Grain size number
The grain size number indicates the average size of crystallites in a metal. A higher number means finer grains and a higher yield strength.
Physical-Chemical Mechanism of Action
The grain size number (grain size index) is a measure of the average size of crystallites in a metal. It is determined by the number of crystals per unit area and indicates how fine or coarse the structure is.
Metallurgical Relevance & Welding Risks
A high grain size number (fine grains) leads to higher yield strength and improves mechanical properties such as strength and toughness. Conversely, a low grain size number (coarse grains) can result in lower yield strength and increased risk of cracking, especially under high loads.
Workshop Practice & Action Instructions
To determine the grain size number, a metallographic cross-section analysis is performed. The results help in selecting the appropriate welding process and optimizing process parameters to achieve the desired structure and corresponding mechanical properties.