MAKING VARIOUS WELDED JOINTS

Types of Weld Joints

There are two major classes of weld ‑ fillet and butt.

1. Fillet welds. These welds are roughly triangular in cross section and between two surfaces not in the same plane and the weld metal is substantially placed alongside the components being joined.

2. Butt welds. A butt weld is made between two pieces of metal usually in the same plane, the weld metal maintaining continuity between the sections.

In addition there are lap welds, corner welds and edge welds, which are to some extent special variations of the fillet and butt welds. The various weld joints and some associated terms are illustrated on page 7.

Making a Welded Joint in the Flat Position

Take two pieces of 250 x 75 x 10mm plate and tack (a small or temporary holding weld) them together at each end to form a right angle section and set it in the V position between two bricks, as shown in Fig 15. Using your 3.2mm o electrode at 130 amps, run your first pass into the joint, bisecting the angle with your electrode and making sure that you obtain complete penetration to the corner with no lateral movement of the electrode. Remove the slag and your weld should be flat with a good flow into each side and probably have a 8mm wide surface. Deposit you next layer using a weaving motion, remembering to pause slightly at each edge.

This fillet weld could probably have a face width of 12mm (and a leg length of 10mm) and of maximum desirable size for this thickness material. However, in using the specimen for practice it could be assumed that the material was thicker and a larger weld required.

A larger electrode could be employed (4mm or 5mm) and/or it may be found necessary to restrict the width of weaving to where there are two or three passes (weld beads) in each layer of weld material as indicated in Fig. 17.

The same technique and procedure would apply for single Vee butt welds, although of course the included angle is usually restricted to 70° max. Where a single vee butt weld is employed, the first run should achieve full penetration, with a cover weld placed on the reverse side. Alternatively, the gap between the two plates is widened and a backing bar that become part of the structure is employed.

It should of course be remembered that it is not essential to use other than a square butt joint for material less than 6mm thick. Light sheet (2.Omm and under) should be tightly butted together while heavier sheet should be gapped up to half the material thickness to assist in full penetration by a weld from each side.

Source : aussieweld.com.au