The level of the heat input affects the mechanical properties and microstructures of the joint. From a user´s perspective the principal interest are how it affects:

  • The mechanical properties in the joint
  • The resistance to discontinuities and defects in the joint

The type of current used determines how this parameter is to be calculated.

During welding there is a loss of energy in the arc. The thermal efficiency k expresses the part of the heat input that is transferred to the joint during the welding performance. The value of this parameter depends on the welding process being used and the specific welding conditions. Approximate values for different welding processes are according to the table below.

Thermal efficiency k [dimensionless]
 MMA  0.8
 MAG, all types  0.8
 SAW  1.0
 TIG  0.6
Thermal efficiency
 MMA
k [dimensionless]
 0.8
Thermal efficiency
 MAG, all types
k [dimensionless]
 0.8
Thermal efficiency
 SAW
k [dimensionless]
 1.0
Thermal efficiency
 TIG
k [dimensionless]
 0.6

The thermal efficiency factors for different welding methods.