SMAW Fundamentals on Carbon Steel — Flat and Horizontal

SMAW Fundamentals on Carbon Steel — Flat and Horizontal

Shielded Metal Arc Welding (SMAW) — commonly called "stick welding" — is the foundation of structural and marine fabrication. Before you run a single bead, you need to understand the equipment, the consumables, and the quality standards that will govern every coupon you produce in this lab.

How SMAW Works

SMAW uses a flux-coated consumable electrode. The welding machine drives current through a work clamp and electrode holder, creating an arc between the electrode tip and the base metal. That arc generates intense heat — melting both the electrode core and the base metal to form a weld puddle. The flux coating burns and produces a gas shield and a slag layer that protect the molten metal from atmospheric contamination. When the weld cools, you chip away the slag to reveal the bead underneath.

Machine Setup — Polarity and Amperage

SMAW machines are constant-current (CC) machines. Polarity matters: E6010 runs on DC electrode positive (DCEP), which drives deeper penetration — critical for root passes on marine hull plating. E7018 also runs on DCEP for most applications, though some brands allow AC; always check the manufacturer's data sheet on the electrode box.

Amperage selection is the most important variable you will set today. Too low and the arc is unstable, the bead is narrow, and you risk incomplete fusion. Too high and you get excessive spatter, burn-through on thinner plate, and wide flat beads with undercut at the toes. The electrode manufacturer's data sheet lists a recommended amperage range for each diameter. For 3/32-inch E7018, a typical range is roughly 70–110 amperes; for 1/8-inch E7018, roughly 110–165 amperes. Always start in the middle of the recommended range and adjust based on what you observe in the puddle.

Electrode Handling — The Rod Oven Rule

E7018 is a low-hydrogen electrode. Its coating absorbs moisture from the air, and moisture causes hydrogen-induced cracking — a serious structural defect. Once a fresh container is opened, E7018 must be stored in a rod oven at the temperature specified by the manufacturer (typically around 250–300 °F). Never leave E7018 rods lying on the bench. E6010 is a cellulosic electrode that is less sensitive to moisture and does not require oven storage, though it should be kept dry.

Arc Striking and Bead Restart

Use the scratch-start or tap-start method your instructor demonstrates. If the electrode sticks, release the holder immediately — do not yank — then break the electrode free with a rocking motion. A stuck electrode can overheat and ruin the coating.

Bead restarts matter for inspection. When restarting on a stopped bead, strike the arc about 1/2 inch ahead of the crater, drag back into the crater to fill it, then continue forward. A poorly filled crater will show as a visible crater crack or undercut — both rejection criteria under AWS D1.1.

Flat (1G/1F) and Horizontal (2G/2F) Positions

In the flat position (1G groove, 1F fillet), gravity works with you: the puddle wants to stay where you put it. Maintain a consistent travel angle (drag angle of roughly 5–15 degrees from vertical, pointing in the direction of travel) and a work angle of 90 degrees for groove welds or approximately 45 degrees to both plates for fillet welds.

In the horizontal position (2G groove, 2F fillet), gravity pulls the puddle downward toward the lower plate. To compensate, tilt the electrode slightly upward — about 5–10 degrees above horizontal — and move at a pace that keeps the puddle from sagging. A weave bead in the horizontal position requires tighter control: slow at the top of the weave, faster across the middle, pause briefly at the bottom to fuse without overlap.

AWS D1.1 Visual Acceptance Criteria

AWS D1.1 is the Structural Welding Code — Steel, and it sets the acceptance standard for the work you produce today. For visual inspection, the key criteria are:

• Crack prohibition: No cracks of any kind.
• Fusion: The weld must fuse completely to the base metal; no incomplete fusion visible at the toe.
• Crater: Craters must be filled to the full cross-section of the weld.
• Weld reinforcement (groove welds): Crown height must not exceed limits specified in the code for the plate thickness.
• Undercut: Undercut at the weld toe must not exceed 1/32 inch for most structural applications under D1.1.
• Overlap: Cold lap (where the weld metal rolls over the base metal without fusing) is not permitted.
• Fillet size: The measured fillet leg must meet the specified size; for this lab, the tolerance is +1/4 inch / -0 inch.

Use your laminated AWS visual acceptance reference card every time you inspect — never rely on memory alone.

Safety in the Welding Bay

• PPE: Auto-darkening or fixed-shade welding helmet (shade 10–12 for SMAW depending on amperage), welding gloves, leather jacket or flame-resistant sleeves, leather boots. No synthetic fabrics near the arc.
• Ventilation: SMAW generates fumes containing manganese and other metals. Work under local exhaust ventilation or a fume extraction arm. If ventilation is inadequate, wear a respirator rated for welding fumes.
• Fire watch: Clear combustibles from your work area. A fire watch is required after hot work.
• Electrical safety: Inspect the electrode holder, leads, and work clamp before every use. Report damaged insulation immediately. Keep your body out of the electrical circuit — never touch the electrode and work clamp simultaneously.
• Slag hazard: Chipping slag from a hot weld can project fragments at high velocity. Keep your helmet down and wear safety glasses under your welding helmet at all times in the bay.
• Grinder safety: Angle grinders used for surface prep require a face shield in addition to safety glasses, and a grinding disc rated for the RPM of your machine.