Molybdenum
Molybdenum increases high-temperature strength and improves the corrosion resistance of steels by targeted incorporation into the crystal lattice. It prevents pore formation and increases toughness.
Physical-Chemical Operating Mechanism
Molybdenum is used in the molten weld pool as a deoxidizing agent because it binds oxygen. This prevents porosity and improves the mechanical properties of the microstructure. Molybdenum increases the lattice spacing and stabilizes the grain structure, which leads to improved high-temperature strength.
Metallurgical Relevance & Welding Risks
A molybdenum content that is too high (above 1.5 %) can lead to a coarser microstructure and reduced toughness. This increases susceptibility to hot cracking and pitting corrosion. A content that is too low (below 0.2 %) has little effect on strength and corrosion resistance.
Workshop Practice & Instructions
Use molybdenum in steels with a content between 0.5 % and 1.0 % for optimal high-temperature strength and corrosion protection. During welding, make sure that the melt time is long enough (approx. 2-3 seconds) to ensure a homogeneous distribution of molybdenum. Do not cool the weld too quickly (t8/5 > 10 s) to avoid porosity and hot cracking.