Weld bead size

With procedures of this type no control of weld bead size is normally necessary. However, when conditions are severe (for example, high carbon content, thick plate, or high restraint levels) there is some advantage in producing relatively small beads. These require little time at the interpass temperature for much of their... 

A wide range of micro-structures can be developed, based on cooling rates, and these microstructures are dependent on energy input, preheat, metal thickness (heat-sink effects), weld bead size, and reheating effects due to multi-pass welding. 

Step 3 Decide combined thickness of joint in question (Chapter 3). Step 4 Decide limitations on heat input, bead size, or electrode size which can he used (Chapter 3). These limitations may arise because of positional welding or because of a need to achieve minimum toughness levels in weld metal or HAZ. Step 5 Trace horizontal line to obtain required preheat level. 

In some cases it is possible for a limitation on preheat to require a minimum bead size which is larger than that which can be produced, particularly when welding in the overhead position. In such circumstances the diagram indicates that it is necessary to use a... 

Mild steel is the first, and generally the most weldahle class of steel. It has very low hardenability and any suitable electrode may be used. For thin section welds preheat is not necessary, and with CE values less than 0.30 no control of bead size is needed for any combined thickness. Overhead and vertical-down welding can be performed successfully at 1.3 kj/mm on any thickness up to a CE of... 

Horizontal-vertical welding at 1.8kJ/mm can be undertaken up to a CE of 0.34. For mild steels generally, composition may not be known and a maximum CE of 0.38 must be assumed. Table 4.1 summarises the heat inputs to be used to control bead size when welding without preheat mild steels of assumed maximum CE 0.38. 

These steels are of relatively low hardenability and preheat is not usually necessary for thin sections. Those thicknesses which can be welded without preheat however depend on composition, hydrogen level, and bead size Fig. 4.1 relates these factors to define those thicknesses which can be handled without preheat. In this diagram the appropriate CE axis. A, B, C, or D, selected from Table 3.2,... 

It is general practice, at the design stage, to assume an inhibitor efficiency of 0.9 (more precisely this figure should be 0.85 for condensate, 0.9 for gas, and 0.95 for oil streams), thus Fj = 0.1. However, lower figures should be considered where high flow velocities are expected to produce erosion-corrosion attacks in the presence of disturbances. In fact, it is possible to have erosive liquid flow at local flow disturbances such as weld beads, pin ends in connections, bends, size reduction. 

Corner Welds No beveling is required, vreld outside. Size of fillet is not to be specified—fillet a tittle heavier than plate is understood. For heavy strains v td one bead ir de in addition to outside weld. See folowing examples ... 

Butt Welds, too percent penetration is undeistooo-no size o bead specification is required-specity single oi double butt weld Gnno. ifusn and bevel as required. 

At the end of the welding train , it is advisable to provide a tractor, even of small size for the manual repair of defects on the external bead. 

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