What Do 1G, 2G, 3G, 4G, 5G, and 6G Mean in Welding?

In the welding industry, if you hear welders saying things like “I can weld 6G now” or “This job requires a 3G certificate,” they are definitely not talking about mobile networks. In welding terminology, these combinations of numbers and letters represent welding positions.

These classifications are defined by international standards such as those from the American Welding Society (AWS) and the American Society of Mechanical Engineers (ASME). They are important indicators of a welder’s skill level. Generally speaking, the higher the number, the greater the welding difficulty.

I. What Does the Letter “G” Mean?

Before understanding the numbers, it’s important to know what the letters represent:

• G (Groove Weld): Refers to groove welding (also called butt welding). Two metal plates or pipes are joined together with a groove prepared at the joint and then filled by welding.
• F (Fillet Weld): Refers to fillet welding. Two metal pieces are joined in a T-joint or lap-joint configuration.

This article mainly focuses on the commonly discussed “G” series (groove welding positions).

II. 1G to 4G: Plate Welding Positions

These four levels mainly apply to groove welding on metal plates.

1. 1G (Flat Position)

• Position: The weld joint lies flat on a table or the ground, and welding is performed from above.
• Difficulty: The easiest and most basic position. Gravity helps the molten metal flow into the weld joint.
• Simple analogy: Like writing on a desk.

2. 2G (Horizontal Position)

• Position: The weld joint is vertical, while the welding direction is horizontal.
• Difficulty: Medium difficulty. Molten metal tends to sag downward due to gravity, requiring better control of speed and angle.
• Simple analogy: Like drawing a horizontal line on a wall.

3. 3G (Vertical Position)

• Position: The weld joint is vertical, and welding is usually performed upward from bottom to top.
• Difficulty: High difficulty. Gravity constantly pulls the molten metal downward, requiring excellent hand control.
• Simple analogy: Like drawing a vertical line upward on a wall.

4. 4G (Overhead Position)

• Position: The weld joint is above the welder’s head.
• Difficulty: Very high. Molten metal can drip downward, visibility is limited, and operation is uncomfortable. This is considered the most difficult plate welding position.
• Simple analogy: Like writing on a ceiling.

III. 5G and 6G: The “Top Level” of Pipe Welding

When pipe welding is involved, the difficulty increases significantly because the welding path is circular.

5. 5G (Horizontal Fixed Position)

• Position: The pipe is placed horizontally and fixed in place. The welder must move around the pipe to complete the weld.
• What it includes: During the full rotation, the welder continuously transitions through flat, vertical, and overhead welding positions.
• Difficulty: Requires strong overall welding control and adaptability.

6. 6G (Inclined Fixed Position)

• Position: The pipe is fixed at a 45-degree angle and cannot rotate.
• Difficulty: Considered the “gold standard” in welding qualifications. The welder must handle nearly every possible welding angle and gravity effect.
• Significance: A 6G certification is widely recognized as proof of a highly skilled welder. Welders qualified in 6G are generally capable of performing almost all welding positions, including 1G–5G.

Summary

• 1G: Easiest — flat welding.
• 2G: Horizontal welding.
• 3G: Vertical welding.
• 4G: Overhead welding.
• 5G: Welding around a fixed horizontal pipe.
• 6G: Welding around a fixed 45-degree inclined pipe (highest difficulty).