Weld cracking transverse crack

Figure 4 A radiographic image of a welded joint (defect transversal crack), a Original image, b Edge image (only the defect is maintained).

Account for the HAZ cracking. After the collapse, the other transverse welds in the bridge were milled-out and re welded. What procedures would you specify to avoid a repeat of the HAZ cracking ... 

Figure 2. Passing cracks transversal to the weld bead of a Fe 410 vessel after exercise.

Cracks in the HAZ are usually sited either at the weld toe, the weld root or in an underbead position. These positions are shown schematically for fillet welds and butt welds in Fig. 1.1. In fillet welds, HAZ cracks are usually oriented along the weld length, but in butt welds subsurface cracks can be transverse to the weld. Hydrogen cracks examined in sections of a weld under the microscope may be intergranular, transgranular or a mixture with respect to the transformed microstructures in which they lie. 

The identification of hydrogen cracks is not simple, as they can occur in a variety of locations and orientations, and can be trans-granular or intergranular, the latter being more likely if the steel or weld metal is of the alloyed type, or exceptionally hard. In the HAZ, hydrogen cracks are usually longitudinal to the weld (unless they are extensions of transverse weld metal cracks) and usually have a portion close to the fusion boundary. However, the cracks may divert into the fine-grained HAZ, as in Fig. 1.2(b), or into the weld metal. 

Similar comments are applicable to weld metal hydrogen cracks, with the further observations that cracking in weld metals is frequently transverse to the weld and that in weld metals of the acicular ferrite type, cracking is most common in the primary ferrite (if it is present) at the prior austenite grain boundaries, as in Fig. 1.3(a). In relatively hard, alloyed weld metals (e.g. in the Cr-Mo steels) any transverse weld metal cracking is usually perpendicular to the weld surface, but in C-Mn weld metals the chevron type of cracking (Fig. 1.3(c)) at 45° to the surface is common. 

Fig. 2. Left crack initiation within the Heat Affected Zone (HAZ) during the so-called Erichsen test. 2nd picture shrinkage of the seam at the upper and lower side of two dissimilar sheet geometries. 3rd picture Transverse crack due to shrinkage. Right welding pore at the surface of the seam.

Corrosion damage was limited to minor pitting of the bottom head in the deaerator vessel. Inspection of deaerator vessel B revealed cracking at one weld. Tray sections were removed from the deaerator vessel, and shell welds were grit-blasted. Except for the top head-to-shell weld in the deaerator, all internal welds in both B nnits were then ground smooth and magnetic particle inspected. Three transverse cracks were found at the bottom circumferential weld in the deaerator vessel. These were removed by grinding to a depth of 1.5 mm (0.06 inch). 

A section was cut from a circumferential weld region in storage tank B. The cracking was predominantly transverse to the weld. Chemical analysis was performed on samples cut from weld metal and base metal the results are given in Table 12.5 and show that the steel plate was not aluminium-or silicon-killed, but was most likely a rimmed grade. Cross sections were cut perpendicular to both transverse and longitudinal cracks and were examined metallographically. 

Figure 12.6 shows a crack extending into base metal, transverse to the weld, with secondary cracking to the periphery of the oxidized region. It was clear that the oxide exhibited extensive internal cracking. The figure also shows the entrainment of a lamellar pearhte phase (dark) within the oxide corrosion product. In addition, the crack tips are blunt... 

Cracks are generally transverse to the weld HAZ, and occur both parallel and perpendicular to the... 

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