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
2) Fillet Weld
3) Plug Weld and Slot Weld
A 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
All 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
Flanged 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.