NRL type crack starter explosion tests and explosion bulge tests of mother plate and welded specimens were conducted on 5 Japanese high strength steels, HT-50 (Mn-Si steel), HT-60 (Mn-Si steel, quenched and tempered), HT-70 (HY-80 steel type), HT-80 (T-1 steel type) and stainless clad steel (HT-50base).
As a result of crack starter test, FTP temperature of HT-70 was found to be -60°C, and was considered as a sufficient material for naval ship structures.
Bulge tests at room temperature and -20°C showed that welded specimens of all steels tested had almost same strength as their mother plates for explosive force. Stainless clad steel showed no superiority than 50 HT. No remarkable effect of preheat of welded specimen of HT-70 was observed. Various notch-toughness tests (2 mm V-, 2 mm U- and press notch charpy and drop weight tests) were also conducted and comparisons were made with the result of crack starter explosion test.
