The flame-spray technology can contribute to improving such filters by increasing the deposition capability of inclusions and decreasing the impairment of the filter substrate by the steel melt. This makes them suitable for application to the continuous steel casting process and foundry casting. The ball-on-three-balls test was utilized at elevated temperatures to determine the high-temperature behaviour of thermally sprayed alumina. Additionally, the flame-spray technology was used to produce carbon-free filters composed of flame-sprayed alumina by coating and burning out the Al2O3–C filter substrate during a sintering step. The B3B revealed a ductile behaviour with increasing temperature and a bending strength of 23.28 MPa at 1400 °C. After sintering at 1400 °C, the filters showed a sufficient CCS of 0.16 MPa, which allows the performance of casting tests (immersion and pouring) with molten steel at 1580 °C.

THE INFLUENCE OF CHEMICAL COMPOSITION, HEATING TEMPERATURE AND COOLING RATE ON THE FORMATION OF STRUCTURAL COMPONENTS OF STEELS

Problem statement. The formation of structural components starts with the hardening of steels. Therefore, it is important to investigate the influence of chemical composition, temperature of additional heating and cooling rate of the melt on the formation of structural components of steels. The purpose of the research – to compare the influence of the chemical composition, heating temperature and cooling rate on the formation of structural components in steels. Methods. To determine the features of the structural state of steels, we use microstructural analysis, X-ray microanalysis, X-ray diffraction method and surface etching of specimens with nital and hot solution of sodium picrate. Results. In the work, a study of steel specimens with different carbon, manganese and silicon content was carried out. We compared the structural state of steel in the cross-section of continuous cast steel billet and steel of a similar chemical composition after additional heating above the liquidus line at 50 °C, 150 °C and cooling at rates of 10–104 °C/s. Scientific novelty. It was found that in the process of manufacturing of continuous cast steel billets, when cooling in a crystallizer at the rate of ~104 ºС/s in the surface zone of the billet of steels with a carbon content of ≥ 0.5 wt.%, manganese ≥ 0.75 wt.% and silicon ≥ 0.45 wt.% the δ-ferrite formation and γ-iron dendrites formation from the melt are completely suppressed. For the first time, the effect of heating temperature above the liquidus line up to 150 °С and cooling rate of 10–103 °С/s on the structure formation of experimental carbon steels was investigated. It was established that additional heating above the liquidus line and cooling at rates of 102–103°C/s almost completely inhibits the formation of ferrite along the grain boundaries, enhances formation of a more uniform structure, an increase in the dispersion of structural components, simultaneous solid-solution and dispersion hardening of steel, and improvement of mechanical properties of steels. In addition, a decrease in the volume fraction of the areas containing liquation elements (manganese and silicon) was observed. The areas were distributed more evenly, which suggests that there could be a decrease in the difference in the content of chemical elements, compared to the condition without additional heating of the melt. Practical value. The use of the obtained results could allow to develop technologies for obtaining steels with a more uniform structure.

Pseudo‐dynamic hybrid simulations of steel eccentrically braced frames equipped with cast steel replaceable modular yielding links

AbstractPrevious studies have underlined the importance of establishing a database of high‐fidelity benchmark experimental test results under random loading histories such as earthquake excitations for both existing structural systems as well as newly proposed ones. Such experimental results are useful for understanding the limitations of previously developed numerical models, proposing new numerical models for more recently developed structural systems, better assessing the ultra‐low cycle fatigue (ULCF) life of energy dissipative components, and improving the loading protocols used for element assessments or developments of numerical model. This paper presents experimental results from pseudo‐dynamic hybrid simulations on steel eccentrically braced frames (EBF) equipped with novel cast steel replaceable modular yielding links. The first set of experiments are carried out on a four‐story EBF, with the first‐floor yielding link physically tested in the laboratory. The second set of experiments are performed on a two‐story EBF where the second‐floor link is physically tested in the laboratory, while considering axial loads due to the imbalanced distribution of the seismic weight in the building. Each building structure is subjected to three Maximum Credible Event (MCE) level earthquakes. A framework for performing hybrid simulations on EBFs is proposed where the response of the yielding link is physically captured in a single degree of freedom control system, with or without axial loads. A substructuring strategy is proposed in conjunction with a modeling approach in the integration module. The results confirm the effectiveness of the hybrid simulation framework, which can be adopted in similar studies. Two numerical models are proposed for capturing the response of cast steel links using a simplified and a more advanced approach. The models are first calibrated using incremental reversed‐cyclic experimental test results, and then refined using the hybrid simulation test results. The effects of this calibration improvement are quantified through critically comparing the response prediction for different response parameters before and after improving the calibration with the experimental results. The numerical model which captures the physical mechanism of the cast steel links provides a more accurate response prediction compared to the simplified numerical model using a phenomenological truss with calibrated force‐deformation. The remaining ULCF life of the tested yielding links is experimentally investigated after having sustained three MCE level earthquakes, which indicates a large reserve ductility capacity which is more than twice the required plastic rotation capacity for cast steel links after seismic events.

A Novel Dual Receiver–Storage Design for Concentrating Solar Thermal Plants Using Beam-Down Optics

Advanced power cycles—such as the supercritical carbon dioxide (sCO2) cycle—have the potential to reduce the levelized cost of energy (LCOE) of concentrated solar thermal power (CST) plants by significantly boosting their overall solar-to-electric efficiency. To successfully integrate these cycles into CST plants, the industry may need to transition away from liquid working fluids (e.g., synthetic oils and molten salts) to solid and/or gaseous heat transfer media, which are more stable at high temperatures. To address this challenge, this study investigates a novel rotating receiver–storage unit that could enable high-temperature CST plants. A validated numerical model is presented for the charging and discharging processes of the proposed design. It was found that with cast steel as the storage medium in the proposed design, it is possible to achieve >70% receiver efficiency for operation temperatures of 850–1000 K. The overall plant model shows this design is best for relatively small CST systems as modularized units of 10 m diameter (reaching an energy density around 80 kWh/m3), which can be used to drive a 5 MWe sCO2 CST plant. These findings suggest that such a design would have up to 9 h of storage and could be effectively employed as an efficient peaking plant.

Hot-rolled Al-added medium Mn steel (Fe-8Mn-2.85Al-1Si-0.2C): Microstructural evolution and tensile behavior

In this study, a low Al (<3%) added medium manganese steel has been developed through melting casting route in an open-air induction furnace. The cast steel ingot has been intercritical annealed at 720 °C after hot deformation, that includes hot forging and hot rolling treatment, respectively. Microstructure characterization coupled with X-ray diffraction (XRD) has been performed after each processing step to understand the extent of austenite formation and its subsequent transformation to ferrite/martensite. The processed steel possesses the ultimate tensile strength, yield strength and ductility of 1000±20 MPa,700±10 MPa and 18.5 ± 0.5, respectively. To understand the possible cause of enhanced strength and deformation mode rietveld analysis has been carried out. It reveals that developed (final processed) steel possesses ∼18% (volume%) of austenite that subsequently reduced to ∼6.139% after tensile testing, indicating significant transformation of austenite to martensite (continuous and enhanced TRIP effect). The morphological characteristic of martensite in developed steel has been investigated using transmission electron microscopy (TEM). It reveals lath morphology of martensite due to low carbon content. The TEM and 3D atom probe analysis reveals the precipitation of intergranular type kappa (k) carbide in intercritically annealed specimens due to probable segregation of C and Al. However, volume fraction of the same is low. The SFE of the steel has been found to be ∼16 mJ m− 2, calculated by the modified Olson and Cohen method that also concludes TRIP is the preferred deformation mechanism in the developed steel.

Influence of thermal diffusion treatment on microstructure evolution and corrosion behavior of hot-dipped Al coated Fe-Cr-Si-B cast steel

The influence of thermal diffusion treatment on the microstructure and corrosion behavior of hot-dipped Al coated Fe−Cr−Si−B cast steel in a 5 wt.% NaCl solution was studied. The results showed that the product obtained from the interfacial reaction between the Fe matrix in Fe−Cr−Si−B cast steel and molten Al was FeAl3 with a columnar crystal structure. Periodic layered structures at the (Cr, Fe)2B/Al interface were formed during the subsequent thermal diffusion treatment but not hot dip aluminizing. The corrosion behavior of the residual Al layer predominated that of the hot dip aluminizing and thermal diffusion treatment coatings over a short duration till the Al topcoat was consumed completely. Localized corrosion caused by Cl− preferentially began from the block-like B−Al−Cr phase/FeAl3 interface and propagated along periodic layered structures. The Si particles acted as a cathode and promoted the corrosion of the coating. The steel substrate retained its cathodic protection until the Fe−Al intermetallic compounds layer was corroded completely. Additionally, the corrosion in the NaCl solution at an elevated temperature was greatly accelerated.

Effect of zirconium and niobium on the microstructure and mechanical properties of high-strength low-alloy cast steels

The aim of this work is to study the effect of zirconium and niobium on the refinement of grain size and mechanical properties of micro-alloyed cast steels in heat treated conditions. Five micro-alloyed cast steels with different compositions, as steel without microalloying elements and micro-alloyed steel with (i) 0.05% Zirconium (Zr), (ii) 0.05% Zirconium (Zr) and 0.05% Niobium (Nb), (iii) 0.10% Zirconium (Zr), and (iv) 0.10% Zirconium (Zr) and 0.10% Niobium (Nb) were investigated. The heat treated samples are normalized at 1000 °C followed by air cooling and were characterized to study the characteristics of carbide precipitates by SEM and TEM and mechanical properties were evaluated by tensile test as per ASTM A370. Among these five cast steels, steel containing 0.10% Zr and 0.10% Nb showed a higher tensile strength of 1184 MPa and yield strength of 740 MPa with reasonable impact energy of 42 J compared to other steels under the same heat treated conditions. Due to the combined addition of Zr and Nb elements in the micro-alloyed steel, a remarkable improvement of mechanical properties particularly strength and impact energy was observed. As evident from microstructure investigation, these improved mechanical properties in the present steel could be attributed due to the effective refinement of ferritic grain size in the normalized condition.

Modeling of oxide inclusions in steel casting

A model is presented that predicts the amount and location of oxide inclusions in steel castings. A number and size distribution of inclusions, defined about a mean diameter, enters the casting system at its inlet during the filling process and are transported to their final locations in the casting. Model parameters for inclusion density, drag and wall friction are used to calculate the motion and locations of the oxide particles. Model results are presented to study the effects of casting shape and surface orientation on the final inclusion locations and distributions within castings. These results are compared with inclusion tracking experiments where the geometry of the gating system and orientation of casting cope surfaces affect the final distribution of inclusions in the castings. Measured and simulated inclusion area percent coverage, inclusion count and mean diameter are compared for a range of modelling parameters and inclusion size distributions. The size and number distribution at the casting system inlet, and other model parameters, are determined which provide the best agreement between measured and simulated inclusion area, count, and size.

Hot tear prediction in large sized high alloyed turbine steel parts - experimental based calibration of mechanical data and model validation

The main defects in heavy steel castings are related to hot tear formation during solidification. Depending on the steel grade, design, and local solidification conditions, it is possible to predict regions with higher risk of hot tear formation during the casting process. However, steels containing Boron show more complex crack and defect patterns compared to common steel casting alloys. The mechanisms behind the Boron induced hot tearing is investigated in this work to understand the influence of Boron enrichment during solidification and the influence on hot tearing. The experimental work includes the investigation of phase diagrams and the corresponding fractions of the solid and liquid phases depending on temperature using thermal analysis e.g. DSC and HT-LSCM. The hot tearing sensitivity and mechanical properties during solidification are obtained in the Submerged Split Chill Test, SSCT. In addition IMC-B 3-point bending tests are performed to determine high-temperature material properties in the solid state. The work is part of a research project where the final goal is to improve the hot tear predictions based on experimental work and carry out a benchmark simulation of a real sized casting and use it to show the agreement between the numerical results and extensive non-destructive testing from industrial observations.

Influence of the adjustable EMBr on the asymmetric flow in a thin slab caster with a misaligned SEN

The thin slab casting (TSC) of steel is a type of the continuous casting (CC) with a narrow funnel-shaped mold, characterized by the rapid solidification and fast production rates. A highly turbulent flow impacts on a growing solid shell due to the constant feeding of the fresh hot melt. That strongly affects the solidification profiles and final quality of the TSC slabs. The presented work numerically investigates the solidification inside the TSC mold with the asymmetric flow pattern caused by the misalignment (tilting) of the submerged entry nozzle (SEN). These effects were considered with and without the applied electromagnetic brake (EMBr). The influence of the adjustable EMBr on the asymmetric flow and solidification profiles including turbulent and magnetohydrodynamic (MHD) effects were studied. During consistent series of simulations, the EMBr was varied between the magnetic poles and the time-averaged velocity and temperature fields were collected. The results showed that symmetric EMBr of a local type could partially improve the asymmetry. An optimal braking scenario was found for the casing speed of 5.5 m/min and maximum EMBr value of 180 mT. The solidification and MHD models including turbulence were developed using OpenFOAM®.

In situ observation of solidification in peritectic steels and evaluation of the strains induced in the solidifying shell

In the continuous casting of peritectic steels, unevenness and cracks of the solidifying shell are typical casting defects. This study focuses on the ferrite–austenite transformation and the influence of the transformation on the solidifying shell deformation. In situ observations revealed that the austenite hardly nucleated and, consequently, the undercooled ferrite massively transformed to the austenite in the solid state. Simultaneously, the austenite rapidly solidified in the remaining liquid. The volume changes due to the ferrite–austenite transformation and the solidification shrinkage were measured using time-resolved tomography. On the basis of the observations and measurements, a model that includes the ferrite–austenite transformation and the austenite solidification was proposed to evaluate the volumetric strains in the solidifying shell. There was a sharp peak in the volumetric strains derived from the model at hypo-peritectic compositions. This work demonstrates the need to include the ferrite–austenite transformation in the solid state and the rapid austenite solidification for understanding the solidifying shell deformation in peritectic steels.

How electromagnetic stirring influences fluid flow in continuous casting of steel

State-of-art simulation models provide quantitative insights into flow, solidification and stress formation for continuous casting processes. This includes the entire process, from the tundish and the flow into the mold to the solidifying strand, which is withdrawn through various cooling zones. Process simulation and optimization provides important information about quality and productivity to evaluate process alternatives. This is only be possible if all relevant process parameters can be taken into account. The use of electromagnetic stirring is a technology which plays a significant role in the majority of continuous casting processes worldwide and its effects cannot be neglected in simulation models. This paper will discuss the modeling of electromagnetic stirring (EMS) and its impact on steel slab continuous casting.Two cases with and without EMS are presented. The theoretical background to calculate the Lorentz force are described. The EMS calculation described here works with traveling (linear) magnetic fields. The effect of the EMS on the flow behavior, solidification and macrosegregation is shown on an industrial-scale slab casting.This information leads to a better understanding of the EMS process in industrial applications to avoid casting defects, improve the quality of the final product, and increase the efficiency of the casting process.

Model of multiphase flow, superheat transport, and particle capture in a steel continuous caster

A model of turbulent multiphase flow, heat transfer, and particle entrapment during continuous casting of steel is presented. The model includes the top 7m of the vertical and curved strand, and considers the effects of argon gas injection and thermal buoyancy. RANS model flow results are compared with LES. Lagrangian particle transport through the Eulerian-Eulerian multiphase flow field from the k-ɛ RANS model is based on random walk and features advanced particle capture criteria, improved from previous work by including anisotropic turbulent velocity fluctuations near the walls. Particle capture via 3 mechanisms is included: capture by solidified hooks at the meniscus, entrapment between dendrites, and engulfment by surrounding large particles. The fluid flow and bubble/inclusion capture results are validated with plant measurements, including nail board dipping tests and ultrasonic tests of particle locations, and good agreement is seen. The superheat has negligible effect on flow in the mold region but causes complex flow in the lower strand by creating multiple recirculation zones due to the thermal buoyancy. With high (30 K) superheat, this leads to less penetration, and slightly fewer and shallower capture of particles. Lower (10 K) superheat may enable significant top surface freezing, leading to very large internal defect clusters. Lower superheat also leads to deeper meniscus hooks, and more surface capture. Capture bands occur near the transition from vertical to curved, where downward liquid flow velocity balances the particle terminal velocity.

Transient simulation of melt flow, clogging, and clog fragmentation inside SEN during steel continuous casting

Clogging of submerged entry nozzle (SEN) during continuous casting of steel is an undesirable phenomenon leading to different problems like flow blockage, slag entrainment, nonuniform solidification, etc. A transient numerical model for nozzle clogging based on an Eulerian-Lagrangian approach was developed and it covers the main steps of clogging: (a) formation of the first oxide layer by chemical reactions on the steel-refractory interface; (b) motion of non-metallic inclusions (NMIs) due to the turbulent melt flow towards the SEN wall; (c) interactions between the melt, the NMI, and the wall; (d) formation and growth of the clog by the deposition of NMIs on the clog front and the flow-clog interactions; and (e) detachment/fragmentation of a part of clog due to the flow drag force. Clogging in an industrial scale SEN was simulated. The simulated clog front was compared with real as-clogged SENs. The modeling results have successfully explained the SEN clogging induced transient flow phenomenon in the mold region, i.e. the transition from the stable to an unstable and non-symmetrical flow.

Numerical simulation and casting process optimization of cast steel node

Numerical simulation and casting process optimization of cast steel node

The Optimized Homogenization Process of Cast 7Mo Super Austenitic Stainless Steel.

Super austenitic stainless steels are expected to replace expensive alloys in harsh environments due to their superior corrosion resistance and mechanical properties. However, the ultra-high alloy contents drive serious segregation in cast steels, where the σ phase is difficult to eliminate. In this study, the microstructural evolution of 7Mo super austenitic stainless steels under different homogenization methods was investigated. The results showed that after isothermal treatment for 30 h at 1250 °C, the σ phase in steels dissolved, while the remelting morphologies appeared at the phase boundaries. Therefore, the stepped solution heat treatment was further conducted to optimize the homogenized microstructure. The samples were heated up to 1220 °C, 1235 °C and 1250 °C with a slow heating rate, and held at these temperatures for 2 h, respectively. The elemental segregation was greatly reduced without incipient remelting and the σ phase was eventually reduced to less than 0.6%. A prolonged incubation below the dissolution temperature will lead to a spontaneous compositional adjustment of the eutectic σ phase, resulting in uphill diffusion of Cr and Mn, and reducing the homogenization efficiency of ISHT, which is avoided by SSHT. The hardness reduced from 228~236 Hv to 220~232 Hv by adopting the cooling process of "furnace cooling + water quench". In addition, the study noticed that increasing the Ce content or decreasing the Mn content can both refine the homogenized grain size and accelerate diffusion processes. This study provides a theoretical and experimental basis for the process and composition optimization of super austenitic stainless steels.

A Numerically Efficient Method to Assess the Elastic–Plastic Strain Energy Density of Notched and Imperfective Cast Steel Components

The fatigue strength of cast steel components is severely affected by manufacturing process-based bulk and surface imperfections. As these defect structures possess an arbitrary spatial shape, the utilization of local assessment methods is encouraged to design for service strength. This work applies the elastic–plastic strain energy density concept to study the fatigue strength properties of a high-strength cast steel alloy G12MnMo7-4+QT. A fatigue design limit curve is derived based on non-linear finite element analyses which merges experimental high-cycle fatigue results of unnotched and notched small-scale specimens tested at three different stress ratios into a unique narrow scatter band characterized by a scatter index of 1:TΔW¯(t)=2.43. A comparison to the linear–elastic assessment conducted in a preceding study reveals a significant improvement in prediction accuracy which is assigned to the consideration of the elastic–plastic material behaviour. In order to reduce computational effort, a novel approximation is presented which facilitates the calculation of the elastic–plastic strain energy density based on linear–elastic finite element results and Neuber’s concept. Validation of the assessment framework reveals a satisfying agreement to non-linear simulation results, showing an average root mean square deviation of only approximately eight percent in terms of total strain energy density. In order to study the effect of bulk and surface imperfections on the fatigue strength of cast steel components, defect-afflicted large-scale specimens are assessed by the presented elastic–plastic framework, yielding fatigue strength results which merge into the scatter band of the derived design limit curve. As the conducted fatigue assessment is based solely on linear–elastic two-dimensional simulations, the computational effort is substantially decreased. Within the present study, a reduction of approximately 400 times in computation time is observed. Hence, the established assessment framework presents an engineering-feasible method to evaluate the fatigue life of imperfective cast steel components based on rapid total strain energy density calculations.

Failure analysis of Al2O3–C–SiO2 slide gate plates during continuous casting based on numerical simulation

The thermo-mechanical and failure behavior of the burning-free Al2O3 –C–SiO2 slide gate plate materials during the steel casting process are investigated. Firstly, the instantaneous coefficient of thermal expansion and the Young's modulus of the slide gate plate materials with different component contents at high temperature are measured. Secondly, a material constitutive model and a concrete damage plasticity mode are established based on the experiments, and adopted to simulate the failure behavior of the burning-free Al2O3–C–SiO2 slide gate plate during casting based on Finite Element Method (FEM) analysis. Results show that temperature gradient in the slide gate plate near the casting hole increased significantly and had a significant influence on cracking. The area near the casting hole of the slide gate plate is under tensile stress conditions, and then changes towards compressive stress conditions. Under those severe thermal stress conditions, crack formation is evaluated and an optimized composite structure of the slide gate plate combining advantages of reducing the risk of cracking and extending the service life is proposed. Moreover, the thermal shock test further verified that the microcrack extension was significantly alleviated due to the SiC distributed in whisker form and formed an interlocking structure in material. This work provides a reliable theoretical and experimental basis for the design and optimization of high performance Al2O3–C–SiO2 slide gate plates.