ULTRATOUGH HIGH-STRENGTH WELDABLE PLATE STEEL

摘要

A transformation toughened, high-strength steel alloy useful in plate steel applications achieves extreme fracture toughness (Cv > 80 ft-lbs corresponding to KId = 200 ksi.in1/2) at strength levels of 150-180 ksi yield strength, is weldable and formable. The alloy is characterized by dispersed austenite stabilization for transformation toughening to a weldable, bainitic plate steel and is strengthened by precipitation of M2C carbides in combination with copper and nickel. The desired microstructure is a matrix containing a bainite-martensite mix, BCC copper and M2C carbide particles for strengthening with a fine dispersion of optimum stability austenite for transformation toughening. The bainite-martensite mix is formed by air-cooling from solution treatment temperature and subsequent aging at secondary hardening temperatures to precipitate the toughening and strengthening dispersions.