A localized coalescence of materials (metals or non-metals) produced either by heating the metals to suitable temperatures, with or without the application of pressure, or by the application of pressure alone, with or without the use of filler materials.

The word “coalescence” is used since coalescence is defined as “growing together, or growing into one body”. In welding metals, the metallic bond is formed as the weld is being made.

Basic Types of Welds

There are five basic types of welds which are:
1) groove weld
2) fillet weld
3) plug and slot welds
4) surfacing weld
5) flanged weld


1) Groove Weld

groove-weldA groove weld is a weld made in a groove between the workpieces. There are many different shapes of grooves. Figure 3.4 shows one type of groove weld.

2) Fillet Weld

fillet-weldA fillet weld is a weld of approximately triangular cross-section joining two surfaces approximately at right angles to each other in a lap joint, T-joint or corner joint as shown in Figure 3.5.

3) Plug Weld and Slot Weld

plug-weldA plug weld is a weld made in a circular hole in one member of a joint fusing that member to another member. A slot weld is similar to a plug weld except that the hole is elongated. See Figure 3.6.
In preparation for plug and slot welds, holes or slots are made in the upper plate. On relatively thinner material, such welds can be made without holes or slots and are called arc spot and arc seam welds, in which the upper sheet is melted and fused to the lower sheet.

4) Surfacing Welds

surface-weldAll welds are composed of one or more weld beads. A bead is a single run or pass of weld metal. A weld bead or beads may be applied to a surface, as opposed to making a joint, to obtain desired properties or dimensions. Such a weld is called “surfacing welds”, as shown in Figure 3.7.

5) Flanged Weld

flange-weldsFlanged weld is a group term which covers: corner-flange welds, edge welds and edge flange welds. As shown in Figure 3.8, they are apparently neither groove welds nor fillet welds. They are not surfacing welds because these welds are forming joints along two members.