What are the Parts of a Weld?- Explain with Diagram

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

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 Weld

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 a Weld Explained

Before proceeding with any welding operation, welders must understand common welding terms.

Parts Of Weld

Base Metal: The base metal is the metal or alloy that is to be welded.

Electrode: An electrode is a component of the welding circuit that conducts electrical current to the weld area. Electrodes may be consumable or non-consumable, depending on the welding process. Some electrodes such as those used in shielded metal arc welding, are covered with a flux coating.

Weld bead: A weld bead is a weld that results from a weld pass.

Weld Pass: A weld pass is a single progression of welding along a weld joint. A single-pass weld requires only one weld pass. When laying a bead in a multiple-pass weld, each weld pass builds on the previous pass. The movement of the heat source creates ripples as the weld bead is deposited.

Ripple: A ripple is the shape within the deposited bead caused by the movement of the welding heat source.

Crater: A crater is a depression in the base metal that is made by the welding beat source at the termination of the weld bead.

Joint Penetration: A joint penetration is the depth of the weld metal from the weld face into the joint. The joint penetration measurement does not include the weld reinforcement measurement.

Weld Reinforcement: A weld reinforcement is the amount of weld metal in excess of that required to fill the joint.

Root Reinforcement: A root reinforcement is a reinforcement on the side opposite the one on which welding took place.

Face Reinforcement: It is reinforcement on the same side as the welding.

Root Face: The root face is the portion of the groove face within the joint root.

Root Opening: The root opening is the distance between joint members at the root of the weld before welding. The root opening must be accurate so that excess welding is not necessary.

Weld width: A Weld width is the distance from toe to toe across the face of the weld.

Weld Toe: The weld toe is the point where the weld metal meets the intersection of the base metal and the weld face. The toes are the points where the base metal and weld metal meet.

Weld Face: The weld face is the exposed surface of the weld, bounded by the weld toes on the side on which welding was done. The face may be either concave or convex.

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.

Weld Root: The weld root is the area where filler metal intersects the base metal and extends the furthest into the weld joint.

Joint Root – That portion of a joint to be welded where the members approach closest to each other. In cross-section, the joint root may be a point, a line, or an area.

Root Bead: A root bead is a weld bead that extends into or includes part or all of the joint root.

Root Pass: A root pass is the initial weld pass that provides complete penetration through the thickness of the joint member.

Filler metal is metal deposited in a welded, brazed, or soldered joint during the welding process.

Fusion welding is welding that uses the fusion of the base metal or base metal and filler metal to make a weld. Fusion welding is the most common method of joining metals.

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.

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 actual throat is the shortest distance from the faces of the fillet weld to the weld root after welding.
  • Effective Throat: The minimum distance minus any reinforcement 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. 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 become 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.