Slag-Metal Equilibria and Oxygen Sources in Electroslag Process

Chemical Reaction in Electroslag Welding Process (Report 1)

Abstract

A few has been known on the reaction between slag and metal in ESW process except the concern of high basic or highly contained CaF₂ flux, nevertheless the reaction determines the mechanical properties.
This report cosiders the effect of compositions of the electrode and the slag on oxygen, silicon and manganese content in welded or remelted metal by electroslag process.
The experiment is carried out using fluxes with a wide range of basicity in CaO-SiO₂-Al₂O₃, CaO-MnO-Al₂O₃, and CaF₂-SiO₃-Al₂O₃ system.
The elements in metal deposited by electroslag process are not in equilibria with slag compositions in detail, although the solubility products calculated from the analyses agree apparently with the equilibrium values at the temperatures of 1800-2000°C.
Oxygen sources in electrosalg process are considered to be the oxidation of electrode surface by welding atmosphere, which is about 0.1 g oxygen per 100 g metals, and decomposition of oxides.
The slag oxidation ability can be well evaluated by "the Slag Stability Ss" proposed by Narita, while Mori's basicity B_L is only applicable to highly SiO₂ containing slag.