CRACK PROPAGATION TESTS OF HIGH-STRENGTH SHEET MATERIALS PART Ⅲ-LOW-ALLOY AIR-HARDENING STEEL

摘要

The results of crack propagation tests, using center-cracked sheet tensile specimens, 0.5 inch wide and 0.075 inch thick, are presented for a proprietary, low-alloy, air-hardening steel (0.4% C, Cr-Mo-V), capable of being heat-treated to a tensile yield strength of at least 230 ksi. In this condition of highest strength the fracture-appearance transition temperature (FATT) was 200° F and the net fracture stress was much less than the yield strength at all temperatures in the range -200 to +500° F. Considerable improvements in these features were obtained by the use of two other tempering treatments, each of which resulted in a yield strength of slightly less than 200 ksi; however, the FATT was still above room temperature in each case.