Meaning
Standard test methods for the particle size distribution of metal powders utilize a series of progressive mesh screens to segregate fractions by dimension. The ASTM B214 sieve test provides a structured methodology for determining the dry classification of granular metallic materials via mechanical agitation. This analysis establishes the weight percentage of powder retained on each specified sieve screen, assisting in quality control for powder metallurgy.
The procedure applies specifically to metal powders that are dry and free-flowing.
Laboratory Procedure
A nested stack of brass or stainless steel screens arranges the finest mesh at the bottom and the coarsest mesh at the top. The ASTM B214 sieve test requires a standard sample size of approximately one hundred grams placed onto the topmost screen. Mechanical vibration then shakes the assembly for a set duration, allowing particles to fall through the openings until they reach a screen with apertures smaller than their physical dimensions.
Each fraction is weighed afterward to calculate the relative concentration of different size fractions. This process involves a mechanical tapping action that prevents blinding, where particles wedge into the mesh openings and block others from passing. Scales used for the subsequent gravimetric measurement must have an accuracy of at least one hundredth of a gram to secure dependable data.
Sizing Limit
Sieve apertures used in this procedure generally measure down to forty five micrometres. The ASTM B214 sieve test becomes unreliable for sub-sieve particles because electrostatic forces and surface moisture cause very fine powders to agglomerate. Agglomerated material fails to pass through the mesh, which distorts the mass distribution data.
Dry sieving therefore does not measure sub-micron battery materials like cathode active powders or synthetic graphite.
Industrial Application
Material specifications for metallic raw materials rely on sieve results to verify feedstock consistency before consolidations like sintering or thermal spraying. The ASTM B214 sieve test ensures that incoming metal powders conform to nominal size limits, avoiding flowability problems during transport and deposition. Inconsistent particle distribution reduces the density of green parts, leading to structural voids.
Sieve compliance is thus a standard contractual requirement in powder distribution agreements.
