Weld joint type
Corner Joint
A corner joint brings two members together at their edges to form an L, and unlike a T-joint the upright lands on the end of the other member rather than in the middle of it.
Geometry and preparation
| Configuration | Two members meeting at approximately 90 degrees at their edges, forming an L in section. |
|---|---|
| Edge preparation | None for a filleted corner. Open corners with a groove preparation are used where full penetration or a flush outside corner is required. |
| Strength | Depends heavily on configuration. A closed corner with a single inside fillet is weak in the opening direction; welding both inside and outside, or using a groove weld, transforms it. |
Characteristics
- Easy to confuse with a T-joint on a drawing — the difference is that the upright sits at the END of the other member.
- The outside corner is prone to burn-through because there is little metal to absorb the heat.
- Welding only the inside corner leaves the joint able to open under load; outside welds or a groove preparation fix that.
- Very common on box sections, frames and enclosures where two faces meet.
- Distortion pulls the included angle closed, so tacking and sequence matter more than on a T-joint.
Weld types used on a corner joint
Where it is used
- Box sections, frames and enclosures
- Tank and hopper corners
- Machine guarding and cabinets
- Structural corner connections
Corner Joint — common questions
What is the difference between a corner joint and a T-joint?
Where the upright lands. In a T-joint it meets the face of the other member somewhere in the middle; in a corner joint it meets the end, so the two members form an L.
Should you weld the inside or outside of a corner joint?
Both where the joint carries load. An inside fillet alone lets the corner open under load. The outside weld, or a groove preparation welded from outside, is what closes the load path.
Why does my corner joint keep burning through?
There is little base metal at an outside corner to conduct heat away. Drop the amperage, speed up travel, or use a smaller electrode. On thin material, backstepping and skip welding also help.
How do you get full penetration on a corner joint?
Bevel one or both members into an open corner preparation, which lets the root pass reach the joint root, and back weld or back gouge if both sides are accessible.
Other joint types
Butt Joint
A butt joint places two members edge to edge in the same plane — the simplest joint to draw and the one that most…
Lap Joint
A lap joint overlaps two members and welds along the exposed edges — no edge preparation, forgiving fit-up, and the…
T-Joint
A T-joint sets one member perpendicular to the face of another, and it is normally filleted on both sides — the most…
Edge Joint
An edge joint lays two members face to face and welds along their common edge — a light-duty joint used to join…