ASTM Grain-size Number is a measure of the average size of grains in a metal or alloy. It is determined by comparing the grain size of a sample to a standard chart and assigning a number based on the average grain size.
Grain size has a significant impact on the mechanical properties of metals and alloys. A smaller grain size typically results in higher strength and hardness, while a larger grain size can lead to lower ductility and toughness. Therefore, ASTM Grain-size Number is an important factor to consider when designing and selecting materials for various applications.
ASTM Grain-size Number is measured using a microscope with a calibrated eyepiece reticle. The sample is polished and etched to reveal the grain boundaries, and then the number of grains per square inch is counted and compared to the standard chart.
The ASTM Grain-size Number scale ranges from 1 (coarse grains) to 8 (fine grains). Each number represents a specific range of grains per square inch, with higher numbers indicating smaller grain sizes.
The ASTM Grain-size Number of a material can be affected by various factors such as the composition, heat treatment, and processing of the material. For example, a higher cooling rate during solidification can result in a finer grain size, while a higher temperature may lead to larger grain sizes.