"The presence of some delta ferrite (estimated to be about 4 to 8% in austenitic stainless-steel weld metal can minimize or retard the susceptibility of austenitic weld metal to fissuring or cracking during or immediately after welding of heavy sections greater than about in. thick. However@ relatively large amounts (estimated to be greater than about 10%) of delta ferrite can have deleterious effects on the ductility of the weldment after exposure to elevated temperatures because of the possible conversion of the ferrite to sigma. Because of these effects of ferrite@ attempts have been made to impose restrictive limits on the maximum allowable ferrite content of austenitic welds and stainless-steel plates. The present study was undertaken as part of an investigation and a ""round-robin"" examination on samples by the Advisory Subcommittee on the Welding of Stainless Steels to evaluate the problems involved in the measurement of delta ferrite in austenitic stainless steels@ and to determine (1) the ""yardstick"" of ferrite measurement to be used@ (2) the method of calibration of the yardstick@ and (3) the type and size of specimen required for calibration."