# Heat Input Formula

Under the arc welding process, heat input and arc energy are the measures of energy that has been supplied to the piece to form a weld. Both are measured in units of energy per unit length.
It refers to a characteristic or dimension such as weld length, a bead, the diameter of a weld spot, or cross-section. The amount of heat input that goes into a weld is determined as a function of time.

## Formula for Heat Input

The heat input formula is given by,

$$\begin{array}{l}Heat\;Input = \frac{60\times Current \times Volts}{1000\times \left ( distance travelled in /min \right )}\end{array}$$

KJ/in is the unit.

The accurate measurement of arc voltage is the difficulty here, but we mostly measure load voltage at the output terminals of the current source.

### Solved Examples

Example 1

YouÂ weldÂ atÂ 400Â inchesÂ andÂ 39Â voltsÂ perÂ minute.Â TheÂ weldÂ isÂ 35Â inchesÂ long,Â andÂ weldingÂ takesÂ 4Â minutes.Â WhileÂ weldingÂ youÂ findÂ thatÂ theÂ systemÂ showsÂ anÂ amperageÂ ofÂ 425.Â WhichÂ isÂ yourÂ inputÂ heat?
Solution:
$$\begin{array}{l}Travel speed = \frac{Length of the weld}{Time to weld}\end{array}$$
Travel speed = 35/4
Travel speed = 8.75 inches per min
$$\begin{array}{l}Heat Input = \frac{60\times Current \times Volts}{1000\times \left ( distance travelled in /min \right )}\end{array}$$
$$\begin{array}{l}Heat Input = \frac{60\times 425 \times 39}{1000\times \left ( 8.75 \right )}\end{array}$$
Heat input = 113.65 KJ/in