ASTM A182: Forged Stainless Steel Flanges and Fittings

Quick Answer

ASTM A182 is the primary specification for forged stainless steel components in pressure piping systems. While A312 covers pipe and A240 covers plate, A182 covers the connecting elements — flanges, elbows, tees, reducers, unions, caps, and valve bodies — that are forged (or rolled from solid bar) rather than fabricated from flat stock.

The "F" prefix in A182 grade designations (F304L, F316, F316L, etc.) identifies these as forging grades. The "F" does not imply a different alloy composition; the underlying chemistry is essentially the same as the equivalent plate or pipe grade, but the forging process and heat treatment requirements are specific to this product form.

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Scope and Product Forms

A182 applies to:

• Pipe flanges: slip-on, weld neck, blind, socket weld, lap joint, threaded
• Forged fittings: elbows, tees, reducers, couplings, unions, crosses
• Valves and valve bodies: gate, globe, check, ball, needle
• Other forged pressure-retaining parts: bonnets, bodies, end caps

The standard covers components produced by:

• Die forging
• Open-die (hand) forging
• Rolled or forged ring
• Machined from bar (under specific conditions)

Minimum forging reduction ratios are specified to ensure adequate working of the material and elimination of as-cast microstructure.

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Grade Coverage

A182 includes a comprehensive range of stainless steel forging grades:

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Chemical Composition Requirements

A182 chemical composition requirements for the forging grades are essentially identical to those of the equivalent A240 plate or A312 pipe grade. This is intentional — the material in the flange or fitting must be compatible with the adjacent pipe, allowing welding without concern for dissimilar alloy behavior.

Key composition limits for common grades (wt%, max unless range given):

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Mechanical Property Requirements

Forging processes and heat treatment affect mechanical properties independently of composition. A182 minimum mechanical requirements:

Note the reduction-of-area requirement — this is characteristic of forgings and is not typically required for plate. It confirms that the forging achieved adequate hot-working to refine the grain structure.

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Heat Treatment Requirements

All A182 forgings must be supplied in the heat treated condition appropriate for the alloy:

• Austenitic grades (300-series): solution anneal at 1040–1120°C (1900–2050°F) followed by rapid quench (water or air)
• Duplex grades: solution anneal at 1020–1100°C followed by rapid quench
• Ferritic grades: anneal at specified temperature range

For duplex grades, the annealing temperature and quench rate are critical to achieving the correct ferrite/austenite phase balance (~50/50). The MTC must state the heat treatment temperature and method.

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Testing Requirements

Tensile Testing

One tensile test per lot, where a lot = same heat, same heat treatment condition, same nominal size/thickness.

Hardness Testing

Brinell or Rockwell hardness, one test per lot. For austenitic grades, hardness limits are typically 92 HRB (200 HB) max.

Ferrite Content (Duplex Grades)

Duplex grade forgings require ferrite content measurement. Target range is typically 35–65% ferrite by point count or by magnetic response measurement per ASTM A799/A800.

Impact Testing

Charpy impact testing is not required for standard austenitic grades but may be required for duplex grades in low-temperature applications if specified on the purchase order.

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Identification and Marking

A182 requires each forging to be marked with:

• The ASTM designation (A182)
• The grade (e.g., F316L)
• The heat number (or a code traceable to the heat number)
• The manufacturer's identification mark

For flanges, the ASME/ANSI pressure class (e.g., Class 150, Class 300) and facing designation are also required per the applicable dimensional standard (ASME B16.5, ASME B16.47).

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MTC Review Checklist for A182 Flanges

When receiving and verifying A182 forging test certificates:

• Standard cited: ASTM A182 / ASME SA-182 (for pressure service)
• Grade designation with "F" prefix is correct
• Heat number present and traceable to physical marking
• Chemical composition within A182 grade limits
• Tensile strength, yield strength, elongation, and reduction of area meet minimums
• Hardness value within limits
• Heat treatment condition and temperature stated
• For duplex: ferrite content measurement reported
• Dimensional compliance to ASME B16.5 / B16.47 confirmed (on separate dimensional inspection report)

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Frequently Asked Questions