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

You weld at 400 inches and 39 volts per minute. The weld is 35 inches long, and welding takes minutes. While welding you find that the system shows an amperage of 425. Which is your input heat?
\(\begin{array}{l}Travel speed = \frac{Length of the weld}{Time to weld}\end{array} \)
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


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