Evaluation of high-strength steel castings possessing improved weldability

Naval components fabricated from HY-80 high-strength steels require an expensive preheat during welding to avoid heat-affected zone (HAZ) cracking. Quenched-and-tempered low-C, high-Ni steels were evaluated as potential alternatives to HY-80 steel castings with section sizes of 230 to 300 mm thickness. The investigation examined the feasibility of obtaining mechanical properties equivalent to HY-80 by heat treatment and evaluated weldability. The steel resulted in a crack-free casting, and preliminary tests suggest that it could be welded without preheating. Optimized heat treatment provided reasonably good yield strength (517 to 538 MPa) and Charpy impact toughness (63 to 80 J Charpy V-notch (CVN) energy at −73 °C). The former properties were just below HY-80 casting requirements of 550 MPa. Thus, while this composition might not be a suitable replacement for HY-80, there are other potential casting applications. These include surface ship shaft struts and rudder inserts that have less stringent strength and toughness requirements.