The Chemistry Of Oxygen In Gas Shielded Welding Of Steel: Part II

TWI Industrial Member Report Summary 143/1981

By J Moreton and P J Boothby

Background

In previous work, equations relating weld pool and shielding gas oxygen concentrations were derived, based on a thermodynamic approach. The equations were found valid for a range of Ar/O2, and Ar/CO2 shielding gas mixtures and weld carbon contents in the range 0.06 to 0.11%. The present investigation has studied the application of the equations for low weld carbon levels (c. 0.04%) and at pressures of 5 & 10 bar. It was concluded that under the conditions employed, reasonable agreement was obtained between experimental results and theoretical predictions.

Examination was carried out using the particle analysing scanning electron microscope on welds selected so that the principal variables were (a) gas shield composition and (b) deoxidant element content of the wire.

The results indicated that although deoxidant elements did not greatly affect total weld metal oxygen level, they did determine the form in which oxygen was present.