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This report presents results of a 3 month study to evaluate metallurgical and acoustic properties of HF-1 steel. The multiple objectives were to determine the cause and solution for reduced ultrasonic signal generation efficiencies evident during ultrasonic inspection of M549 (RAP) artillery projectiles with electromagnetic acoustic transducers (EMATs). It was shown that reduced generation efficiencies were the result of an in process heat-treatment during fabrication and that the phenomenon was limited to the first 0.007 in. of surface material. Accordignly, surface material prior to and following heat-treatment was examined in an attempt to determine the metallurgical and/or morphological changes that impeded generation of ultrasonic waves with EMATs. Techniques used to characterize surface conditions before and after heat-treatment included chemical analysis, Auger spectroscopy, metallography, scanning electron fractography, transmission electron microscopy, X-ray measurement of residual stresses, strain gage measurement of magnetostriction properties and material acoustic response as a function of magnetic bias. In addition, similar evaluations were performed on other iron alloys containing varying levels of carbon. A compilation of results has led to the hypothesis that reduced ultrasonic signal efficiencies are possibly the result of a weakly magnetic continuous grain boundary phase of Fe3C.Some results are contradictory, however, and as such, studies should be continued so that this hypothesis can be more completely evaluated. It was also shown that in a normal magnetic bias, as opposed to a tangential bias, the surface condition of M549 (RAP) artillery projectiles had no effect on EMAT ultrasonic wave generation efficiencies. It was therefore recommended that the EMAT prototype inspection system for ultrasonic inspection of 155 mm M549 (RAP) artillery projectiles be designed and fabricated with transducers located in a normal magnetic bias. This design change is considered minor and will have neither a significant financial impact on program performance nor influence the capability of the final product to perform reliably.