Titanium grain refinement mechanism
The titanium grain refinement mechanism forms high-melting titanium nitrides that act as nuclei and prevent grain coarsening. This leads to a finer structure and increases toughness.
Physical-Chemical Operating Principle
The titanium grain refining mechanism refers to the formation of high-melting-point titanium nitrides in the melt or the heat-affected zone. These nitrides act as heterogeneous nuclei, influencing the primary solidification structure and preventing uncontrolled grain growth.
Metallurgical Relevance & Risks in Welding
The formation of titanium nitrides can lead to a finer structure, which increases toughness. However, excessive titanium content can cause fusion problems and low strength. Insufficient titanium content, on the other hand, may not effectively prevent coarse grain growth.
Shop Practice & Action Guidelines
To effectively utilize the titanium grain refining mechanism, the titanium content in the melt must be precisely controlled. A typical titanium content is about 0.1 to 0.3 %. Post-weld heat treatment must be carefully performed to promote the formation of titanium nitrides while preventing grain growth. Rapid cooling can result in insufficiently fine grains, whereas slow cooling may allow coarse grain growth.