Welding Heat Input Calculator
A critical tool for welders and welding engineers. Accurately calculate the heat input of a weld to control the microstructure, mechanical properties, and overall quality of the weldment.
The Critical Role of Heat Input in Welding
Heat input is one of the most important variables in arc welding. It represents the amount of electrical energy transferred to the workpiece per unit length of the weld. Controlling heat input is crucial because it directly influences the weld's cooling rate, which in turn determines the microstructure and mechanical properties (like strength and toughness) of both the weld metal and the Heat-Affected Zone (HAZ). Too much heat input can lead to a coarse grain structure, reduced toughness, and increased distortion. Too little heat input can result in a lack of fusion and increased susceptibility to cracking.
The Formula for Heat Input
Heat input is calculated using a standard formula recognized throughout the industry:
Heat Input (kJ/mm) = (Voltage × Amperage × 60 × Efficiency Factor) / (Travel Speed [mm/min] × 1000)
The components of this formula are:
- Voltage (V): The electrical potential of the arc.
- Amperage (I): The electrical current flowing through the arc.
- Travel Speed (S): How quickly the arc is moved along the joint, typically in millimeters per minute.
- Thermal Efficiency (k): A dimensionless factor that accounts for how much of the arc's energy is actually transferred to the workpiece. This varies by welding process. Submerged Arc Welding (SAW) is very efficient (k=1.0), while processes like GTAW (TIG) are less so (k≈0.6) because more heat is lost to the surroundings.