How is weld heat input calculated (basic formula)?

How is weld heat input calculated (basic formula)?

• A. Heat input = Volts × Amperes × 60 / travel speed (in/min)
• B. Heat input = Current × Time
• C. Heat input = Area × Time
• D. Heat input = Voltage × Travel speed

Answer: (A)

The main idea here is that heat input is the energy delivered to the weld per unit length, coming from the arc’s electrical power and how long the arc acts on each inch of weld. The arc power is volts multiplied by amperes (that's watts). To find how much energy goes into one inch, you look at how long that inch is exposed to the arc: time per inch equals the travel time for one inch, which is 1 divided by the travel speed (in inches per minute). Convert that time to seconds by multiplying by 60. So heat input per inch = volts × amperes × 60 / travel speed (inches per minute). This gives energy per inch, typically in joules per inch. For example, with 20 V, 120 A, and a travel speed of 5 inches per minute, heat input = 20 × 120 × 60 / 5 = 28,800 J per inch (about 28.8 kJ/in). Other forms don’t line up with the units or the physical meaning: current times time would give total charge or energy without accounting for the arc duration per length; area times time isn’t related to the welding heat input; voltage times travel speed mixes units in a way that doesn’t represent energy per length.

The main idea here is that heat input is the energy delivered to the weld per unit length, coming from the arc’s electrical power and how long the arc acts on each inch of weld. The arc power is volts multiplied by amperes (that's watts). To find how much energy goes into one inch, you look at how long that inch is exposed to the arc: time per inch equals the travel time for one inch, which is 1 divided by the travel speed (in inches per minute). Convert that time to seconds by multiplying by 60. So heat input per inch = volts × amperes × 60 / travel speed (inches per minute). This gives energy per inch, typically in joules per inch.

For example, with 20 V, 120 A, and a travel speed of 5 inches per minute, heat input = 20 × 120 × 60 / 5 = 28,800 J per inch (about 28.8 kJ/in).

Other forms don’t line up with the units or the physical meaning: current times time would give total charge or energy without accounting for the arc duration per length; area times time isn’t related to the welding heat input; voltage times travel speed mixes units in a way that doesn’t represent energy per length.