15.2 Groove Welds
Cameron Kjeldgaard
Groove Joints and Terminology
In manual and semi-automatic arc welding processes, groove welds are probably the most widely produced welds, with fillet welds, the next type of weld discussed, coming in a close second. Groove welds apply to all five basic weld joints discussed above.
With the exception of a square groove weld, most groove welds require some sort of special cut through the thickness of the workpiece. In industry, these cuts are sometimes colloquially referred to as an edge preparation. These cuts increase the penetration of the weld into the material and increase weld strength. Figure 15.5 is a chart illustrating the geometry of the different types of groove weld joints. There are many groove preparations that may be cut into the edges of workpieces, with different advantages, disadvantages, and applications. These different joint preparations also have a variety of terms to describe them and dimensions to measure them.
Bevel grooves and V grooves
Before going any further, we should define what exactly a groove weld is. The American Welding Society defines groove weld as “A weld in a weld groove on a workpiece surface, between workpiece edges, between workpiece surfaces, or between workpiece edges and surfaces” (AWS A3.0 pg. 21). A weld groove is a preparation or opening between two workpieces that provides space for weld metal to be deposited. The simplest configuration, a square groove, is a butt joint between two pieces with their ends cut square with or without a root opening; this type of groove doesn’t require special cuts to prepare the groove but is typically only applicable to thinner materials or joints that don’t require a high level of strength. However, the weld groove is most commonly prepared with a bevel or chamfer. Though there is a distinction between a bevel and chamfer when these cuts are made for the purpose of welding, it is common in industry to refer to both as a bevel without drawing a distinction; moving forward, we will do the same.
This type of bevel has several terms and dimensions that are associated with it:
- The angled surface made by the bevel cut is referred to as the groove face. Other types of grooves may have a more complex surface than a simple bevel, but the groove face may be considered the entire surface exposed by the preparative cut.
- The bevel angle is the angular dimension of the bevel cut.
- In the case of the workpiece not being beveled to a point, a root face is present and is expressed as a linear dimension. The root face is also commonly referred to as a “landing.”
- The bevel depth is a linear measurement of how far below the material’s surface the bevel cut extends. Bevel depth and the resulting groove depth, once assembled with another joint member, have the strongest influence on the finished weld size and strength
These bevels are one of the most common edge preparations used in groove welds, they are fast and simple to make while greatly increasing weld strength. These cuts are used in both bevel groove and v groove weld joints. In a bevel groove weld, only one of the joint members is prepared with a bevel, while in a v groove, both are. In a bevel groove, the total groove angle is equal to that of the bevel, since only one of the joint members is beveled. In a v groove, however, both the bevel angles are added together, and that included angle gives us the groove angle.
These edge preparations have one more complicating factor, that is, whether one or both sides of the same joint member are beveled. If only one side is prepared in a bevel groove, it would be called a single bevel groove, while if both sides are prepared we would refer to it as a double bevel groove. This same naming convention of single and double can also be applied to v grooves and all the groove types and fillet welds we will discuss going forward.
J grooves and U grooves
The first thing you may notice is that the relationship between the J and U groove is similar to that of bevel and V grooves, in the former only one member of the joint is prepared while in the latter both are.
In these grooves, the groove face is radiused rather than simply angled. These cuts are more difficult to prepare than simple angled bevels. These curves must be prepared by hand, which is time-consuming, or machined, which requires specialized tooling and equipment. These grooves are commonly used on materials that are sensitive to cracking or distorting during welding. The curved geometry can more evenly distribute the heat of welding and reduce the stress it puts on the material. This groove geometry is also the result of back-gouging operations.
The curved groove is measured by a groove radius; if this radius is equal to the bevel depth, this measurement describes the whole bevel. In a J or U groove where the bevel depth is greater than the groove radius, there will typically be a groove angle as well.
Flare bevel and Flare V grooves
Similar to J and U grooves Flare bevel and Flare V grooves also have a radiused groove face, but it is an outside radius rather than an inside radius. This radius is always equal to the bevel depth. These grooves are not usually purposefully cut but are usually a result of the shape of what is being welded together. The shape of these grooves is not ideal, the groove becomes extremely narrow close to the joint root, which limits weld penetration into the joint root.
Groove Welds and Sizing
It is important to realize that there are distinct terms and measurements for talking about an unwelded joint versus a finished weld. The above section discussed the terms and measurements used to describe the joint prior to welding. Once welding is complete, there are special terms to describe the “anatomy” of the finished weld.
Before delving into the specific parts of the finished groove weld, we should lay out some more generic terms that make up an everyday part of the welder’s vocabulary:
- base metal, sometimes referred to by the non-standard term parent metal, is the term used to designate the metal which is to be welded together. Not any specific type of metal, but any metal to be welded. If I wish to weld two pieces of steel together, or perhaps two pieces of aluminum, I would refer to those pieces as the base metal.
- With a few exceptions, in most welding processes, the finished weld doesn’t just consist of melted and fused base metal but also of additional metal that has been deposited in the joint. This added metal, which typically comes from the welding electrode or a separate welding rod, is called filler metal
- When completed a weld consists of some base metal that has been melted and mixed with the added filler metal before cooling and re-solidifying. The term weld metal is used to describe all added filler metal and any of the mixed-in base metal that make up the finished weld.
- A weld pass refers to a single progression made by the welder along the weld joint; the resulting weld metal from this singular pass is called a weld bead. Some weld grooves, if they are small enough or the bead is big enough, may be filled in one pass. Other grooves will require the welder to complete multiple passes along the joint. We call these welds single-pass and multi-pass welds, respectively.
With the above terms in mind it will be much easier to comprehend the diagram below, which examines the different parts of a completed weld:
The weld face has been mentioned earlier in this chapter, it is “the exposed surface of a weld from the side at which welding was done” (American Welding Society, 2010). The span of the weld face is given as a linear measurement of the weld width. In the case of the weld above weld metal has melted all through the joint root, exposing a root face. Where the weld face and root face intersect the unmelted base metal is referred to as a toe.
Where the weld metal extends past the surface of the base metal at the weld and root face is known as weld reinforcement and root reinforcement, respectively. In industry, this reinforcement is sometimes called weld “crown”, root reinforcement may also be referred to as melt-through or burn-through. A linear measurement of reinforcement is used to define it. Positive reinforcement is also called convexity, weld convexity is not considered an effective part of the weld, too much convexity (reinforcement) can be detrimental. If there is no reinforcement the weld face is in line with the base metal surface the weld would be considered flush. If the weld face is below the base metal surface, reinforcement is negative, the weld is concave. Typically weld grooves must be at least filled flush, but in some applications, concavity may be acceptable or even desirable.
As explained earlier, when welding occurs some base metal melts and mixes with filler metal to create weld metal. How far the welding heat source melts into the groove is called penetration. Penetration of weld metal into the joint root is called root penetration and is expressed as a linear measurement. A linear measurement is also used to express joint penetration, the depth of weld metal penetration past the base metal surface, it is the original groove or bevel depth plus any root penetration. Groove weld size is synonymous with joint penetration, a 1-inch groove weld must have 1 inch of joint penetration. In the diagram above weld metal has penetrated entirely through the joint thickness; whenever weld metal penetrates fully through the thickness of either joint member it is a complete joint penetration weld, often abbreviated CJP. If penetration only extends partially into the joint root, it is a partial joint penetration weld, often abbreviated PJP.
The cumulative effect of the above factors, joint penetration, weld width, convexity or concavity et cetera, make up the weld profile. The overall shape of the weld when viewed in a cross-section. The shape of the weld profile is of great consideration when determining the quality and acceptability of the finished welded product.
Attributions
- Figure 15.5: Various Types Of Groove Geometries That May Be Cut Into Material To Prepare It For Welding by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.6: Bevel vs. Chamfer by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.7: Parts & Measurements Of A Bevel Cut by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.8: Groove Angle Measurements by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.9: Single Bevel & Double Bevel by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.10: J Groove Dimensions by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.11: Flare V Groove by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 15.12: Completed Groove Weld by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
A manual process is a welding process in which the welder manipulates all aspects of the weld by hand, including arc length, rod or torch angle, weave or oscillation pattern, and travel speed.
A semi-automatic process is a welding process in which the welder manipulates all aspects of the weld by hand, except for the wire-feed speed which is controlled by the feed unit.
A preparation or opening between two workpieces that provides space for weld metal to be deposited
a preparative cut made on the edge of material to improve weld penetration and size
A bevel is a preparatory cut made on the edge of a workpiece to increase the size and improve the penetration of a groove weld. Bevels can be cut in various shapes, but they all remove base metal from the weld area, making room for more filler metal to be deposited deeper into the weld joint's thickness
An angular measurement between the faces of two edge preparations
the process in which the root of a joint is carved away via CAC-A from the backside.
Base metal is the material being assembled to form the weldment, upon which the weld is made. An older term for base metal is parent metal.
Filler metal is the external metal being added to the weld during welding.
Weld metal refers to metal in the finished weld and includes all the filler metal which was deposited and all base metal which was melted during welding
The weld toe is the intersection of the weld metal and base metal
refers to a groove weld where the weld metal has penetrated through the entire material thickness of one or both joint members
Weld profile is the general shape of the weld when viewed in cross section