Resistance welding of high-strength steel grades with coatings

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Mainly on account of the automotive industry, stronger steel grades and sheet materials consisting of galvanised steel with organic coatings are being developed. The data about the weldability of these materials is not always up-to-date or available. Companies lose the overview regarding materials because of the fast developments.

Project goals

The project's objective was to increase the knowledge related to the weldability of a number of new high-strength steel grades and steel grades with coatings. The user committee of 15 to 20 companies made a choice regarding the materials and the material-coating combinations to be investigated, in oàrder to obtain a relevant reflection of current requirements of the industry.

At least one high-strength steel grade and one steel-coating combination were extensively tested for each participating project partner. The real welding tests provided the optimum welding parameters as well as the settings for which the longest electrode life was achieved.

Faster and unambiguous testing procedures were also developed to characterise additional materials and to investigate the weldability. In addition to the optimum welding parameters and weld cycle (for example, application of a normalising treatment), data was also produced about the corrosion resistance after welding. The way in which non-destructive testing should be performed and the way in which this data can be interpreted and validated were specific results of the research project. The research project also checked the usefulness of existing software to determine the life of electrodes.