Metallurgical and Materials Transactions B

Tian, Huiyu; Zhang, Yanyun; Shi, Shuai; Wang, Guanyi; Wang, Cong

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03252-6

Recycling presents a waste-free solution to substantial disposal of welding slags which retain most components originated from the original fluxes. However, uncertainties in weld appearance and element contents render it unjustified to reuse welding slags as fluxes. In the present study, a manganese-silicate flux has been demonstrated to be fully recyclable subject to submerged arc welding (SAW) for three times. The weld appearance is assessed against the initial weld metal (WM), while alloying element contents are evaluated according to AWS (American Welding Society) requirements. Flux composition and structure, two decisive factors affecting welding performance, are quantified. It is manifested that compositional changes mainly occur in the contents of MnO (39.50 to 34.66 wt pct), SiO2 (38.46 to 34.25 wt pct), and FetO (1.55 to 6.78 wt pct). Moreover, crystalline structures of MgMnSiO4, and Mg0.6Mn1.4SiO4 appear in the initially amorphous flux. The crystallinity is enhanced to 32.7 wt pct through flux recycling. Slight depolymerization is found in the amorphous structure, as the NBO/Si (non-bridging oxygens per silicon atom) is elevated by 0.2. Overall, this study demonstrates the capability of recycling welding fluxes and is poised to offer insight into further sustainable applications.

Wang, Bo; Xing, Lidong; Li, Xin; Bao, Yanping; Wang, Min

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03263-3

Enameled steel is widely used owing to its superior fatigue and strength properties. However, the presence of inclusions formed during the steelmaking process significantly affects these properties. Therefore, this study investigated a factory-enameled steel slab to elucidate its behavior. Additionally, the study analyzed the distribution of inclusions across the slab thickness, and characterized the variation in oxygen, nitrogen, carbon, manganese and sulfur contents. Moreover, the type, number density, size, and morphology of inclusions were examined across the slab thickness. The findings revealed that the center of the slab exhibited the lowest sulfur and manganese contents, which gradually increased toward the edges. Conversely, nitrogen content reached the maximum at the slab center and decreased toward the edges. The oxide inclusions mainly comprised Al2O3–MgO cores. Furthermore, the oxide inclusions in the slab mainly exhibited ellipsoidal morphology, with sizes concentrated between 1 and 5 μm. Moreover, the slab contained MnS and TiN inclusions, which exhibited symmetric variations in number density and average size from the edge to the center of the slab. The number density of MnS first decreased and then increased from the inner arc to the outer arc, while TiN exhibited the opposite trend. Additionally, MnS had a smaller average size than TiN, despite its higher number of inclusions. Furthermore, Ti4C2S2 inclusions were mainly distributed between 1 and 3 μm and clustered in the slab. Additionally, theoretical calculations revealed that the elemental segregation trend followed the order of S > Ti > N > Mn. The sequence of precipitation formation was Ti4C2S2 > TiN > MnS. This indicated a negative correlation between the cooling rate and inclusion size. Particularly, MnS exhibited the smallest size, while TiN featured the largest size at the center of the slab.

Wei, Hong; Yang, Wen; Zhang, Lifeng

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03257-1

The rare earth element Gd was added into a resulfurized steel to enhance its performance. Non-metallic inclusions in the steel, the hardness and the microstructure of the steel were analyzed. The addition of Gd resulted in the formation of Gd–O–S and Gd–S inclusions which served as cores of MnS inclusions so that the resistance to the deformation of inclusions was improved. When the content of the total gadolinium (T.Gd) increased from 0 to 198 ppm, the hardness of the steel matrix increased from 60.4 to 80.4 HRA. The microstructure predominantly consisted of a substantial number of pearlites with a minor presence of ferrites distributed in a network-like pattern. The distribution of ferrites along the grain boundary was weakened when the T.Gd content in the steel was 79 ppm. The tensile fracture of the steel exhibited a mixed ductile-brittle pattern while its impact fracture displayed brittle characteristics.

Rai, Praveen Kumar; Dish, Nilabh

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03264-2

The research conducted on the low-temperature epitaxial growth of vapor-deposited thin face-centered cubic (fcc) metal films on the cleavage face of sodium chloride (NaCl) reveals a notable gap in comprehensive studies concerning the influence of deionized water on specially prepared (110) and (211) crystal faces of NaCl. This study emphasizes the crucial role of active contaminants in the oriented growth of thin continuous metal films, specifically silver (Ag), gold (Au), and copper (Cu), on the (110) and (211) polished faces using the flash-evaporation technique. The impact of flash evaporation on orientation changes during coalescence is highlighted, influencing the epitaxial orientation of metal films. Moreover, the research introduces a significant enhancement of epitaxy on ethanol-treated and furnace-annealed NaCl faces without the need for post-deposition annealing of wet-stripped free-standing films. The epitaxial relationships between substrates and deposits were determined through electron diffraction, while transmission electron microscopy was employed to examine crystalline defects present in wet-stripped films. This work contributes valuable insights into the intricacies of thin metal film growth on specifically treated NaCl crystal faces.

Bohacek, J.; Karimi-Sibaki, E.; Vakhrushev, A.; Mraz, K.; Hvozda, J.; Wu, M.; Kharicha, A.

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03254-4

An advanced 2D axisymmetric magnetohydrodynamics model, including calculations for electromagnetic, thermal, and flow fields, fully coupled with a thermal stress-strain model, allowing the computation of solid mechanical parameters like stress, strain, and deformation within the ingot of the vacuum arc remelting process is presented. This process encounters challenges due to solidification shrinkage, which causes losing contact between the ingot and the mold, reducing the cooling efficiency of the system, resulting in a deeper melt pool and decreasing ingot quality. Herein, the width of the air gap along the ingot, the precise position of contact between the ingot and mold, and the profile of the melt pool, affected by gas cooling, are calculated. The global pattern of transport phenomena, such as (electro-vortex) flow and electromagnetic fields in the bulk of the ingot, is insensitive to helium gas cooling through the shrinkage gap. However, including gas cooling significantly improves heat removal through the mold, which consequently reduces the pool depth of the Alloy 718 ingot, leading to an improvement in the quality of the ingot.

Li, Yaqiong; Cai, Hongzheng; Wang, Yifan; Zhang, Lifeng; Yang, Wen

2024 Metallurgical and Materials Transactions B

doi: 10.1007/s11663-024-03250-8

The disposal of end-of-life photovoltaic components presents a substantial challenge. This study introduces a novel one-step heat treatment process for the efficient recovery of Ag from Si solar cells. Through the utilization of a high-temperature microscope, the behavior of Ag during the heating process was carefully observed, revealing a sequence of melting, aggregation, and ultimately the formation of Ag droplets. Notably, this process significantly minimizes the use of hazardous chemicals and reduces operational costs.