Welding definition

Fig. 9.26 Weld definitions, (a) Fusion weld and (b) resistance spot weld...

The macrographic examination of a welded joint shows two distinct zones, namely the fusion zone with its immediate surroundings and the parent metal. It is apparent therefore, that such processes produce differences in micro-structure between the cast deposit, the heat-affected zone, which has undergone a variety of thermal cycles, and the parent plate. Figure 11.11 shows the basics of weld definition. 

Figure 11.11 Weld definitions. (Top) Fusion welding a - center of weld metal b - fusion line c - fusion line +1 mm d - fusion line +3 mm e - fusion line +5 mm I - parent metal 2 - weld 3 - HAZ. (Bottom) Resistance spot welding.

The following methods are acceptable for manual welding and brazing, semiautomatic welding, and/or mechanized welding or brazing. See Chapter GR-1, ASME BPV Code Section IX para. QW/QB-492, and AWS A3.0 for terms and definitions. 

The following examples are intended to illustrate the application of the rules and definitions in para. IP-3.4.2 for welded branch connections. 

Welding is very difficult for PTFE and definitely alters mechanical properties. 

Di, = outside diameter of branch Ri = bend radius of welding elbow or pipe bend r = see definition in para. 304.3.4(c) and Table 10-48 r2 = mean radius of matching pipe s = miter spacing at centerline... 

The Standard includes a definition too for solvent bonding solvent welding (see Chapter 6). 

Radiographing metals to determine weld quality. (Iridium-192, with a 0.3 MeV gamma ray, provides better definition than Co-60 in some cases but has a shorter half-life.)... 

Many of the design and fabrication details for equipment are governed by various codes, such as the ASME Codes. These codes can be used to indicate definite specifications or tolerance limits without including a large amount of descriptive restrictions. For example, fastening requirements can often be indicated satisfactorily by merely stating that all welding should be in accordance with the ASME Code. 

The stability of both foam films and the foam, plays an important role in the effective application of the foams. They should satisfy special requirements for stability which might differ significantly even within the same group. Several techniques for controlling the quality of the products, for example, of beer, tea and whisky [8], or the tightness of pipe and reservoir welds, are based on the formation of a foam with a definite lifetime. 

Some studies have associated ALS associated with exposures to solvents,I44-45 60 Hz magnetic fields, and welding,I46l whereas others have questioned these associations. I47 49l A study of twins, however, strongly suggested an association between exposures to solvent chemicals and ALS.1501 As of this writing, the connection between neurotoxic chemical exposure and ALS remains suggestive, but not definitively proven. 

Results (fig.2) show that the parent material is almost stress free. In the weld pool tensile bulk (around 60 MPa) stresses were found, whereas the opposite occurs in the heat-affected zones (HAZ). Curve shapes are consistent with theoretical and experimental behaviours reported in literature [6,7], and suggest the presence of structure change stresses , according to Macherauch s definition [7], This means that a superposition of the shrinkage stress due to different cooling rates inside and at the borders of the weld, and structural change stresses due to the presence of different phases can be outlined. 

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