Welder — Year 2 Exam Prep
Year 2 of the welder apprenticeship significantly expands your process knowledge. GMAW (MIG), FCAW, and GTAW (TIG) join SMAW as processes you must understand in depth. Intermediate metallurgy, weld distortion, weld defects, and more detailed code awareness define the second period curriculum. TradeBenchPrep gives you practice built on the Year 2 welding curriculum.
What a Year 2 Welder Apprentice Needs to Know
GMAW — Gas Metal Arc Welding (MIG)
GMAW process fundamentals — the wire electrode is fed continuously through the welding gun and the arc is shielded by externally supplied shielding gas. Know the four metal transfer modes: Short circuit transfer — low voltage and wire feed speed, wire touches the puddle and shorts, creating a small weld with low heat input. Used for thin materials and out-of-position welding. Globular transfer — higher voltage, molten drops larger than the wire diameter fall into the puddle irregularly, high spatter. Spray transfer — high voltage and wire feed speed, very fine droplets transfer axially across the arc in a continuous stream, very smooth bead, high deposition rate, flat and horizontal only. Pulse transfer — rapidly alternates between high and low current, achieves spray-like droplet transfer at lower average heat input, all-position capable. Shielding gas selection — 100% CO₂ (deep penetration, high spatter), 75%Ar/25%CO₂ (C25, the most common all-purpose mix for carbon steel), and argon-rich mixes for stainless and aluminum. Wire classification — AWS ER70S-6 is the most common carbon steel GMAW wire — know what each designation element means.
FCAW — Flux Cored Arc Welding
Two types of FCAW: Gas-shielded FCAW (FCAW-G) — requires external shielding gas similar to GMAW, produces high quality welds, used in fabrication shops. Self-shielded FCAW (FCAW-S) — no external gas required, the flux core generates its own shielding, more portable for field work, more sensitive to technique. Wire classification — E71T-1 (gas-shielded, all-position, excellent for structural) and E71T-11 (self-shielded, all-position) are the most common. Know when FCAW is preferred over SMAW or GMAW — high deposition rate for production welding on heavier sections, field work capability with self-shielded wire.
GTAW — Gas Tungsten Arc Welding (TIG)
GTAW uses a non-consumable tungsten electrode to create the arc and filler metal is added separately by hand. This produces the highest quality, most controlled weld of any arc welding process. Tungsten electrode types — pure tungsten (green, for AC aluminum welding), 2% thoriated (red, DCEN for steel and stainless — being phased out for radioactivity concerns), 2% ceriated (grey, DCEN for steel, stainless, and some aluminum applications, now the preferred alternative to thoriated). Tungsten preparation — for DCEN, grind the tungsten to a point with the grind marks running lengthwise. For AC, allow the tungsten to form a hemispherical ball. Shielding gas — argon for most GTAW applications, helium for higher heat input requirements, argon/helium mixtures. Back purging — why the back side of a stainless or titanium root pass must be shielded with argon to prevent oxidation. Current selection — DCEN for steel, stainless, copper. AC for aluminum (the positive half-cycle removes the oxide layer).
Intermediate Metallurgy — Heat Effects on Metal
The iron-carbon phase diagram — the basis for understanding how steel transforms through heating and cooling. Know the critical temperature (approximately 723°C for eutectoid transformation) and how it relates to heat treatment and preheat requirements. Heat affected zone (HAZ) — the region adjacent to the weld that has been heated above the critical temperature but not melted. The HAZ experiences metallurgical changes including grain growth, hard martensite formation in higher-carbon steels, and sensitization in austenitic stainless steels. Carbon equivalent (CE) — the formula that combines carbon content and alloying elements to predict weldability and preheat requirements. Higher CE = higher preheat required to prevent hydrogen-assisted cracking. Preheat — heating the base metal before welding to slow the cooling rate, reduce hard martensite formation, and allow hydrogen to diffuse out. Post-weld heat treatment (PWHT) — stress relief annealing to reduce residual stresses in thick sections and certain alloy steels.
Weld Distortion — Causes and Control
Distortion is caused by differential thermal expansion and contraction during welding — the weld metal and HAZ contract on cooling and pull the surrounding base metal with them. Types of distortion — angular distortion (the plate bends away from the weld), longitudinal shrinkage (the weld gets shorter as it cools), and transverse shrinkage (the joint closes up). Distortion control methods — pre-setting (welding the joint at an angle opposite to the expected distortion so it comes out straight when distortion occurs), back-step welding (welding short segments in the direction opposite to the overall progression to distribute heat more evenly), balanced welding (alternating welds on both sides of a neutral axis), and fixturing (clamping or tacking the assembly to resist movement). Residual stress — internal stresses that remain in the weldment after it has cooled. High residual stresses increase the susceptibility to fatigue cracking and stress corrosion.
Weld Defects — Types, Causes, and Prevention
Know every major weld defect — what it looks like, what causes it, and how to prevent it: Porosity (gas pockets in the weld) — caused by contamination (moisture, oil, rust, mill scale), insufficient shielding gas coverage, or too long an arc. Undercut (groove at the weld toe that reduces the base metal cross-section) — caused by too high a current, too fast a travel speed, or incorrect electrode angle. Incomplete fusion — caused by too low a heat input, incorrect technique, or a contaminated joint surface. Incomplete penetration (in groove welds) — caused by too small a root opening, too large a root face, or insufficient current. Overlap (weld metal rolls over the base metal surface without fusing to it) — caused by too low a current or too slow a travel speed. Cracks — hot cracks (solidification cracks that form in the weld metal while it is still hot) caused by high sulfur or phosphorus content or highly restrained joints. Cold cracks (hydrogen-assisted cracks) — form after cooling, caused by hydrogen in the weld, a susceptible microstructure (martensite), and residual tensile stress. Prevented by low-hydrogen electrodes, preheat, and proper PWHT.
What Year 2 Welders Must Understand Deeply
GMAW transfer modes are the most commonly tested Year 2 topic and require understanding beyond just naming the modes. Know what parameters produce each mode, what the weld bead looks like, what the spatter level is, and what applications each mode is suited for.
Cold cracking (hydrogen-assisted cracking) — understanding why it occurs (hydrogen + martensite + tensile stress) is more important than memorizing the name. This understanding lets you answer questions about prevention (low hydrogen consumables, preheat, PWHT) correctly even if they are phrased in unfamiliar ways.
How to Use TradeBenchPrep for Year 2
Study Mode for GMAW transfer modes and weld defect questions gives you the detailed explanations that build the understanding needed for both Year 2 and Year 3 exams. Quiz Mode for GTAW electrode and current selection questions is most efficient for that specific topic. Full Exam Mode with timed conditions is essential in your final week of preparation.