When discussing anything with multiple components, you need to know the names of each part. This also applies to welds. There are multiple “parts” that every welder needs to know.
To understand the different parts of a weld, use the image below along with the definitions below (the image of a weld above is a cross-section view of a fillet weld):
Fillet Weld. A fillet weld joins two pieces of metal at an angle (60 to 120 degrees) or two lapped, flat ends. The bead sits on the inside corner created by the base metal.
Groove Weld. A groove weld is a bead placed into a groove made on the surface of the workpiece or the opening between two butted pieces.
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: This is the melted area of the base metal (not the weld metal or filler metal you are welding with). 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 the exceeds the amount of metal you need for the size of the weld.
Fillet Weld Throat: When you discuss the throat of a weld there are two to consider: 1) theoretical weld throat 2) actual weld throat.
The Theoretical throat is where you take the distance of the perpendicular space from the weld root and the longest side of a right-angle triangle (the hypotenuse) of the right triangle you can create inside of a cross-section of a fillet weld.
The Actual weld throat is simply where you take the space between fillet weld root all the way to the center of the weld face (the cross-section of) and measure it.
What Is the Size of The Weld?
- Equal Leg Length Fillet Welds. For fillet welds with equal leg length, the size of the weld is designated by the leg length of the largest isosceles right triangle that can be scribed within the fillet weld cross-section.
- Unequal Leg Length Fillet Welds. For unequal leg length, the size of the weld is designated by the largest leg length of the largest right triangle that can be inscribed within the fillet weld cross-section.
- Groove Welds. The size of the weld is the depth of chamfering, plus the root penetration when specified.
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.