Document Type Master's Dissertation Author Du Plessis, John email@example.com URN etd-05152007-131110 Document Title Control of diffusible weld metal hydrogen through arc chemistry modifications Degree MSc (Metallurgy) Department Materials Science and Metallurgical Engineering Supervisor
Advisor Name Title Prof M du Toit Keywords
- water vapour
- shielded metal arc welding
Date 2006-08-28 Availability unrestricted AbstractThis project examined the feasibility of using flux modification to reduce the
as-deposited hydrogen content of basic-type shielded metal arc welds.
Additions of oxidizing ingredients (micaceous iron oxides) to the reference
flux formulation lowered the diffusible weld hydrogen content by up to 70%.
Increasing amounts of silica caused a slight reduction in hydrogen content,
probably as a result of the reaction between SiO2 and CaF2, which produces SiF4 and CaO as reaction products. Flux formulations containing additions of fluorine-containing compounds and calcite displayed lower hydrogen levels, with the diffusible weld metal hydrogen content reaching a minimum with increasing additions. Higher levels caused an increase in the weld hydrogen content. Thermodynamic slag modelling attributes the existence of these minima to a decrease in slag water capacity with an increase in slag fluorine content (at constant basicity), brought about by higher concentrations of fluorine-containing compounds in the flux
formulation. The effect of flux additions on the weld mechanical properties
and the electrode operating characteristics was not evaluated during the
course of this investigation.
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