Novel method for quantitative assessment of slag detachability in austenitic stainless steels welds made by SMAW

Abstract

It is essential and important that slag which protects the molten metal from atmospheric contamination during shielded metal arc welding (SMAW) process gets removed as the weld metal gets solidified. During multipass welding in particular it is desirable that slag gets removed easily and totally before the next pass of welding. Otherwise it would lead to slag inclusions in the weld. Hence, the ease with which the slag gets detached from the weld termed as slag detachability is a vital parameter in deciding the weld quality. Till date, slag detachability has been assessed on qualitative terms only. Hence, it is necessary to develop test procedures and methodology for assessing the slag detachability in quantitative terms. In this work, the authors propose a novel slag detachability testing technique called slag detachability tester and a methodology for quantitative assessment of slag detachability. The test procedure and the methodology have been tested first on austenitic stainless steels. The slag on the weldment was removed by dropping varieties of hammers with different end shapes from a standard height with a custom designed drop weight tester. After the test, the adherent slag on the weldment was inspected and measured using infrared (IR) thermography. The acquired IR images were suitably processed using image processing software to identify the area of slag particles sticking on the weld. Testing parameters were standardised and using these data, an expression is proposed for assessing the slag detachability in quantitative terms.