TYPES OF WELDING JOINTS

A weld joint refers to how the parts to be joined are assembled prior to welding. There are five basic types of joints used in welding which are Butt, Lap, Corner, T & Edge.

The metal to be joined is called the base metal. If the part to be welded is not metal, it is called base material. It is also known as work piece or work. The edge of base metal are often machined, sheared, gouged, flame cut, or bent to prepare them for welding. Weld joint design and metal thickness usually determine how the joint is prepared. Generally, the weld joint design is determined by an engineer.

BUTT JOINT

Joins two members that meet at their edges on the same plane
Used in applications where a smooth weld face is required
Fillet or groove welded; groove welding requires added expertise and expense
Improper design/welding risks distortion and residual stresses

T-JOINT

Joins two members that meet at a T-shaped angle
Good mechanical properties, especially when welded from both sides
Easily welded with little or no joint preparation
Usually fillet welded, although J-grooves are possible

LAP JOINT

Joins two members having overlapping surfaces
Good mechanical properties, especially when welded from both sides
Usually fillet welded
Thicker material requires more overlap

CORNER JOINT

Joins two members that meet at an angle
Two main types: open corner and closed corner
Easily welded with little or no joint preparation
Increase travel speed on light-gauge material to avoid burn-through

EDGE JOINT

Joins two parallel, or nearly parallel, members
Not recommended if either member will be subject to impact or high stresses
Square groove is most common, but other groove configurations are possible
Very deep penetration is impossible

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