Fundamentals of welding science and technology

A: At 0.1 kJ/mm you'd predict almost no HAZ width, which contradicts observed bead profiles at these currents. At 0.5 kJ/mm the implied travel speed would be unrealistically high for SMAW. At 5 kJ/mm you'd expect excessive penetration and burn-through on typical plate thicknesses. Using P=VI, applying efficiency, and dividing by a plausible 3–4 mm/s travel speed lands near 1–2 kJ/mm.

A: Starting with continuity logs can let an unqualified procedure slip through if the paperwork looks clean. Jumping to visual acceptance ignores whether the procedure itself is permitted. Reviewing NDT first risks validating welds made to an invalid process window. Ensuring the WPS is backed by a compliant PQR gates all downstream checks and prevents rework.

A: Excessive dilution mainly shifts chemistry but doesn't explain delayed cracking at the toe. Solidification cracking appears along the weld centerline during freezing, not after cooldown. Lamellar tearing tracks through-thickness inclusions and shows a different crack path. Hydrogen trapped by high restraint and rapid cooling produces delayed toe cracks hours after welding.

A: Arc eye to bystanders is mitigated by correctly placed screens. UV exposure drops sharply with opaque barriers. Visible glare is also blocked when screens are intact. Metal fumes travel over and around screens and still require ventilation and respiratory controls.