Understanding Welding Heat Input
Heat Input (kJ/in) = (Voltage x Amperage x 60) / (Travel Speed [in/min] x 1000)
Net Heat Input = Heat Input x Thermal Efficiency Factor
Heat input is a critical parameter in welding procedure specifications (WPS). It affects the heat-affected zone (HAZ), grain growth, residual stress, and distortion.
Why Heat Input Matters
- Too high: Excessive grain growth, reduced toughness, increased distortion
- Too low: Lack of fusion, insufficient penetration, cold cracking risk
- Many codes specify maximum heat input limits for specific materials
- Preheat and interpass temperature requirements depend on heat input