Metal welding - Figure 5 - surface profile of carbon steel DH36 after 1 year of corrosion at Dalat site (a) base metal, (b) heat affected zone, (c) weld. Through CO2 gas shielded welding (250A, 29V, 300mm / min, 14.5 kJ / cm).
Typical steel DH36 welding joint base metal, fusion line and weld area are subject to different degrees of corrosion, the surface is full of large and small pitting pits, from the base metal area to the weld area pitting pits gradually become larger and deeper, the maximum radius of the weld position pitting pit even reaches 580 μ m. Maximum depth 130 μ m； However, the maximum radius of pitting pit in base metal area is only 200 μ m. Depth 48 μ m。 It shows that the weld zone of typical steel DH36 welded joint is more seriously damaged in tropical marine atmosphere, which is mainly related to the thermal cycle process of the welded joint. After two years of in-situ corrosion, dense pits were distributed in each area of the surface, in which the number of pits in the base metal was more, while the pits in the heat affected zone showed a large and deep morphology, indicating that the corrosion in the heat affected zone was more serious.
