SS 347 Heavy Hex NutASTM A194 · ASME B18.2.2 · Manufacturer, trader & exporter, India
AISI 347 · UNS S34700
An SS 347 heavy hex nut is a thicker and wider hexagon nut for pressure bolting. ASTM A194 8C where specified; confirm grade and class in the purchase specification. Heavy hex nuts go with stud bolts on flanges. They spread load better and resist thread stripping at high preload. Made to ASME B18.2.2.
- ASTM A194
- ASME B18.2.2
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 347 Heavy Hex Nut?
- What it is
- A thicker and wider hexagon nut for pressure bolting
- Finished spec
- ASTM A194 8C where specified
- Material / feedstock
- Within the finished specification (A194 8C)
- Dimensions
- ASME B18.2.2
- Grade
- SS 347 · UNS S34700
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Heavy Hex Nut Specification
| Product | SS 347 Heavy Hex Nut |
|---|---|
| Finished fastener specification | ASTM A194 8C where specified |
| Material / feedstock specification | Within the finished specification (A194 8C) |
| Dimensional standard | ASME B18.2.2 |
| Manufacturing route | To the finished specification and purchase specification |
| Project / purchase specification | Yes — finished fastener requirements are to the purchase specification or project drawing |
| Sizes | M10 – M64 · ½" – 4" (others on request) |
| Threads | UNC · UN-8 · metric coarse |
| Testing | PMI (as specified in the PO) · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 or 3.2 on request / as specified in the PO |
When to Choose a Heavy Hex Nut
Heavy hex nuts go with stud bolts on flanges. They spread load better and resist thread stripping at high preload. Made to ASME B18.2.2.
- Thicker than standard hex nuts
- ASME B18.2.2
- Paired with A193 studs
More on choosing: Heavy hex nut guide.
SS 347 Heavy Hex Nut: Why 347 for heavy hex nuts
Heavy hex nuts go with stud bolts on flanges. They spread load better and resist thread stripping at high preload. Made to ASME B18.2.2. In SS 347, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless fasteners resist atmospheric and process corrosion. SS 347 is picked for welded high-temperature piping in refineries and power plants. |
|---|---|
| Typical service | Refinery hydroprocessing — Reactor effluent piping and exchangers. |
| Bolting | ASTM A193 B8C studs with A194 8C nuts |
SS 347 Heavy Hex Nut Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Niobium | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S34700.
SS 347 Heavy Hex Nut Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S34700 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 347 grade page.
Other SS 347 fasteners
SS 347 Heavy Hex Nut — questions buyers ask
Why use heavy hex nuts on flanges?
They provide more thread engagement and bearing area for the high preload flange joints need.
What nut is used with SS 347 heavy hex nuts?
ASTM A194 8C heavy hex nuts.
Which standard covers SS 347 heavy hex nuts?
Finished fastener specification: ASTM A194 8C where specified. Material / feedstock: Within the finished specification (A194 8C). Dimensions: ASME B18.2.2. State the finished specification, material and dimensions on your purchase order or project drawing.
What decides the price of a SS 347 heavy hex nut?
The alloy price, the size and dimensions, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 or 3.2 certificates available on request / as specified in the PO; dimensional reports as required. PMI can be arranged depending on product and requirements, as specified in the PO.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026