Welding heat effects

Figure 3a shows the microstructure of the initial parent metal the structure of d-phase inclusions (CuAh intermetallic compound-based solid solution) is shown in Fig. 3b. As a result of the welding heat effect, most of the inclusions of the intermetallic phase in the HAZ were subjected to partial local melting and were converted into clusters and interlayers of eutectics (Figs. 3c, 3d, 4a, and 4b), while others changed shape only slightly. This is probably explained by the fact that in the condition of nonequilibrium primary solidification, they had a composition considerably different from that prescribed by the equilibrium diagram [%...

Throughout the world, many arc welding methods are used to fabricate large-capacity structures from these steels. The weldability of both steels was evaluated using various methods of welding. Thin samples of both steels were satisfactorily welded. Nevertheless, weld metal of the same composition was susceptible to pore and hot crack formation and resulted in decreased ductility and low impact strength at low temperatures. Both steels were sensitive to the welding heat effect this was... 

Solidification. The heat of the electric arc melts a portion of the base metal and any added filler metal. The force of the arc produces localized flows within the weld pools, thus providing a stirring effect, which mixes the filler metal and that portion of the melted base metal into a fairly homogeneous weld metal. There is a very rapid transfer of heat away from the weld to the adjacent, low temperature base metal, and solidification begins nearly instantaneously as the welding heat source moves past a given location. 

Friction welding Heat zone effect Heli-arc welding Pressure welding Spot welding... 

The effect of the welding process on the severity of weld decay varies according to the process and the plate thickness so that no single recommendation is possible for every thickness of plate if resistance to attack is essential. The severity of weld decay correlates quite well with sensitisation times as calculated from recorded weld heating cycles. 

With some materials, there are specific heat treatments that are known to reproduce the worst effects of the heat of welding. It is recommended, therefore, that in tests made to qualify a material for a particular service environment, in addition to the exposure of welded test specimens in order to observe effects of welding heat, specimens should be included that have been given a controlled abusive or sensitising heat treatment. As an illustration, austenitic stainless steels may be held at 650-700° forO-5-1 h, followed by testing for susceptibility to intercystalline attack as in ISO 3651-1 or -2 1976. 

B. In this instance, heat is conducted from the thennite to the steel during the combustion period. Thus, the steel is heated to nearly the same temperature as the slag and a weld is effectively made. 

M. Attallah and H.G. Salem, Effect of Friction Stir Welding Process Parameters on the Mechanical Properties of the As-Welded and Post-Weld Heat Treated AA2095, Proceedings of the Fifth International Conference on Friction Stir Welding, Sept 14—16, 2004 (Metz, France), TWI, paper on CD... 

This worked example illustrates the use in practice of the removal curves given in the main text. Clearly the problem could be dealt with in greater detail by considering the extremes of likely behaviour indicated in the first part of Table 5.4. In addition, the sequence of heat treatments could be further subdivided to correspond more precisely to actual fabrication procedures and to include the effect on the preheat level of heating cycles due to welding. The effect of a local postweld heat treatment above 150 °C could also be examined. 

Polymers of different colors can be expected to weld differently by infrared welding. Not only are the issues of pigment-polymer interactions present such as the differences in weldability caused by white (titanium dioxide), hlack (carbon black) or other pigments, but heating times and depth of heating are likely to he affected by part color. This kind of phenomenon can already occur in conventional hot plate welding when, in some cases, red and black parts weld differently. It can be expected to become even more of an issue with infrared welding. These effects can he easily handled, but workers must be aware of their presence and how to control them. 

The materials behavior (austenitic, austeno-ferritic, and ferritic steels - base metal, welds, heat affected zones) in terms of thermal aging and its effect on mechanical properties, embrittlement, sensitiveness to corrosion (in normal and incidental environment), and radiation effect on the potentially exposed structures. 

Heat Conduction Mode Welding Heat conduction mode welding describes a family of effects in which the laser beam is adjusted to give a power irradiance of / 1 lO which is used to create a joint without significant... 

The CVN transition and Kid properties of 9Cr-l Mo plate steel in normalised and tempered (N+T) and in two simulated post-weld heat treated (PWHT) conditions were also evaluated. PWHT had no significant effect on the properties which is in conformity with the trend in literature where this steel is stated to be remarkably tolerant to wide variations in heat treatment conditions. Moreover, the cleavage strength of this steel was higher than that for the weld reported above, indicating comparatively poorer fincture resistance for the weld material. 

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