1. Defining Quality Levels (Based on EN ISO 5817)

The table below defines the quality levels for welding service (A,B,C). Unless otherwise specified, quality level B is required. 

3.0 Welding Defects

This specification defines welding defects and visual identification. Understanding these defects helps ensure high-quality finishes and helps to align expectations between different parties. For allowed / not allowed defects, please table in section 1.

3.1 Cracks

Welding cracks are defects that occur when the welded material fractures during or after welding due to high stresses, rapid cooling or unsuitable material composition. They can appear in the weld metal, heat-affected zone, or base material and may significantly reduce the strength and reliability of the joint. 

3.2 Undercut

Welding undercut is a groove or depression formed along the edge of a weld where base material has been melted away and not properly filled with weld metal. It weakens the joint by reducing the effective thickness and can become a point for crack initiation or corrosion. 

3.3 Porosity

Welding porosity is a defect where gas pockets become trapped in the solidifying weld metal, forming small holes or cavities. It is usually caused by contamination, moisture, or improper shielding gas and can reduce the strength and durability of the weld. 

3.4 Spatter

Welding spatter consists of small droplets of molten metal that are expelled from the weld pool and stick to surrounding surfaces. It is mainly caused by improper welding parameters or technique and can affect surface appearance, require extra cleaning, and in some cases lead to coating or corrosion issues. 

3.3 Undersize Weld

Undersize weld refers to a weld that does not meet the specified size or throat thickness required by the design or standard. This reduces the load-carrying capacity of the joint and can compromise its structural strength and reliability. 

3.4 Heat Affected Zone (HAZ)

The Heat Affected Zone (HAZ) is the area of the base metal that wasn’t melted but experienced high temperatures during welding. HAZ defects are critical because they weaken the structure even if the weld itself is fine. 

5.1 Continuous weld

A continuous weld is a single, uninterrupted bead of filler metal applied along the entire length of a joint. Unlike "tack" or "stitch" welding, which leaves gaps between weld segments, a continuous weld provides a complete seal between two workpieces.

5.2 Tack weld

A tack weld is a small, temporary weld used to hold components in the proper alignment and position prior to the final welding process.

5.3 Spot weld

Spot welding (specifically Resistance Spot Welding or RSW) is a process used to join two or more overlapping metal sheets. Instead of using a filler material or a continuous flame, it relies on pressure and electrical resistance to create a bond.

5.4 Stitch weld

A stitch weld (also known as an intermittent weld) consists of a series of short weld segments spaced at regular intervals along a joint. It is used when a full continuous weld is unnecessary for structural requirements or when excessive heat must be avoided.

5.5 Corner joint

A corner joint is one of the most common weld joints, formed when two workpieces are joined at an angle (usually 90°) to create an "L" shape.

5.6 Weld dressings