Weldability of Recycled Steel Bars in Uganda

摘要

The metallurgical reliability of welded recycled steel made in Uganda has been studied through the examination of manual metal arc weldments of steel samples of 0.27%C and less using the dye penetrant flaw detection method, micro-hardness plots and spark spectromentry. This method was selected to ensure reproducibility by taking repeated readings on the same sample since it is largely non-destructive. About thirteen percent of the samples exhibited post-weld cracks. Of these, 3% of the samples yielded hot cracks while the other 10% showed typical hydrogen assisted cracks. The cracking sensitivity has been attributed to the presence of large numbers and quantities of residual elements rather than high carbon content in particular. This resulted from the predominantly recycled production mode in the country. The use of more elaborate refining methods and the exploitation of virgin iron resources have been recommended. Pre- and post-heating techniques have been advised whenever weld cracking threatens.