Lokomo Steels started duplex stainless castings production already in mid 1920's. Today Lokomo Steels manufactures large range of different grades of duplex and super duplex stainless steel castings for various purposes, e.g. for valves, process industry, offshore etc. There has been very few studies on fracture mechanics of duplex stainless steel and the acceptance criteria or testing procedure of duplex stainless steels fracture toughness have not been established. This study gives fracture test data for cast and welded duplex stainless steel.

In this work 70mm thick test plates of Duplok 4A Vaculok (UNS J92205) duplex stainless steel with nominal composition of 22% Cr – 6% Ni – 3.0% Mo – 0.13% N were welded using flux cored wire and shielded metal arc welding processes. K-edge preparation with 45° angle in the weld groove was used. The welding was carried out in 3G position (PF-position) using 1.2mm diameter rutile flux cored wire in the FCA welding and 3.25mm rutile electrode in SMA welding. The heat input in the FCA welding was 1.6–1.8 kJ/mm and in the SMA welding 1.4–2.6 kJ/mm.

Crack Tip opening Displacement (CTOD) test specimens with cross section of 60´ 60mm were manufactured and tested at –40°C temperature. The notch of the CTOD specimens was located both at the centre line of the weld metal and at the heat affected zone (HAZ). The CTOD tests were carried out in the as welded condition. The base material was in the solution annealed condition. Cross weld tensile tests and side bend tests were made for plates of both welding processes, as well as, Charpy V-notch tests with the notch different locations at –40°C temperature. The strength and impact toughness values were also determined for the base plate. Critical pitting corrosion temperature (CPT) of the base material, welds and HAZ was determined using standard FeCl₃ practice.