ASTM F3125 Grade A490 Heavy Hex Structural Bolts | Quenched & Tempered Alloy Steel

Product Introduction
Heavy hex structural bolts manufactured to ASTM F3125/F3125M, Grade A490 (inch-series). This grade consolidates the former ASTM A490 specification into the current umbrella standard for high-strength structural bolting. Quenched and tempered alloy steel, supplied in Type 1 (medium carbon alloy steel) and Type 3 (weathering steel). Diameters 1/2" to 1-1/2" inclusive. Minimum tensile strength 150 ksi, minimum yield strength 130 ksi.

Material & Mechanical Properties
Minimum tensile strength 150 ksi (1040 MPa), minimum yield strength 130 ksi (940 MPa), elongation 14% in 4D, reduction of area 40%. Proof load 120 ksi. Hardness: 33–38 HRC for bolts up to 1" diameter; longer or larger bolts per ASTM F3125. Type 1 is chromium-molybdenum alloy steel; Type 3 is weathering steel with a corrosion index of 6 or greater. Full-length quench and temper, minimum tempering temperature 800°F (427°C).

Geometry & Thread
Dimensional conformity to ASME B18.2.6 for heavy hex structural bolts. Inch-series threads include 5/8"-11, 3/4"-10, 7/8"-9, 1"-8, 1-1/8"-7, 1-1/4"-7, and 1-1/2"-6. Lengths per ASME B18.2.6 tables. Bolts supplied with non-standard thread length or head dimensions under F3125 Supplemental Requirements are marked "S" immediately after the grade designation.

Surface Finish
Grade A490 bolts must not be hot-dip galvanized; the galvanizing bath temperature exceeds the tempering temperature and risks hydrogen embrittlement. Permitted corrosion protective coatings: zinc/aluminum systems per ASTM F1136 Grade 3, ASTM F2833 Grade 1, or ASTM F3393. Type 3 weathering steel is typically supplied bare to develop a protective oxide patina. Black oxide may be applied for mild indoor corrosion resistance.