SS 316 / 316L / 316H
Fasteners
Manufacturer India
SS 316 vs 316L vs 316H — Which Grade to Specify
316, 316L, and 316H share the same base Ni-Cr-Mo chemistry. The only difference is carbon content — and carbon content governs sensitisation risk, weld performance, and high-temperature creep resistance. Specify correctly by service condition, not by habit.
SS 316
SS 316L
SS 316H
316L vs 304 — What 2% Mo Actually Changes
The difference between SS 304 and SS 316L is 2% molybdenum. That single addition raises chloride pitting resistance from PRE≈18 to PRE≈24 and transforms the alloy from a general-purpose stainless steel into the standard specification for chloride-containing chemical process environments.
PRE ≥ 40 required? Consider SS 904L (PRE≈36) or Hastelloy C276 (PRE≈66) for concentrated chloride or direct seawater immersion service.
| Property | Value |
|---|---|
| Min UTS (Annealed) | ≥ 485 MPa |
| Min YS (0.2%) | ≥ 170 MPa |
| Elongation | ≥ 40% |
| Hardness | ≤ 95 HRB |
| Mo Content | 2.0–3.0% |
| Max Carbon | 0.030% |
| PRE (nominal) | ≈ 24 |
| Magnetic | No (austenitic) |
| ASTM Bolt Grade | A193 B8M |
| ASTM Nut Grade | A194 8M |
| ISO Prop. Class | A4-70 / A4-80 |
| EN Material No. | 1.4404 |
316L Fastener Types & Standards
316L (S31603) is the primary stocking grade — suitable for ASME B16.5 stud bolts, ASTM A193 B8M certification, and the full range of welded and non-welded applications. 316H on order for elevated-temperature service. M4–M100.
316L Stud Bolts
ASTM A193 B8M (316L S31603) fully threaded stud bolts to ASME B16.5 lengths — the most widely specified exotic stainless stud bolt in global chemical process, pharmaceutical, and food industry ASME flanges. Class 150–2500, NPS ½”–24″, M12–M100, lengths to 3,000mm. Matching ASTM A194 Grade 8M heavy hex nuts. NABL tensile and hardness testing on every lot.
Hex Bolts
Full thread and partial thread hex bolts in 316L. M4–M100. ISO property class A4-70 and A4-80. Chemical plant and process equipment hex bolts, marine infrastructure hex bolts, food processing equipment connection bolts, pharmaceutical cleanroom hardware, and all general industrial applications requiring chloride-resistant stainless steel bolting above SS 304 capability.
Hex Nuts
ASTM A194 Grade 8M (316L) heavy hex nuts to ASME B18.2.2 for ASME B16.5 stud bolt assemblies. M4–M100. Standard hex (DIN 934) and heavy hex (ASME B18.2.2). Matched from same A193 B8M certified heat as stud bolts for single-document MTC. NABL hardness testing on every lot confirming A4 property class range.
Washers
Plain flat (DIN 125) and large OD (DIN 9021) washers in 316L. M4–M100. For complete A193 B8M + A194 8M + 316L washer assembly sets — single MTC for stud bolt, nut, and washer from the same certified bar stock heat. DIN 9021 large OD washers for soft-face flange connections and FRP equipment where bearing area distribution is required.
Threaded Rods
Full thread and end-thread in 316L. M4–M100, lengths to 3,000mm. Process plant structural tie-rods, heat exchanger internal structural rods, tank support rods, chemical plant structural threaded rod, and all applications where continuous threaded rod in 316L is required at lengths beyond standard fastener range.
Socket Cap Screws
Hex socket cap screws in 316L. M4–M24. Confined-access chemical plant connections, pharmaceutical process equipment screws, food industry cleanroom panel screws, marine instrument housing, and all applications where a hex socket cylindrical head in 316L’s chloride-resistant chemistry is required in a confined-access location.
316H Stud Bolts
SS 316H (S31609) stud bolts and hex bolts for process piping above 300°C where 316L’s very low carbon reduces creep resistance and 316H’s 0.04–0.10% C provides the required long-term creep and stress-rupture strength. Petrochemical fired heater piping flanges, heat exchanger shell connections in higher-temperature service. ASTM A276 S31609 certified material.
Custom 316/316L/316H
Non-standard sizes, inch UNC thread in 316L, fine pitch, coupling nuts, dome nuts, and any drawing-specific 316 grade fastener. Contact sales@akbarfasteners.in with grade (316/316L/316H), form, dimensions, and documentation requirement.
316L vs 904L vs Hastelloy C276 — Chloride Resistance Ladder
SS 316L handles mild chloride environments. When the application exceeds 316L’s PRE≈24 capability, the correct upgrade sequence is 317L → 904L → Hastelloy C276. This table helps identify the threshold.
| Criterion | SS 316L This Page | SS 317L | SS 904L | Hastelloy C276 |
|---|---|---|---|---|
| CORROSION RESISTANCE | ||||
| PRE (Pitting Resistance) | ≈ 24 | ≈ 30 | ≈ 36 | ≈ 66 |
| Molybdenum content | 2–3% | 3–4% | 4–5% | 15–17% |
| Dilute H₂SO₄ resistance | Moderate | Good | ✔ Excellent | ✔ Excellent |
| Seawater immersion (stagnant) | Pitting risk | Borderline | Good | ✔ Excellent |
| Concentrated HCl (any temp) | Fails | Fails | Fails | ✔ Excellent |
| PROCUREMENT POSITION | ||||
| ASTM A193 bolt grade | B8M (standard) | B8MN | B649 (bar) | ASTM B574 |
| ISO property class | A4-70 / A4-80 | A4-80 | Not ISO 3506 | Not ISO 3506 |
| Relative cost vs 316L | Baseline 1× | 1.3–1.6× | 3–4× | 8–12× |
316L Fasteners Application Areas
The global default stainless fastener for chemical processing, pharmaceutical, food industry, marine, and ASME pressure vessel service where chloride resistance above SS 304 is required.
Chemical Processing
process flange assemblies
Pharmaceutical / Biotech
CIP/SIP vessel connections
Food & Beverage
FDA-compliant fasteners
Marine / Coastal
marine deck hardware
Petrochemical
refinery process flanges
Offshore / Subsea
non-wetted offshore connections
Desalination
brine management flanges
Cryogenic / LNG
low-temp impact tested
SS 316 / 316L / 316H Standards Coverage
Same ISO 9001:2015 quality system across all 316 grades. PMI XRF confirms Mo 2–3% before machining — the critical verification that distinguishes 316L from 304L.
Complete Documentation Package
A193 B8M / S31603 Stated
Tensile · Hardness
Cr 16–18% Confirmed
Conformance
TÜV · BV · Lloyds
Related Higher-Alloy Fastener Grades
316L for general chloride service (PRE≈24). 317L for higher-chloride duty. 904L for concentrated sulphuric acid and PRE≈36. Hastelloy C276 for concentrated HCl and multi-acid environments.
SS 317L Fasteners
The step up from 316L — 3–4% Mo raises PRE from 24 to approximately 30, extending the chloride pitting resistance range. When 316L shows borderline pitting in field service and the environment is a moderate-chloride process stream, specify 317L before moving to the significantly more expensive 904L.
View SS 317L →SS 904L Fasteners
For dilute sulphuric acid, high-chloride environments, and applications where PRE≈36 is required. 904L’s 4.5% Mo and copper addition specifically target H₂SO₄ resistance in conditions where 316L and 317L both fail — chemical dosing systems, fertiliser plant, and seawater-cooled heat exchanger connections.
View SS 904L →Hastelloy C276 Fasteners
When 316L’s PRE≈24 and 904L’s PRE≈36 are both insufficient — Hastelloy C276’s 15–17% Mo and PRE≈66 handles concentrated HCl, mixed acids, oxidising and reducing environments, and seawater immersion where any stainless steel grade would fail by pitting or crevice corrosion.
View C276 →SS 321 Fasteners
When 316L service temperature exceeds 425°C — Ti-stabilised 321 prevents sensitisation in the 425–870°C range where 316L would carbide-precipitate and lose intergranular corrosion resistance. For high-temperature flanges, specify 321 or 321H rather than 316H above 400°C.
View SS 321 →Need SS 316 / 316L
Fasteners?
Grade (316/316L/316H) · form · size · ASME B16.5 Class/NPS · documentation. Akbar Fasteners responds within 24 hours.
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