Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASTM A638 Grade 660 — A286 Forgings
ASTM A638 grade 660 is the canonical industrial spec for A286 (UNS S66286) forgings — covers the alloy in forged condition for high-temperature pressure-bearing service. Two types: Type 1 (sol 1650 °F + aged, higher room-temperature tensile) and Type 2 (sol 1800 °F + aged, higher stress-rupture strength). The spec is referenced in ASME Section III Subsection NB for nuclear pressure-vessel components, and in petrochemical / refinery forgings for high-temperature service. Distinguished from ASTM A453 grade 660 by scope: A453 is bolting; A638 is forgings. See parent A286 AMS specifications hub, related A286 forged bar, A286 forgings, flanges.
Spec Scope & Coverage
ASTM A638 grade 660 covers A286 forgings for high-temperature pressure-bearing service. Material is VIM-VAR melted ingot, hot-forged in open-die or closed-die operation at 1095-1150 °C, then heat-treated per Type 1 or Type 2. Type 1: sol 1650 °F + aged 1325 °F × 16 h, hardness 29-32 HRC, higher room-temperature yield. Type 2: sol 1800 °F + aged 1325 °F × 16 h, hardness 24-30 HRC, higher stress-rupture strength at 1100-1300 °F. Used for nuclear pressure-vessel internals, petrochemical forgings, and gas-turbine casing forgings.
A286 Chemical Composition (UNS S66286)
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Iron (Fe) | Balance | Balance | ~53 % typical |
| Nickel (Ni) | 24.0 | 27.0 | Solid-solution stabilizer |
| Chromium (Cr) | 13.5 | 16.0 | Corrosion + oxidation resistance |
| Titanium (Ti) | 1.90 | 2.35 | Gamma-prime former (Ni3Ti) |
| Molybdenum (Mo) | 1.00 | 1.50 | Solid-solution strengthener |
| Vanadium (V) | 0.10 | 0.50 | Carbide stabilizer |
| Aluminium (Al) | 0 | 0.35 | Gamma-prime former (Ni3Al) |
| Boron (B) | 0.001 | 0.010 | Grain-boundary strengthening |
| Carbon (C) | 0 | 0.08 | Per ASTM A453 |
| Manganese (Mn) | 0 | 2.00 | Per ASTM A453 |
| Silicon (Si) | 0 | 1.00 | Per ASTM A453 |
| Phosphorus (P) | 0 | 0.025 | Trace impurity |
| Sulphur (S) | 0 | 0.015 | Trace impurity |
ASTM A638 Grade 660 — A286 Forgings — Spec Requirements
| Type | Heat treatment | Tensile MPa | Yield MPa | Hardness HRC | Best for |
|---|---|---|---|---|---|
| Type 1 | Sol 1650 °F + aged 1325 °F × 16 h | ≥ 895 | ≥ 655 | 29-32 | Higher RT tensile + yield. Lower stress-rupture vs Type 2. |
| Type 2 | Sol 1800 °F + aged 1325 °F × 16 h | ≥ 895 | ≥ 585 | 24-30 | Higher stress-rupture strength at 1100-1300 °F. |
When to Specify ASTM A638 Grade 660 — A286 Forgings
- Nuclear pressure-vessel forgings: ASTM A638 grade 660 Type 1 — accepted in ASME Section III Subsection NB. Used for control-rod-drive housings, primary-coolant-pump casings.
- Aerospace forgings (alternate): AMS 5731 / 5732 typically cited for aerospace; ASTM A638 acceptable as alternate.
- Petrochemical / refinery forgings: ASTM A638 grade 660 Type 2 for hot-section refinery forgings (1100-1300 °F service). Higher stress-rupture strength.
- Gas-turbine casing forgings: Type 1 or Type 2 — Type 1 for casing-split bolted joints; Type 2 for hot-section structural forgings.
- Forged flange manufacture: A286 flanges per ASME B16.5 are typically forged from ASTM A638 grade 660 Type 1 stock.
ASTM A638 Grade 660 — A286 Forgings — Frequently Asked Questions
What is ASTM A638 grade 660?
ASTM industrial spec for A286 (UNS S66286) forgings for high-temperature pressure-bearing service. Type 1: sol 1650 °F + aged (higher RT tensile). Type 2: sol 1800 °F + aged (higher stress-rupture strength). Nuclear and petrochemical pressure-vessel forgings.
Type 1 vs Type 2 — which to specify?
Type 1: higher room-temperature yield (655 MPa vs 585 MPa Type 2). Type 2: higher stress-rupture strength at 1100-1300 °F. Choose Type 1 for room-temperature high-load service; Type 2 for hot-section stress-rupture-critical.
Is ASTM A638 grade 660 the same as ASTM A453 grade 660?
Different scope: A638 is forgings; A453 is bolting. Chemistry identical (UNS S66286). Heat-treatment requirements similar but the spec applies to different forms — pressure-bearing forgings vs bolted-joint fasteners.
Is ASTM A638 grade 660 ASME III nuclear-acceptable?
Yes — Type 1 is accepted in ASME Section III Subsection NB for primary-pressure-bearing nuclear forgings. Used for control-rod-drive housings, primary-coolant-pump casings, pressuriser bolted-flange forgings.
What forging route is used for ASTM A638?
Open-die forging from VIM-VAR ingot at 1095-1150 °C — provides superior grain-flow continuity and isotropic mechanical properties vs hot-rolled. Closed-die for higher-volume standard sizes.
Can ASTM A638 grade 660 forgings be NACE MR0175 compliant?
Yes — when supplied with hardness ≤ HRC 35 per NACE MR0175 / ISO 15156-3. Specify on PO; each heat receives Vickers traverse before release.
What's the lead time on ASTM A638 forgings?
Standard sizes 75-150 mm: 12-16 weeks from heat release. Larger sizes 150-300 mm: 16-24 weeks. ASME III certified with EN 10204 3.2 third-party witness: 16-24 weeks. Custom sizes > 300 mm: 20-32 weeks.
Is ASTM A638 grade 660 ultrasonically inspected?
Yes — 100 % UT per ASTM A388 with Class 1 acceptance for nuclear and aerospace lots. Internal flaw detection critical for forging-grade applications. Class 2 acceptance for industrial.
Is ASTM A638 magnetic?
No. Magnetic permeability < 1.005 verified per ASTM A342. Compatible with non-magnetic pressure-vessel and aerospace forging applications.
Mechanical Properties per This Spec
| Type | Tensile (MPa) | Yield (MPa) | Hardness HRC |
|---|---|---|---|
| Type 1 (Sol 1650 °F + aged) | ≥ 895 | ≥ 655 | 29-32 |
| Type 2 (Sol 1800 °F + aged) | ≥ 895 | ≥ 585 | 24-30 |
A286 Products Manufactured per This Spec
TorqBolt manufactures the following A286 products to this specification:
Mating & Related Specifications
Common mating and related A286 specifications used alongside this spec:
- ASTM A453 grade 660 — Bolting spec for fasteners that mate with A638 forgings.
- AMS 5731 / 5732 — Aerospace bar / forging alternate.
- UNS S66286 — Underlying chemistry.
Drawing Call-Out Example
A286 forged bar, ASTM A638 grade 660 Type 1, sol-treated and aged, ⌀ 150 mm × 3000 mm length, +5/-0 mm OD tolerance, ASTM A388 ultrasonic Class 1, EN 10204 3.2.
Related A286 Specifications & Reference
Other A286 specifications: AMS / ASTM hub · AMS 5525 · AMS 5731 · AMS 5732 · AMS 5737 · AMS 5853 · AMS 5895 · ASTM A453 grade 660 · ASTM A638 grade 660 · ASTM B637 · DIN 1.4980 · UNS S66286.
Canonical A286 reference: A286 chemical composition · A286 mechanical properties · A286 heat treatment · alloy comparisons (vs Inconel 718 · vs Waspaloy).
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