Butt welds are welds where two pieces of metal to be joined are in the same plane.[1] These welds require only some preparation and are used with thin sheet metals that can be welded with a single pass.[2] Common issues that can weaken a butt weld are the entrapment of slag, excessive porosity, or cracking. For strong welds, the goal is to use the least amount of welding material possible. Butt welds are prevalent in automated welding processes, such as submerged-arc welding, due to their relative ease of preparation.[3] When metals are welded without human guidance, there is no operator to adjust non-ideal joint preparation. Because of this necessity, butt welds can be utilized for their simplistic design to be fed through automated welding machines efficiently.
Types
Butt joint geometries
There are many types of butt welds, but all fall within one of these categories: single-welded butt joints, double-welded butt joint, and open or closed butt joints. A single welded butt joint is the name for a joint that has only been welded from one side. A double-welded butt joint is created when the weld has been welded from both sides. With double welding, the depths of each weld can vary slightly. A closed weld is a type of joint in which the two pieces that will be joined are touching during the welding process. An open weld is the joint type where the two pieces have a small gap in between them during the welding process.
Square butt joints
The square groove is a butt welding joint with the two pieces being flat and parallel to each other. This joint is simple to prepare, economical to use, and provides satisfactory strength but is limited by joint thickness. The closed square butt weld is a type of square-groove joint with no spacing in between the pieces. This joint type is common with gas and arc welding. For thicker joints, the edge of each member of the joint must be prepared to a particular geometry to provide accessibility for welding and to ensure the desired weld soundness and strength. The opening or gap at the root of the joint and the included angle of the groove should be selected to require the least weld metal necessary to give needed access and meet strength requirements. Only metal up to 4.5mm thick is usually used for square butt joints.
V-joints
Single V welds are similar to a bevel joint, but instead of only one side having the bevelled edge, both sides of the weld joint are beveled. In thick metals, and when welding can be performed from both sides of the work piece, a double-V joint is used. When welding thicker metals, a double-V joint requires less filler material because there are two narrower V-joints compared to a wider single-V joint. Also the double-V joint helps compensate for warping forces. With a single-V joint, stress tends to warp the piece in one direction when the V-joint is filled, but with a double-V-joint, there are welds on both sides of the material, having opposing stresses, straightening the material.
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13. RULES TO BE OBSERVED WHILE APPLYING SYMBOLS
1. Symbols for fillet and similar welds be shown such that the
vertical position of the symbol are indicated on the left hand
side of the symbol,irrespective of the orientation of the weld
metal.
2. If the welds are to be made on the arrow side of the joint,the
corresponding symbol should be placed either above or below
the continuous reference line (Fig.)
3. If the welds are to be made on the other side of a joint ,the
corresponding symbol should be placed above or below the
dashed reference line (Fig.)
4. If the welds are to be made on both sides of the a joint, the
corresponding symbols should be placed on both sides of the
reference line and the dashed line is not shown (Fig.)
5. The arrow of the symbol must point towards the joint which
required welding (Fig.)
14. 6. When only one member is to be edge prepared to make the joint ,
the arrow should point at the plate (Fig. ---)
7. Dimensions of size are indicated in mm without writing the unit
mm.
8. If unequal legs of fillet are to be used ,they should also be given on
the left hand side.
9. If a welding is required to be made on the site or during erection or
assembly, it is re
10. If a weld is to be made all around a joint , a circle should also be
placed at the elbow ,connecting the arrow and the reference
line.(Fig.----)
11. If a weld is to have a flush or flat finish , a straight line should be
added above the symbol.
12. The welding process is indicated , if required ,at the end of the
arrow.(fig----)
RULES TO BE OBSERVED WHILE APPLYING SYMBOLS
