A method and apparatus is disclosed for removing chevron cracks from the corner edges of a steel billet as it advances in a hot condition from a continuous casting operation. The apparatus includes a framework which mounts four plasma arc torches which are adapted to operate in the non-transfer arc mode, and with the torches being positioned so that the heated plasma engages respective ones of the four corner edges of the billet, to melt and heal any cracks. The framework is cyclically advanced rearwardly and forwardly along the path of travel of the billet, so as to permit effective control of the level of heating and so as to assure all longitudinal portions of the advancing billet are effectively treated.