Sanitary-Grade Stainless Steel Coil Tube — ASTM A270 Seamless & Welded
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. presents a premium line of sanitary-grade stainless steel coil tubes manufactured in strict accordance with ASTM A270, the American standard specification for seamless and welded austenitic stainless steel tubing intended for sanitary, food-processing, and pharmaceutical applications. Available in both seamless and continuous-welded configurations, these coil tubes are engineered to deliver exceptional surface integrity, hygienic performance, and dimensional consistency for the most demanding process industries.
Unlike straight-length tubing, coil tube is delivered in continuous lengths wound onto spools, significantly reducing the number of joints, fittings, and potential contamination points in a piping system. This makes coil tube the preferred choice for automated sanitary piping, CIP (Clean-in-Place) systems, and applications where internal surface quality is paramount.
Material & Properties
Coil tubes are fabricated from austenitic stainless steel grades specified under ASTM A270, with the following grades commonly offered:
- Type 304 (UNS S30400): Excellent general-purpose corrosion resistance, formability, and weldability; the industry-standard grade for food and beverage processing.
- Type 304L (UNS S30403): Low-carbon variant offering superior resistance to intergranular corrosion during welding and heat exposure.
- Type 316 (UNS S31600): Enhanced molybdenum content provides superior resistance to pitting and crevice corrosion in chlorinated environments.
- Type 316L (UNS S31603): Low-carbon version of 316, ideal for welded sanitary systems requiring maximum weld integrity and corrosion resistance.
Key Mechanical Properties (ASTM A270)
| Property | Type 304 / 304L | Type 316 / 316L |
|---|---|---|
| Tensile Strength (Min.) | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield Strength (Min., 0.2% Offset) | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Elongation (Min., 50 mm gauge) | 40% | 40% |
| Density | 8.0 g/cm³ | 8.0 g/cm³ |
| Thermal Conductivity (at 100 °C) | 16.3 W/(m·K) | 14.6 W/(m·K) |
Specifications
| Parameter | Specification |
|---|---|
| Applicable Standard | ASTM A270 / A270M |
| Manufacturing Method | Seamless and Welded (ERW / TIG) |
| Sanitary Grade | Hygienic (Food, Pharmaceutical, Dairy) |
| Outer Diameter Range | 6.35 mm (¼") to 168.3 mm (6½") |
| Wall Thickness Range | 0.50 mm (0.020") to 6.35 mm (¼") |
| Internal Surface Roughness (Ra) | ≤ 0.5 µm (≤ 0.00002") — Polished |
| Internal Surface Roughness (Ra) | ≤ 0.25 µm (≤ 0.00001") — Electropolished |
| External Surface Finish | No. 4 Brushed, 2B, or Mirror (Ra ≤ 0.1 µm) |
| Weld Treatment | Internal weld grinding and polishing to Ra ≤ 0.5 µm |
| Passivation | Nitric acid or citric acid passivation per ASTM A967 |
| Delivery Form | Coil / Spool (continuous length) |
| Coil Length | Custom (typically 100 m – 500 m per coil) |
| End Preparation | Plain end, beveled, or threaded (as required) |
Manufacturing Process
Seamless Coil Tube
- Piercing & Hot Rolling: Stainless steel billets are heated and pierced to form seamless hollow blanks, which are then hot-rolled to near-final dimensions.
- Cold Drawing / Cold Sizing: The hot-rolled tube is cold-drawn through precision dies to achieve exact dimensional tolerances and superior surface finish.
- Internal Polishing: Rotating abrasive brushes or wire-drawing tools are pulled through the tube bore to achieve the required internal surface roughness (Ra ≤ 0.5 µm or ≤ 0.25 µm for electropolished grades).
- Coiling: The finished tube is wound onto a steel spool under controlled tension to prevent deformation.
Welded Coil Tube
- Strip Slitting & Edge Preparation: Precision cold-rolled stainless steel strip is slit to width and edges are trimmed for consistent weld quality.
- Tube Forming & Welding: The strip is formed into a round cross-section and continuously welded using TIG (Tungsten Inert Gas) or ERW (Electric Resistance Welding) processes under argon shielding.
- Internal Weld Grinding & Polishing: A critical step for sanitary applications — the weld seam is ground and polished flush with the tube wall to eliminate crevices where microbial contamination could accumulate, achieving Ra ≤ 0.5 µm.
- Heat Treatment & Annealing: The tube is annealed to relieve welding stresses and restore full austenitic microstructure and corrosion resistance.
- Acid Pickling & Passivation: Per ASTM A967, the tube undergoes nitric acid or citric acid pickling to remove surface oxides, followed by passivation to restore the protective chromium oxide layer.
- Final Internal Polishing & Inspection: Electropolishing or mechanical polishing is applied as specified, followed by visual and dimensional inspection.
- Coiling & Packaging: The finished coil is wound, wrapped in protective film, and packaged for shipment.
Unique Selling Points
- Sanitary-Grade Internal Surface: Internal Ra values as low as 0.25 µm (electropolished) ensure minimal bacterial adhesion and facilitate complete CIP cleaning, meeting the most stringent hygiene requirements of FDA and 3-A standards.
- Flush Internal Weld Finish: Welded coil tubes feature precision-ground and polished internal weld seams, eliminating dead legs and crevice corrosion risks inherent in standard welded tubing.
- Comprehensive Passivation: Every coil undergoes rigorous acid passivation per ASTM A967, guaranteeing a stable, protective chromium oxide film that maximizes corrosion resistance from the point of delivery.
- Continuous Coil Delivery: Eliminates field welding and joint assembly, reducing contamination risk, installation labor, and total system cost.
- Dual Configuration Availability: Seamless and welded options allow customers to optimize cost-performance for their specific application while maintaining full sanitary compliance.
- Full Traceability: Each coil is heat-number traced with complete mill test reports, ensuring full material provenance and regulatory compliance.
Applications
ASTM A270 sanitary-grade coil tubes from Wenzhou Jixing are deployed across a wide range of hygienic and process-critical industries:
- Food & Beverage Processing: Milk processing, dairy, brewing, winemaking, juice production, and general food-handling piping systems.
- Pharmaceutical & Biotechnology: Water-for-Injection (WFI) loops, purified water (PW) systems, steam distribution, and process fluid transfer in GMP-regulated facilities.
- Dairy Industry: Milk collection, pasteurization, and distribution piping compliant with 3-A Sanitary Standards.
- Beverage & Canning: Carbonated beverage lines, concentrate handling, and filling equipment.
- Chemical Processing: Transfer of corrosive liquids, acids, and alkalis where hygienic transfer is required.
- Cosmetics & Personal Care: Processing and filling of cosmetic, pharmaceutical, and personal-care products.
- Semiconductor & Ultra-Pure Water: High-purity water delivery systems requiring exceptionally low surface roughness and zero particulate contamination.
- Heat Exchangers & Cooling Coils: Sanitary-grade heat transfer applications in food and pharmaceutical processing.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System certification, demonstrating systematic commitment to quality, customer satisfaction, and continuous improvement.
- ISO 22000 / HACCP — Food safety management system certification for food-grade stainless steel products.
- 3-A Sanitary Standards — Compliance with the U.S. Dairy Sanitary Standards, ensuring suitability for dairy and food-grade applications.
- CE Marking — Conformity with European health, safety, and environmental protection standards.
- ASTM A270 / A270M — Full compliance with the American specification for seamless and welded austenitic stainless steel tubing.
- ASTM A967 — Chemical cleaning and passivation of stainless steel products per recognized industry standard.
- FDA 21 CFR — Materials comply with U.S. Food and Drug Administration regulations for food-contact surfaces.
- Mill Test Reports (MTRs): Each coil is accompanied by a comprehensive heat-number-traceable test report including chemical composition, mechanical properties, and surface finish verification.
Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil tube solutions. Customers may specify outer diameter, wall thickness, surface finish grade (mechanically polished, electropolished, or mirror), coil length, end preparation, and packaging requirements. Our engineering team provides technical consultation for application-specific selection, system design support, and compliance documentation for regulatory audits.