Numerical Simulation of Welding Stress of Enamel Coatings

摘要

The service life of pipeline, which was replaced organic coatings by enamel coatings as protective layer, can be increased, but when the pipeline with enamel coatings is welded, the differences of thermo-physical properties between the base metal and enamel coatings will do harm to the bond strength of the enamel coatings to the base metal. The stress of the coatings was simulated with SYSWELD and the interface between coatings and base metal was examined with SEM. The results showed that the weaknesses of the welded joints occurred in imperfect normalized zone, fusion zone and overheated zone. The micro-cracks generated at the interface between the enamel coatings and the base metal because high level compressive stress occurred and some coatings fused incompletely in the imperfect normalized zone. The coatings of the fusion zone and the overheated zone could be pulled off from the base metal easily because high tensile stress formed during cooling that was dangerous to the brittle enamel coating, the bond layer was damaged by excessive welding heat and the pores generated on the interface between the coatings and the base metal.