50 Modern Welding the addition of a fi ller material and with or without the use of pressure. See Figure 3-7. Welding is the process of making a weld on a joint. Fillet welds are made at the intersection of a surface and an edge or in a corner where two surfaces meet. Fillet welds are generally triangular in shape, as shown in Figure 3-8, and are placed into lap, inside corner, and T-joints. A groove weld is a weld made in a groove or gap created between two pieces of metal. Groove welds can be used on all types of weld joints. When the edges of thicker metal are machined or fl ame cut, metal is removed from the pieces. Filler mate- rial must be added to replace the metal that is removed. The addition of fi ller metal ensures that the completed weld joint is as thick and as strong as the base metal. Edge, fl ange, or fl are-groove joints for thin metal may be welded without the addition of fi ller material. Figures 3-2, 3-4, 3-5, and 3-6 show edge, fl ange, and fl are-groove joints. The parts and dimensions for fi llet welds are the same for lap, inside corner, and T-joints. Refer to Figure 3-8. The weld face is the outer surface of the weld bead. As previously mentioned, the weld toe is the point where the weld face touches the surface of the base metal. A fi llet weld is made up of three primary dimensions. The fi llet weld size is the length of one side. The leg is the shortest distance from the toe to the surface of the other piece of base metal. The effective throat is the minimum distance from the weld face to the root of the weld without any convexity. Figure 3-8 shows two fi llet welds with the same leg dimensions, but different sizes. The size of the weld with a concave bead, Figure 3-8A, is smaller than the size of the weld with a convex bead, Figure 3-8B. A fi llet weld with a convex bead is stronger than one with a concave bead because of the additional fi ller metal. 3.2.1 Weld Beads and Weld Passes A weld bead is one weld pass of fi ller metal that is added to a weld joint. A weld pass occurs each time a welder lays one weld bead across a weld joint. Only one weld bead or weld pass is required for fusing thin base metal, Figure 3-9A. If the metal is thick, more Figure 3-7. A square-groove weld for an edge joint is in progress. The weld pool extends to the outer edges of the base metal. Filler metal may not be required on thin pieces of base metal. Torch tip Weld bead Weld pool Tack weld Figure 3-8. Look at the parts of these fi llet welds. Weld A is concave. Its weld size is smaller than Weld B, which is a convex weld. Notice that the leg sizes in Weld A and B are the same, but the weld size is larger with a straight or slightly convex bead. A B Leg Size Leg Size Effective throat Effective throat Leg and size Leg and size Weld face Toe of weld Toe of weld 1/8" (3.2mm) 1/2" (13mm) A B Figure 3-9. A—On this single-pass weld on thin base metal, notice the build-up of weld metal and complete penetration. B—On this multiple-pass weld on thick base metal, the edges have been prepared to form a V-groove joint. Notice the root opening required. Three beads were used, with each bead measuring less than 1/4″ (6.4mm) thick. A weaving bead may be used for the wider, upper bead.
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