Cracks weld metal

General description. In incomplete fusion, complete melting and fusion between the base metal and the weld metal or between individual weld beads does not occur (Fig. 15.8). Incomplete fusion that produces crevices or notches at surfaces can combine with environmental factors to induce corrosion fatigue (Chap. 10), stress-corrosion cracking (Chap. 9), or crevice corrosion (Chap. 2). See Fig. 15.9. 

The cracks illustrated in Fig. 15.18A resulted from weld metal-shrinkage along the long axis of the weld. The cracks in Fig. 15.18B were caused by shrinkage along the short axis of the weld. The cracking illustrated in Fig. 15.18D may be caused by lack of penetration. 

Austenitic types. These are susceptible to hot cracking which may be overcome by balancing the weld metal composition to allow the formation of a small amount of 5-Fe (ferrite) in the deposit, optimum crack resistance being achieved with a 5-Fe content of 5-10%. More than... 

L. Gas-oil hydrodesulfurization unit. Elbow cracked intergranularly and decarburized at fusion line between weld metal and heat-affected zone no postweld heat treatment. 

Detection Capability Has been shown to detect advanced stages of microscopic HTHA in base metal, away from welds. Can distinguish HTHA from plate laminations. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Con reliably detect HTHA only after cracks have formed. Cannot detect microscopic HTHA. e i m z tr> r t- a -0 1 a -j. UJ ai ru o, a a Ln tr UJ UJ Ln -U UJ tr -u 1... 

Cross section of channel of exchanger./Note cracking in weld metal at right (light colored area) of specimen.3... 

As the hquid metal in a weld solidihes, it becomes at least partially constrained by the surrounding parent metal. When the weld metal cools to ambient temperature, the resulting residual stress in the weld is approximately equal to the ambient temperature yield strength of the parent metal. Stress relief heat treatment for welds is called postweld heat treatment. An additional benefit of such treatment is a reduction of the hardnesses of the weld metal and heat-affected zone (HAZ), thns reducing the risk of stress corrosion cracking. 

Weld metal hydrogen cracks in (a) single-run manual metal-arc fillet weld, (b) root bead of Y groove welding test, (c) submerged-arc weld (longitudinal section). 

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