A194 nuts · ASTM A194 / ASME SA-194

ASTM A194 Grade 8 (304 Stainless)

304 stainless heavy hex nut for A193 and A320 B8 studs — solution treated, 80 ksi proof load, corrosion resistant from cryogenic to 1500 °F.

UNS S30400Alloy AISI 304Type Austenitic 18-8 stainless steel nut, forged or machined from bar (A type solution treated after finishing)

Overview Chemistry Mechanical Standards Products Applications Guide

Material overview

What A194 8 is.

ASTM A194 Grade 8 is the 304 stainless steel nut that pairs with A193 and A320 Grade B8 studs. It is forged or machined from solution-annealed bar for maximum corrosion resistance and ductility, with an 80 ksi proof load and a hardness range of 126 to 300 HBW.

Strain-hardened nuts for B8 Class 2 studs are ordered under Supplementary Requirement S1; the 8A type is the solution-treated, softer variant. We machine Grade 8 nuts from certified 304 and 304L bar and can supply them silver plated or oversize tapped to prevent galling on stainless studs.

Get a Quote Download the A194 8 data sheet (PDF)

Proof load stress80 ksi heavy hex · 75 ksi hex

Hardness126–300 HBW

Heat treatmentNone required; 8A type is solution treated after finishing

PatternHeavy hex (ASME B18.2.2)

Companion studASTM A193 / A320 B8

Typical service−425 °F to 1500 °F

Nominal composition

Fe balance ≈ 69.9%Cr ≈ 19.00%Ni ≈ 9.50%Mn ≈ 1.00%Si ≈ 0.50%C, P, S trace

Midpoints of the specification ranges, for orientation only. Limits are in the table below.

Specifications & technical data

Chemical composition.

Download the data sheet (PDF) →

Chemical composition — ASTM A194 Grade 8 (AISI 304, UNS S30400)

Element	Symbol	Min %	Max %
Carbon	C	—	0.08
Manganese	Mn	—	2.00
Phosphorus	P	—	0.045
Sulfur	S	—	0.030
Silicon	Si	—	1.00
Chromium	Cr	18.0	20.0
Nickel	Ni	8.0	11.0

Values per ASTM A194/A194M-24, Tables 1, 2 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.

Physical properties (typical)

Density0.289 lb/in³ (8.00 g/cm³)

Modulus of elasticity28.0 × 10⁶ psi (193 GPa)

Thermal expansion (68–212 °F)9.6 µin/in·°F

MagneticNo in the annealed condition; slightly magnetic after cold work

Specifications & technical data

Mechanical properties.

Mechanical properties — ASTM A194 Grade 8

Nut style and size (in.)	Proof load stress (ksi)	Hardness, min	Hardness, max
Heavy hex, all sizes	80	126 HBW / 60 HRB	300 HBW / 32 HRC
Hex (finished pattern), all sizes	75	126 HBW / 60 HRB	300 HBW / 32 HRC
Grade 8A (solution treated in the finished condition), all sizes	80 heavy hex · 75 hex	126 HBW / 60 HRB	192 HBW / 90 HRB

Values per ASTM A194/A194M-24, Tables 1, 2 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Jam nuts: 46 % of the tabulated proof load. Strain-hardened Grade 8 nuts (S1) are proof tested to 125 / 115 / 105 / 100 ksi heavy hex by size and hardness limits do not apply.

Heat treatmentGrade 8 nuts are hot or cold forged, or machined from hot-forged, hot-rolled or cold-drawn bar, with no heat-treatment requirement (A194 clause 6.6). The 8A type is carbide solution treated after forging or machining (clause 6.7), which lowers hardness to the 126–192 HBW / 60–90 HRB window.

Standards

Specifications that apply.

ASTM A194 / ASME SA-194Nuts for bolts for high-pressure or high-temperature service

ASTM A193 / A320 Grade B8Companion studs

ASME B18.2.2Heavy hex nut dimensions

ASTM F594Stainless steel nuts (commercial)

Forms we supply

How A194 8 ships from Houston.

Heavy hex nuts (the default for pressure bolting)
Finished hex nuts
Jam nuts
Custom and special nuts to drawing

Companion grades

Companion studASTM A193 Grade B8 Class 1 (304 Stainless)

Chloride resistanceASTM A194 Grade 8M (316 Stainless)

9 products in this grade

A194 8 fasteners we make.

All products →

Nuts A194 8 Finished Hex Nuts A194 8 Heavy Hex Nuts A194 8 Machine Screw Hex Nuts A194 8 Hex Jam Nuts A194 8 Lock Nuts A194 8 12-Point Flange Nuts A194 8 Hexagon Cap Nuts A194 8 Tommy Bar Nuts A194 8 Casing Cap Nuts

Every item is manufactured to your drawing or standard in A194 8, imperial or metric, with an EN 10204 3.1 certificate.

Where A194 8 is used

Waterworks and water treatment flangesFood, beverage and pharmaceutical equipmentCryogenic and LNG pipingArchitectural and marine-atmosphere hardwareChemical process piping in mild media

The buyer’s guide

What is ASTM A194 Grade 8?

Grade 8 is A194's 304 stainless nut. It uses the same 18-8 austenitic chemistry as an A193 B8 stud and is machined from solution-annealed bar, so it is soft, ductile and non-magnetic. The 80 ksi proof load is matched to Class 1 studs; for strain-hardened Class 2 studs the specification provides strain-hardened nuts under Supplementary Requirement S1, marked with the grade symbol underlined. Because stainless nuts and studs of the same alloy gall easily, Grade 8 nuts are frequently silver plated, PTFE coated or supplied with an anti-seize compound.

The Grade 8 family

8: 304 stainless, solution treated.
8M: 316 stainless, with molybdenum for chloride resistance.
8C: 347 stainless, niobium stabilised for welded or high-temperature service.
8T: 321 stainless, titanium stabilised.
8A / 8MA: carbide solution treated after finishing, the softest variants (126–192 HBW), used where the finished nut must be free of cold-work effects.

Testing, certification and marking

Hardness tested per lot; proof-load tested on request or where the specification requires it
Grade symbol 8, or 8B on nuts machined from bar (ASTM A194 Table 7), and manufacturer's identification on one face of every nut
EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
Oversize tapping for coated studs and PTFE / zinc / hot-dip galvanized finishes available

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