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 4 minutes. While welding you find that the system shows an amperage of 425. Which is your input 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
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