Alloy steel SHCS spec · ASME B18.3 dimensional · For corrosion-resistant equivalent in super duplex / Zeron 100, see ASTM A1082 + this page
ASTM A574 is the standard specification for alloy steel socket head cap screws (SHCS) in inch and metric series. It defines mechanical properties, hardness limits, dimensional tolerances, and certificate requirements for high-tensile precision fasteners used in machined-hole installations: bolted joints with limited bearing surface, recessed installations, hydraulic and pneumatic equipment, machine-tool components, jigs and fixtures.
A574 is a carbon / low-alloy steel specification, it does not cover stainless or super duplex SHCS. For corrosion-resistant socket-head cap screws, the matching specification stack is ASTM A1082 (super duplex stainless steel fasteners) + ASME B18.3 (dimensional) + the buyer's service spec (NACE MR0175, NORSOK M-650, API 6A). TorqBolt manufactures super duplex SHCS in UNS S32760 (Zeron 100) per A1082 with mechanical properties that match the A574 inch tensile classes, so a designer specifying A574 SHCS who later upgrades to corrosion-resistant service can swap to a Zeron 100 SHCS with the same dimensional and tensile envelope.
| Attribute | ASTM A574 (alloy steel) | ASTM A1082 (super duplex SS) |
|---|---|---|
| Material | AISI 4137M, 4140 mod, similar low-alloy steels | UNS S32760 / S32750 / S31803 |
| Tensile, inch series | 180 ksi min (1240 MPa) for sizes ≤ 1/2 in | Class S (cold-worked): 750 MPa min, full-scale matching available |
| Yield, inch series | 153 ksi min (1055 MPa) | Class S: 550 MPa min |
| Hardness | 39-45 HRC | ≤ 28 HRC for sour-service per NACE MR0175 |
| Corrosion resistance | None, coating-dependent (zinc plate, dacromet) | Excellent, PREN ≥ 40, CPT ≥ 50°C inherent |
| Sour-service rating | Not qualified | NACE MR0175 / ISO 15156-3 qualified at ≤ 28 HRC |
| Dimensional standard | ASME B18.3 (inch) / B18.3.1M (metric) | ASME B18.3 (inch) / B18.3.1M (metric), same |
| Typical use | Machine tools, hydraulics, jigs, internal-clearance bolting | Subsea instrumentation, FPSO topside enclosures, sour-service flange bolting where SHCS pattern is required |
| Series | Size range | Tensile class | Standard |
|---|---|---|---|
| Inch SHCS | #0 to 1-1/2 in | Class S (FG cold-worked) or Class A (SA solution-annealed) | ASME B18.3 + ASTM A1082 |
| Metric SHCS | M2 to M36 | Class S or Class A | ASME B18.3.1M + ISO 4762 + ASTM A1082 |
| Low-head SHCS | #5 to 3/4 in (inch) / M3 to M20 (metric) | Same | ASME B18.3 / ISO 7984 |
| Button-head + flat-head SHCS | #0 to 5/8 in / M3 to M16 | Same | ASME B18.3.4M / ISO 7380 / ISO 10642 |
Send the spec (size + length + drive type + tensile class + service spec + quantity + destination port) to info@torqbolt.com or +91-22-66157017 / WhatsApp. Cross-reference: Zeron 100 SHCS catalog, FG fastener-grade cornerstone, Zeron 100 bolts hub.
