TWI Industrial Member Report Summary 159/1981
By W O Dinsdale and S B Dunkerton
Charpy impact tests have been carried out on continuous drive friction welds in 25mm diameter carbon-manganese steel bar (BS 2772:150M19), to examine the effects of welding parameters on toughness. Very poor toughness properties were obtained in the as-welded state in comparison with the parent material, with no apparent effect observed by variation of welding parameters. A conflict was found between the conventional methods of measuring percentage crystallinity and examination of the Charpy fracture faces in the scanning electron microscope. This latter technique revealed fractures to be inclusion dominated when they appeared brittle on visual examination. The improved discrimination allowed some investigation of the effect of parameters, where the burnoff distance was found to be the most significant variable. The effect of postweld heat treatments was also examined. These improved the toughness of the welds although parent material toughness was not achieved as a result of the inclusion re-orientatiomduring the welding cycle. Limited work has been carried out on two clean steels: a carbon steel JIS G3103 Class SB49 (Japan) and a carbon-manganese steel BS 4360 Grade 50D. With these very low inclusion levels it is possible to obtain welds having similar toughness to the parent material.