Papers by Keyword: Steel

Abstract: Post-weld heat treatment (PWHT) was investigated to evaluate its effects on dissimilar friction stir welded (FSWed) T-joints of AA6061 and low carbon steel. The non-PWHT joint was compared with four PWHT conditions involving solution treatment, quenching, natural aging, and subsequent artificial aging at 0-12 hours. Microstructural characterization revealed a largely continuous Al/steel interface in the non-PWHT joint, while PWHT promoted interfacial cracking and modified precipitation behavior in the stir zone and heat-affected zone of AA6061. Hardness increased monotonically with aging time, reaching ~95–100 HV after PWHT artificial aging at 12 hours. Tensile strength peaked at 212MPa after 4 hours of artificial aging, while maximum strain decreased from ~9% to ~5.3% after 12 h artificial aging, indicating ductility loss under prolonged aging. Fracture location after PWHT consistently occurred at SZ, highlighting a critical failure region governed by joint geometry and microstructural heterogeneity.

Abstract: Some steels exhibit the Lüders effect. This phenomenon depends on the material and structure (test piece geometry, loading speed, etc.). Most work hardening laws do not take this phenomenon into account. The objective of this work is to define the most appropriate hardening law to highlight the characteristics of Lüders effects. First, the various aspects of the Lüders effect are presented. Several local hardening laws are proposed to describe the plateau or not, some of which are taken from the bibliography. Simulations of uniaxial tensile testing and forming of stamped parts are performed to compare these different hardening laws in predicting the Lüders effect. The Exp_Swift hardening law is recommended for forming cards because it is fully compatible with all software dedicated to steel sheet formability analysis and does not require inverse calibration during identification to accurately predict the plateau length.

Abstract: Isothermal forging is a common method for manufacturing titanium alloys, but it involves complex processes and equipment. The oxidation of titanium leads to the formation of an alpha-case, which in turn promotes increased crack formation. To prevent this, inert gas is typically required. However, by encapsulating the titanium billet (Ti-6Al-4V) in a steel casing made of AISI 316L, a quasi-isothermal process can be achieved without the need for inert gas. This method maintains protection against oxidation while simultaneously reducing cooling. The sealing of the capsules is crucial to ensure that the titanium is effectively enclosed and protected from the surrounding gases. In this study, various encapsulation methods are compared, including rotary friction welding, diffusion bonding, and press-fitting a lid with an interference fit. The investigation involves differing contact conditions between the titanium and steel sleeve, as well as steel wall thicknesses of 2 mm and 4 mm. These factors showed no impact on the material flow or microstructure of the formed components. Encapsulation can prevent the formation of an alpha-case. Intermetallics form between the titanium and the steel capsule, depending on the contact conditions. The use of graphite as a separating agent prevents the formation of them.

Abstract: In this study, we develop a Bayesian data assimilation framework that combines a mean-field model of static recrystallization (MiReX) with a Sequential Importance Resampling (SIR) particle filter to estimate key material parameters from controlled synthetic experiments. MiReX, originally developed as a microstructurally based extension of Johnson–Mehl–Avrami–Kolmogorov kinetics, is used as a forward model in which the uncertain quantities include the grain-boundary mobility parameters (prefactor and activation energy), a stored-energy coefficient, an Avrami-type exponent, and an interface length scale. Synthetic recrystallized-fraction measurements are generated at two isothermal holding temperatures using a reference parameter set and are perturbed with Gaussian noise to mimic experimental uncertainty. Starting from broad uniform prior ranges, the particle filter propagates an ensemble of MiReX trajectories in time, updates particle weights using a Gaussian likelihood, and applies systematic resampling combined with Liu–West kernel regularization to reduce particle degeneracy while preserving posterior variance. The posterior obtained after assimilating the first temperature dataset is used as the prior for the second dataset, enabling sequential multi-temperature calibration. The synthetic experiments show that the framework recovers the reference parameters within credible intervals and provides tight uncertainty bounds on the predicted recrystallization kinetics. These results demonstrate that combining a physically based mean-field recrystallization model with sequential Monte Carlo methods provides a robust route for probabilistic parameter estimation and uncertainty quantification in microstructure evolution models.

Abstract: Lightweighting plays a critical role in reducing vehicle emissions, a major source of air pollution in the European Union. While weight reduction during the use phase is important, environmental impacts across production and end-of-life stages must also be considered. Advanced forming technologies enable the use of high-strength materials while maintaining formability and energy efficiency. Continuous-bending-under-tension (CBT) is a promising forming technique capable of inducing higher plastic deformation than conventional processes. In this study, CBT experiments were conducted on dual-phase 1000 low-yield (DP1000-LY) steel. The material was subjected to uniaxial tensile loading combined with cyclic bending through a moving three-roll system. The effects of key process parameters, bending depth and speed ratio between the bending assembly and tensile loading, were systematically investigated. The results show that lower bending depths allow greater total deformation before fracture and result in higher tensile forces. Higher speed ratios lead to earlier failure both during and after CBT processing. Hardness measurements indicate comparable surface hardness on both sides of the specimens, regardless of single or double roll contact. These findings contribute to a better understanding of CBT process parameters and support its potential application in lightweight automotive component manufacturing.

Abstract: This study presents a comprehensive cost-benefit analysis of formwork systems commonly used in the Nigerian construction industry. The research evaluated the economic viability and overall impact of traditional timber and prefabricated steel formwork systems in Nigeria construction projects. The study employs a quantitative method through data collection from questionnaires and Life Cycle Cost (LCC) analysis. The findings indicated that fabricated steel formwork is durable, cost-effective, and promotes environmental sustainability compared to traditional timber formwork. The initial cost of timber formwork was found to be 19.76% cheaper than the fabricated steel formwork. However, the LCC analysis suggests that the cost of timber formwork is 5% higher than that of fabricated steel formwork. Therefore, this research provides actionable recommendations for construction stakeholders to optimize formwork selection, enhance economic efficiency, and promote sustainable construction practices in Nigeria’s construction industry.

Abstract: Steel is the most used material for concrete reinforcement; however, it performs poorly in aggressive environments (e.g. coastal areas) owing to corrosion (moisture and chlorides). This study aims to analyse the tensile strength of steel and glass fibre-reinforced polymer (GFRP) bars through laboratory testing to assess their feasibility and application in construction. Steel bars were tested by ASTM E8/E8M–22, obtaining values of 606.61 MPa (Ecuador) and 676.46 MPa (Peru), whereas GFRP bars were tested following ASTM D7205/D7205M–21 (1,000 MPa). The analysis indicated that GFRP bars offer structural advantages (suitable for elements in coastal zones with low to moderate seismic activity), environmental benefits (lower CO₂ emissions during production), and enhanced durability (corrosion resistance).

Abstract: The importance of iron and steel to any nation’s economy cannot be overstressed. This paper X-rays the importance of iron and steel to the development of any nation’s economy with reference to China, South Africa and Nigeria. It discusses that iron and steel companies are needed to provide high-quality and efficient services. Benefits that can be derived from iron and steel which includes; revenue generation for the sustenance of nation’s economy, employment generation, industrialization are discussed. Government policy, lack of commitment on the part of policy makers of this country among others have been outlined as barriers that militate against the development of iron and steel in the country. Commitment, implementation of every policy formulated for the industry and partnership with experienced private sector was identified as among the solution to move the sector forward. Keywords: Industry, Iron and Steel, Economic, Production, Consumption, Policy

Abstract: The operational integrity of supercritical steam power units necessitates comprehensive understanding of welded joint behaviour under high-temperature service conditions. Advanced steam cycle technology requires meticulous periodic evaluation of pressure-bearing components to ensure structural integrity throughout extended service periods. This requirement is particularly critical for components subjected to the most severe operational parameters, including superheater tubes, main steam pipelines, and steam collectors operating above critical temperature. For pressure components not directly exposed to exhaust gases, microstructural degradation represents the primary degradation mechanism governing component lifespan.P92 (X10CrWMoVNb9-2) steel, characterized by a tempered martensitic microstructure with 9% chromium content, has been extensively utilized for high-pressure applications in supercritical steam power generation systems. This advanced creep-resistant steel demonstrates superior mechanical properties, including exceptional high-temperature strength retention, oxidation resistance, and creep rupture strength under prolonged thermal exposure.Welded joints of pressure elements in steam boilers are potentially the weakest points when assessing their service life. These joints exhibit enhanced susceptibility to microstructural degradation and mechanical properties deterioration, particularly within the heat-affected zone (HAZ), during extended high-temperature operation. Therefore, systematic material characterization of welded joints relative to base material performance is essential for understanding long-term degradation mechanisms.This investigation presents systematic creep testing methodology and experimental results for P92 welded joint specimens subjected to annealing at temperatures of 600°C and 650°C for durations up to 10,000 hours. Both abridged and long-term creep tests were performed with the results of determination of creep strength and creep speed in steady state.

Abstract: The effects of common electric arc furnace (EAF) impurities, including copper (Cu), nickel (Ni), molybdenum (Mo), and chromium (Cr), were investigated in low-carbon steels. These steel scrap originating tramp elements can influence the microstructures and mechanical properties of steel products. Tramp elements containing test materials were thermo-mechanically rolled to achieve yield strengths between 400–450 MPa with different cooling routes. Various methods of microstructure characterization and mechanical testing were utilized to study the resulting steels. Additionally, thermo-mechanical simulations were conducted using Gleeble 3800 equipment to gather information about flow stress properties. The results indicate that with a lower cooling rate, the microstructure is not significantly affected by tramp elements, however strength levels can be increased and elongation properties decreased, mostly due to the solid solution strengthening effect of impurities. In water-quenched steels, the addition of tramp elements can alter the final microstructure morphology, increasing the ultimate tensile strength but simultaneously improving the ductility. Flow stress is not significantly affected by tramp elements in the temperature range of 950–1050 °C.