INVESTIGATION OF MEANS FOR EVALUATING THE QUALITY OF HULL PLATE STEEL BY TESTS CONDUCTED ON FURNACE OR LADIE SAMPLES

A simple but reliable method for evaluating the notch sensitivity of hull plate steel before the steel has been rolled into plate was sought. Tests made on cast ladle samples from open hearth heats verified the results obtained on laboratory steels which showed that small hot-worked ladle samples will distinguish relatively large differences in the notched-bar impact resistance of hull plate steels. Correlation between the deoxidation practice and the notched-bar impact properties was obtained for both the commercially rolled plate and the hot-worked ladle samples although the actual impact values for the ladle samples were highxer than for the plate samples. The Walker Wedge-impact test was investigated as a possible method for evaluating the quality of hull plate steel on samples poured from the furnace or ladle. The Walker wedge test was not sufficiently sensitive to distinguish a difference in impact resistance between an aluminum-killed steel and a silicon-killed steel when each was either in the as-cast or normalized condition. Notched-bar impact tests showed an appreciable difference in the impact resistance of these two steels. When the as-cast surface was removed by grinding, normalized wedges free from defects failed to break at a testing temperature of minus 80F.