- if at low arc energy the hardness is too high, then the notch toughness of the heat affected
zone tends to be poor. Conversely, if the arc energy is too high, the grain size in the
microstructure becomes too large and this also reduces the toughness. The best level of
notch toughness will be obtained at intermediate levels of arc energy, .
- the optimum level of arc energy for maximum notch toughness depends on the chemical
composition; as the hardening capacity increases, the optimum arc energy level will
increase. The preheat and interpass temperatures act in the same direction as the arc
energy but the effect is usually smaller.