Scope
The ASTM A490 specification covers quenched and tempered, alloy steel, heavy hex structural bolts from 1/2″ diameter through 1-1/2″ diameter with a minimum 150 ksi tensile. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. Refer to the Structural Bolts page of our site for thread lengths and other related dimensions. A490 bolts are similar in application and dimensions to A325 heavy hex structural bolts but are made from an alloy steel rather than a medium carbon steel, resulting in a higher strength fastener. The A490 specification is applicable to heavy hex structural bolts only. For bolts with different thread lengths than specified for structural bolts but with similar mechanical properties, see Specification A354 grade BD. ASTM A490 bolts shall not be coated by hot-dip galvanizing, mechanical deposition, or electroplating with zinc due to the potential risk of hydrogen embrittlement. ASTM has approved coating A490 bolts with Zinc/Aluminum Corrosion Protective Coatings per ASTM F1136 Grade 3, commercially called dacromet. Additional testing in the form of Magnetic Particle Inspection for Longitudinal Discontinuities and Transverse Cracks is a requirement of the A490 specification.
A490 Types
TYPE 1 | TYPE 2 | TYPE 3 | M |
Medium carbon and alloy steel. | Withdrawn in 2002. | Weathering steel. | Metric A490. |
A490 Connection Types
SC | N | X |
Slip critical connection. | Bearing type connection with threads included in the shear plane. | Bearing type connection with threads excluded from the shear plane. |
A490 Mechanical Properties
Size | Tensile, ksi | Yield, ksi | Elong. %, min | RA %, min |
1/2 – 1-1/2 | 150-173 | 130 | 14 | 40 |
A490 Chemical Properties
Type 1 Bolts | ||
Element | Sizes 1/2 to 1-3/8 | Size 1-1/2 |
Carbon, max | 0.30 – 0.48% | 0.35 – 0.53% |
Phosphorus, max | 0.040% | 0.040% |
Sulfur, max | 0.040% | 0.040% |
Alloying Elements | * | * |
* Steel, as defined by the American Iron and Steel Institute, shall be considered to be alloy when the maximum range given for the content of alloying elements exceeds one of more of the following limits: Manganese, 1.65%, silicon, 0.60%, copper, 0.60%, or in which a definite range or a minimum quantity of any of the following elements is specified or required within the limits of the recognized field of constructional alloy steels: aluminum, chromium up to 3.99%, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium or any other alloying elements added to obtain a desired alloying effect. | ||
Type 3 Bolts | ||
Element | Sizes 1/2 to 3/4 | Size above 3/4 |
Carbon | 0.20 – 0.53% | 0.30 – 0.53% |
Manganese, min | 0.40% | 0.40% |
Phosphorus, max | 0.035% | 0.035% |
Sulfur, max | 0.040% | 0.040 |
Copper | 0.20 – 0.60% | 0.20 – 0.60% |
Chromium, min | 0.45% | 0.45% |
Nickel, min | 0.20% | 0.20% |
or | ||
Molybdenum, min | 0.15% | 0.15% |
A490 Recommended Hardware
Nuts | Washers | ||
Type 1 | Type 3 | Type 1 | Type 3 |
A563DH | A563DH3 | F436-1 | F436-3 |
Note: Nuts conforming to A194 Grade 2H are a suitable substitute for use with A490 heavy hex structural bolts. Follow the link for an ASTM A563 Nut Compatibility Chart. | |||