Wetting of 430ss by molten lead-free glass solder (SiO2–B2O3–Na2O–CaO–Al2O3)

A SiO 2 -B 2 O 3 -Na 2 O-CaO-Al 2 O 3 lead-free glass solder was developed for 430ss sealing. This material demonstrates excellent performance, as confirmed through comprehensive characterization. Thermal analysis indicates optimal processing temperatures and a significant reduction in viscosity (from 970 to 56 Pa·s in the range of 500–600°C). Structural characterization identified [BO 3 ] triangles and Q 2 /Q 3 SiO 4 units as the primary network components, with Na 2 O/CaO reducing polymerization to enable low-temperature wetting. Wetting tests showed temperature-dependent behavior with initial contact angles (138-145°) decreasing to 25-27°, exhibiting viscous-dominated kinetics (τ 1 =14-114 s) and a 5-6 s lag between angle reduction and spreading. Interfacial analysis confirmed 1-3 μm oxide layer formation at grain boundaries and critical Cr-O-Si/Fe-O-Si bonding. Arrhenius analysis showed that the spreading activation energy (123.40–129.83 kJ/mol) matched the weighted value (124.12 kJ/mol) of the Fe-Fe (118 kJ/mol) and Cr-Cr (152 kJ/mol) bond energies in 430ss. The system ensures reliable sealing by controlling viscosity, optimizing structure, enhancing bonding, and matching thermal expansion. It offers low-temperature processing, excellent wettability, eco-friendliness, and stable interfaces, supporting advanced lead-free seals with tailored properties.