What are proper base-metal preparation steps prior to GTAW, including cleaning and fit-up?

What are proper base-metal preparation steps prior to GTAW, including cleaning and fit-up?

• A. Remove oil/grease, scale, and oxides; de-burr and square edges; ensure clean, dry surfaces; fit up with minimal gap and secure alignment; use dedicated brushes or grinders for different metals.
• B. Rinse with water and wipe dry; no scrubbing.
• C. Only clean with water after assembly.
• D. Do not deburr or square edges.

Answer: (B)

Proper base-metal preparation for GTAW centers on having a clean, oxide-free surface and a well-aligned joint. Oils, greases, scale, and oxides create barriers to proper fusion and can trap hydrogen, leading to porosity and weak welds. That’s why you remove oil/grease, scale, and oxides; de-burr and square edges to remove irregularities; keep surfaces clean and dry to prevent moisture; ensure fit-up with a minimal gap and secure alignment so the weld metal can wet and fill the joint evenly; and use dedicated brushes or grinders for different metals to avoid cross-contamination. Rinsing with water and wiping dry doesn’t reliably remove oils or oxide layers, and neglecting deburring, squaring, or proper fit-up can cause poor fusion, root defects, and misalignment.

Proper base-metal preparation for GTAW centers on having a clean, oxide-free surface and a well-aligned joint. Oils, greases, scale, and oxides create barriers to proper fusion and can trap hydrogen, leading to porosity and weak welds. That’s why you remove oil/grease, scale, and oxides; de-burr and square edges to remove irregularities; keep surfaces clean and dry to prevent moisture; ensure fit-up with a minimal gap and secure alignment so the weld metal can wet and fill the joint evenly; and use dedicated brushes or grinders for different metals to avoid cross-contamination. Rinsing with water and wiping dry doesn’t reliably remove oils or oxide layers, and neglecting deburring, squaring, or proper fit-up can cause poor fusion, root defects, and misalignment.