It is essential for welding associates especially that of Inspection, to have work knowledge about basic elements of weldment. For this he must have a good practical experience of observing and examining the very basic weld components. He must have great skills to make a clear distinction between weld components and to identify them. Some elements are the points of great significance and must not be neglected in Inspection. Any negligence may cause severe weld defects. For example Hydrogen Induced Cracking at Weld Toes; weak toes are the primary source of serious cracking. Following are the ten basic weld components that a welding personnel must know.
1. Base metal
This is also called as parent metal. These are the pieces or parts of metal that are joined with the help of brazing and welding techniques. The parent metals are of different materials ranging from metals to some plastics. In welding industry some metals and alloys are being used that have superior metallurgical and physical properties. It is said that parent metal is being selected on the basis of good corrosion resistance and welding characteristics.
2. Filler metal
The metal which is introduced after melting for joining purposes. For the joining of different materials there is also a variety of filler metals. Wide range of filler materials are available in the form of;
- Bare or covered electrodes
- Flux coated or flux cored
- Rods and wires.
One additional advantage of filler metal is to make repair welds. Moreover some non-consumable electrodes like tungsten and tungsten alloys are also being used.
3. Weld metal
The piece of metal that after melting, flows and covers the joint and allows the base metal to be connected due to firm fusion. The weld metal must correspond to the parent metal in the sense of chemical composition and physical properties. So the suitable filler metals should be added according the type of parent material.
4. Heat Affected Zone
The zone of base metal that is affected by the heat of welding. It changes the metallurgical attributes of that zone or part without going in melting state. The microstructure along with properties tend to be changed due to thermal cycle while the heat input, filler metal and the parent metal define the extent of alteration in microstructure.
5. Fusion Line
The distinction between weld metal and heat affected zone is identified with the help of imaginary line called fusion line. See the fusion line in the figure. The fusion line is also source of different weld defects (like lack of fusion). So care should be taken in order to avoid weld defects.
6. Weld Zone
The weld zone in conjunction with heat affected zone is collectively called Weld zone. In other words the combination of weld metal and HAZ is called weld zone. An Inspection personnel must have good knowledge about examining the components of weld zone.
7. Weld Face
The weld surface which is exposed to the welding personnel. In brief the surface that is situated on the other side of the root from where the weld is deposited.
8. Root Pass
The first weld pass that is laid to make a connection of joint. The separation between the two plates at the unbeveled portion of joint is called root where the first weld layer is deposited.
9. Weld Toe
The distinction between the weld surface (weld face) and base metal is identified by the boundary line. In other words weld toe is a dividing line between the weld face and parent metal. Moreover weld toe is also termed as a boundary line between the weld runs. As it has been previously stated that weld toe is very imperative weld feature for inspection purposes. Since high stress concentration occurs at weld toes, and consequently cause the initiation and propagation of catastrophic stresses. So an Inspection personnel must keep an eye on such kinds of toe defects.
10. Excess weld
It is a kind of an excess metal that is deposited during welding just to impart reinforcement to joint. For this purpose an extra amount weld metal is deposited from both upper (weld cap) and lower side (root) of the joint. It should be noted that overfill may also impair the strength of weld.