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Stainless Steel 304 Parts, CNC Machined AISI 304 Parts
Stainless Steel 304 Parts – CNC Machined AISI 304 Parts
AISI 304 Stainless Steel (UNS S30400, EN 1.4301, BS 304S31, DIN X5CrNi18-10) is the most widely specified austenitic stainless steel in industrial manufacturing, combining excellent corrosion resistance, good mechanical strength, hygienic surface finish capability, and cost-effectiveness in a non-magnetic, non-hardenable alloy system. Electrical Accessories India manufactures AISI 304 CNC machined parts, stainless steel 304 turned components, and SS 304 stamped fittings for electrical OEMs, EPC contractors, power utilities, process industry customers, and global distributors. Applications span electrical panel hardware, cable management components, process fittings, hygienic food-grade components, structural fasteners, and precision instrument parts requiring the corrosion resistance and cleanliness of austenitic stainless steel at a lower material cost than AISI 316.
Product Overview
AISI 304 Stainless Steel – Metallurgy and Material Properties
AISI 304 is an 18% chromium – 8% nickel austenitic stainless steel (commonly called “18/8 stainless”) with carbon content ≤0.08%. The chromium forms a passive chromium oxide layer (Cr₂O₃) on the surface that self-repairs in oxidizing environments, providing the alloy’s characteristic corrosion resistance. The austenitic (FCC) microstructure is non-magnetic in the annealed condition, has no ductile-to-brittle transition temperature, and cannot be hardened by heat treatment. Tensile strength of 515–690 MPa and yield strength (0.2% offset) of 205–310 MPa provide good structural integrity for machined components, fasteners, and fittings. Elongation of 40–60% and high work-hardening rate require attention to machining parameters and tooling compared to free-cutting brass or aluminium. Hardness is typically 150–200 HB in the annealed condition. AISI 304 is passivated per ASTM A967 or AMS 2700 for enhanced corrosion resistance on machined surfaces, removing free iron and promoting the chromium oxide layer.
CNC Machined AISI 304 Parts – Precision Turning and Milling
CNC machining of AISI 304 requires specific tooling strategies due to the alloy’s high work-hardening rate and tendency to build up on cutting edges (BUE – Built-Up Edge). Electrical Accessories India uses coated carbide inserts (TiAlN, TiCN, AlCrN coatings), ceramic-tipped tools for high-speed finishing, and coolant-fed tooling for all AISI 304 CNC turning and milling operations. CNC turning centers with driven tooling, CNC Swiss-type lathes for small-diameter bar work (up to 32 mm), and 3/4/5-axis CNC machining centers process AISI 304 bar stock (ASTM A276), plate (ASTM A240), and tube (ASTM A312) into finished components. Achievable tolerances are ±0.01–0.025 mm on turned diameters, ±0.02 mm on milled features, and Ra 0.4–1.6 µm surface finish. CMM (coordinate measuring machine) inspection is performed on first articles and AQL-based sampling on production lots per ISO 2859-1.
SS 304 Electrical Panel Components and Enclosure Hardware
For electrical OEM and EPC applications, AISI 304 stainless steel machined parts include cable gland bodies (metric PG, M-thread, and NPT types), conduit fittings, panel lockouts, earth terminal studs, busbar support brackets, DIN rail clips, enclosure door hinges, stainless steel cable tie mounts, junction box screws, panel nuts, and waterproof cable entry sealing systems. AISI 304 cable glands for use in hygienic food and beverage processing environments are produced to IP66/IP68/IP69K sealing levels with compliant elastomeric seals. For ATEX hazardous area applications, machined AISI 304 components are used in Zone 1/Zone 2 and Zone 21/Zone 22 certified enclosures and cable entry systems per IEC 60079-0/1. Marine and coastal installation hardware in AISI 304 withstands salt-spray exposure for extended periods; for more aggressive environments, AISI 316 is recommended.
Process Industry and Chemical Plant Fittings
In process plant, petrochemical, pharmaceutical, and water treatment applications, AISI 304 CNC machined fittings serve as instrument tees, manifold adapters, sample valves, pressure gauge sockets, thermowell fittings, chemical dosing line adapters, hygienic tri-clamp fittings, and sanitary tube fittings. Machined surfaces are electropolished (EP) to Ra ≤0.4 µm for pharmaceutical and biotechnology applications where surface bioburden retention must be minimized. Process fittings are produced to DIN 11851 (dairy fittings), ISO 2853 (clamp fittings), BS 4825 (sanitary tube fittings), and ASME BPE (bioprocessing equipment) standards as required. Material certification includes EN 10204 3.1 mill certificates with Positive Material Identification (PMI) using XRF verification.
Structural Fasteners and Hardware from AISI 304
AISI 304 is the dominant material for stainless steel fasteners in general industrial, construction, marine, and outdoor applications. Electrical Accessories India machines 304 fasteners including hex bolts (DIN 933/931), hex socket screws (DIN 912), cheese head screws (DIN 84), countersunk screws (DIN 963), hex nuts (DIN 934), flange nuts (DIN 6923), flat washers (DIN 125), spring washers (DIN 127), threaded rod, and stud bolts. Thread forms include metric (ISO 965, 6g/6H), UNC/UNF (ASME B1.1, 2A/2B), BSW, BSF, BA, NPT, and BSPT. High-strength configurations with cold-worked or strain-hardened bar stock (1/4 hard, 1/2 hard) are available for high-load applications requiring improved yield strength up to 480 MPa. Full dimensional compliance with DIN, ISO, ASME B18, and BS specifications is verified by gauge inspection before dispatch.
Food-Grade and Hygienic Applications of AISI 304
The food and beverage processing industry extensively specifies AISI 304 machined and pressed components for mixing vessel parts, pump impeller blanks, agitator shafts, valve plugs, sanitary fittings, nozzle bodies, spray ball bodies, clean-in-place (CIP) fittings, and conveyor components that contact food products. AISI 304 meets FDA 21 CFR material requirements for food-contact metals and is compliant with EU Food Contact Materials Regulation (EC) No 1935/2004 for stainless steel components. Electropolished or mechanically polished finishes (Ra ≤0.8 µm, 2B, #4, or mirror finish) are specified for hygienic contact surfaces. Passivation per ASTM A967 Method C (citric acid) is preferred for food-grade components to avoid nitric acid residues. Welds on fabricated assemblies are pickled and passivated per ASTM A380.
Water Treatment and Utility Infrastructure Components
For water treatment plants, desalination facilities, power station cooling water systems, and utility infrastructure, AISI 304 machined components include pump shaft sleeves, impeller wear rings, diffuser vanes, pressure vessel nozzles, flanged adapters, valve body components, strainer bodies, and flow meter bodies. AISI 304 performs well in fresh water and mildly aggressive process streams, though seawater, chloride-rich, and acidic environments may require upgrade to AISI 316L or duplex stainless. Material certificates per EN 10204 3.1 and PMI (XRF) verification are standard for utility infrastructure orders. Weld-quality CNC machined joint preparation (bevel angles, root face dimensions) per AWS D1.6 or ISO 9692-3 is available for fabricated assemblies.
Precision Instrument and Sensor Components
AISI 304 CNC machined precision parts for instrumentation include thermowell bodies, pressure sensor ports, Coriolis flow meter tube fittings, ultrasonic transducer housings, level sensor mounting flanges, analytical instrument sample fittings, chromatography column fittings, and high-pressure tubing adapters (up to 350 bar / 5,000 psi in heavy wall configurations). Tight bore tolerances of ±0.005 mm (IT5), surface finishes of Ra 0.4 µm, and concentricity ≤0.005 mm are achievable on critical instrument components with precision grinding and honing as final operations. Leak testing by helium mass spectrometry or pneumatic pressure test is available for pressure-retaining instrument fittings.
Pricing
AISI 304 Stainless Steel CNC Machined Parts: US$ 9.90/kilogram (subject to order quantity, part geometry, tolerance requirements, and surface finish. MOQ: 50 kg. Volume pricing for annual contracts ≥500 kg.)
Key Features
- 18% Cr – 8% Ni austenitic stainless steel – excellent atmospheric and mild chemical corrosion resistance
- Non-magnetic (annealed condition) – suitable for applications near sensitive instruments and MRI environments
- Hygienic surface finish capability: Ra ≤0.4 µm (electropolished), #4 brushed, 2B, mirror finish
- Food-grade compliant: FDA 21 CFR, EU 1935/2004 for food-contact applications
- Wide bar/tube/plate material range: ASTM A276 (bar), ASTM A312 (tube), ASTM A240 (plate)
- Passivation per ASTM A967 / AMS 2700 included on precision machined parts
- Full material traceability: EN 10204 3.1 mill certs, PMI (XRF) available
Corrosion Resistance Profile
AISI 304 resists corrosion in atmospheric environments, fresh water, mild acids (dilute nitric acid, dilute organic acids), alkalis, and food-contact media. It is susceptible to pitting and crevice corrosion in chloride-containing environments (seawater, swimming pools, de-icing salt) and to stress corrosion cracking (SCC) above 60°C in chloride media. For chloride-rich environments, AISI 316 (molybdenum-bearing) or duplex grades (2205, 2507) should be specified. All machined surfaces are passivated to maximize the chromium oxide passive layer and eliminate free iron contamination from machining operations.
Machinability and CNC Tooling Strategy
AISI 304 has a machinability rating of approximately 45% relative to C36000 free-cutting brass, requiring coated carbide tooling, rigid setups, and positive rake cutting geometry. Work hardening is managed by maintaining continuous cutting engagement (no rubbing), adequate depth of cut, and high-pressure coolant delivery (≥70 bar) through-tool cooling on CNC Swiss and turning centers. Feed rates of 0.05–0.25 mm/rev and cutting speeds of 80–200 m/min are typical for roughing and finishing operations with TiAlN-coated inserts. Drill cooling and peck cycle control are critical for deep hole drilling operations to prevent drill walking and work hardening at the hole base.
Weldability and Fabrication
AISI 304 is readily weldable by TIG (GTAW), MIG (GMAW), plasma arc, resistance, and laser welding processes using 308L filler wire. Post-weld heat treatment is not required, but solution annealing (1050–1120°C, water quench) improves corrosion resistance in HAZ (Heat-Affected Zone) by re-dissolving chromium carbide precipitates. For highly corrosive environments, AISI 304L (low-carbon, ≤0.03% C) is specified to prevent sensitization and intergranular corrosion in the HAZ. Machined and fabricated assemblies can be supplied by Electrical Accessories India as complete weldments with post-weld grinding, pickling, and passivation.
Surface Finish Options for AISI 304 Parts
Available surface finishes on AISI 304 machined parts include: as-machined (tool marks visible), vibratory deburred, #4 brushed (industrial finish, Ra ~0.8 µm), 2B (bright rolled, Ra ~0.5 µm), electropolished (Ra ≤0.4 µm, EN 1.4301 electropolish), mirror polished (Ra ≤0.1 µm, #8 finish), and bead blasted (matte uniform appearance). Electropolishing removes the work-hardened surface layer, improves corrosion resistance, and produces a bright hygienic finish preferred for pharmaceutical, food, and biotech applications.
Certification and Quality Compliance
All AISI 304 CNC machined parts are produced under ISO 9001:2015 quality management. Pressure-retaining components are manufactured to applicable ASME (B16, B31.3), EN (1092, 10253), or customer-specific pressure equipment standards. Positive Material Identification (PMI) by XRF is performed on all production lots where customer specification requires elemental verification. EN 10204 Type 3.1 mill certificates are provided as standard; Type 3.2 (independent inspection) certificates are available on request for critical applications.
Technical Specifications – AISI 304 / SS 304 / 1.4301
| Property | Value / Range | Standard |
|---|---|---|
| UNS Designation | S30400 | ASTM / SAE |
| EN Designation | 1.4301 | EN 10088 |
| Common Name | AISI 304, SS 304, 18/8 Stainless Steel | – |
| Chromium (Cr) | 18.0–20.0% | ASTM A276 |
| Nickel (Ni) | 8.0–10.5% | ASTM A276 |
| Carbon (C) | ≤0.08% | ASTM A276 |
| Manganese (Mn) | ≤2.0% | ASTM A276 |
| Silicon (Si) | ≤0.75% | ASTM A276 |
| Phosphorus (P) | ≤0.045% | ASTM A276 |
| Sulfur (S) | ≤0.030% | ASTM A276 |
| Tensile Strength | 515–690 MPa | ASTM E8 |
| Yield Strength (0.2%) | 205–310 MPa | ASTM E8 |
| Elongation | 40–60% | ASTM E8 |
| Hardness | 150–200 HB / 80–88 HRB | ASTM E10 |
| Density | 7.93 g/cm³ | – |
| Thermal Conductivity | 16.2 W/m·K at 100°C | – |
| Machinability Index | ~45% (C360=100%) | CDA scale |
| Magnetic | Non-magnetic (annealed) | – |
International Equivalent Grades – AISI 304
| Standard | Designation | Notes |
|---|---|---|
| USA (AISI/UNS) | AISI 304 / UNS S30400 | Standard 18/8 austenitic SS |
| Europe (EN) | 1.4301 / X5CrNi18-10 | EN 10088-3 |
| UK (BS) | 304S31 / BS 970 | British Standard equivalent |
| Germany (DIN) | X5CrNi18-10 / WNr 1.4301 | DIN 17440 |
| France (AFNOR) | Z6CN18-09 | – |
| Japan (JIS) | SUS 304 | JIS G4303 |
| China (GB) | 0Cr18Ni9 / 06Cr19Ni10 | GB/T 3280 |
| India (IS) | 10Cr18Ni8 / IS 6527 | Indian Standard |
| Sweden (SS) | SS 2333 | – |
Product Types and Variants
| Product Type | Description | Size Range |
|---|---|---|
| CNC Turned Parts | Precision turned components from 304 bar | Dia 3–100 mm |
| CNC Milled Parts | Machined 3D profiles from 304 bar/plate | Up to 300×300 mm |
| Cable Gland Bodies | Stainless 304 cable glands (M/PG/NPT) | M16–M63, PG7–PG48 |
| Fasteners | Hex bolts, socket screws, nuts, studs | M2–M30, #2-56 to 1″ |
| Pipe Fittings | Threaded and socket-weld fittings | 1/8″–2″ BSP/NPT |
| Hygienic Fittings | Tri-clamp, DIN 11851, ISO 2853 fittings | DN25–DN150 |
| Instrument Fittings | Gauge sockets, thermowell fittings, adapters | Custom |
| Stamped Parts | Brackets, clips, shields from 304 sheet | 0.5–6 mm thickness |
Applications by Industry
| Industry | AISI 304 Applications |
|---|---|
| Electrical OEM | Cable glands, conduit fittings, panel hardware, earth terminal studs |
| EPC / Power Utilities | Switchgear hardware, cable tray fasteners, substation fittings |
| Food & Beverage | Hygienic fittings, pump parts, tri-clamp connectors, nozzle bodies |
| Pharma / Biotech | Electropolished instrument fittings, BPE fittings, sample valves |
| Water Treatment | Pump impellers, valve bodies, pipe flanges, strainer bodies |
| Chemical Process | Instrument tees, pressure gauge sockets, thermowell nozzles |
| Construction | Structural fasteners, anchor bolts, handrail fittings |
| Marine | Mild marine fittings (non-seawater contact), deck hardware |
Manufacturing Process
Raw Material: AISI 304 bar (ASTM A276), tube (ASTM A312), and plate (ASTM A240) from certified mills. Incoming PMI (XRF) verification and EN 10204 3.1 certificates.
CNC Machining: TiAlN-coated carbide inserts, high-pressure through-tool coolant (≥70 bar), rigid setups, and optimized cutting parameters for austenitic stainless work hardening control.
Secondary Operations: Drilling, milling, threading, deburring, electropolishing, passivation (ASTM A967), and bead blasting as required.
Inspection: CMM first article, AQL sampling on production, thread gauge inspection, surface finish measurement (profilometer).
Packaging: Individual protection (oiled paper, foam), bulk in box, or tray packaging depending on part geometry and export requirements.
Quality Standards and Certifications
| Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ASTM A276 | 304 stainless bar and rod specification |
| ASTM A312 | 304 stainless seamless and welded tubes |
| ASTM A967 | Passivation of stainless steel |
| EN 10088-3 | 1.4301 stainless steel semi-finished products |
| EN 10204 3.1 | Material test reports |
| FDA 21 CFR | Food-contact material compliance |
| EU 1935/2004 | Food contact materials regulation |
| ASME BPE | Bioprocessing equipment standard |
Why Choose Electrical Accessories India for AISI 304 CNC Parts
- Multi-material expertise: Dedicated 304 SS machining lines alongside brass and copper – single-source supply for mixed-material BOM.
- Hygienic finish capability: Electropolishing and Ra ≤0.4 µm finishes for food, pharma, and biotech customers.
- Full PMI and traceability: XRF verification, EN 10204 3.1 certificates, and lot traceability on every order.
- Passivation in-house: ASTM A967 passivation available without outsourcing delay.
- Competitive pricing: Indian manufacturing cost base with internationally certified quality. US$ 9.90/kg.
Frequently Asked Questions
1. What is the difference between AISI 304 and AISI 316 stainless steel?
AISI 316 contains 2–3% molybdenum, which significantly improves chloride pitting resistance, crevice corrosion resistance, and performance in seawater and chemical environments. AISI 304 is suitable for fresh water, food contact, and mild industrial environments; AISI 316 is specified where chloride resistance is critical.
2. Is AISI 304 magnetic?
In the annealed (solution-treated) condition, AISI 304 is non-magnetic. Cold working and machining can induce slight magnetic permeability due to strain-induced martensite transformation. For fully non-magnetic applications (MRI, sensitive instruments), specify fully annealed 304 or consider 316L which has lower work-hardening tendency.
3. Can AISI 304 parts be electropolished?
Yes. AISI 304 is electropolished using phosphoric/sulfuric acid electrolyte to achieve Ra ≤0.4 µm (pharmaceutical and food grade). Electropolishing removes approximately 10–30 µm of surface material, eliminating machining stress and improving passive layer quality and corrosion resistance.
4. What is the maximum operating temperature for AISI 304?
AISI 304 has a maximum continuous operating temperature of approximately 870°C in air and 925°C for intermittent service. However, in the 425–860°C sensitization range, chromium carbide precipitation at grain boundaries reduces corrosion resistance; AISI 304L (low-carbon) or 321 (titanium-stabilized) should be specified for sustained elevated-temperature applications.
5. Are AISI 304 cable glands suitable for ATEX Zone 1 installations?
Yes, provided the cable gland assembly has been certified under IEC 60079-0/1 for the specific Ex category, equipment group, and temperature class. The base material (AISI 304) is suitable; the ATEX certification is dependent on the complete assembly design and IP sealing. We supply ATEX-certified cable gland assemblies on request.
6. What tolerances are achievable on AISI 304 CNC turned parts?
Standard turned OD tolerance: ±0.025 mm (IT8). Precision CNC turned: ±0.01 mm (IT6). Ground/honed: ±0.005 mm (IT5). Thread tolerance class 6g/6H is standard for metric threads.
7. Is AISI 304 suitable for potable water applications?
Yes. AISI 304 is approved for potable water contact under WRAS (UK), NSF 61, and DIN 50930-6. It is used for water treatment fittings, storage tank fittings, and plumbing components. Note: for high-chloride water, AISI 316 is preferred to avoid pitting corrosion.
8. What is the MOQ for AISI 304 CNC machined parts?
Standard MOQ is 50 kg per part number. Prototype samples (10–50 pieces) can be arranged for new designs. Annual contract pricing is available for volumes of 500 kg and above per year.
9. Can AISI 304 parts be passivated after machining?
Yes. Passivation per ASTM A967 (citric acid Method C or nitric acid Method 1) is performed after final machining and deburring to remove free iron, machining oils, and contaminants, and to restore the chromium oxide passive layer. Passivation test verification by copper sulfate test (ASTM A967 Section 10) is available.
10. Does Electrical Accessories India supply AISI 304L (low-carbon)?
Yes. AISI 304L (UNS S30403, EN 1.4307, ≤0.03% C) is available for welded assemblies and elevated temperature applications requiring resistance to sensitization. Specify 304L on your drawing or enquiry; pricing is comparable to standard 304 with minor mill cost premium.
Equivalent Terms in Major Languages
| Language | Term 1 | Term 2 | Term 3 |
|---|---|---|---|
| Spanish | Acero inoxidable 304 mecanizado CNC | Piezas AISI 304 torneadas con precisión | Componentes inox 18/8 mecanizados |
| Russian | Детали из нержавеющей стали 304 с ЧПУ | AISI 304 точёные компоненты | Нержавеющая сталь 1.4301 детали |
| French | Pièces en acier inoxydable 304 usinées CNC | Composants tournés AISI 304 | Pièces inox 18/8 de précision |
| Portuguese | Peças em aço inoxidável 304 usinadas CNC | Componentes torneados AISI 304 | Partes inox 18/8 de precisão |
| Italian | Parti in acciaio inossidabile 304 lavorate CNC | Componenti torniti AISI 304 | Parti inox 18/8 di precisione |
Related Products and Linked Terms
- Stainless Steel 316 Turned Parts
- Brass CNC Machined Parts
- Brass Screw Machine Parts
- Brass Turned Parts & Components
- C360 Brass Screw Machine Parts, CDA 360 Brass Machining
- C69300 ECO Brass Machined Parts
- Copper Machined Parts
- Brass Forging Parts
- Copper Milled Parts
Request a Quote – AISI 304 Stainless Steel CNC Machined Parts
Electrical Accessories India manufactures AISI 304 / SS 304 CNC machined parts, cable glands, fittings, fasteners, and hygienic components for global OEM, EPC, and process industry customers. Indicative pricing: US$ 9.90/kilogram. Submit your drawing or specification for a quotation within 24–48 hours.
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