Weld Types and Positions
Any discussion on weld types and positions starts with the idea that it is important to distinguish between the joint and the weld.
Each must be described to completely describe the weld joint.
There are many different types of welds, which are best described by their shape when shown in cross section.
The most popular weld is the fillet weld, named after its cross-sectional shape. Other types of welds include flange welds, plug welds, slot welds, seam welds, surfacing welds, and backing welds.
Joints are combined with welds to make weld joints.
Types of Welds
A fillet weld joins two surfaces at an approximate right angle to each other. There are several types of fillet weld:
- A full fillet weld is a weld where the size of the weld is the same as the thickness of the thinner object joined together.
- A staggered intermittent fillet weld refers to two lines of intermittent welding on a joint. An example is a tee joint (see below) where the fillet increments that are in one line are staggered in comparison to the other line.
- Chain Intermittent Fillet Weld: Refers to two lines of intermittent fillet welds in a lap joint or T where the welds in one line are approximately opposite those in the other line.
Other terms associated with fillet welds include:
- Boxing which refers to the continuation of a fillet weld around a corner of a member. It is an extension of the principal weld.
- Convexity: Refers to the maximum perpendicular distance from the face of a convex fillet weld to a line joining the toes.
See figure 6-31 below for fillet weld positions.
The second most popular type of weld is the groove weld. There are seven basic types of groove welds, which are shown in figure 6-25.
The groove weld refers to beads that are deposited in a groove between two members to be joined.
More examples are shown in figure 6-26. The type of weld used will determine the manner in which the seam, joint, or surface is prepared. See figure 6-27 for the standard types of groove welds.
These are welds composed of one or more strings or weave beads deposited on an unbroken surface to obtain desired properties or dimensions.
This type of weld is used to build up surfaces or replace metal on worn surfaces. It is also used with square butt joints.
See figure 6-28 below for examples.
Plug welds are circular welds made through one member of a lap or tee joint joining that member to the other.
The weld may or may not be made through a hole in the first member; if a hole is used, the walls may or may not be parallel and the hole may be partially or completely filled with weld metal.
Such welds are often used in place of rivets.
A fillet welded hole or a spot weld does not conform to this definition.
See figure 6-28 below for examples.
This is a weld made in an elongated hole in one member of a lap or tee joint joining that member to the surface of the other member that is exposed through the hole.
This hole may be open at one end and may be partially or completely filled with weld metal.
NOTE: A fillet welded slot does not conform to this definition.
A weld made by flash welding. Flash welding is referred to as a resistance welding process where fusion is produced over the entire abutting surface. Heat is created by the resistance to the current flow between two surfaces and by the application of pressure after heating is mostly complete. Flashing is accompanied by the expulsion of metal from the joint.
See Figure 6-29 below for an example of a flash weld.
A weld made by arc seam or resistance seam welding where the welding process is not specified. This term infers resistance seam welding.
Refer to figure 6-29 below for an example of a seam weld.
A spot weld is a weld made by arc spot or resistance spot welding where the welding process is not specified. This term infers a resistance spot weld.
A weld made by upset welding. An upset weld is a resistance welding process where fusion occurs progressively along a joint of over the entire abutting surface. The application of pressure before heating is required and occurs during the heating period. Heat comes from the resistance to the flow of electric current in the area of contact between the surfaces.
Welding is often done on structures in the position in which they are found.
Techniques have been developed to allow welding in any position. Some welding processes have all-position capabilities, while others may be used in only one or two positions.
All welding can be classified according to the position of the workpiece or the position of the welded joint on the plates or sections being welded.
There are four basic welding positions, which are illustrated in figures 6-30 and 6-31.
Fillet Weld Positions
Flat Position Welding
In this position, the welding is performed from the upper side of the joint, and the face of the weld is approximately horizontal.
Flat welding is the preferred term; however, the same position is sometimes called downhand. (See view A, figure 6-30 and view A, figure 6-31 for examples of flat position welding for fillet and groove welds).
Horizontal Position Welding
The axis of a weld is a line through the length of the weld, perpendicular to the cross section at its center of gravity.
a. Fillet Weld.
In this position, welding is performed on the upper side of an approximately horizontal surface and against an approximately vertical surface.
View B, figure 6-31, illustrates a horizontal fillet weld.
b. Groove Weld.
In this position, the axis of the weld lies in an approximately horizontal plane and the face of the weld lies in an approximately vertical plane. View B, figure 6-30, illustrates a horizontal groove weld.
c. Horizontal Fixed Weld.
In this pipe welding position, the axis of the pipe is approximately horizontal, and the pipe is not rotated during welding. Pipe welding positions are shown in figure 6-32.
d. Horizontal Rolled Weld.
In this pipe welding position, welding is performed in the flat position by rotating the pipe. Pipe welding positions are shown in figure 6-32.
Vertical Position Welding
a. In this position, the axis of the weld is approximately vertical. Vertical welding positions are shown in view C, figures 6-30 and 6-31.
b. In vertical position pipe welding, the axis of the pipe is vertical, and the welding is performed in the horizontal position.
The pipe may or may not be rotated. Pipe welding positions are figure shown in figure 6-32.
Overhead Position Welding
In this welding position, the welding is performed from the underside of a joint. Overhead position welds are illustrated in view D, figures 6-30 and 6-31.
Pipe Welding Positions
Pipe welds are made under many different requirements and in different welding situations.
The welding position is dictated by the job.
In general, the position is fixed, but in sane cases can be rolled for flat-position work. Positions and procedures for welding pipe are outlined below.