Heat Affected Zone Broadening
Heat-affected zone widening is the undesirable expansion of the thermally stressed area around the weld due to excessive and uncontrolled heat input. This leads to an increased risk of cracking and distortion.
Physical-Chemical Mechanism of Action
Heat-affected zone widening occurs when the weld is overheated. This leads to an extended microstructure area with elevated temperatures, resulting in uneven stress states in the material.
Metallurgical Relevance & Welding Risks
A wide heat-affected zone can lead to the following problems:
• Cracking: The increased stress in the widened zone can cause cracks and distortion in the material.
• Distortion: Uneven heating and cooling can lead to mechanical distortion of the part.
• Weld Degradation: Uncontrolled heat input can impair weld quality by altering the microstructure and increasing hardness.
Workshop Practice & Action Instructions
To minimize heat-affected zone widening, the following measures should be taken:
• Controlled Heat Input: Use controlled welding radiation or a stable welding process.
• Low Stress States: Keep the stress in the workpiece as low as possible during welding to avoid the occurrence of cracks.
• Short Heat Input Time: Use a short heat input time and low heat input (EEV) to control temperature build-up in the material.