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ASTM A638 Specification

Forgings, Fasteners, Boltings, Stud Bolts, Screws, Nuts

Scope

ASTM A638 specification covers hot-finished or cold-finished precipitation hardening iron base superalloy bars, forgings, and forging stock for high-temperature service. The mechanical properties of these alloys are developed by suitable solution treating and precipitation hardening treatments.
Two grades of iron base alloy are covered. Selection will depend upon design, service conditions, mechanical properties, and elevated temperature characteristics.

Related Specifications of ASTM A638

ASTM A638 Chemical Composition

Element C Mn Si P S Cr Ni Mo Ti Cu Al V B
Grade 660
(UNS S 66286)A		 Ladle Analysis Range, % 0.08 max 2.00 max 1.00 max 0.040 max 0.030 max 13.50-16.00 24.00-27.00 1.00-1.50 1.90-2.35 ... 0.35 max 0.10-0.50 0.0010-0.010
Check Analysis Over or Under 0.01 over 0.04 over 0.05 over 0.005 over 0.005 over 0.20 0.20 0.05 0.05 ... 0.05 over 0.03 0.0004 under 0.001 over
Grade 662
(UNS S 66220)A		 Ladle Analysis Range, % 0.08 max 1.50 max 1.00 max 0.040 max 0.030 max 12.00-15.00 24.00-28.00 2.50-3.50 1.55-2.00 0.50 max 0.35 max ... 0.0010-0.010
Check Analysis Over or Under 0.01 over 0.04 0.05 0.005 over 0.005 over 0.15 0.20 0.10 0.05 0.03 over 0.05 over ... 0.0004 under 0.001 over
  • A New designation established in accordance with Practice E527 and SAE J 1086.

ASTM A638 Mechanical Requirements

Grade Heat treatmentB Tensile strength, psi[MPa] min: Yield strength (0.2 % offset), psi[MPa] min: Elongation in 4D min, % Reduction of area min, % Brinell hardness
ASTM A638 Grade 660 solution + precipitation harden 130 000[895] 85 000[585] 15 18 248 min
ASTM A638 Grade 662 (bars) solution + precipitation harden 130 000[895] 85 000[585] 15 18 248 min
ASTM A638 Grade 662 (forgings)A solution + precipitation harden 125 000[860] 80 000[550] 15 18 248 min

Stress-Rupture Requirements

Grade Heat TreatmentA Test Temperature Applied Stress During
Stress Rupture Testing		 Minimum HoursB Minimum Elongation, %
°F [°C] psi [MPa]
ASTM A638 Grade 660 solution + precipitation harden 1200 [650] 65 000 [450] 23 3
ASTM A638 Grade 662 solution + precipitation harden 1200 [650] 60 000 [415] 15 3
  • A The elongation of tensile specimens machined tangentially from near the center of large disk forgings over 50 in.2 [320 cm2] in cross section may be as low as 10 %.The reduction of area may be as low as 12 %.
    B Refer to Table 3 of heat treatment.

ASTM A638 Heat Treatment

Grade Solution Treatment Precipitation Hardening TreatmentA
ASTM A638 Grade 660 Type 1 1650 ± 25°F [900 ± 15°C], hold 2 hr, oil or water quench 1300 to 1400°F [705 to 760°C], hold 16 h, air cool or furnace cool
ASTM A638 Grade 660 Type 2 1800 ± 25°F [980 ± 15°C], hold 1 h, oil or water quench 1300 to 1400°F [705 to 760°C], hold 16 h, air cool or furnace cool
ASTM A638 Grade 662 1750 to 1900°F [955 to 1040°C] hold 1 h, min, oil or water quench 1250 to 1400°F [675 to 760°C], hold 5 h, min, slow cooling in 5 h,
min to 1200 ± 15°F [650 ± 10°C], hold 20 h, min, air cool or furnace cool

ASTM A638 Certifications

  • EN 10204 3.1
  • EN 10204 3.2
  • PED 2014/68/EC
  • MERKBLATT AD 2000 W2/W7/W10
  • API 20 E BSL 1/ BSL 2
  • NACE MR 0175
  • NACE MR 0103