Stainless Steel 316 Parts and AISI 316 Fittings

Stainless Steel 316 Parts and AISI 316 Fittings

AISI 316 Stainless Steel (UNS S31600, EN 1.4401, DIN X5CrNiMo17-12-2, BS 316S31) is the standard marine-grade, molybdenum-bearing austenitic stainless steel, offering superior resistance to chloride pitting, crevice corrosion, and stress corrosion cracking compared to AISI 304. The addition of 2.0–3.0% molybdenum provides critical protection in seawater, halide-containing process streams, coastal environments, chemical plant service, and pharmaceutical processing where AISI 304 is susceptible to pitting attack. Electrical Accessories India manufactures AISI 316 precision machined parts, SS 316 fittings, cable gland bodies, valve components, and process fittings for electrical OEMs, EPC contractors, offshore and marine operators, power utilities, pharmaceutical and food processing plants, and global distributors requiring the highest corrosion performance available in standard austenitic stainless steel at a commercially competitive price point.

Product Overview

AISI 316 vs 304 – The Role of Molybdenum

The defining difference between AISI 316 and 304 is the addition of 2.0–3.0% molybdenum (Mo) in AISI 316, which significantly raises the Pitting Resistance Equivalent Number (PREN = %Cr + 3.3 × %Mo + 16 × %N) from approximately 18–20 (304) to 24–26 (316). This PREN increase translates directly into improved resistance to chloride pitting, crevice corrosion initiation, and stress corrosion cracking in warm chloride solutions. Critical pitting temperature (CPT) for 316 is approximately 15–20°C versus 0–5°C for 304, making 316 suitable for seawater splash zones, coastal industrial installations, swimming pool environments, pharmaceutical process streams, and de-icing salt-exposed structural hardware. Tensile strength and hardness are essentially identical to AISI 304 (515–690 MPa tensile, 205–310 MPa yield, 40–60% elongation, 150–200 HB), but AISI 316 carries a 10–15% material price premium over 304 due to molybdenum content.

AISI 316 CNC Machined Parts – Precision Turned Components

Electrical Accessories India machines AISI 316 bar stock (ASTM A276), tube (ASTM A312 Grade TP316), and plate (ASTM A240 Grade 316) on CNC turning centers, CNC Swiss lathes, and multi-axis CNC machining centers. AISI 316 is machined with TiAlN or AlCrN coated carbide inserts, high-pressure through-tool coolant, and rigid workholding to manage its slightly higher work-hardening tendency compared to AISI 304. CNC turned 316 parts include valve stems, bonnet nuts, cable gland bodies, compression fittings, instrument tees, thermowell fittings, pump shaft sleeves, impeller wear rings, bearing housings, manifold adapters, and pressure sensor ports. Dimensional tolerances of ±0.01–0.025 mm on turned diameters, surface finishes of Ra 0.4–1.6 µm, and thread tolerances to 6g/6H (metric) or 2A/2B (UN) are standard. CMM first article inspection and AQL production sampling are performed per ISO 2859-1.

AISI 316 Fittings – Pipe, Instrument, and Process Fittings

Electrical Accessories India supplies a comprehensive range of AISI 316 precision machined fittings for pipe systems, instrument connections, and process plant applications. Products include NPT and BSP threaded nipples, hex nipples, close nipples, street elbows, reducing bushes, barrel unions, hex plugs, hex sockets, weld-end adapters, socket-weld elbows and tees, instrument tee fittings, gauge sockets, thermowell nozzle fittings, tube fittings (Swagelok-style and Gyrolok-style compression fittings), Autoclave-style high-pressure fittings, and manifold block assemblies. Thread dimensions conform to ASME B1.20.1 (NPT), ISO 228-1 (BSP), ASME B1.1 (UN/UNF), and customer-specific thread forms. Pressure ratings for machined 316 SS fittings range from 25 bar (standard wall BSP/NPT fittings) to 700 bar (high-pressure Autoclave-type fittings) depending on geometry and wall thickness.

AISI 316 Cable Glands and Electrical Enclosure Fittings

AISI 316 stainless steel cable glands are specified in offshore platforms, chemical plants, food processing facilities, pharmaceutical manufacturing, coastal power substations, water treatment plants, and ATEX Zone 1 / Zone 2 hazardous area installations where standard brass or AISI 304 cable glands are insufficient for the corrosion environment. Electrical Accessories India manufactures 316 SS cable gland bodies for metric thread (M16–M63), PG thread (PG7–PG48), NPT thread, and G thread entry configurations. Gland bodies are paired with EPDM, silicone, or nitrile sealing components for IP66, IP68, and IP69K ratings per IEC 60529. ATEX-certified assemblies to IEC 60079-0/1/14 (Ex d, Ex e, Ex n) are produced in AISI 316 for Group IIC, Category 2G/2D, T4–T6 temperature class applications. Laser engraving of thread size, IP rating, Ex marking, and lot codes is available on all AISI 316 cable gland bodies.

Marine and Offshore AISI 316 Components

Marine and offshore applications represent the core market for AISI 316 machined components. Products for marine and offshore customers include deck fittings, cable penetration seals, hull gland fittings, underwater connector housings, ROV (Remotely Operated Vehicle) component bodies, subsea instrument housings, platform structural hardware, mooring fittings, hatches and manhole cover bolting, bilge pump fittings, and seawater cooling system adapters. Salt-spray testing to ASTM B117 (2000+ hours) is available on 316 SS components to verify coating (if applied) or bare metal performance. Crevice corrosion testing per ASTM G48 Method B is available for critical submerged applications. Material certificates to NACE MR0175 / ISO 15156 for H₂S service are available for oilfield applications.

Pharmaceutical and Biotech Process Fittings

The pharmaceutical, biotechnology, and life science industries specify AISI 316L (low-carbon variant) for all product-contact process equipment. Electrical Accessories India machines ASME BPE-compliant fittings including butt-weld tube fittings, tri-clamp ferrules, tee fittings, elbows, reducers, sample valves, diaphragm valve bodies, spray nozzle bodies, CIP (Clean-In-Place) risers, and SIP (Steam-In-Place) fittings in AISI 316L. Electropolished internal surfaces to Ra ≤0.25 µm (SF1 surface finish per ASME BPE) are available for product-contact applications. PMI (XRF) verification confirms 316L composition (Mo 2–3%, C ≤0.03%) on every production lot. Documentation includes EN 10204 3.1 mill certificates, FDA 21 CFR compliance declaration, EU 1935/2004 declaration, and electropolish test reports with Ra measurements.

Chemical Plant and Petrochemical Applications

In chemical plant and petrochemical service, AISI 316 is used for instrument manifolds, chemical injection fittings, sample conditioning components, corrosion coupon holders, drain plugs, flush ring assemblies, flow orifice plates, restriction orifice fittings, level gauge body components, pressure transmitter adapters, and process isolation valve bodies. For sulfuric acid, phosphoric acid, and organic acid services where AISI 316 is borderline, AISI 316L or super austenitic grades (904L, 254SMO) are evaluated; Electrical Accessories India can supply machined components in these grades on request. Material selection guidance, NACE MR0175 suitability, and corrosion resistance data for specific process chemicals are available from our technical team.

AISI 316 Fasteners and Structural Hardware

AISI 316 fasteners (hex bolts, socket head cap screws, hex nuts, flat washers, spring washers, threaded rod, and studs) are specified wherever standard 304 fasteners are inadequate for the corrosion environment. Common applications include coastal structural steelwork, swimming pool handrails and ladders, marine deck hardware, chemical plant pipe flanges, water treatment filter housings, offshore lighting poles, and pharmaceutical clean-room equipment. Thread forms, dimensional standards (DIN, ISO, ASME B18), and mechanical properties comply with the same specifications as standard stainless fasteners. Certification to DIN EN ISO 3506 (stainless fasteners – mechanical properties) Class A4-70 or A4-80 is available. Full material certification (EN 10204 2.1, 2.2, or 3.1) is supplied as standard for all 316 SS fastener orders.

Pricing

AISI 316 / SS 316 Machined Parts and Fittings: US$ 9.90/kilogram (subject to order quantity, part geometry, tolerance, surface finish, and material form. MOQ: 50 kg. Volume pricing for annual contracts ≥500 kg. AISI 316L available at comparable pricing.)

Key Features

• 2.0–3.0% Molybdenum addition – superior chloride pitting and crevice corrosion resistance vs. AISI 304
• PREN 24–26 – suitable for seawater splash zones, coastal installations, and halide process streams
• Electropolished finish available: Ra ≤0.25 µm (ASME BPE SF1) for pharma and food contact
• ATEX-certified cable gland assemblies available in 316 SS for IIC Group, Zone 1/Zone 2
• Full NACE MR0175 / ISO 15156 compliance documentation for oilfield H₂S service
• Available in 316 and 316L (≤0.03% C) for welded assemblies and elevated-temperature service
• PMI (XRF) Mo verification on every production lot

316 vs 316L – When to Specify Each Grade

AISI 316L (UNS S31603, EN 1.4404, ≤0.03% C) is the low-carbon variant of 316, required when the machined component will be welded or used in the 425–860°C sensitization range, where standard 316 (≤0.08% C) may experience intergranular corrosion in the HAZ due to chromium carbide precipitation. For machined components that will NOT be welded, standard 316 is adequate and may be marginally stronger. For welded pharmaceutical, food processing, and chemical plant components, always specify 316L. Electrical Accessories India stocks both 316 and 316L bar, tube, and plate, with OES chemical verification to distinguish grades before machining.

ATEX and Hazardous Area Compliance

AISI 316 cable glands and enclosure fittings are used in ATEX and IECEx certified equipment for Zone 1 (Gas Group IIA, IIB, IIC) and Zone 21 (dust) hazardous area installations. Electrical Accessories India manufactures 316 SS cable gland bodies for Ex d (flameproof), Ex e (increased safety), and Ex n (non-sparking) enclosures. Certified assemblies include EPDM or silicone IP66/IP68 seals and are marked with CE mark, Ex symbol, equipment group, category, T-class, and notified body certificate number. Certificates issued under ATEX Directive 2014/34/EU and IECEx Scheme are available for IIC Group equipment in 316 SS.

High-Purity and Hygienic Processing Applications

AISI 316L electropolished components for pharmaceutical WFI (Water for Injection) systems, bioreactor manifolds, and USP purified water systems are produced per ASME BPE-2022 requirements. Surface finish Ra ≤0.25 µm (15 µin) on product-contact surfaces is verified by profilometer measurement at multiple points per component. Weld-end components are supplied with square-cut weld ends per ASME BPE Table SF-1 to facilitate orbital welding without internal backing rings. Batch documentation includes material certificates, electropolish records with Ra measurements, PMI reports, passivation records, and dim inspection reports in a single batch dossier.

Subsea and Deep-Water Applications

For subsea applications (up to 3000 m water depth), machined AISI 316 components serve as instrument housing bodies, cable penetration fittings, subsea connector shells, pressure housing end-caps, and ROV tooling components. At depths above 1000 m, hydrostatic pressure, low temperature, and cathodic protection interaction must be considered in material selection. Electrical Accessories India provides machined 316 SS pressure housing components with full hydrostatic proof testing at rated depth pressure, leak testing to 10⁻⁶ mbar·l/s helium mass spectrometry, and dimensional report on all features per customer’s engineering drawing package.

Industrial Water and Desalination Plant Fittings

Desalination plants (reverse osmosis, multi-effect distillation, multi-stage flash), cooling water treatment systems, and industrial water processing facilities specify AISI 316 for pump components, valve bodies, heat exchanger heads, membrane housing end-caps, flow control valve internals, pH sensor fittings, dosing injection points, and instrument connections exposed to treated seawater, brine, or chlorinated process water. AISI 316’s improved pitting resistance vs. 304 in chlorinated water (>200 ppm Cl⁻ at elevated temperature) makes it the standard specification for Middle East desalination projects and coastal power station cooling water systems. Electrical Accessories India has established relationships with EPC contractors and utilities in the GCC region supplying AISI 316 machined components with ARAMCO, SABIC, and utility project documentation requirements.

Technical Specifications – AISI 316 / SS 316 / 1.4401

International Equivalent Grades – AISI 316

Product Types and Variants

Applications by Industry

Manufacturing Process

Raw Material: AISI 316/316L bar (ASTM A276), tube (ASTM A312 TP316/316L), plate (ASTM A240 316/316L) from certified mills. Incoming PMI (XRF) verification of Mo 2.0–3.0% and C ≤0.03% (316L) before production release.

CNC Machining: AlCrN/TiAlN coated carbide tooling, high-pressure through-tool coolant (≥70 bar), rigid collet or chuck workholding. Live tooling on CNC turn-mill centers for cross-drilling, milling, and slot operations in single setup.

Electropolishing (EP): Phosphoric/sulfuric acid EP bath for ASME BPE SF1 (Ra ≤0.25 µm) finish on pharma and food-grade components. Ra verified by profilometer at minimum 3 points per component.

Passivation: ASTM A967 citric acid passivation on all machined components. Copper sulfate test (ASTM A967 Section 10) verification available.

Inspection: CMM first article (ASME Y14.5 / ISO 1101 GD&T), AQL sampling on production, XRF PMI, profilometer Ra measurement, thread gauge inspection, pressure/leak test as applicable.

Quality Standards and Certifications

Why Choose Electrical Accessories India for AISI 316 Parts

• PMI (XRF) on every lot: Confirms Mo 2–3% content and distinguishes 316 from 304 before machining.
• 316L stock: Both 316 and 316L in bar, tube, and plate for welded and non-welded applications.
• ASME BPE capability: Electropolished fittings to SF1 (Ra ≤0.25 µm) for pharma and biotech customers.
• ATEX certifications: 316 SS cable gland assemblies certified to IEC 60079-0/1 for Zone 1 IIC applications.
• GCC/Offshore supply experience: ARAMCO, SABIC, and utility project documentation package available.
• Competitive pricing from India: US$ 9.90/kg – cost-effective 316 SS machined parts with internationally certified quality.

Frequently Asked Questions

1. When should I specify AISI 316 instead of 304?

Specify AISI 316 when the application involves seawater or brine exposure, chloride concentrations above ~200 ppm at elevated temperatures, marine coastal environments, chemical plant service (halides, dilute acids), pharmaceutical product contact, or swimming pool hardware. AISI 304 is adequate for fresh water, food processing, indoor applications, and mild industrial environments.

2. What is the difference between AISI 316 and 316L?

AISI 316L has carbon content ≤0.03% versus ≤0.08% for standard 316. The lower carbon prevents chromium carbide sensitization in weld HAZ, maintaining corrosion resistance in welded assemblies. For machined, non-welded components, both grades perform identically in corrosion resistance. For welded or elevated-temperature service (425–860°C), specify 316L.

3. Is AISI 316 suitable for seawater immersion?

AISI 316 resists seawater corrosion in splash, tidal, and immersion zones better than 304, but is not immune to pitting in stagnant seawater at elevated temperatures. For continuous full seawater immersion service, consider duplex 2205 (UNS S32205, PREN ~35) or super austenitic 254SMO (PREN ~43). Electrical Accessories India can supply machined components in these grades on request.

4. Can AISI 316 cable glands be supplied with ATEX certification?

Yes. We supply AISI 316 cable gland assemblies with ATEX 2014/34/EU certification for Gas Group IIC, Equipment Category 2G, T4–T6, Zone 1 installations. IECEx certification is also available. Certificates and technical documentation are provided with each certified assembly.

5. What is the Ra surface finish achievable on AISI 316 machined parts?

As-machined: Ra 0.8–3.2 µm (tool-mark visible). CNC finish-turned: Ra 0.4–0.8 µm. Electropolished (ASME BPE SF1): Ra ≤0.25 µm. Mirror polished: Ra ≤0.1 µm. Bead blasted: uniform matte, Ra ~1.0–2.0 µm.

6. Are AISI 316 parts suitable for H₂S (hydrogen sulfide) service?

AISI 316 is listed in NACE MR0175 / ISO 15156-3 Table A.2 for use in oilfield H₂S service under defined conditions (maximum hardness HRC 22, solution annealed condition). For critical H₂S environments, confirm specific temperature, H₂S partial pressure, and chloride conditions against NACE MR0175 allowable service limits. NACE-compliant material certification is available.

7. What thread forms are available on AISI 316 fittings?

Available thread forms include: NPT (ASME B1.20.1), BSPT/BSPP (ISO 7-1/ISO 228-1), Metric (ISO 965-1), UNC/UNF (ASME B1.1), PG (DIN 40430), NPTF (ASME B1.20.3), and special threads to customer specification.

8. What is the MOQ for AISI 316 machined parts?

Standard MOQ is 50 kg per part number. For prototype samples, 10–50 pieces can be arranged. Annual contract pricing and blanket order agreements with monthly call-off are available for OEM and EPC customers at volumes ≥500 kg/year.

9. Can AISI 316 components be supplied with EN 10204 Type 3.2 inspection certificates?

Yes. EN 10204 Type 3.2 (witnessed by an independent inspection body) certificates are available for critical applications requiring independent verification of chemical composition and mechanical properties. Additional cost and lead time applies. Please specify 3.2 certification requirement at time of enquiry.

10. Does Electrical Accessories India supply AISI 316Ti (titanium stabilized)?

Yes. AISI 316Ti (UNS S31635, EN 1.4571, DIN X6CrNiMoTi17-12-2) is available for sustained elevated-temperature service (400–800°C) where sensitization resistance is required without the limitation on carbon content. 316Ti machined parts are quoted on request; lead time is 6–10 weeks from drawing approval.

Equivalent Terms in Major Languages

Related Products and Linked Terms

• Stainless Steel 304 Parts – CNC Machined AISI 304 Parts
• Stainless Steel 316 Turned Parts
• Brass CNC Machined Parts
• Brass Screw Machine Parts
• C360 Brass Screw Machine Parts
• C69300 ECO Brass Machined Parts
• C87850 Brass Fittings and Machined Parts
• Copper Machined Parts
• Brass Turned Parts & Components
• Brass Forging Parts

Request a Quote – AISI 316 Stainless Steel Parts and Fittings

Electrical Accessories India manufactures AISI 316 / SS 316 CNC machined parts, precision fittings, cable gland bodies, valve components, and hygienic process fittings for global OEM, EPC, offshore, pharmaceutical, and industrial customers. Indicative pricing: US$ 9.90/kilogram. Contact our technical sales team with your drawing or specification for a formal quotation within 24–48 hours.

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