What are types of welding joints and welding positions?

Types of welding joints and welding positions – the properties of a welded joint depend mainly upon the correct preparation of the metal edges being welded. All mill scale, rust oxides, and impurities should be removed from the surfaces to be joined so as to prevent their inclusion in the metal. Proper preparation will reduce the amount of heat needed and minimize distortion caused by expansion and contraction.

Depending upon the thickness of the metal pieces to be welded together, their edges are to be given proper shape in order to produce a reliable joint, Resistance welded joints must be prepared more accurately and be made cleaner than those for other processes.

5 Types of welding joints and symbols

1.Butt joint welding

butt joint welding

This type of joint is used to join together the ends or edges of two plates or surfaces located approximately in the same plane with each other. Preparation of edges varies mainly according to the thickness of the metal pieces to be welded and the welding process to be used. Light gauge sections (1 to 3 mm) are generally welded by a plain butt joint.

Metals ranging in thickness from 4 mm to 12 mm, that can be welded only from one side should have their edges reduced either to a single V-joint or a single U- joint. Heavier plates are prepared from both sides. A single strap butt joint is a modification of butt joint and produces a stronger joint than a plain butt joint.

2.Lap joint welding

Lap joint welding

This type of joint is used in joining two overlapping plates so that the edge of each plate is welded to the surfaces of the other. Common lap joints are single lap, double lap and joggled (or offset) lap joints.

Single welded lap joint does not develop full strength, whereas double lap joint does it. But single lap joint is sometimes preferred to the butt joint, e.g., in tubular construction where the tube end goes into the other one and these tubes are joined by a single lap weld.

3.T-joint welding

T-joint welding

This type of joint is used to weld two plates or sections whose surfaces are at approximately right angles to each other. Edge preparation of the vertical member of a t-joint is the same as that of butt joints.

4.Corner joint welding

Corner joint welding

This type of joint is used to join the edges of two sheets or thin plates whose surfaces are approximately at right angle to each other. This type of joint is very commonly used in the construction of boxes, tanks, frames and similar items. Welding can be done on one or both sides of the joint, depending on the position and type of corner joint used.

5.Edge joint welding

Edge joint welding

This type of joint is used to join parallel plates by means of a weld. This joint is often used in sheet metal work. Flange joint is a modification of this joint. In case of sheet metal, the two edges can be easily and quickly melted down, eliminating the need for any filler metal. In heavy plates (more than 6 mm thick), where beveling of the edges may also be done to get deeper penetration, some filler rod is also used.

Types of welding position

The common positions are given below

  1. Flat position
  2. Horizontal position
  3. Vertical position
  4. Overhead position

1.Flat position welding

Flat position welding

In this welding position, the upper faces of the workpieces during welding are nearly in a horizontal plane, or they are held or moved during welding in such a way that the axis of the weld being made remains horizontal. This welding is sometimes also known as “downward position” because of the welding material being normally applied in a downward direction. It is the easiest position for making welds.

2.Horizontal position welding

Horizontal position welding

The horizontal position may be for a grooved weld or fillet weld. In a grooved weld, the two workpieces rest one over the other with their flat faces in vertical plane. After tacking, the welding bead is laid from one end to the other end of the joint. The axis of weld lies in a horizontal plane while its face lies in a vertical plane.

In a fillet weld, the two workpieces are held at right angles to each other. The welding usually proceeds on the workpieces after tacking them. The welding is done on the upper side of the horizontal piece and against the vertical face of the vertical piece. In this case, the axis of the weld remains horizontal and inclined with both horizontal and vertical workfaces.

4.vertical position welding

vertical position welding

The axis of the weld is either vertical or inclined less than 45° to the vertical. The welding usually commences at the bottom and proceeds upwards.

4.overhead position welding

overhead position welding

In this welding position, welding is done on the underside of work while the workpieces remain over the head of the welder. The axis as well as face of the weld remains approximately horizontal.

It is the most difficult welding position and calls for a very high degree of skill from the operator. Welder should try to keep the temperature of molten pool as close to its lowest flow temperature in order to decrease the chances of falling down of the molten metal. The surface tension of the molten pool helps to keep it in position.

Conclusion

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Also read this – What is welding and types of welding process ?

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