*3.5.2 Groove welds*

Groove welds are classified by the various shapes and sizes of the preparation on the base materials. The types of groove weld classifications are shown in **Figure 12** and listed below:


Groove welds can be used in corner joints, T-joints, and butt joints. Groove welds are often used for tight fitment applications. Each of the groove weld types listed in the text above has its own symbol and associated dimensioning method per the AWS symbol standard. There are significant material preparation techniques associated with groove weldments, and they typically concern the construction of the specific groove. These details are specified within the weld symbol structure. Beveling the ends of the material in a specific manner is necessary to form the groove. The beveling

**Figure 12.** *Groove weld preparations in base material to be joined.*

extent is specified by different bevel angles. Bevels allow for weld metal to fill the beveled-out area more easily and increase the strength of the weld.

**Figure 13** above represents the material preparation of two steel plates for a 60<sup>o</sup> Vgroove weldment. The angular dimension for the groove is specified within the weld symbol structure. After the weld has been applied between the pieces of base metal, the excess can be ground-away to present a smooth surface of the steel plates, as if the plate is one piece. If executed properly, groove welds can provide superior penetration and strength.

#### *3.5.3 Plug and slot welds*

Plug welds and slot welds are similar and are often used to join two overlapping plates. One of the two plates will have drilled holes or milled-out elongated slots. This internal opening to the second piece is where the weldment will be produced. When dimensioning a plug or slot weld, the hole diameter will be shown to the left of the plug symbol, and the plug spacing (distance between each hole) is shown to the right of the symbol. For slot welds, the width of the slot is shown to the left of the symbol, while the length and pitch are shown to the right of the symbol. A drawing detail is often referenced in the tail of the weld symbol structure. If the slot or plug is not to be filled completely with weld metal, the fill depth will be specified [14].

#### **3.6 Determining weld size**

Determining the proper size of a weld is essential in conducting a welding repair. Over-welding by repairmen does not generally enhance the chances of success for a repair. A common misconception is that applying an excess of weld material provides additional strength to the joint. This is false, and over-welding can actually weaken the joint by the additional application of heat transferred to the material around the joint. Over-welding is quantifiable and can be calculated in manufacturing applications to minimize production costs. For repairs, it adds time to the job without any benefit to the customer, and it may be counterproductive. The depth of weld penetration is a more important factor in creating a good weld, and it can be properly gauged by correctly sizing the thickness of the weld.

The thickness of the weld is controlled by the depth of the material being welded. It is critical to understand that the material thickness input must be the thinnest material associated with the joint that is being welded. This is especially important in weldment strength calculations. *Design of Welded Structures* define the recommended size of a fillet weld using Eqs. (3) and (4) [1]:

$$L\_s = \frac{3}{4} \ast (\mathcal{M}\_t) \tag{3}$$

**Figure 13.** *Material preparation for V-groove weldment.*

*Engineering Challenges Associated with Welding Field Repairs DOI: http://dx.doi.org/10.5772/intechopen.104263*

$$\mathcal{W}\_t = \cos\left(45^\circ\right) (L\_t) \tag{4}$$

where *Mt* is the base material thickness;

*Ls* is the weld leg size; and.

*Wt* is the weld throat size.

**Figure 14** illustrates these variables on an illustration of a cross section of a tee joint. Following this recommendation for the fillet size will create the proper amount of weld penetration into the base material for a solid joint.

When calculating the throat size, a 0.71 scale factor sometimes appears in the equation for calculating throat size. This is the rough equivalent of cos 45° ð Þ. Depending on the structural application, type of stress on the effective weldment, and how much stress the weld will endure, different welds will require different lengths of run. Determining the proper length for a weld minimizes the potential for overwelding. For instance, if two plates needed to be joined, but no load or minimal load was applied in shear, then the most effective way to join the two plates would be to apply a series of small stitch welds across the connection. Stitch welds are intermittent, rather than continuous welds. Fillet welds used to transmit forces should not be less than four times its leg size in length or 3.8 cm, whichever is greater [1]. Neither should the effective weld size of the fillet weld exceed ¼ of the length of the weldment [1]. **Figure 15** presents these fillet length constraints graphically.

Stitch welding is a technique used to connect base material pieces that will see little stress and fatigue in their duty cycles. Additional weld fillet length beyond the structural need is wasteful and costly. Stitch welding is generally a great technique for field repairs that require lengthy connections, eliminating the need to weld a solid bead that would introduce a significant amount of heat into the base material, potentially causing distortion and warpage. Engineering drawings feature unique callouts for stitch welding that include dimensions referencing the length of the stitch weld, the distance between each stitch weld, the weld type, and the size of the weld [15]. The drawings will also feature callouts for the intermittence of the weldment, such as intermittent welds on one or both sides of the joint and the staggered intermittent interval for the weldments [15]. In field repairs, it is usually up to the repairman to evaluate the stitch weld dimensions and the weld runs intermittently, depending on

**Figure 15.** *Minimum effective weld length of run.*

the stress of the joint. Significant guidance for the design of the weld can be had through the proper estimation of the needed weld strength.
