Grade 2H Through-Hardened Nut Blanks
Forged carbon steel nut blanks through-hardened to Grade 2H requirements, the standard companion nut to A193 Grade B7 studs in refinery, power plant, and general high-temperature/high-pressure flange bolting.
ASTM A194
Carbon & Alloy Steel Nuts — Matched to A193 Studs
Grade 2H (Most Common)
Through-Hardened, Paired with A193 B7
Grade 7/7M/8/8M
Grade-Matched to Corresponding A193 Stud Grades
EN 10204 3.1/3.2
Full Proof Load & Hardness Certification
Why A194 Cannot Be Specified Correctly Without Reference to Its Stud Standard
ASTM A194 is, by design, a companion standard rather than a standalone one: it was developed alongside ASTM A193 specifically to cover the nut half of high-temperature and high-pressure bolted joints, and its grades are structured so each corresponds to a specific stud grade or strength class rather than existing as an independent product line. Grade 2H, a through-hardened carbon steel nut, is by far the most common grade because it's engineered to develop proof load capacity matched to A193 Grade B7 studs — the dominant stud grade in refinery and power plant flange bolting — ensuring the nut doesn't become the joint's weak point under the tensile preload B7 is capable of carrying. This matched-pair engineering matters because a bolted joint's performance is governed by the weaker of its two threaded components: an undersized or under-strength nut paired with a high-strength stud will strip, gall, or yield before the stud reaches its design preload, defeating the purpose of specifying high-strength bolting in the first place. A194 correspondingly offers grades like 7 and 7M (matched to A193 B7 and B7M respectively, with 7M carrying the same NACE-compliant hardness restriction its stud counterpart does) alongside austenitic stainless grades 8 and 8M matched to B8 and B8M studs — meaning correct A194 grade selection is inseparable from the A193 stud grade already specified for the joint, not an independent decision made from the nut catalog alone.
ASTM A194 Forged Nut Products
Grade 7 and 7M Alloy Steel Nut Blanks
Forged alloy steel nut blanks for Grade 7 and NACE-compliant Grade 7M nuts, engineered to match the strength and, for 7M, the hardness-restricted sour-service compliance of A193 Grade B7 and B7M studs respectively.
Grade 8/8M Austenitic Stainless Nut Blanks
Forged 304- and 316-base stainless nut blanks for Grade 8 and 8M nuts, the correct companion to A193 B8 and B8M studs where corrosion resistance or non-magnetic joint properties are the governing requirement.
Large-Diameter and Heavy Hex Nut Forgings
Forged heavy hex nut blanks in diameters beyond typical stocked sizes, machined and tapped to match large-bore flange and pressure vessel stud requirements.
Heat Treatment, Testing and Certification for A194 Nuts
Through-Hardening to Match Companion Stud Grade
Heat treatment developing the proof load and hardness specified for the ordered grade, engineered specifically so the nut's strength capacity is matched to — not exceeded or undercut by — its companion A193 stud grade under the joint's design preload.
Proof Load Testing
Proof load testing verifying the nut assembly withstands the specified axial load without thread stripping or permanent deformation, the primary mechanical qualification for nut grades under A194.
Hardness Testing for 7M/8M Sour Service Compliance
Hardness verification confirming Grade 7M and 8M nuts meet the maximum hardness limits required by NACE MR0175/ISO 15156 for sour service joints, matched to the same restriction applied to their companion 7M/8M studs.
EN 10204 3.1/3.2 Certification with Full Traceability
Material test certificates per EN 10204 3.1 as standard, with 3.2 third-party witnessed certification available for refinery, power generation, and other regulated bolted-joint documentation requirements.
Why A194 Cannot Be Specified Correctly Without Reference to Its Stud Standard
ASTM A194 occupies a specification role that's easy to underappreciate if it's read in isolation: it was developed as the direct nut counterpart to ASTM A193, and its grade structure only makes full sense when read alongside its companion standard. Where A193 covers stud and bolt material for high-temperature and high-pressure service, A194 covers the nuts engineered to complete those same joints — and its grade numbering deliberately mirrors A193's, with Grade 2H and Grade 7 matched to B7, Grade 7M matched to B7M, and Grades 8/8M matched to B8/B8M. Specifying an A194 grade correctly is therefore inseparable from knowing which A193 stud grade the nut will be paired with on the joint.
Grade 2H's dominance as the most commonly specified A194 nut grade traces directly back to Grade B7's dominance as the most commonly specified A193 stud grade — the two exist together on the overwhelming majority of refinery, petrochemical, and power generation flange joints, and 2H's through-hardened proof load capacity is engineered specifically to match B7's tensile strength. This matching matters mechanically, not just administratively: a bolted joint's real load-carrying performance is set by whichever of its two threaded components is weaker, so a nut with insufficient proof load capacity paired against a high-strength stud will strip or gall under load before the stud ever reaches its design preload, effectively wasting the extra strength margin the stud grade was specified to provide.
This same matched-pair logic extends through the rest of the A194 grade table, and it becomes especially important in sour service applications. Grade 7M carries the identical NACE MR0175/ISO 15156 maximum hardness restriction that its stud counterpart, A193 B7M, is subject to — both restrictions exist to limit susceptibility to hydrogen-induced sulfide stress cracking in wet H2S environments, and specifying one half of the pair without the other leaves a joint that doesn't actually satisfy the sour service requirement it was meant to meet. The same discipline applies to the austenitic stainless pairing of Grade 8/8M nuts with B8/B8M studs, where corrosion resistance and non-magnetic behavior, not raw strength, are the governing selection criteria on both halves of the joint.
For refinery, petrochemical, and power generation contractors sourcing A194 nut material, Shivam Forge manufactures forged Grade 2H, 7, 7M, 8, and 8M nut blanks engineered as matched companions to the corresponding A193 stud grade on your bolted joint. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your flange schedule and the A193 stud grade already specified for a manufacturability review and quotation.
Frequently Asked Questions
Which A194 nut grade should be paired with A193 Grade B7 studs?
Grade 2H is the standard companion nut for A193 Grade B7 studs in most flange and pressure vessel applications — it's a through-hardened carbon steel nut engineered to develop proof load capacity matched to B7's tensile strength, so the nut doesn't become the joint's weak point. Grade 7 is also matched to B7 strength but uses an alloy steel base, and is sometimes specified where 2H's hardenability in larger sizes is a concern.
Is there an A194 grade for sour service, matched to A193 B7M?
Yes — Grade 7M is the direct companion to A193 Grade B7M, carrying the same NACE MR0175/ISO 15156 maximum hardness restriction applied to protect against hydrogen-induced sulfide stress cracking in wet H2S environments. Specifying B7M studs without also specifying 7M (or equivalent NACE-compliant) nuts leaves a mismatched joint that doesn't actually meet sour service requirements end to end.
What happens if a mismatched nut grade is paired with a high-strength stud?
A bolted joint's real capacity is limited by its weaker component. If a lower-strength nut is paired with a high-strength A193 stud, the nut can strip, gall, or yield before the stud develops its design preload — meaning the joint never actually achieves the clamping force the stud specification was chosen to deliver. This is precisely why A194 grades are structured as matched companions to specific A193 stud grades rather than as an independently chosen commodity item.
What's the difference between A194 Grade 8 and Grade 8M?
Both are austenitic stainless nut grades matched to their respective A193 stud counterparts — Grade 8 to B8 (304-base chemistry) and Grade 8M to B8M (316-base chemistry, with added molybdenum for improved corrosion resistance, particularly against chlorides). The grade selection should mirror whichever stud chemistry the joint's corrosion environment already requires.
Do you supply A194 nuts already matched and tested alongside A193 studs?
Yes. We supply forged and heat-treated A194 nut blanks machined and tapped to your specified thread series and quantity, matched to the corresponding A193 stud grade for your flange or pressure vessel joint, with proof load, hardness, and chemistry certification covering both halves of the bolted assembly.
Why Choose Shivam Forge
Trusted forging manufacturer — Rajkot, Gujarat
Shivam Forge delivers precision hot-forged components from our integrated Shapar, Rajkot facility — covering forging, CNC machining, heat treatment, and quality inspection under one roof.
- Hot forging from quality alloy steel billets (42CrMo4, C45, EN8, SS316L)
- In-house CNC/VMC machining to drawing — ±0.05mm tolerances
- Heat treatment — normalizing, hardening, tempering, annealing
- CMM inspection and full EN 10204 3.1 material certification
- Custom OEM forging from customer drawings — PPAP/ISIR available
- Fast export from Mundra Port — CIF worldwide, FOB India
- Export expertise — Europe, Middle East, Americas, Asia-Pacific