ASTM E112 A480 A240 Requirements for Grain Size

Standard	Title / Purpose
ASTM E112	Standard Test Methods for Determining Average Grain Size. This is the fundamental method for measuring grain size using comparison charts, intercept procedures, or planimetric methods .
ASTM A480	General Requirements for Flat-Rolled Stainless Steel Plate, Sheet, and Strip. It covers dimensional tolerances and general conditions but often references grain size requirements for specific grades .
ASTM A240	Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels. Defines material properties and heat treatment conditions .
Product Specs	Standards like A167, A666, etc., contain the specific grain size requirements for the respective products .

Typical Industry Requirements (Based on 316/316L Examples)

Since ASTM standards often leave specific limits to the purchaser or product specification, here are practical examples derived from typical industrial practice:

For Forgings (e.g., 316L Medical Implants or Industrial Valves) :
- The typical specified grain size range is ASTM G4 to G6 (or finer).
- G3 to G2 (coarse grains) are considered undesirable.
- Achieving G5 or finer is considered a “not difficult” target if thermal cycles are controlled properly .
- Critical Strain Warning: Light reductions (less than 10-15%) followed by annealing can cause “blown grains” (abnormal grain growth), resulting in a duplex or mixed grain structure .
For Extruded Pipes (316H) :
- Research and production data indicate that achieving a grain size finer than Grade 4 requires specific parameters (e.g., 80% extrusion deformation) .
- Solution treatment temperature and time must be controlled (e.g., 1050°C / 40 min) to prevent rapid grain growth .
General Quality Rejection Criteria :
- Mixed Grain Structure (Duplex) : The presence of both very fine and very coarse (millimeter-grade) elongated grains is generally unacceptable for high-performance applications as it deteriorates comprehensive performance .
- Too Coarse: Large grains (G1, G2, G0) are typically rejected for structural applications requiring high strength and toughness.

ASTM E112 A480 A240 Requirements for Grain Size

Typical Industry Requirements (Based on 316/316L Examples)

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