5.2 Joint Types, Weld Types, and Welding Positions
Key Takeaways
- Five basic joint types: butt, T-joint, corner, lap, edge
- CJP groove welds extend through full thickness (critical joints); PJP welds are partial (shear connections)
- Groove weld types include square, V, bevel, U, J — each in single or double configurations
- Four basic positions: 1 (flat), 2 (horizontal), 3 (vertical), 4 (overhead); G = groove, F = fillet
- Pipe positions: 1G (rotated), 2G (vertical fixed), 5G (horizontal fixed), 6G (45° fixed)
- 6G qualifies a welder for ALL positions — it is the most challenging qualification test
Last updated: March 2026
5.2 Joint Types, Weld Types, and Welding Positions
Five Basic Joint Types
All welded connections fall into one of five basic joint configurations:
| Joint Type | Description | Common Welds Used |
|---|---|---|
| Butt joint | Two members aligned in the same plane, edge-to-edge | Square groove, V-groove, U-groove, bevel, J-groove |
| T-joint (Tee) | One member perpendicular to another (forms a T shape) | Fillet weld, PJP groove + fillet |
| Corner joint | Two members meet at approximately 90° forming an L | Fillet, groove, or combination |
| Lap joint | Two overlapping members | Fillet weld (one or both sides) |
| Edge joint | Two members with edges parallel or nearly parallel | Edge weld, square groove |
Groove Weld Types
| Type | Preparation | Applications |
|---|---|---|
| Square groove | No bevel — straight edges | Thin material (up to ~3/16" with CJP) |
| Single-V groove | Both edges beveled symmetrically | Most common CJP groove for plates <1" thick |
| Double-V groove | Both edges beveled from both sides | Thick plates — reduces weld volume and distortion |
| Single-bevel groove | One edge beveled, one edge straight | T-joints, plates of unequal thickness |
| Double-bevel groove | One edge beveled from both sides | T-joints in thick plate |
| Single-U groove | Both edges have J-shaped preparation | Thick plates — less weld volume than V-groove |
| Double-U groove | U-prep from both sides | Very thick plates |
| Single-J groove | One edge J-shaped, one straight | T-joints in thick plate |
| Double-J groove | J-prep from both sides | T-joints in very thick plate |
CJP vs. PJP Groove Welds
| Feature | CJP (Complete Joint Penetration) | PJP (Partial Joint Penetration) |
|---|---|---|
| Definition | Weld extends through full joint thickness | Weld extends through only a portion of thickness |
| Strength | Full base-metal strength across the joint | Reduced strength (designed for specific load) |
| Typical use | Moment connections, critical joints, seismic | Shear connections, non-critical joints |
| Back-gouging | Often required to ensure complete root fusion | Not required |
| NDE | Often required (RT or UT) | Usually only VT |
| Cost | Higher (more weld metal, more inspection) | Lower |
Welding Positions
| Position Number | Groove (G) | Fillet (F) | Description |
|---|---|---|---|
| 1 | 1G | 1F | Flat — weld on top, gravity assists |
| 2 | 2G | 2F | Horizontal — weld axis horizontal, face vertical |
| 3 | 3G | 3F | Vertical — weld axis vertical |
| 4 | 4G | 4F | Overhead — weld on bottom, gravity opposes |
Pipe Welding Positions:
| Position | Description | Pipe Orientation |
|---|---|---|
| 1G | Pipe rotated, weld on top | Horizontal axis, rotated |
| 2G | Pipe fixed vertical, weld horizontal | Vertical axis, fixed |
| 5G | Pipe fixed horizontal, weld around circumference | Horizontal axis, fixed |
| 6G | Pipe fixed at 45° incline | 45° incline, fixed |
| 6GR | 6G with restriction ring | 45° incline with ring simulating obstruction |
6G is the most challenging pipe position because it requires the welder to weld in flat, vertical, and overhead positions continuously around the joint without repositioning the pipe.
Welder Qualification by Position
Important rule: A welder qualified in a more difficult position is automatically qualified for easier positions:
| Qualified Position | Also Qualifies For |
|---|---|
| 1G/1F | 1G/1F only |
| 2G | 1G, 2G |
| 3G | 1G, 3G (and sometimes 2G per code) |
| 4G | 1G, 4G (and sometimes 2G per code) |
| 3G + 4G | All plate positions (1G, 2G, 3G, 4G) |
| 6G (pipe) | All pipe and plate positions |
For the Exam: 6G qualifies a welder for ALL positions — it is the "ultimate" qualification test. Also know the five basic joint types and the difference between CJP and PJP groove welds. Position numbering (1G/1F through 4G/4F) is heavily tested.
Test Your Knowledge
Which welding position is considered the MOST difficult and qualifies a welder for ALL positions?
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Test Your Knowledge
What are the five basic joint types in welding?
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Test Your Knowledge
What is the key difference between a CJP and PJP groove weld?
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