A STUDY ON CRACKS ON THE OXY-GAS CUT SURFACES OF WELD GROOVES OF 14MnMoVN STEEL PLATES DURING COLD FORMING

This paper presents a study of cold forming cracks on oxy-gas cut surfaces of weld grooves of 14MnMoVN steel plates for spiral casing.If 14MnMoVN steel plates are cut with the same parameters for mild steel plates of same thickness,cracking might take place in the cutting HAZ during subsequent cold bending.Metallographical tests show that there is a thin ledeburite layer at the surface of the gas-cut surface.The observation of cracking process reveals the ledeburite layer is so low in ductility that micro-cracks occur at the very beginning of bending.These micro-cracks will extend under certain conditions.From the viewpoint of minimizing the detrimental influence of ledeburite layers,the paper proposes facile technical methods to improve bending ductility.