No abstract

For additive manufacturing (AM) products such as structural and machinery components, the quality should be verified. In maritime industry, this task is performed by classification societies who are acting as independent third party and certifying such components. In the case of, eg, cast‐steel products, standards are available, which specify sampling procedures, properties, and destructive and nondestructive test methods as well as relevant material requirements for design purposes. For AM products, currently only few supportive standards are available. In tough market situation products must be cost‐efficient. Therefore, mandatory verification of products can only be enforced for vital applications. Unified, meaningful sampling and testing scopes are needed for application at different manufacturing locations and for evaluation by “no AM expert” staff. The impact of manufacturing defects in the AM process on the integrity on the AM product has to be evaluated. Contract partners may, or have to ask for evidence for the integritiy of AM products by certificates issued by third‐party institutions. DNV GL as a classification society has set up procedures for initial qualification and certification of AM products. This paper focusses on inspection and certification of AM maritime products and fit‐for‐purpose assessment.

Longitudinal hot tearing, popularly called as end cracking, frequently takes place in the end portions of large steel panels’ butt joints, using one-sided, submerged-arc welding with flux copper backing welding process (FCB welding). The study was to look for the possibility to improve and/or prevent the end cracking issue during FCB welding, center blind-hole drilling technique was used to measure the welding residual stress for five different cases, considering hot tearing mechanism, its influence factors and the relevant reported prevention measures. Unpredictable result was observed subsequently that transverse compressive stress is found on the shallow surface of weld seams, which could give supplementary information to the common assumption for conventional low heat input welding method that cracks initiation is caused by tensile stresses across the welded joints. The study concluded that FCB welding end cracking issue is caused by the comprehensive function of different stresses, and also properly use tack welding practice, suitable elastic run-off plate and relatively low heat input energy which will reduce the end cracking susceptibility for the tested materials.