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 Weld
The fillet weld is used to make lap joints, corner joints and T joints. As its symbol suggests, the fillet weld is roughly triangular in cross-section, although its shape is not always a right triangle or an isosceles triangle.
Weld metal is deposited in a corner formed by the fit-up of the two members and penetrates and fuses with the base metal to form the joint.
Note: for the sake of graphical clarity, the drawings below do not show the penetration of the weld metal. Recognize, however, that the degree of penetration is important in determining the quality of the weld.
The perpendicular leg of the triangle is always drawn on the left side of the symbol, regardless of the orientation of the weld itself. The leg size is written to the left of the weld symbol.
If the two legs of the weld are to be the same size, only one dimension is given; if the weld is to have unequal legs (much less common than the equal-legged weld), both dimensions are given and there is an indication on the drawing as to which leg is longer.
The length of the weld is given to the right of the symbol. If no length is given, then the weld is to be placed between specified dimension lines (if given) or between those points where an abrupt change in the weld direction would occur (like at the end of the plates in the example above).
For intermittent welds, the length of each portion of the weld and the spacing of the welds are separated by a dash (length first, spacing second) and placed to the right of the fillet weld symbol.
Groove Weld
Groove welding is used to create a beveled opening in a weld joint before welding to achieve the necessary penetration. The process of creating the bevels is known as groove machining, and welding the beveled surfaces together is known as groove welding.
Groove welding is an essential welding technique for situations where the deformation of the base metals must be limited and high-strength welding is required.
Grooving increases weld strength by enabling full-penetration welding, making groove welding widely used in various applications, especially when arc welding thick plates.
Groove welding is also effective for laser welding, which has narrower weld lines than arc welding, as groove welding allows for narrower weld lines and lower heat input, helping to suppress deformation and residual stress in the base metal.
However, because the weld line is narrower than with fillet welding, higher accuracy is required during groove machining and in tracer control during welding.
Parts Of A 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.