Análise da geração de energia elétrica por meio da utilização de conversores do tipo TEG em lingotamento contínuo de aços

A fabricação do aço é um processo que requer enormes quantidades de recursos, como por exemplo combustíveis,minério de ferro, carvão, entre outros. Com a crescente preocupação com o meio ambiente, seja pelascargas ambientais ou pelo aquecimento global, cresce também a necessidade do desenvolvimento de novastecnologias que possibilitem um melhor aproveitamento dos recursos disponíveis. Portanto, para as indústriasdo aço, torna-se importantíssima a conservação de energia, de forma que a recuperação de calor ganhe destaque.Este trabalho descreve a utilização de um conjunto Thermoelectric Generator (TEG) na recuperação deenergia residual. Os módulos TEG, feitos de óxido de manganês e óxido de cálcio, convertem diretamente ocalor das placas de aço 1045, ao final do processo de lingotamento contínuo, em energia elétrica. Cada móduloquadrado (lados de 64,5mm e espessura de 8,5mm) gera 12,3W quando a temperatura do lado quente é de800⁰ C e a do lado frio é de 50⁰ C. Neste trabalho foi estimada a quantidade de energia possível de recuperarpor este conjunto TEG. Para tanto, foram utilizadas simulações matemáticas e métodos de ajuste, avaliandoassim os efeitos da temperatura, tempo e da espessura na geração de energia pelo conjunto TEG. Considerandoo lingotamento contínuo de placas com 400 mm de espessura e 1050 ⁰ C de temperatura, lingotada a umavelocidade de 0,3 m/min, foi estimado um fornecimento de energia elétrica capaz de abastecer 23 residênciasbrasileiras de acordo com a média nacional de consumo.Palavras-chave: TEG. Geração de energia elétrica. Lingotamento continuo. Simulação

Experimental assessment of low-temperature martensite transformations in Ni-rich polycrystalline Ni-Ti alloys

Ultrasonic velocity and attenuation measurements of a commercially available Ni-rich polycrystalline NieTi alloy were simultaneously obtained upon cooling from room temperature (RT) down to 130 K. The anelastic spectra show multiple anomalies in both velocity and attenuation curves, which evidence a complex nature of structural rearrangements exhibited by NieTi alloy, associated with relaxations and phase transformations. In particular, some evident anomalies at 285 and 180 K, not previously exploited using ultrasonic measurements on Ni-rich polycrystalline NieTi alloy, were associated with austenite to pre-martensitic (B2 / R) and pre-martensitic to martensitic (R/ B19’) phase transitions, respectively. The peculiar temperature separation between these transformations was interpreted based on chemical composition and the NieTi alloy microstructure evolution. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were also used to add complementary results about phase transformations and thermal events exhibited by NieTi alloy at low temperatures

Influence of Zr Content in Ti-40Nb-xZr Alloys on the Microstruture, Elastic Modulus and Microhardness

In recent years, there has been a growing interest in the search for metallic alloys with favorable mechanical and chemical characteristics that elicit a positive biological response. Among these alloys, β-Ti alloys have attracted significant attention due to their low elastic modulus and excellent biocompatibility. The addition of Nb contributes to stabilizing the β phase at room temperatures, leading to the transformation of β into β + α (β-isomorph). Additionally, despite Zr being commonly considered a neutral element, it can exhibit a β-stabilizing characteristic when combined with betagenic elements. Both Nb and Zr have been shown to effectively increase the lattice parameter of the β phase, which is advantageous for reducing the elastic modulus. The primary objective of this study was to characterize β-Ti alloys within the Ti-Nb-Zr system, specifically Ti-40Nb-20Zr, Ti-40Nb-30Zr, and Ti-40Nb-40Zr (wt.%) produced via arc furnace casting. The study aimed to investigate the influence of the proportion of β-stabilizing or betagenic elements on the microstructure and properties of the alloys, including Vickers microhardness and elastic modulus

Characteristics of ceramic-like coatings obtained by plasma electrolyte oxidation on different Ti alloys

Plasma electrolyte oxidation was used to modify the surface of different Ti alloys: c.p. Ti (α hcp structure), Ti–15Nb (α′ + β structure) and Ti–33Nb–33Zr (stable β cubic structure) and the influence of elements and microstructure in the TiO2-based ceramic layer formed as well as the surface properties was analyzed. The XRD patterns confirmed the presence of TiO2 (anatase and rutile) in the c.p. Ti. For Ti–15Nb (wt.%) indicated the presence the same oxides also of pentoxide niobium (Nb2O5). For Ti–33Nb–33Zr (wt.%) indicated just the presence of rutile as the stable oxide one at room temperature and dioxide zirconium (ZrO2). In addition, the formation of calcium carbonate CaCO3 and calcium phosphate Ca3(PO4)2 was detected in all 3 materials. The ceramic-like layer was more homogeneous for c.p. Ti and Ti–15Nb and more irregular hole like-pores for Ti–33Nb–33Zr. Bioactive ions used were detected in all alloys and the roughness for Ti–15Nb was higher compared to c.p. Ti. and Ti–33Nb–33Zr. The contact angle for the three samples was higher than 100°. Resumen: La electro oxidación por plasma fue utilizada con el objetivo de sintetizar recubrimientos de óxidos en la superficie de diferentes aleaciones de Ti tales como: Ti c.p. (estructura α hcp), Ti-15Nb (estructura α′+β) y Ti-33Nb-33Zr (estructura cúbica β estable). Así mismo, esta técnica permitió evaluar el efecto de los elementos de la aleación; la microestructura de la capa cerámica formada, cuya base es TiO2; así como las propiedades superficiales. Los patrones de XRD confirmaron la presencia de TiO2 (anatasa y rutilo) en el Ti c.p., así como la presencia de los mismos para la aleación Ti-15Nb (% en peso) y la formación del pentóxido de niobio (Nb2O5), mientras que para la aleación Ti-33Nb-33Zr (% en peso), el análisis de DRX mostró la presencia del rutilo, como el óxido estable a la temperatura ambiente, así como del dióxido de zirconio (ZrO2). Además, en los 3 materiales se detectó la formación del carbonato de calcio CaCO3 y fosfato de calcio Ca3(PO4)2. Adicionalmente, la capa cerámica fue más homogénea para el Ti c.p. y Ti-15Nb, mientras que los microporos formados fueron más irregulares en la aleación Ti-33Nb-33Zr. Los iones bioactivos utilizados se detectaron en todas las aleaciones. Sin embargo, la rugosidad para el Ti-15Nb fue mayor en comparación con la del Ti c.p. y Ti-33Nb-33Zr, aun cuando el ángulo de contacto para las tres muestras fue superior a 100° indicando una superficie más hidrofóbica

Assessment of β stabilizers additions on microstructure and properties of as-cast β Ti–Nb based alloys

The novelty of the present work lies in elucidating the correlation of Moeq with mechanical and surface parameters. The Ti–15Nb (TN-15), Ti–40Nb (TN-40), Ti–33Nb–33Zr (TNZ-33), Ti–40Nb–40Zr (TNZ40) and Ti–35Nb–7Zr–5Ta (TNZT) alloys were obtained by casting. The alloys were formed by β-Ti grains with a micrometric morphology, except the as-cast TN-15 alloy formed by α + β. Adding Nb and Zr influenced the lattice parameters of phase β, as well as the crystal structure. Grain size (GS) decreased adding Nb and Zr following this relation: TN-40 > TNZ-33>TNZT > TNZ40. The roughness decreased with rising Nb and Zr contents being in the range of 1.3–3 μm, and it was possible to correlate it with the Moeq. The contact angle and free energy surface values were inversely proportional, and the as-cast TNZ40 alloy with smaller GS was less wettable (60) than TN40 (GS: 1423 μm). The mechanical properties decreased to Moeq of 14.9 wt% then their significantly went above this value, except for the as-cast TN-15 alloy (E: 65 GPa, microhardness: 264 HV) formed mainly by a hardener phase α. Both elastic modulus and microhardness showed the same tendency as the Moeq values and the cell parameter of phase β (aβ). The oxygen content was all in accordance with ASTM E1409-13 for applications as metallic biomaterials being in the range of 0.044–0.195 wt%