Stainless Steel 316 Coil Tube — Austenitic Corrosion-Resistant Grade
Product Overview
The Stainless Steel 316 Coil Tube is a premium continuous-length tubular product supplied in coiled configuration, manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product falls under the austenitic corrosion-resistant classification within the stainless steel material family. The designation "Coil Tube" (盘管) indicates that the tubing is produced as a continuous, helically wound coil rather than in discrete straight lengths, enabling seamless downstream processing through automated cutting, bending, forming, and welding operations. The 316 grade is distinguished from the standard 304 austenitic alloy by the deliberate addition of 2–3% Molybdenum (Mo), which confers significantly enhanced resistance to chloride-induced pitting corrosion and organic acid attack.
This coil tube product is engineered for demanding industrial environments where conventional austenitic stainless steels exhibit accelerated degradation. Its material integrity, dimensional precision, and metallurgical consistency make it the conventional material selection for chemical processing, pulp and paper manufacturing, and marine atmospheric service.
Material & Properties
Chemical Composition (ASTM A213 / EN 10216-5)
The 316 grade stainless steel is an austenitic chromium-nickel-molybdenum alloy. The base composition adheres to recognized international standards, with the following key compositional ranges:
- Carbon (C): ≤ 0.08% — limits carbide precipitation at grain boundaries
- Chromium (Cr): 16.00% – 18.00% — primary passive film former providing general corrosion resistance
- Nickel (Ni): 10.00% – 14.00% — stabilizes the austenitic crystal structure and enhances ductility
- Molybdenum (Mo): 2.00% – 3.00% — critical alloying element that substantially improves resistance to chloride pitting, crevice corrosion, and organic acid environments
- Manganese (Mn): ≤ 2.00%
- Phosphorus (P): ≤ 0.045%
- Sulfur (S): ≤ 0.030%
- Silicon (Si): ≤ 0.75%
Mechanical Properties (Typical Values)
- Tensile Strength (UTS): ≥ 515 MPa (75 ksi)
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa (30 ksi)
- Elongation: ≥ 40% (minimum in 50 mm / 2 in. gauge length)
- Hardness: ≤ 253 HB (Brinell) / ≤ 30 HRC (Rockwell C)
- Crystal Structure: Face-Centered Cubic (FCC) — fully austenitic, non-magnetic in annealed condition
Corrosion Resistance Characteristics
The incorporation of 2–3% Molybdenum in the 316 alloy matrix provides the following corrosion performance advantages over the standard 304 grade:
- Chloride Pitting Resistance: Substantially elevated pitting resistance equivalent number (PREN ≈ 24–26) compared to 304 (PREN ≈ 19–20), enabling reliable service in chloride-containing media at elevated temperatures and concentrations.
- Organic Acid Resistance: Demonstrates superior resistance to weak organic acids including acetic acid, citric acid, and formic acid at moderate concentrations and temperatures.
- Crevice Corrosion Resistance: Improved performance in tight geometries where oxygen-depleted microenvironments can initiate localized attack.
- Atmospheric Corrosion Resistance: Excellent durability in marine and coastal atmospheric conditions where airborne chloride deposition accelerates degradation of lower-grade alloys.
- Intergranular Corrosion Resistance: Low carbon content (≤ 0.08%) minimizes chromium carbide precipitation during welding and thermal processing, preserving grain boundary integrity.
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Material Grade | Stainless Steel 316 (UNS S31600 / 1.4401) | ASTM A213 / EN 10216-5 |
| Alloy Classification | Austenitic — Corrosion Resistant | — |
| Molybdenum Content | 2.00% – 3.00% (by mass) | ASTM A240 |
| Outer Diameter (OD) | 6.0 mm – 168.0 mm (custom ranges available) | ASTM A213 |
| Wall Thickness | 0.5 mm – 12.0 mm | ASTM A213 |
| Coil Length | 5 m – 100 m per coil (negotiable) | — |
| OD Tolerance | ±0.5 mm or ±0.5% (whichever is greater) | ASTM A213 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A213 |
| Surface Finish | Mill Annealed (2B), Pickled & Passivated, or Polished | ASTM A480 |
| Delivery Condition | Solution Annealed and Pickled (SA&P) | — |
| Maximum Service Temperature | 870°C – 1100°C (continuous) | ASTM A213 |
| Minimum Service Temperature | Cryogenic (no ductile-to-brittle transition) | — |
| Coil Core Diameter | 50 mm – 250 mm (standard options) | — |
| Coil Weight | Up to 2,000 kg per coil (typical) | — |
Manufacturing Process
The production of 316 stainless steel coil tube follows a rigorously controlled multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical homogeneity, and surface integrity:
- Raw Material Procurement & Verification: Certified 316 stainless steel slabs or strip stock are sourced from approved mills with full mill test certificates (MTC) confirming chemical composition and mechanical properties per ASTM/EN standards.
- Hot Rolling & Annealing: The raw stock undergoes hot rolling to achieve preliminary dimensional specifications, followed by controlled furnace annealing to restore full austenitic microstructure and eliminate residual stresses.
- Pickling & Passivation: The hot-rolled coil is subjected to acid pickling (typically a mixed HNO₃/HF solution) to remove oxide scale and surface contaminants, followed by passivation treatment to establish a protective chromium oxide passive film.
- Cold Drawing / Cold Forming: The prepared coil stock is cold-drawn through precision-die tooling to achieve final outer diameter and wall thickness dimensions. This process enhances mechanical properties and surface finish quality.
- Intermediate Annealing (if required): For tight tolerance or multi-pass drawing operations, intermediate solution annealing cycles are performed to relieve work hardening and maintain ductility.
- Final Coiling: The finished tube is wound onto precision-machined coil cores under controlled tension to prevent deformation, kinking, or surface damage. Coils are wrapped and protected for storage and shipment.
- Quality Inspection & Testing: Each production lot undergoes comprehensive quality verification including chemical analysis (OES), mechanical testing (tensile, hardness), dimensional gauging, visual surface inspection, and hydrostatic or eddy current leak testing as applicable.
Applications
The 316 stainless steel coil tube is the conventional material selection for the following industrial sectors and service environments:
- Chemical Processing Industry: Heat exchangers, reactor tubing, process piping, distillation columns, and chemical transfer lines handling chlorinated solutions, sulfuric acid dilutions, and aggressive process media.
- Pulp & Paper Manufacturing: Recovery furnace components, bleaching plant piping, black liquor systems, and effluent treatment equipment where organic acids and chlorinated byproducts are present.
- Marine & Offshore Engineering: Seawater cooling systems, ballast water piping, marine atmospheric-exposed structures, offshore platform tubing, and desalination plant components.
- Pharmaceutical & Food Processing: Sanitary-grade tubing, CIP (Clean-In-Place) systems, and processing equipment requiring resistance to cleaning agents and mild corrosive environments.
- Environmental & Water Treatment: Wastewater treatment plant components, desalination equipment, and atmospheric corrosion-exposed structural tubing in coastal regions.
- Automotive & Heat Exchanger Manufacturing: Radiator tubing, condenser tubes, and evaporator coils requiring corrosion resistance in coolant and refrigerant service.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certification framework to assure international market compliance:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control throughout the manufacturing lifecycle.
- ISO 14001 — Environmental Management System certification demonstrating commitment to environmentally responsible manufacturing practices.
- ASTM A213 Compliance — Product specifications conform to ASTM A213 standard for austenitic stainless steel seamless and welded tubes.
- EN 10216-5 Compliance — European standard conformity for austenitic stainless steel tubes for pressure purposes.
- Mill Test Certificate (MTC / EN 10204 3.1) — Full chemical composition and mechanical property documentation provided with each shipment.
- NACE MR0175 / ISO 15156 — Available upon request for applications requiring resistance to sulfide stress cracking in sour service environments.
- Third-Party Inspection — Products are available for third-party quality assurance inspection by recognized bodies (e.g., SGS, Bureau Veritas, DNV) at the manufacturer's facility.
Unique Selling Points
- Enhanced Chloride Resistance: The 2–3% Molybdenum addition provides a Pitting Resistance Equivalent Number (PREN) of 24–26, offering approximately 25–30% greater pitting resistance than standard 304 grade in chloride environments.
- Coil Configuration Advantage: Continuous coil supply eliminates butt welds present in straight-length pipe, reducing potential corrosion initiation sites and improving production efficiency for downstream fabricators.
- Full Austenitic Structure: Non-magnetic, fully ductile microstructure suitable for cold forming, deep drawing, and seamless integration into complex geometries.
- Broad Temperature Envelope: Maintains mechanical integrity from cryogenic temperatures up to 870–1100°C continuous service, with no ductile-to-brittle transition.
- Cost-Effective Alternative: Provides the corrosion performance required for many aggressive service environments at a lower cost point than super-austenitic grades (e.g., 6Mo, 904L, or duplex alloys), making it the optimal balance of performance and economics for conventional applications.