NCCER Certification Welding Syllabus

How does plasma arc cutting (PAC) sever metal?

PAC uses a constricted, high-velocity ionized gas (plasma) jet at very high temperature to melt the metal, while the high-velocity gas blows the molten metal out of the kerf. It cuts any electrically conductive metal.

What is the key advantage of plasma arc cutting over oxyfuel cutting?

PAC can cut any electrically conductive metal—including aluminum, stainless steel, and copper—that cannot be oxyfuel cut, and it cuts thin material faster with a narrower kerf and smaller heat-affected zone.

What is the function of the air carbon arc cutting/gouging (CAC-A) process?

CAC-A uses a carbon electrode arc to melt the metal and a high-velocity compressed-air jet to blow the molten metal away. It is used to gouge grooves, remove defective welds, and back-gouge joints.

In air carbon arc gouging, why must the compressed air be turned on, and where is the air directed?

The compressed air blows the molten metal out of the gouge before it resolidifies. The air jet is directed behind the carbon electrode, beneath it, flowing in the direction of travel.

What polarity is normally used for air carbon arc gouging, and what does the electrode consist of?

Direct current electrode positive (DCEP / reverse polarity) is normally used. The electrode is a copper-coated carbon-graphite rod; the copper coating improves conductivity and electrode life.

What does SMAW stand for, and what is its common nickname?

Shielded Metal Arc Welding, commonly called 'stick' welding or manual arc welding.

In SMAW, what two functions does the electrode covering (flux) perform?

It produces a shielding gas to protect the molten weld pool from atmospheric contamination and forms a slag covering that protects the cooling weld; it may also add alloying elements and stabilize the arc.

Decode the AWS electrode classification E7018: what does each part mean?

E = electrode; 70 = minimum tensile strength of 70,000 psi; 1 = weldable in all positions; 8 = low-hydrogen iron-powder covering usable with AC or DCEP.

In a four-digit SMAW electrode number (EXXYZ), what do the first two digits and the third digit represent?

The first two (or three) digits give the minimum tensile strength in thousands of psi (e.g., 60 = 60,000 psi). The third digit (Y) gives welding position: 1 = all positions, 2 = flat and horizontal only.

What does the fourth digit of an SMAW electrode classification (the 'Z' in EXXYZ) indicate?

It indicates the type of coating and the welding current/polarity to use (e.g., the '8' in E7018 indicates a low-hydrogen coating usable with AC or DCEP).

Why must low-hydrogen electrodes (like E7018) be kept in a heated rod oven?

Their coatings readily absorb atmospheric moisture, which introduces hydrogen into the weld and can cause hydrogen-induced (cold) cracking. Heated ovens keep them dry until use.

What is the difference between DCEP and DCEN polarity in SMAW?

DCEP (DC electrode positive / reverse polarity) puts more heat on the electrode, giving deeper penetration. DCEN (DC electrode negative / straight polarity) puts more heat on the work, giving faster melt-off and shallower penetration.

What is a stringer bead versus a weave bead?

A stringer bead is made with little or no side-to-side motion, producing a narrow bead. A weave bead is made with a side-to-side oscillating motion, producing a wider bead used to fill larger joints or for out-of-position welding.

What are the three weld positions for a fillet weld and the standard AWS position codes?

Flat (1F), horizontal (2F), vertical (3F), and overhead (4F). The number gives the position; F denotes fillet.

What are the standard AWS groove-weld position codes?

1G = flat, 2G = horizontal, 3G = vertical, 4G = overhead, 5G = horizontal fixed pipe, 6G = inclined fixed pipe (45°).

Define 'leg' and 'throat' of a fillet weld.

The leg is the distance from the joint root to the toe of the fillet weld. The throat is the shortest distance from the root of the joint to the face of the weld (the effective load-carrying dimension).

What is the root pass in a multi-pass groove weld?

The root pass is the first weld bead deposited at the bottom (root) of the joint. It establishes penetration and fusion at the root and forms the foundation for subsequent fill and cover passes.

What is weld undercut, and why is it a problem?

Undercut is a groove melted into the base metal adjacent to the weld toe and left unfilled. It reduces cross-sectional thickness and creates a stress concentration that can lead to cracking and failure.

What causes weld porosity, and what does it look like?

Porosity is gas pockets (cavities) trapped in the weld, appearing as holes or pits. It is caused by contamination (moisture, oil, rust), inadequate shielding gas, or improper technique.

What is incomplete (lack of) fusion in a weld?

Incomplete fusion occurs when the weld metal fails to fuse completely with the base metal or with previously deposited weld metal, leaving an unbonded interface—often from low heat, fast travel, or contamination.

What is incomplete joint penetration?

Incomplete joint penetration is a condition where the weld metal does not extend fully through the joint thickness (does not reach the root), leaving an unfilled gap at the joint root.

What is the difference between a weld 'crack' and 'overlap' as discontinuities?

A crack is a fracture-type discontinuity (linear separation) and is the most serious defect. Overlap is weld metal that flows over the base metal at the toe without fusing to it, creating a sharp notch and stress riser.

What is 'slag inclusion' and how is it prevented?

Slag inclusion is nonmetallic slag trapped in the weld, usually from failing to clean slag between passes. It is prevented by thoroughly removing slag with a chipping hammer and wire brush before each subsequent pass.

What do GMAW and FCAW stand for, and what is GMAW's common nickname?

GMAW = Gas Metal Arc Welding (commonly 'MIG' welding); FCAW = Flux-Cored Arc Welding. Both are continuous solid- or tubular-wire processes.

What is the key difference between GMAW and FCAW regarding shielding?

GMAW uses a solid wire and relies entirely on an externally supplied shielding gas. FCAW uses a tubular wire with internal flux; self-shielded FCAW (FCAW-S) needs no external gas, while gas-shielded FCAW (FCAW-G) uses both internal flux and external gas.

Name the four GMAW metal-transfer modes.

Short circuit (short arc), globular, spray (axial spray), and pulsed spray transfer.

Which GMAW transfer mode is best for thin metal and out-of-position welding, and why?

Short-circuit transfer, because it uses low heat input and produces a small, fast-freezing weld pool that is easy to control out of position and minimizes burn-through on thin material.

What shielding gas combination is commonly used for GMAW short-circuit welding of carbon steel, and what does CO2 content affect?

A 75% argon / 25% CO2 mix is common. Higher CO2 increases penetration but also increases spatter; pure argon is used for nonferrous metals like aluminum.

What does GTAW stand for, its nickname, and what electrode does it use?

Gas Tungsten Arc Welding, nicknamed 'TIG' (tungsten inert gas) welding. It uses a non-consumable tungsten electrode and a separately added filler rod, shielded by an inert gas (usually argon).

What current type is used for GTAW welding of aluminum versus steel, and why?

Aluminum is welded with AC because the reverse-polarity half-cycle provides a cleaning action that breaks up the tough aluminum oxide layer. Steel and stainless are welded with DCEN for good penetration and electrode life.

What is the purpose of a welder qualification (performance) test, and who governs it?

A performance qualification test verifies that a welder can produce sound welds following a specific Welding Procedure Specification (WPS). It is governed by codes such as AWS D1.1 or ASME Section IX, and qualification is limited to the positions, processes, and material thickness ranges tested.

What is the difference between a WPS and a PQR in welder qualification?

A WPS (Welding Procedure Specification) is the written instruction listing the approved variables for making a weld. A PQR (Procedure Qualification Record) documents the actual test data and results proving the WPS produces acceptable welds.