Effect of slag variations on ANSI/AWS A5.1–91 E6013 electrode properties: replacement of TiO2 in electrode coating with MnO, FeO, CaO, MgO, K2O, or Na2O

Abstract

The present work is part of a research programme to study the effect of variation of the coating composition of covered rutile manual electrodes on both operational and deposited weld metal properties. According to previous results obtained for rutile electrodes, an increase of slag basicity, achieved through modifications in the coating, produces an improvement of the impact properties of the deposited weld metal, as well as a decrease in the diffusible hydrogen, along with beneficial changes in the operational properties of the electrode. The aim of the present work is to study the influence of the replacement of titanium oxide with oxides of alkali metals (sodium and potassium), alkaline earth metals (calcium and magnesium), and iron and manganese oxides in the coating of an ANSI/AWS A5.1–91 E6013 type electrode on the operational characteristics of the electrode and the microstructure, mechanical properties, and diffusible hydrogen content of the electrode weld metal. Tensile strength and Charpy V notch impact properties were measured in the all weld metal samples produced using each of the seven electrodes designed for the present study. A cross-section from each coupon was used to determine the chemical composition of the deposit and to carry out a metallographic study using a light microscope. As a result of the addition of different oxides, changes in the operational properties were observed using both direct and alternating current, as well as a decrease in the diffusible hydrogen content in the weld metal. Also, electrodes in which rutile was substituted by sodium oxide in the coating showed an improvement in the impact properties of the deposit.