Heterogeneous weld

This occurrence had raised some fundamental questions, on the authority s side, not only with regard to elementary operational considoations but above all with a view to safety. Priority in the following discussions was given to the integrity of the heterogeneous weld seam in the upper area of the vessel and to the functioning of the shutdown systems. 

A.2 Results from Visual Inspection of the Heterogeneous Weld on SG16 in April 2002... 

In the period 2002-2003 we focused on performing phase analyses of corrosion-induced damage to feed water pipelines in SGI6 near the heterogeneous weld. Visual inspections were done, and original in situ specimens were scraped off. The conclusions from the visual inspections (performed on 19 and 29 April 2002 at SG16) were as follows. 

Visual inspection on 29 April 2002 focused on the heterogeneous weld, which connects a feed water pipe made of carbon steel (GOST 20K) to a new feed water pipeline system made from austenitic steel (CSN17248). Several samples were taken for MS analysis from the weld as well as the surrounding area in the form of powders or small particles (descriptions of the samples are given in Table 4.25 and Figures 4.67 and 4.68). The heterogeneous weld was well polished. 

Table 4.25 Descriptions of specimens taken from the region of the heterogeneous weld...

Feed water pipeline (GOST 20), about 40 cm from the heterogeneous weld, close to the internal body surface of SG16... 

After visual inspection, the corrosion phase compositions of the samples taken from close to the heterogeneous weld were evaluated. The MS results are summarized in Table 4.26. 

In this final section, emphasis will be placed on the relationship between the behaviour of the homopolymer and that of heterogeneous systems containing interfaces. Thus, in Sect. 4.2, rather than dwell on the (albeit very important) technological aspects of welding, the discussion centres on the extent to which studies of interfaces might help in understanding the fundamentals of fracture in semicrystalline polymers, as they have in the case of interfaces between amorphous polymers [137]. 

Processing of rubbery materials The effect of milling on the heterogeneity of rubbery materials and changes in their chemical and physical structures is determined by means of optical spectroscopy, NMR relaxation experiments and NMR imaging (Chapters 3, 7 and 10). Welding of crosslinked polyethylenes is discussed in Chapter 5. 

Very pure single crystals have defects that can effect corrosion, but impurities and alloying elements, grain boundaries, second phases, and inclusions often have serious effects. Welded structures invariably corrode first at the welds because of metallurgical heterogeneities that exist in and near welds. The most susceptible site or defect in a metal will be the first to be attacked on exposure to a corrosive environment. Sometimes such attack simply results in innocuous removal of the susceptible material, leaving a surface with improved corrosion resistance. (Frankel)5... 

D.P. Field, T.W. Nelson, Y. Hovanski, and K.V. Jata, Heterogeneity of Crystallographic Texture in Friction Stir Welds of Aluminum, Metall. Mater. Trans. A, Vol 32, 2001, p 2869-2877... 

N. Kamp, A. Sullivan, R. Tomasi, and J.D. Robson, Modelling of Heterogeneous Precipitate Distribution Evolution during Friction Stir Welding Process, Acta Mater., Vol 54, 2006, p 2003-2014... 

Welded joints in the Al-6Cu-Mn alloy are distinguished by considerable structural and chemical heterogeneity, the result of high Cu content and the presence of slight soluble impurities of Fe and Si. Impurities in the parent metal are concentrated in intermetallic clusters, and, in the weld and fusion zone, they are contained in eutectics, located as intergrain layers. 

The macrostructure of all joints was heterogeneous across the weld. Lower (root) weld passes were distinguished from the upper ones by their finer crystalline structure. When welding with the 5183 electrode, the heterogeneity was less noticeable. 

The reactor block is suspended to the slab via 21 upper hangers. These hangers have three welds that are difficult to access, one of which is heterogeneous. A test programme for these three welds was developed on a model. Applying this to the reactor required the development of automatic ultrasonic inspection equipment ... 

Ono (1995) characterized the alite in raw (poorly) burned clinker in relation to the occurrence of the alite (1) next to free lime and (2) next to a belite nest. Where alite is next to a free lime cluster, the alite is small, isolated and dispersed, separated from free lime, con tains a large amount of melt, is strongly etched, and is heterogeneous and zoned. Alite next to a belite nest is relatively large, connected and welded, touching the belite, contains a small amount of melt, is weakly etched, and is homogeneous and flat (not zoned). 

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