ASTM A194 Grade 4 Heavy Hex Nuts
ASTM A194 Grade 4 heavy hex nuts — quenched and tempered carbon-molybdenum alloy steel (C 0.40–0.50%, Mo 0.20–0.30%), the low-temperature/pressure-duty alloy grade paired with A320 L7 studs on the collected tables. Hardness and proof-load rows are not tabulated in the collected sources and are not asserted.
Last updated: 2026-11
Specifications
Grade 4 is the carbon-molybdenum alloy member of ASTM A194: the collected grade table titles it "Quenched & tempered carbon-molybdenum hvy hex nut", and the chemistry row carries the molybdenum addition (0.20–0.30%) on a higher-carbon base (0.40–0.50%) with tightened phosphorus and sulfur ceilings (0.035% / 0.04%) against the plain 2-family row. Molybdenum in this range is what the grade uses to hold strength and structure in elevated-temperature and pressure-duty service, and in stud-bolt practice the collected pairing tables list grade 4 — alongside grade 7 — as the nut side for A320 L7 studs in cryogenic and low-temperature assemblies. The collected sources print no hardness or proof-load table rows for grade 4, so none are asserted here; the chemistry and the role on the pairing table are the confirmed content, and mechanical figures should be taken from the mill certificate against the size of record.
| Standard | ASTM A194 — Grade 4 (heavy hex pattern) |
|---|---|
| Material | Carbon-molybdenum alloy steel, quenched and tempered |
| Chemistry | C 0.40–0.50%, Mn 0.70–0.90%, P max 0.035%, S max 0.04%, Si 0.15–0.35%, Mo 0.20–0.30% |
| Service pairing | Listed with grade 7 as the nut side for A320 L7 studs — cryogenic / low-temperature assemblies (collected pairing table) |
| Hardness / proof load | Not tabulated in the collected sources for grade 4 — confirm per mill certificate against the size of record |
Materials
- Carbon-molybdenum alloy steel, quenched and tempered
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 4 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
Grade 4 or Grade 7 with my A320 L7 studs?
The collected pairing tables list both grades 4 and 7 as the nut side for A320 L7 low-temperature stud assemblies, so the choice follows the specification of record rather than a published ladder — the collected sources print no hardness or proof-load rows for either grade that would rank them. Practically: grade 4 is the carbon-molybdenum chemistry (Mo 0.20–0.30% on a 0.40–0.50% carbon base), grade 7 the AISI 4140-type chromium-molybdenum alloy; name the grade the engineer called out and require the mill certificate with the shipment.
What does the molybdenum addition do in a nut grade?
At the 0.20–0.30% level grade 4 carries, molybdenum is a strengtheners' alloy: dissolved in the quenched-and-tempered structure it helps the steel hold its strength at elevated temperature and resists temper softening, which is why pressure/temperature duty is the grade's listed role. It is a different job from the chromium-molybdenum combination in grade 7 (Cr 0.75–1.20% plus Mo 0.15–0.25%), which hardens more deeply for high-strength alloy assemblies. Chemistry rows for both grades are printed above; mechanical rows for neither are in the collected set.
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