Heat tint on stainless steels caused by an oxidation leads to unnecessary expense to both users and producers of plants and components. An important cause for this is that there is no clear standard or recommendation generally valid for specification and testing the quality of welds that have to meet corrosive conditions. Projects, failure analysis and consulting jobs have given The FORCE Institute a basis for elaborating a set of recommendations. Full corrosion resistance defined as a resistance at the same level as the unaffected base material can be obtained only by following strict requirements for the root gas shielding or by post weld treatment. At low corrosiveness relative to the alloy selected, these requirements can be somewhat less strict. As a help for specifying acceptance criteria and for the subsequent testing, colour photographs in the Reference Charts 4 have been established. Here heat tint levels are designated from "A" to "H". In the process of elaborating a purging procedure to reach a specified quality, help can be gained from another FORCE Institute report (at present available only in Danish). It shows that critical parameters for the purging and the purging tools can be identified and gives recommendations for the design and test of tools. One of the main factors in exploiting the full benefits of stainless steel is to achieve proper gas shielding of the root zone during welding or to perform an efficient post weld treatment.
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