AWS Certified Welder cheat sheet

SMAW: electrode coating shields the arc and forms slag; E7018 is a low-hydrogen electrode that must be stored dry and used from a heated rod oven to prevent hydrogen-induced cracking.

GMAW transfer modes: short-circuit (thin sheet, low heat input), globular (coarse, spatter-prone), spray (high current, argon-rich gas, deep penetration), and pulsed-spray (spray-like transfer at lower average current).

GTAW uses a non-consumable tungsten electrode with separately supplied filler; it requires DCEN for steel and AC for aluminum to break the surface oxide and provide cleaning action.

FCAW self-shielded electrodes rely on flux for shielding and tolerate wind; gas-shielded FCAW needs external CO2 or mixed gas and is more sensitive to drafts.

SAW uses a blanket of granular flux and achieves high deposition rates in flat or horizontal positions; it is not suited to vertical or overhead work.

Electrode classification EXXYY: the first two digits give minimum tensile strength in ksi (E70 = 70,000 psi); the third digit gives welding position and coating/current type.

Heat input (kJ/in) = (arc voltage x amperage x 60) / (travel speed in in/min x 1000); higher heat input raises grain growth and lowers toughness.

Preheat temperature rises with carbon equivalent, section thickness, and base-metal hardenability; it slows the cooling rate to prevent martensite and hydrogen cracking.

1G/1F: flat position, welding from above with the axis horizontal; highest deposition and easiest puddle control because gravity holds the molten metal in the joint.

2G/2F: horizontal position, weld axis horizontal but the face vertical; the puddle tends to sag downward, so current is reduced and a slight weave controls the bead.

3G/3F: vertical position, axis vertical; either uphill (higher penetration, higher current) or downhill (faster, less penetration) progression is used.

4G/4F: overhead position, welded from below; gravity pulls the puddle away from the joint, so lower current, shorter arc, and faster travel are needed.

6G: pipe fixed at 45 degrees with no rotation; the welder must cover all positions in one pass sequence, making it the most demanding pipe test position.

5G: pipe axis horizontal and fixed while the pipe is not rotated; the welder moves around the pipe, covering flat, vertical, and overhead sections.

Position limits are set by the qualification standard; a test in a more difficult position (e.g., 6G or 4G) usually qualifies the easier positions within the range allowed.

Vertical-up with SMAW uses a slight weave and a short arc to keep the puddle from running; vertical-down is generally limited to thin sheet and cellulosic electrodes.

Carbon equivalent (CE) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15; a CE above about 0.40 raises cracking risk and calls for preheat and low-hydrogen practice.

AISI 1018 low-carbon steel (about 0.18% C) welds readily; AISI 1045 (about 0.45% C) needs preheat and post-weld control to avoid hardening and cracking.

Austenitic stainless steel (300 series) has high thermal expansion and low thermal conductivity, so it distorts more and needs lower heat input and faster travel than carbon steel.

Aluminum forms a refractory oxide (melting near 2050 C) above the metal (melting near 660 C); AC GTAW or wire brushing removes the oxide before welding.

Copper and its alloys conduct heat rapidly, so preheat and high current are needed to reach fusion; some alloys (e.g., beryllium copper) require fume controls.

Cast iron is welded with nickel- or iron-based electrodes, low current, short beads, and preheat or a peening step to reduce shrinkage stress.

Dissimilar metals are joined when they are metallurgically compatible; the filler is usually selected to match the lower-strength or more crack-sensitive side.

Hydrogen content matters: moisture, rust, paint, and oil on the base metal are hydrogen sources that promote delayed cracking in high-strength steels.

Five basic joint types: butt, lap, tee, corner, and edge; the butt joint is the most common for full-penetration pipe welds.

Groove types include V, U, J, and square; a V-groove with a 60-degree included angle (30-degree bevel per side) is typical for pipe butt welds.

Root opening, land (root face), and bevel angle together control root penetration, fusion, and the risk of burn-through.

Pipe size is given by nominal diameter and wall thickness (schedule); small-diameter, thin-wall pipe heats fast and needs lower current and faster travel.

Fixed-position pipe tests (e.g., 6G) use a single joint that must be welded in all positions, so the root pass is critical for uniform penetration.

Tack welds must be full penetration and are consumed by the root pass; tacks that are too small crack, and tacks that are too large cause lack of fusion.

Backing (consumable insert, backing ring, or purge gas) supports the root; a purge of argon on stainless and titanium prevents root oxidation.

Joint fit-up tolerance: excessive root gap causes burn-through, while too little gap or a heavy land causes lack of penetration at the root.