When we examine welding in detail, it is important to know the names of the different parts of a weld. To understand the different parts of a weld use the image above along with the definitions.
Fillet welding refers to the joins of two pieces of metal when they are perpendicular or at an angle (60o to 120o). These welds are commonly referred to as T-joints, which are two pieces of metal perpendicular to each other, or lap joints, which are two pieces of metal that overlap and are welded at the edges.
The weld is triangular in shape and can have a concave, flat, or convex surface depending on the welder’s technique. Welders use fillet welds when joining flanges to a pipe and when welding cross-sections and when bolts are not strong enough and wear out easily.
Groove welds are also known as butt welds when two pieces of metal are lined up together without overlap and then welded along the joint as opposed to lap welds, where a piece of metal is placed one on top of the other, or plug welding, where one piece of metal is inserted into the other.
It is important that with a butt joint, the surfaces of the workpieces to be joined are on the same plane and the weld metal remains within the planes of the surfaces.
Parts Of Weld Explained
Weld Toe: This is simply your weld that joins the metal pieces you are welding together (the weld face and the metal).
Weld Face: This is the weld that you create on the side of the metal pieces you are welding using any gas welding or arc welding process.
Weld Root: As you can see in the diagram of a weld above, the root of a weld is where the bottom or underside of a weld crosses the surface of the base metal.
Weld Leg: The length of the fillet weld ‘leg’ is from the ‘toe’ of the fillet weld to the joint root. Every fillet weld has 2 legs.
Fusion Zone: The fusion zone is strictly the portion of materials that have undergone melting. The material that has been altered due to the heat of the welding, but not fully melted (the heat-affected zone), is not considered the fusion zone. This is where you want your filler metal to penetrate and fuse.
Weld Reinforcement: As you can see from the diagram above, it’s the extra weld metal that exceeds the amount of metal you need for the size of the weld.
Fillet Weld Throat: When talking about the throat of a weld, you need to consider two points: 1) theoretical weld throat 2) actual weld throat.
- Actual throat: The shortest distance between the weld root and the face of a fillet weld.
- Theoretical throat: In the cross-section of a fillet weld, the distance from the beginning of the joint root perpendicular to the hypotenuse of the largest right triangle can be inscribed. This dimension is based on the assumption that the root opening is equal to zero.
What Is the Size of The Weld?
- Equal Leg Length Fillet Welds. The size of an equal leg fillet weld is the leg length of the largest inscribed right isosceles triangle. Theoretical throat = 0.7 × size of weld.
- Unequal Leg Length Fillet Welds. The size of an unequal leg fillet weld is the shorter leg length of the largest right triangle that can be inscribed within the fillet weld cross section.
Multi-pass Welds: Heat Affected Zones in The Parts of A Weld.
The parts of a weld include what is called a multi-pass weld. In other words, you will find situations where you will need to lay down more than one weld bead to form a junction or weld…
The heat-affected zones when a butt weld is created using more than one ‘pass’ (or when you create more than one layer).
The affected area in the first weld layer (first pass)? That is called the primary heat zone. And the secondary heat zone goes over the primary heat zone (or overlaps the primary heat zone) and it is affected by the second layer or pass.
The heat caused by the secondary zone of the weld allows the primary heat zone to become fused with the base metal and becomes stronger through the process called annealing.
In addition to the annealing effect on the base metal from the second and primary heat zones, the filler metal you deposited in the first pass (your weld) is actually improved from the heat from the second pass or layer.