Physico-Chemical Study on the Chemical Reaction between Slag and Metal in Welding Process (Report 4)

By Arc Welding Electrode Containing Ni, Cr, Mo, W and V in its Coating as Alloying Element

Abstract

A physico-chemical study has been made on the chemical reactions between slags and metals in the welding processes by five series of electrodes containing Ni, Cr, Mo, W and V in the coatings as alloying elements, and the following results were obtained.
(1) Equilibrium index K'_Ni is independent of slag-basicity B_L and the relation between K'_Ni and B_L is represented by the following equation;
log K'_{Ni (Ni Addition)}=-2.586
(2) K'_Cr decreases with increasing B_L and the relation between K'_cr and B_L is represented by the following equation;
log K'_{cr (Cr Addition)}=-0.08OB_L-2.903
(3) K'_Mo, K'_W and K'_v increase with increasing B_L and the relations between the equilibrium indexes and B_L are represented by the following equations, respectively;
log K'_{Mo (Mo Addition)}=+0.262B_L-3.111
log K'_{W (W Addition)}=+0.277B_L-2.532
log K'_{V (V Addition)}=+0.218B_L-1.427
(4) The activity coefficients yMmon of various oxides in weld slags are represented by the following equations; where yMmOn=1, when B_L→0;
log yNiO=0
log yCr₂O₃=+0.080B_L
log yMoO₂=-0.262B_L
log yWO₂=-0.277B_L
log yV₂O₃=-0.218B_L
(5)The feasibility of the oxidization which is effected by FeO in slag against the elements in liquid steel during welding is approximately analogous to that of the oxidization by oxygen gas against the elements in pure state.
(6)The values of a log yMmOn/∂B_L increase with decreasing values of 2Z/R₂ ; where Z is the valency of a cation, and R is the summation of the radii of the cation and an oxygen ion.