ASTM A638 Bolts

ASTM A638 is the Standard Specification for Precipitation Hardening Iron Base Superalloy Bars, Forgings, and Forging Stock for High-Temperature Service. This specification covers alloys with mechanical properties developed by suitable solution treating and precipitation hardening treatments.Based on design, service conditions, mechanical properties, and elevated temperature characteristics ASTM A638 covers two grades of iron based alloys.

ASTM A638 Bars, Forgings, Forging Stock Manufacturers & Suppliers

Products manufactured under ASTM A638 specification are furnished in three different conditions viz Hot Finished, Solution Annealed, Solution Annealed and precipitation treated.In addition to the requirements of this specification, all requirement of ASTM A 484/A 484M (Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings) Shall Apply.

This Specification Covers three types viz Grade 660 Type 1, Grade 660 Type 2 and Grade 660.

Testing Requirements

Chemical Composition

ASTM A638 Chemical Composition

Grade 660 (UNS S66286)’1Grade 662 (UNS S66220)’1
Ladle Analysis Range, %Check Analysis Over or UnderLadle Analysis Range, %Check Analysis Over or Under
Carbon0.08 max0.01 over0.08 max0.01 over
Manganese2.00 max0.04 over1.50 max0.04
Silicon1.00 max0.05 over1.00 max0.05
Phosphorus0.040 max0.005 over0.040 max0.005 over
Sulfur0.030 max0.005 over0.030 max0.005 over
Copper — —0.50 max0.03 over
Aluminum0.35 max0.05 over0.35 max0.05 over
Vanadium0.10-0.500.03 — —
Boron0.0010-0.0100.0004 under 0.001 over0.0010-0.0100.0004 under 0.001 over

A New designation established in accordance with Practice E 527 and SAE J1086.

Mechanical Properties

ASTM A638 Mechanical Properties

Grade 660Grade 662 (bars)Grade 662 (forgings)-4
Heat treatment®solution + precipitation hardensolution + precipitation hardensolution + precipitation harden
Tensile strength, min:
psi130 000130 000125 000
Yield strength CO.2% offset), min: psi85 00085 00080 000
Elongation in 4D min, %151515
Reduction of area min, %181818
Brinell hardness248 min248 min248 min
AThe 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.

Stress-Rupture Requirements

ASTM A638 Stress-Rupture Requirements

Test TemperatureStressMinimum
GradeHeat Treatment-4°F[°C]psi[MPa]MinimumHours®Elongation,%
660solution + precipitation harden1200[650]65 000[450]233
662solution + precipitation harden1200[650]60 000[4151153

A Refer to Table 2 for details of heat treatment.

fiTest specimens meeting minimum requirements may be overloaded to produce rupture in a reasonable and practical time period.

Heat Treatment

ASTM A638 Heat Treatment

GradeSolution TreatmentPrecipitation Hardening Treatment”4
660 Type 11650 ± 25°F 900 ± 15°C], hold 2 h, oil or water quench1300 to 1400°F [705 to 760oC], hold 16 h, air cool or furnace cool
660 Type21800 ± 25°F 980 ± 15°C], hold 1 h, oil or water quench1300 to 1400°F [705 to 760°C], hold 16 h, air cool or furnace cool
6621750 to 1900°F 955 to 1040°C], hold 1 h, min, oil or water quench1250 to 1400°F [675 to 760°C1, hold 5 h, min, slow cooling in 5 h, min to 1200 ± 15°F [650 ± 10°C1, hold 20 h, min, air cool or furnace cool

A Times refer to the minimum time material is required to be at temperature.

Download PDF: ASTM A638 at

Related ASTM Specification

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