Grain refinement level
Grain size refers to the average size of crystallites in a metal. Smaller grain sizes increase strength and crack resistance, but also improve formability.
Physical-Chemical Mechanism of Action
Grain size is a measure of the average size of crystallites in a metal. With a finer grain (smaller crystal sizes), the interfaces between crystals make up a larger proportion of the total volume of the material, leading to better mechanical properties.
Metallurgical Relevance & Risks in Welding
A finer grain size improves the strength and crack resistance of the weld. However, too fine a grain can impair the formability properties of the material, which can be problematic especially for complex components or under high stress.
Shop Practice & Operating Instructions
To improve grain size, the following measures can be taken:
• Increase melt time: A longer melt time promotes finer grain.
• Use cooling chokes: Controlled cooling with a choke can improve grain refinement.
• Add chemical additives: Additives such as silicon or aluminum can influence grain size and produce a finer structure.