ASTM A490M Heavy Hex Bolts in Quenched and Tempered Alloy Steel with 1040 MPa

ASTM A490M Heavy Hex Structural Bolt – Metric, Quenched & Tempered Alloy Steel, 1040 MPa Minimum Tensile Strength

This product is a metric heavy hex structural bolt manufactured to ASTM A490M (Classes 10.9 and 10.9.3), the metric counterpart to the inch-series ASTM A490 specification. In 2016, A490M was consolidated into ASTM F3125/F3125M as Grade A490M under the unified standard, with head markings intentionally kept unchanged to ensure a smooth transition. The bolt is manufactured from quenched and tempered alloy steel and is available in two types: Type 1 (medium carbon alloy steel) and Type 3 (weathering steel). Nominal bolt diameters range from M12 to M36 inclusive. The bolt delivers a tensile strength range of 1040 to 1210 MPa with a minimum yield strength of 940 MPa. Intended for use in structural steel connections per the Specification for Structural Joints Using High-Strength Bolts, as approved by the Research Council on Structural Connections (RCSC)—widely used in bridges, heavy steel buildings, and critical infrastructure projects requiring maximum joint strength.

What are the specific mechanical property and chemical requirements for ASTM A490M bolts?

For all diameters M12 through M36, the minimum tensile strength is 1040 MPa with a maximum of 1210 MPa; minimum yield strength is 940 MPa; minimum elongation is 14% in 4D; and minimum reduction of area is 40%. The bolts are heat treated by quenching in oil from the austenitizing temperature and tempering at a minimum of 427°C. Type 1 bolts are manufactured from medium carbon alloy steel with heat analysis carbon content of 0.30–0.48% for sizes through M30 and 0.35–0.53% for M36. Type 3 is weathering steel conforming to chemical Composition A, B, or a corrosion index of 6 or greater. Hardness requirements: Rockwell C 33–39 for standard lengths; only maximum hardness 39 HRC applies for longer bolts.

What are the dimensional specifications and coating limitations for Grade A490M heavy hex bolts?

The bolt conforms dimensionally to ASME B18.2.6M for metric heavy hex structural bolts. Diameter range: M12, M16, M20, M22, M24, M27, M30, M36 with ISO metric coarse pitch threads per ISO 261. Key dimensions include width across flats (s) for M16 = 27 mm, M20 = 34 mm, M24 = 41 mm, M30 = 50 mm. Critical coating limitation: ASTM A490M bolts shall not be hot-dip galvanized, as the galvanizing process introduces hydrogen embrittlement risk and the molten zinc bath temperature exceeds the bolt's tempering temperature. Permitted coatings include zinc/aluminum coatings applied per ASTM F1136/F2833/F3393. Type 3 weathering steel bolts are typically supplied bare (uncoated) to develop a protective oxide patina.

What are the assembly components, marking, traceability, and certification requirements for Grade A490M bolts?

The complete assembly comprises the Grade A490M heavy hex bolt, a matching ASTM A194M Grade 2H or A563M Grade DH heavy hex nut, and a hardened washer to ASTM F436M. The bolt head must be permanently marked with the grade symbol “A490M" , the manufacturer’s identification mark, and the type if Type 3 (the “A490M" marking is underlined for Type 3). Full traceability is maintained through lot control, with each batch linked to Material Test Reports (MTRs). The assembly can be supplied with EN 10204 Type 3.1 inspection certificates, providing heat traceability and mechanical-test records. Rotational-capacity tests are required on all bolt, nut, and washer assemblies prior to shipping.