THE INFLUENCE OF HEAT INPUT ON THE FRACTURE AND METALLURGICAL PROPERTIES OF HSLA-65 STEEL WELDS

摘要

HSLA-65 steel (ASTM A 945-05) is regarded as an excellent naval ship steel. Its low carbon equivalent and strength-to-weight ratio make it a candidate for future Canadian naval platforms. Unlike previous naval platforms, future ships might be expected to be deployed to Arctic waters. This increased operational requirement imposes a strict fracture toughness criterion for both the base metal and welds. In particular, the heat affected zone (HAZ) of the weld is of concern, especially for high heat input processes. In this study, welds were fabricated using the flux core arc welding (FCAW) process using two different heat inputs. For the high heat input welds, the ductile-to-brittle transition temperature shifts above the minimum service temperature, while the ductile-to-brittle transition temperature for the low heat input case remains well below the service temperature. The reason for this significant shift in the transition temperature is examined, revealing that the sampling location of the Charpy notch is a significant factor, along with the underlying transformation product.