TWI Industrial Member Report Summary 160/1981
By W O Dinsdale and S B Dunkerton
Charpy impact tests havebeen carried out on orbital friction and inertia (stored energy) welds in a carbon-manganese steel, BS2772:150M19. The results are compared with continuous drive friction welds made in the same batch of steel. It is shown that the inertia welds behaved similarly to the continuous drive welds in that the 'as-welded' toughness was very poor in relation to that of the parent material and that there was some response to postweld heat treatment. The orbital welds however, did not follow the same pattern as in the 'as-welded' condition, they showed reasonable toughness above a temperature of approximately +5degC. Metallurgical examination suggests that the effect may be purely a function of the orientation of the inclusions in relation to the impact specimens and may not apply to other sizes and configurations. The toughness improved in a similar manner to the conventional friction and inertia welds when postweld heat treatment was applied. Some doubt is thrown on the conventional methods of estimating percentage crystallinity from a fracture face and it was necessary to examine the specimens in a scanning electron microscope to obtain a truer estimate.