CWI Welding Terms and Definitions Study Guide (AWS A3.0)

Why terminology matters on Part A

Definitions and Terminology carries the largest minimum share of CWI Part A questions in AWS's published topic list, tied with Welding Processes. The same terms come up in every other topic. A question about a weld symbol, a discontinuity or a code clause often turns on one word. Think throat versus leg, joint penetration versus fusion, or back weld versus backing weld. Part A is closed book, so you need these terms memorized.

The reference is AWS A3.0, Standard Welding Terms and Definitions. AWS separates "standard" terms from "nonstandard" ones. Shop slang such as "land", "full penetration" or "burn-through" may appear in distractors. Learn the standard term for each idea.

The five joint types

A joint type describes how the parts meet, not the weld that joins them. There are five:

• Butt joint: members in about the same plane, meeting edge to edge.
• Corner joint: members at roughly a right angle, meeting at their edges in an L.
• T-joint: one member meets the face of the other at roughly a right angle.
• Lap joint: members overlap in parallel planes.
• Edge joint: members are side by side, parallel or nearly so, and the weld joins their edges.

"Groove joint" is not a joint type. A groove is a preparation, and groove welds are used in several joint types.

Groove geometry

Most groove questions test which dimension is which.

• Bevel angle belongs to one member. It is measured from the bevel to a plane perpendicular to that member's surface.
• Groove angle is the total included angle of the groove. Two members each beveled 30 degrees give a 60-degree groove angle. On a single-bevel joint, only one member is prepared, so the bevel angle and groove angle are equal.
• Root face is the unbeveled part of the groove face at the joint root. "Land" is the nonstandard name. A root face of zero width is a root edge.
• Root opening is the gap between members at the root.
• Depth of bevel is measured from the base metal surface to the root edge or the start of the root face.
• Groove face is the surface of a member included in the groove. The fusion face is any base metal surface that will be melted.

Fillet weld size and throats

Fillet weld size is based on the largest right triangle that fits inside the weld cross section. For an equal-leg fillet, use the largest isosceles right triangle. For an unequal-leg fillet, use the largest right triangle of any proportion.

There are three throats:

• Theoretical throat: from the joint root perpendicular to the hypotenuse of that inscribed triangle. For a flat-faced 45-degree fillet it is about 0.707 times the leg.
• Actual throat: the shortest distance from the weld root to the weld face.
• Effective throat: the distance from root to face minus any convexity. If the actual throat is 0.40 in. and convexity is 0.06 in., the effective throat is 0.34 in.

Convexity adds metal but no design strength. Expect questions that test whether you subtract it. The throat formulas are worked through in the welding calculations guide.

Penetration and fusion

These terms are easy to confuse:

• Joint penetration is how far weld metal extends from the weld face into the joint, not counting reinforcement. For a groove weld, the weld size is the joint penetration.
• Root penetration is how far weld metal extends into the joint root.
• Complete joint penetration (CJP) means weld metal goes through the full joint thickness.
• Complete fusion means fusion over all fusion faces and between all adjoining beads.

A weld can be CJP and still contain incomplete fusion between two passes, so the two terms are not interchangeable.

Weld zones and weld features

• Weld metal is everything that was completely melted: melted filler plus melted base metal. Filler metal is the metal added; deposited metal is filler that ended up in the weld.
• Heat-affected zone (HAZ) is base metal that did not melt but whose properties or microstructure were changed by welding heat.
• Weld toe is where the weld face meets the base metal. Undercut, overlap and stress concentration show up here.
• Weld reinforcement is weld metal beyond what is needed to fill the joint, on the face or root side.
• Crater is the depression at the end of a bead. Unfilled craters tend to crack.
• Dilution is the change in filler metal chemistry caused by mixing with base metal, usually given as a percentage.

Positions

Position designations use a number and a letter: G for groove, F for fillet.

6GR is a 6G test with a restriction ring added. How these positions qualify a welder is covered in the welding performance guide.

Other weld types

• Back weld: made on the back of a single groove weld after the groove weld. A backing weld is made before it. The order is the whole difference.
• Plug weld: made in a round hole. A slot weld uses an elongated hole. A fillet weld around the edge of a hole is still a fillet weld.
• Seal weld: made mainly for leak tightness.
• Tack weld: holds parts in alignment until final welding.
• Buttering: a surfacing layer on groove faces that gives compatible metal for completing the joint. Cladding is for corrosion or heat resistance and hardfacing is for wear.

Backing is material placed at the root to support molten metal. A spacer holds the root opening, and a consumable insert is preplaced filler that becomes part of the root.

Discontinuity vocabulary

A discontinuity is any interruption in the normal structure of the material. It becomes a defect only when it makes the part fail the applicable acceptance criteria. Inspectors report discontinuities and call them defects only after comparing them with the code. Causes of each discontinuity are in the weld examination guide.

• Undercut: a groove melted into the base metal at the toe or root and left unfilled.
• Underfill: the weld face or root surface lies below the adjacent base metal surface.
• Overlap: weld metal that protrudes past the toe or root without fusing.
• Melt-through: visible root reinforcement on a joint welded from one side. "Burn-through" is nonstandard.

Technique and people

• Backhand welding points the electrode back toward the finished weld ("drag"). Forehand welding points toward the direction of travel ("push").
• Travel angle is measured in the plane of the weld axis. Work angle is measured in a plane perpendicular to the weld axis.
• Interpass temperature is the temperature of the weld area between passes. Preheat temperature is measured just before welding starts.
• A welder does manual or semiautomatic welding. A welding operator runs mechanized, automatic or robotic equipment.
• Semiautomatic welding feeds the wire automatically but the welder moves the gun. In mechanized welding, equipment moves the torch and the operator adjusts it. Automatic welding needs little or no adjustment.

How to study this domain

Make flash cards in pairs of easily confused terms. Good pairs are back weld and backing weld, bevel angle and groove angle, and actual and effective throat. Add joint penetration and complete fusion, and undercut and underfill. Sketch each one and label it. Drawing a term makes it easier to tell apart from its look-alike.

Mark J. Curry's tip: when two answer choices both sound right, check which one is the standard AWS term. Nonstandard shop terms are a common trap.

Work through the free terminology practice questions. To see which Part A topic to study first, take the free CWI diagnostic test.

Sources

The Definitions and Terminology questions cite these documents, by document and, where we can confirm it, chapter or section. We never reproduce them.

1. AWS A3.0 (35 questions)

Found a mistake? Use "Report a problem" under any question, and Mark J. Curry checks it.

Questions? support@cwiready.com