What is Grain Size in Steel?🔍 When we talk about grain size in steel, we’re referring to the average size of the internal crystals (grains) that make up the metal's microstructure. This seemingly microscopic feature has a huge impact on the mechanical behavior of steel. 📏 How is Grain Size Measured? Grain size is quantified using the ASTM grain size number (typically from 1 to 10), with higher numbers indicating finer grains. The standard test method is ASTM E112. 🧩 Grain Size vs. Mechanical