Abstract

In 1991, Electric Boat at Connecticut built the hull for the first Seawolf submarine using HY-100 High Strength Steel (HSS). The nominal Carbon content of HY-100 steel is between 0.12 and 0.20 wt-%. When the Carbon content exceeds 0.12 wt-%, the morphology of martensite is likely to change from needles to plates [1,2], and this morphological change in the weld Heat Affected Zone (HAZ) microstructure is known to adversely affect both Charpy V-Notch (CVN) impact toughness and/or fracture toughness besides increasing the sensitivity to Hydrogen-Induced Cracking (HIC). Between June and July of 1991, several micro-cracks related to HIC were found in the hull of the first Seawolf submarine. Professor Thomas W. Eagar at Massachusetts Institute of Technology evaluated the underlying problem. He reported that lubricant contamination on the surface of the solid wire electrode used in Gas Metal Arc Welding (GMAW) was one of two primary causes [3]. The second primary cause was the high Carbon content of the solid wire electrode, but the Carbon content was at the high end of the relevant solid wire electrode specification limits such as MIL-E-23765/2E [4] and AWS A5.28 Specification for Low-Alloy Steel Electrodes and Rods for Gas Shielded Arc Welding [5].

Keywords:Carbon; Solid wire electrode; Welding; Plate steels; Microstructures