ASTM A564 17-4PH Stainless Steel Bar (UNS S17400 / Type 630 / EN 1.4542) is a precipitation-hardening martensitic stainless steel that combines high strength, excellent corrosion resistance, and superior toughness. Compared with conventional stainless steel grades such as 304 and 316, 17-4PH provides significantly higher mechanical strength while maintaining good resistance to corrosion in marine and industrial environments.