Delta Ferrite Former
Delta ferrite formers are additives that promote the formation of primary ferrite during solidification of high-alloy steels and prevent hot cracking.
Physical-Chemical Mechanism of Action
Delta ferrite formers are chemical elements that react in the molten pool and stabilize ferrite crystals. They prevent the rapid solidification of austenite and instead promote the growth of ferrite crystals.
Metallurgical Relevance & Risks in Welding
The use of delta ferrite formers reduces the risk of hot cracking, as they enable a finer and more stable microstructure. Without these additives, the austenite can coarsen into glass-hard martensite upon rapid cooling, leading to cracks.
Workshop Practice & Action Instructions
Use delta ferrite formers in the weld pools of high-alloy steels such as 40Cr or 17CrNiMo6. The amounts vary depending on material and welding process, but typically are between 0.2% and 0.5%. Make sure the additives are properly dosed to achieve a homogeneous structure. If the amount is too high, the material can coarsen and its mechanical properties be impaired.