ASTM A194 Grade 8M Heavy Hex Nuts
ASTM A194 Grade 8M heavy hex nuts — austenitic stainless steel with a deliberate molybdenum addition (Cr 16.00–18.00%, Ni 10.00–14.00%, Mo 2.00–3.00%), carbide solution treated, 550 MPa minimum proof-load stress at 126–321 HBW in Class 1. The A193 B8M stud partner for chloride, marine and chemical service.
Last updated: 2026-11
Specifications
Grade 8M is the molybdenum-bearing stainless member of ASTM A194: the "M" marks the 2–3% molybdenum addition to the chromium-nickel austenitic chemistry, which is what separates it from plain Grade 8 in pitting- and crevice-corrosion resistance. The collected manufacturer datasheet places the chemistry at chromium 16.00–18.00%, nickel 10.00–14.00% and molybdenum 2.00–3.00% with carbon at 0.08% maximum, and the mechanical set at 550 MPa minimum proof-load stress (Class 1) over a 126–321 HBW hardness band. Every nut is carbide solution treated — held at a minimum of 1900°F (1040°C) and rapidly water quenched — to keep corrosive attack out of the weld-adjacent microstructure, and the heavy hex pattern is dimensioned to ASME B18.2.2. On the stud-bolt pairing chart it is the counterpart of A193 B8M: chemical processing, marine and chloride-rich service is exactly where this grade belongs.
| Standard | ASTM A194 — Grade 8M (Class 1) |
|---|---|
| Material | Austenitic stainless steel (AISI Type 316 chemistry), molybdenum-bearing |
| Chemistry | C max 0.08%, Mn max 2.00%, P max 0.045%, S max 0.030%, Si max 1.00%, Cr 16.00–18.00%, Ni 10.00–14.00%, Mo 2.00–3.00% |
| Proof-load stress | 550 MPa minimum (Class 1) |
| Hardness | 126–321 HBW |
| Heat treatment | Carbide solution treatment (solution annealing) at 1900°F (1040°C) minimum, followed by rapid water quench |
| Nut pattern | Heavy hex, dimensioned per ASME B18.2.2 |
| Grade pairing | Pairs with A193 B8M studs — chloride, marine and chemical-processing environments; the molybdenum grade over plain A194 Grade 8 where pitting resistance governs |
Materials
- Austenitic stainless steel (AISI 316 / SS316)
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASTM A194 Grade 8M Heavy Hex Nuts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
What does the "M" in ASTM A194 Grade 8M mean?
It marks the molybdenum addition — 2.00–3.00% in the collected chemistry row — on top of the 16–18% chromium and 10–14% nickel of the austenitic base. Molybdenum is what gives Grade 8M its superior resistance to pitting and crevice corrosion compared with plain Grade 8, which is why chemical processing, marine and chloride-rich service call for the M grade rather than the base grade.
Which stud grade pairs with an A194 Grade 8M nut?
The stud-bolt pairing table puts A193 B8M Class 1 studs with A194 8M nuts for corrosion resistance in chloride and marine environments. Where the assembly is the higher-strength cold-worked B8M Class 2C, the pairing convention is the same family — confirm the exact callout on the specification of record.
What is the MOQ and lead time for this nut type?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common diameters in this nut type are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
What should an RFQ for this nut type state?
State the standard designation (for example DIN 985 or DIN 6923), nominal thread size and pitch (metric coarse unless fine pitch is required), material and strength pairing with the mating bolt, finish (plain, zinc, or hot-dip galvanized where compatible), required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support