15.1 Weld Joints and Positions
Cameron Kjeldgaard
Weld Joints
A weld joint is the junction of two workpieces to be joined by welding, or in some cases brazing. There are five basic joint types.
- A Butt Joint is created when two workpieces are butted against each other along their thickness; their surfaces will typically lie in a common plane.
- A T Joint is created when the edge of one workpiece abuts the surface of the other, creating a T shape. It is most common for the workpieces to be perpendicular, but in some cases, the abutting member may be skewed at an angle, referred to as a skewed T joint.
- A Lap Joint is a joint configuration in which the surfaces of the two workpieces lie in close contact, and neither of their edges abut the other.
- An Edge Joint is created when the surfaces of two workpieces lie parallel or nearly parallel, and their edges lie in a nearly common plane. Welding in these joints takes place at the junction of the two edges.
- In a Corner Joint, the two workpieces form an L shape. There are three possible configurations for a corner joint. In an open corner joint, the edges of the workpieces do not overlap at all. In a closed, sometimes called flush, corner joint, the surface of one workpiece completely overlaps the edge of the other. The joint may also be half-open, where the surface of one workpiece only partially overlaps the edge of the other.
Depending on the type of weld that will be deposited in each of these joints, a fillet weld or groove weld, there will be different terms and measurements used to describe specific parts of the joint and resulting weld. However, all welded joints share a common feature that is of particular importance to the welder: the joint root. The joint root is defined as that portion of the weld joint in which the two workpieces come in closest proximity to one another. Weld size, and by proxy weld quality, is often measured by the penetration of weld metal into the joint root. In many cases, the two workpieces will be in physical contact at the joint root, these roots are closed. However, oftentimes, workpieces will be intentionally spaced apart at the joint root. This gap between the workpieces is called the root opening and is expressed as a linear measurement of the space between the two parts. Root openings permit deeper penetration of the weld metal into the joint root, increasing weld size and strength.
Welding Positions
The best way to begin our discussion of welding positions isn’t with the positions themselves, but with a brief explanation of why the welding position is a critical factor to consider. The most commonly applied welding codes all require welding personnel to pass a welding qualification test prior to welding on any project governed by that code. Once a welder passes this test, they are “certified” to weld under that code, with certain limitations. These limitations are often referred to as “essential variables.” If the conditions of production welding cause any of these variables to deviate significantly from the conditions of the test, then the welder is no longer covered by their certification to perform that production welding. What these variables are and how significantly they can be changed depends on the welding code but often includes the welding process, welding machine electrical settings, base metal, and welding position. These limitations are in place because significant changes to these variables lead to significant changes in required technique and skill level. This may be more true for welding position than any of the other factors mentioned. A change in welding position affects a change in travel speed, electrode angles, electrode manipulation, and welding machine electrical settings. A welder qualification test taken in a given position provides coverage for the welder to perform production welding in that position. The same test may also allow welding to take place in positions considered “easier” to weld in.
There are four basic welding positions, each with a number designation. In addition, there are two more positions specific to qualifying welders who will be welding on round tube or piping. The different welding positions are defined by the American Welding Society (AWS), and they use two factors to define them. First, the axis of the weld joint; the weld joint axis determines our direction of travel as we weld along the joint. The joint axis may have a horizontal orientation level with the world (see the 1F, 2F, and 4F positions shown if Figure 15.4) in this case we would say the weld axis is horizontal. The other factor to consider is the orientation of the weld face once welding is completed. The AWS defines the weld face as “The exposed surface of a weld on the side from which welding was done” (American Welding Society, Standard Welding Terms and Definitions 2010). The simpler way of putting that is that (in most cases) the weld face is the only part of the weld you can see when you’re done. The face of the weld, while not perfectly flat, lies on a plane, and the orientation of that plane is the second factor in defining the weld position. The orientation of the weld face in position 1F is what makes it a flat position weld, even though the axis of the weld joint is horizontal just like position 2F.
- Flat position designated with the number 1, is typically considered the easiest position to weld in. In this position, gravity works in the welder’s favor rather than against them. This position also allows for faster welding speeds and higher amperage settings. The AWS definition of flat position is “The welding position used to weld from the upper side of the joint … where the weld axis is horizontal, and the weld face lies in an approximately horizontal plane” (AWS A3.0 pg 19)
- Horizontal position designated with the number 2, is probably the position most commonly welded in, and certification in horizontal position is a minimum prerequisite for many employers. Though flat position is easier and faster, it is often impractical to position work, especially large assemblies, so welding can take place in flat position. Proper electrode angles and travel speed are essential to keep the molten weld puddle from sagging out of the joint when welding in this position. The AWS definition of horizontal position is “The welding position in which the weld face lies in an approximately vertical plane and the weld axis … is approximately horizontal” (AWS A3.0 pg 23)
- Vertical position, designated with the number 3, takes significantly more operator skill than either flat or horizontal position. There is a higher likelihood of weld defects occurring in this position. The difference is stark enough that welding taking place outside of horizontal or flat position is sometimes colloquially referred to as “out of position” welding. Vertical position has another critical factor to consider: progression. The progression of vertical welding may be upward or downward, referred to as uphill and downhill, respectively. The technique used, and the resulting weld of the two progressions are very different, so much so that progression is an essential variable of welder certification. A vertical test taken with an uphill progression qualifies that welder to weld in that progression only, and the same for downhill. The AWS defines vertical position as “The welding position in which the weld axis… is approximately vertical, and the weld face lies in an approximately vertical plane” (AWS A3.0 pg 45)
- Overhead position designated with the number 4, like vertical position requires more operator skill than flat or horizontal. Additionally, proper PPE is critical when welding in the position. The welder is often positioned underneath the molten weld pool and showered with hot sparks and molten slag. A leather welding jacket with the collar and sleeves buttoned down should be worn. A headcap should be worn to protect the welder’s hair and scalp from burns. The welder should take care to stand off to the side of the weld joint to mitigate the risk of burns. The AWS defines overhead position as “The welding position in which welding is performed from the underside of the joint” (AWS A3.0 pg 30). The orientation of weld axis and weld face are the same as in flat position.
- The previous four welding positions all take place on plate, where the weld joint is a straight line. As mentioned earlier, there are two additional positions for qualifying welders to weld pipe; these positions are designated with the numbers 5 and 6. In pipe welding, the weld joint may run around the circumference of the pipe. In position 5, the length of the pipe is horizontal, putting the pipe’s circumference on a vertical plane. In this position, the welder essentially moves from overhead to vertical to flat position as they progress around the circumference of the pipe if starting from the bottom. In position 6, the situation is essentially the same, but the pipe is inclined to 45 degrees rather than horizontal. Tests in these positions also consider the diameter of the pipe as an essential variable, as smaller piping is more difficult to weld than larger piping.
Attributions
- Figure 15.1: Basic Joint Types by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.2: Corner Joint Configurations by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.3: Open vs. Closed Root by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.4: Open vs. Closed Root by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
The junction of two workpieces that will be joined by welding
a type of weld that joins two pieces of metal together when they are at an angle or perpendicular to each other
A preparation or opening between two workpieces that provides space for weld metal to be deposited
The portion of the weld joint where the two members of the joint approach closest to each other, when viewed in cross-section the joint root may be a point, line, or area
The joint root is a, typically deliberate, spacing between the two members of the joint at the joint root.
The position of the weld joint to the welder. Typically flat, horizontal, vertical, and overhead. Positions at a 45 degree angle are also used for pipes because the welder will weld in the flat, horizontal, vertical, and overhead position as they make their way around the circumference of the pipe.
The axis on which the length of the weld joint lies
the exposed surface of a weld