Magnetic Field Indicator
The stray flux indicator shows how strongly the microstructure of a metal changes heterogeneously in the weld. A high stray flux indicator means strong hardness variations and increased crack risk.
Physical-Chemical Mechanism of Action
The stray flux indicator (SFI) measures the hardness variation in a weld zone. A high SFI means the structure has widely differing hardness levels, which leads to local stress areas.
Metallurgical Relevance & Welding Risks
A high stray flux indicator increases susceptibility to cold cracking and hot cracking. It can also cause loss of toughness and uneven stress relief, risking the whole component.
Workshop Practice & Procedures
To get a low stray flux indicator, watch the correct welding parameters like temperature and time. Use suitable filler metals and protect the weld from overheating. If the SFI is high, a post-weld heat treatment (e.g., tempering) may be needed to improve hardness uniformity.