BIZOMAT MAKEOS · Fabrication
Welding Arc Energy and Heat Input
What energy per length follows from these arc parameters?
Separate unadjusted arc energy from efficiency-adjusted heat input for a steady arc and supplied travel speed.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Arc voltage | V | Measured across the arc using a suitable method; supply-terminal voltage may differ. |
| Welding current | A | Measured current for a sufficiently steady arc. Product of averages is not a general pulsed-power measurement. |
| Travel speed | mm/min | Actual travel per minute along the weld. |
| Process energy efficiency | % | Energy efficiency required by the applicable procedure or convention; not deposition efficiency. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Arc voltage
- What it is
- The voltage across the welding arc during steady welding, measured as close to the arc as practical.
- Units and format
- Enter a number in V: volts. The form accepts 0.001 V to 1000 V. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 24 V as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Arc energy and heat input are directly proportional to voltage.
- Get it right
- The machine terminal display can read higher than the arc because of cable losses.
What this means: Welding current
- What it is
- The welding current flowing through the arc during steady welding.
- Units and format
- Enter a number in A: amperes. The form accepts 0.001 A to 100000 A. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 A as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Arc energy and heat input are directly proportional to current.
- Get it right
- For pulsed processes the product of average voltage and current is not a reliable power; use instantaneous power if required.
What this means: Travel speed
- What it is
- How fast the arc moves along the weld joint, measured as weld length completed per minute.
- Units and format
- Enter a number in mm/min: millimetres per minute. The form accepts 0.001 mm/min to 1000000 mm/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 mm/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Arc energy is inversely proportional to travel speed: slower travel gives more heat per millimetre.
- Get it right
- Measure along the actual weld, not the torch weave path; time a known length.
What this means: Process energy efficiency
- What it is
- The thermal efficiency factor for the welding process, the share of arc energy taken as heat input into the work, as set by the applicable procedure or convention.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0.001% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Heat input is directly proportional to this efficiency.
- Get it right
- This is not the deposition efficiency; use the value the welding procedure or standard requires.
Method and formulas
- Arc power = voltage × current. Arc energy (kJ/mm) = 60 × voltage × current/(1000 × travel in mm/min).
- Adjusted heat input = arc energy × efficiency/100.
- Example: 24 V, 200 A, 300 mm/min gives 4.8 kW and 0.96 kJ/mm arc energy. Supplied 80% efficiency gives 0.768 kJ/mm adjusted heat input.
Limitations
- Pulsed or waveform-controlled welding needs appropriate power integration; multiplying mean current and mean voltage can be wrong.
- Terminology and efficiency conventions differ among standards. Identify whether the requirement concerns arc energy or adjusted heat input.
- No acceptable energy window, preheat, interpass limit or procedure approval is provided.
- Default values are worked examples, not recommended settings or material properties.
Typical uses
- welding energy
- arc energy
- travel speed
Who it is for
- Welding engineers
- Fabrication teams
- Procedure reviewers
What you get
- Steady arc power
- Arc energy per millimetre
- Adjusted heat input
Interpreting the result
- Compare the appropriate quantity with the qualified procedure and applicable standard.
- Record measurement locations, travel method and efficiency source.
References
- TWI: Difference between heat input and arc energy — https://www.twi-global.com/technical-knowledge/faqs/faq-what-is-the-difference-between-heat-input-and-arc-energy
- TWI: Measurement of arc welding parameters — https://www.twi-global.com/technical-knowledge/job-knowledge/measurement-of-arc-welding-parameters-139
- TWI: ISO 15614-1:2017 changes, including waveform energy measurement — https://www.twi-global.com/technical-knowledge/faqs/faq-whats-new-in-iso-15614-1-2017
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
The arc as a heat source
What it covers: Calculate arc power from voltage and current, see where the arc's heat is released, and use the 1921 measurements to show how little of the electrode is vaporised.
Method explained here · BIZOMAT original book
Direction of load and limits on weld size
In Designing Welded Joints by the Numbers
What it covers: Compare fillet welds loaded along and across their length, see why mixing them needs care, and understand the minimum and maximum fillet sizes that thick plate, plate edges and fit-up gaps impose.
Method explained here · BIZOMAT original book
Laser welding: penetration, heat input and fit-up
In Laser Processing by the Numbers
What it covers: Conduction and keyhole laser welding, heat input compared with TIG and MIG, cooling time and hard heat-affected zones in steel, and the fit-up a laser weld needs.
Method explained here · BIZOMAT original book
Travel speed, heat input and over-welding
In Welding Automation by the Numbers
What it covers: Calculate heat input from voltage, current and travel speed, see how unsteady manual travel spreads weld size and heat, and price the over-welding that a steady machine travel speed removes.
Method explained here · BIZOMAT original book
Why welds distort
In Welding Distortion by the Numbers
What it covers: Follow a weld from heating to cooling: expansion held back by cold metal, yielding at a temperature rise of about a hundred degrees, and the shrinkage left behind that pulls parts out of shape.
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