Carbon steel weld defects

Weld attack. Welds are often more susceptible to corrosion than other areas (see Chap. 15, Welds Defects ). Welds may contain porosity, crevices, high residual stresses, and other imperfections that favor attack. Carbon steel welds are usually ditched by acid attack (Fig. 7.10). 

Ferrous-aUoy-clad tube sheets are generally prepared by a weld overlay process in which the alloy material is deposited by welding upon the face of the tube sheet. Precautions are required to produce a weld deposit free of defects, since these may permit the process fluid to attack the base metal below the alloy. Copper-aUoy-clad tube sheets are prepared by brazing the alloy to the carbon steel backing material. 

Although caustic cracking occurs over a wide range of temperatures, these appears to he no correlation between temperature and time to failure. Because few failures have been reported at nearambient temperatures, it appears that crack initiation times are inordinately long unless precracking, for example, in the form of weld defects, has occurred. Caustic cracking of carbon steel has been found to occur over a narrow range of potentials near the active current peak of potential/log current curves. 

Welding is sometimes used to repair broken and defective castings [6]. This process is more difficult than welding steel because the high carbon content in cast iron may lead to brittle structures on cooling, thus... 

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