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Calculate heat input in kJ/in and kJ/mm using the AWS D1.1 / ASME IX formula. Essential for code-compliant WPS procedures requiring toughness testing.
HI = (29 × 280 × 60) ÷ (13 × 1000) = 37.5 kJ/in — typical structural GMAW. Within A36 limits.
HI = (26 × 180 × 60) ÷ (3 × 1000) = 93.6 kJ/in — within limits for A36 heavy section but verify against your WPS.
HI = (10 × 110 × 60) ÷ (2 × 1000) = 33.0 kJ/in × 0.6 (η) = 19.8 kJ/in — typical TIG pipe root with efficiency applied.
AWS D1.1 uses: Heat Input (kJ/in) = (Voltage × Amperage × 60) ÷ (Travel Speed in IPM × 1000). Equivalently: V × A × 0.06 ÷ IPM. For metric, divide by 25.4 to get kJ/mm. See AWS D1.1 Clause 6.8.5 and ASME IX QW-409.1.
Heat input measures energy delivered per unit length of weld in kJ/in or kJ/mm. It controls HAZ grain size, cooling rate, and mechanical properties. It becomes a supplementary essential variable under ASME IX QW-409.1 when notch toughness testing is required.
For A36 steel (CE ≈ 0.35) under 25mm, typical maximum is approximately 110 kJ/in (4.3 kJ/mm). For A572 Gr50 or higher CE steels, limits are more restrictive. Always consult the actual code table and your approved WPS — the code values depend on plate thickness and CE, not just grade.