Stainless Steel Coil Tube with Verified 180° Mandrel Bend Performance

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. supplies high-grade stainless steel coil tubes engineered for superior formability and dimensional consistency. These coil tubes are specifically qualified through rigorous processability testing, including a critical 180° mandrel bend test, ensuring that the material maintains structural integrity under complex forming operations. The coil tube format provides cost-efficient, continuous-length supply ideal for automated manufacturing lines and high-volume production environments.

This product line represents a benchmark in stainless steel tube processability, where each batch undergoes verified bend testing to confirm that the outer surface remains free of cracks and the inner surface exhibits no significant wrinkling after 180° mandrel bending. This foundational verification ensures reliable downstream fabrication performance across diverse industrial applications.

Material & Properties

Material Grades

• 304 / 304L (UNS S30400 / S30403) — General-purpose austenitic stainless steel offering excellent corrosion resistance and formability
• 316 / 316L (UNS S31600 / S31603) — Enhanced corrosion resistance with molybdenum alloying for aggressive environments
• 321 (UNS S32100) — Stabilized grade with titanium addition for high-temperature applications
• 201 (UNS S20100) — Economical austenitic grade for non-corrosive applications

Key Mechanical Properties

• Tensile Strength: ≥ 520 MPa (≥ 75,400 psi) — Grade 304 annealed condition
• Yield Strength: ≥ 205 MPa (≥ 29,700 psi)
• Elongation: ≥ 40% (minimum) in standard gauge lengths
• Hardness: ≤ 95 HRB (annealed condition)
• Bend Performance: 180° mandrel bend with no external cracking and no significant internal wrinkling

Physical Properties

• Density: 7.93 g/cm³ (49.5 lb/ft³)
• Thermal Conductivity: 16.3 W/(m·K) at 100°C
• Thermal Expansion: 17.3 μm/(m·°C) (20–100°C)
• Maximum Service Temperature: 870°C (1,598°F) — Grade 304

Specifications

Parameter	Specification	Standard
Outer Diameter (OD)	6.0 mm – 108.0 mm (0.236" – 4.252")	ASTM A213 / ASME SA-213
Wall Thickness	0.5 mm – 6.0 mm (0.020" – 0.236")	ASTM A213 / ASME SA-213
Coil Length	10 m – 100 m (33 ft – 328 ft) per coil	Manufacturer standard
OD Tolerance	±0.05 mm – ±0.25 mm (±0.002" – ±0.010")	ASTM A213
Wall Thickness Tolerance	±10% of nominal	ASTM A213
Surface Finish	No. 1 / 2B / BA / Pickled & Passivated	ASTM A480
Bend Test	180° around mandrel — No cracks externally, no significant wrinkles internally	ASTM A213 / GB/T 12771
Delivery Condition	Annealed (Solution Treated)	ASTM A213
Welding Method	ERW (Electric Resistance Welded) / Seamless	ASTM A213 / ASME SA-213
Coil Packaging	Wooden pallet / Steel drum with moisture barrier	ISO 11607

Manufacturing Process

Production Workflow

1. Raw Material Selection: Virgin stainless steel strip or wire is sourced from certified mills, with chemical composition verified through spectrometric analysis (OES) to ensure conformance with ASTM and EN specifications.
2. Coiling & Straightening: The raw stock is coiled to precise dimensions and straightened to achieve flatness tolerances critical for uniform tube forming.
3. Forming & Welding: The strip is fed through precision roll-forming dies and welded via ERW (Electric Resistance Welding) or produced via seamless piercing methods, depending on the specified grade and dimensions.
4. Sizing: The formed tube passes through calibrated sizing rolls to achieve tight dimensional tolerances on both OD and wall thickness.
5. Heat Treatment (Solution Annealing): Tubes are annealed at 1050°C – 1150°C (1,922°F – 2,092°F) followed by controlled cooling to restore full austenitic structure and maximize ductility for subsequent forming operations.
6. Pickling & Passivation: Surface scale is removed through pickling, and a protective chromium oxide passive layer is established to ensure optimal corrosion resistance.
7. Processability Verification (Mandrel Bend Test): Representative samples from each production lot undergo 180° bending around a mandrel of specified radius. Acceptance criteria: no cracks on the outer surface and no significant wrinkles on the inner surface. This test serves as the foundational verification of tube bending processability.
8. Final Inspection & Coiling: Qualified tubes are cut to coil length, inspected for surface defects, and wound onto protective cores for shipment.

Key Process Advantages

• Continuous production methodology enables consistent quality across full coil lengths
• Online dimensional monitoring ensures real-time control of OD and wall thickness
• Post-annealing hardness verification confirms material readiness for bending, deep drawing, and other forming operations

Applications

Primary Application Sectors

• Automotive Industry: Fuel lines, brake lines, exhaust systems, and air conditioning tubing requiring reliable bend forming without cracking
• Medical Devices: Endoscopic instruments, surgical tubing, and diagnostic equipment components demanding high cleanliness and formability
• Food & Beverage Processing: Sanitary piping, conveyor systems, and equipment frames requiring corrosion resistance and easy fabrication
• Appliance Manufacturing: Refrigerator tubing, washing machine components, and dishwasher assemblies requiring repeated bending operations
• Architectural & Construction: Handrails, decorative elements, and structural components requiring both aesthetic finish and mechanical performance
• Chemical Processing: Process piping, heat exchangers, and reactor components where corrosion resistance and weldability are paramount
• Furniture & Interior Design: Tubular furniture frames, shelving systems, and architectural features requiring complex bending geometries

Why Bend Performance Matters in These Applications

The verified 180° mandrel bend capability ensures that coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. can be formed into complex geometries — including tight-radius bends, multi-directional curves, and intricate configurations — without material failure. This eliminates costly production stoppages, reduces scrap rates, and enables designers to realize sophisticated product architectures without compromising structural reliability.

Quality Certifications

System & Product Certifications

• ISO 9001:2015 — Quality Management System certification ensuring consistent process control and continuous improvement
• ISO 14001:2015 — Environmental Management System for sustainable manufacturing practices
• ISO 45001:2018 — Occupational Health and Safety Management System
• CE Marking — Conformity with European health, safety, and environmental protection standards
• EN 10204 3.1 Certificate — Mill test certificates with inspection reports for each production batch

Testing & Inspection Standards

• Bend Test: ASTM A213 / GB/T 12771 — 180° mandrel bend verification per lot
• Hydrostatic Test: ASTM A213 — Pressure testing at 1.5× working pressure
• Chemical Analysis: ASTM E1/E4 — Spectrometric and wet chemical analysis
• Mechanical Testing: ASTM A370 — Tensile, hardness, and elongation testing
• Surface Inspection: Visual and magnetic particle testing per ASTM E709
• Dimensional Verification: CMM and laser micrometry per ASTM E29

Traceability & Documentation

• Full heat-number traceability from raw material through final delivery
• Digital inspection records available upon request
• Custom test protocols available for OEM and specification-driven customers

Unique Selling Points

• Verified Bend Processability: Every production lot undergoes 180° mandrel bend testing, providing documented proof of superior formability — reducing customer-side scrap and rework
• Coil Efficiency: Continuous coil format eliminates butt-weld joints, maximizes material utilization, and integrates seamlessly with automated tube processing lines
• Tight Dimensional Control: Precision sizing ensures consistent OD and wall thickness, enabling predictable bending behavior and reliable fit-up in assemblies
• Multi-Grade Availability: Comprehensive range of 304, 304L, 316, 316L, 321, and 201 grades from a single supplier
• End-to-End Quality Assurance: From raw material spectrometric analysis through final bend verification, every quality gate is documented and traceable
• Cost-Effective Supply: Coil format reduces handling costs, minimizes waste, and lowers per-unit pricing compared to cut-length alternatives

Technical Support & Ordering

Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including material selection guidance, forming process consultation, and custom specification development. Customers may request sample coils for pre-production evaluation, including verification of bend performance under specific mandrel radii and bend angles tailored to their manufacturing requirements.

For quotations, technical datasheets, or sample requests, contact the sales engineering team with your required grade, OD, wall thickness, surface finish, and estimated annual volume to receive a tailored supply proposal.