Carola Celada-Casero

This study employs computational thermodynamics to evaluate the feasibility of replacing methane with hydrogen as both burner fuel and reductant during blister copper deoxidation, aiming to enhance deoxidation efficiency and reduce CO₂ emissions. A comprehensive thermodynamic model was developed using FactSage 8.3 for dilute Cu–O and Cu–S–O melts containing trace impurities (Fe, Ni, Pb, Zn), incorporating methane thermal decomposition and temperature-dependent variations in liquid copper density with oxygen and sulfur content. Model parameters were optimized against over 10⁵ deoxidation simulation data points, yielding temperature- and composition-dependent expressions for rapid density estimates. Benchmarking against existing literature models demonstrated improved accuracy. Key findings include: (1) increasing impurities contents from electronics waste recycling (Fe, Ni, Pb, Zn) reduces oxygen activity, deteriorating the deoxidation efficiency; (2) under global equilibrium, methane provides greater reducing power per mole than hydrogen due to full thermal cracking, but real-world mass transfer limitations render hydrogen more consistently effective up to 1200 °C, with methane gas needing to achieve at least 472 °C to match hydrogen’s performance; (3) adiabatic flame equilibrium studies show that O₂/H₂ ratios of 0.5 to 1 yield liquid copper oxygen activities comparable to industrial O₂/CH₄ ratios of 2 to 3, supporting the direct substitution of methane with hydrogen in oxy-fuel anode furnace burners without compromising metal quality.

Scrap for New Steel Carola Celada-Casero, Félix A. López, Carlos Capdevila, Roberto Castelo, Santiago Oliver Steel is the main structural material to our mo

The applicability of laser ultrasonics for the determination of grain size and phase composition in steels under different temperatures was investigated. This was done by obtaining the velocity and attenuation of propagating ultrasonic waves in a simulated steel medium. Samples of ferrite and austenite with varying microstructures were modelled and simulated with the finite difference method, as were samples with varying ratios of austenite and martensite. The temperature of the medium was taken into account as an essential parameter, since both velocity and attenuation are temperature dependent. Results of the velocity and attenuation analysis showed that the use of the wave propagation velocity is not feasible for determination of grain size or phase composition due to a high sensitivity to temperature and sample thickness. The frequency-dependent ultrasonic wave attenuation was less sensitive to the variation of temperature and sample thickness. It can be concluded that accurate knowledge of the temperature is essential for obtaining a correct grain size or phase ratio estimation: a temperature accuracy of 100 °C yields a grain size accuracy in the order of a micrometer using the attenuation. Similarly, a temperature accuracy of 70 °C leads to a phase ratio estimation accuracy of 10%.

Because of their excellent combination of strength and ductility, quenching and partitioning (Q & P) steels have a great chance of being added to the third generation of advanced high strength steels. The large ductility of Q & P steels arises from the presence of 10% to 15% of retained austenite which postpones necking due to the transformation induced plasticity (TRIP) effect. Moreover, Q & P steels show promising forming properties with favourable Lankford coefficients, while their planar anisotropy is low due to a weak texture. The stability of the metastable austenite is the key to obtain tailored properties for these steels. To become part of the newest generation of advanced high strength steels, Q & P steels have to preserve their mechanical properties at dynamic strain rates and over a wide range of temperatures. Therefore, in the present study, a low-Si Q & P steel was tested at temperatures from −40 °C to 80 °C and strain rates from 0.001 s⁻¹ to 500 s⁻¹. Results show that the mechanical properties are well-preserved at the lowest temperatures. Indeed, at −40 °C and room temperature, no significant loss of the deformation capacity is observed even at dynamic strain rates. This is attributed to the presence of a large fraction of austenite that is so (thermally) stable that it does not transform in the absence of deformation. In addition, the high stability of the austenite decreases the elongation at high test temperatures (80 °C). The additional adiabatic heating in the dynamic tests causes the largest reduction of the uniform strain for the samples tested at 80 °C. Quantification of the retained austenite fraction in the samples after testing confirmed that, at the highest temperature and strain rate, the TRIP effect is suppressed.