MIG soldering

Quality improvement of MIG soldered connections in galvanised structures (IGF-No. 16272BR)

Responsible research centres: Rostock University (Prof. Wanner)

Time period: 01.12.2009 bis 31.08.2012

Final report: CMT 20/2013

Project summary:

The increased demands on the quality of outfitting and outfitting processes in shipbuilding have massive impact on the final outfitting of machinery and cargo spaces, passenger cabins, components on the upper deck and below the waterline. For reasons of corrosion a significant proportion of the outfit will be pre-galvanized and further pre- or uncoated before welded or bolted to the respective ship structure. Welding in this case means a loss of corrosion protection that must be restored. This implies complicated subsequent grinding an coating.

The aim of the research project was to increase the connection quality of galvanized outfitting through the use of MIG brazing. As a concrete application, the joining of galvanized ballast water pipes was defined in agreement with the project steering committee. Following questions and problem had to be considered in the course of the project:

  • Development of technological parameters for joining galvanized structures with thicknesses between 4mm and 8mm with CuSi3 CuAl8Ni6 and taking into account the maintenance of corrosion protection.
  • Proof of sufficient bond strength, both under laboratory conditions and in the manual industrial use
  • Proof of receipt of corrosion protection on the inside of the pipe
  • Proof of the tightness of the connection

The realization of the project have been established based on the prior art, and with the development of a suitable test environment, the technological constraints of the process and parameters derived, which visually and anticorrosion technically met the requirements. On this basis, to small and component samples, the mechanical properties are determined and demonstrated sufficient strength. A salt spray test on brazed samples with different damages in the galvanization demonstrated the retention of the corrosion protection by means of soldering. Helium leak tests and pressure tests under laboratory conditions could attest sufficient tightness. The implementation in industrial practice, however, showed that the microstructure of CuSi3 consumables led to an increased error rate in the leak. The causes were analyzed during the project but not yet be eliminated. The applicability of the CuAl8Ni6 consumable under the given conditions has been proven.


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