90° Flange Beading Test Specification for Stainless Steel Coil Tubes
1. Product Overview
The 90° Flange Beading Test (Flanging Test at 90 Degrees) is a critical mechanical performance inspection applied to stainless steel coil tubes manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This test evaluates the end-face ductility and edge quality of the tube by forming a 90° flange bead at the tube end, thereby verifying the material's suitability for flange beading connection processes. As a fundamental quality assurance procedure within the coil tube production line, this inspection ensures that each tube can withstand downstream forming operations without cracking, splitting, or excessive deformation.
The flanging test is classified under Process Performance Inspection (工艺性能检测) and serves as a definitive indicator of the tube's formability, microstructural integrity, and surface condition at the tube end — a region particularly susceptible to residual stresses from coiling, cutting, and heat treatment operations.
2. Material & Properties
2.1 Applicable Materials
- Austenitic Stainless Steels: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100), AISI 310S (UNS S31008)
- Super-Austenitic Grades: AISI 904L (UNS N08904), Alloy 2200 (UNS N082202)
- Duplex Stainless Steels: AISI 2205 (UNS S32205), AISI 2507 (UNS S32750)
- Other Alloy Systems: Custom compositions as specified by the end-user
2.2 Key Mechanical Properties Evaluated
- Ductility (Elongation): Ability of the tube end material to undergo plastic deformation without fracture during 90° flange forming
- Strain Hardening Capacity: Resistance to localized necking during the beading process
- Edge Quality: Freedom from cracks, splits, laps, or surface imperfections at the formed flange perimeter
- Formability Index: Correlation between the successful 90° flange formation and the material's overall forming potential
2.3 Chemical Composition Requirements
| Element | Grade 304 | Grade 316L | Grade 2205 |
|---|---|---|---|
| C (Carbon) | ≤ 0.08% | ≤ 0.03% | ≤ 0.03% |
| Cr (Chromium) | 18.0–20.0% | 16.0–18.0% | 22.0–23.0% |
| Ni (Nickel) | 8.0–10.5% | 10.0–14.0% | 4.5–6.5% |
| Mn (Manganese) | ≤ 2.0% | ≤ 2.0% | ≤ 2.0% |
| Mo (Molybdenum) | — | 2.0–3.0% | 3.0–3.5% |
| N (Nitrogen) | — | — | 0.14–0.20% |
| Si (Silicon) | ≤ 1.0% | ≤ 1.0% | ≤ 1.0% |
3. Test Specifications
3.1 Test Parameters
| Parameter | Specification | Reference Standard |
|---|---|---|
| Flange Angle | 90° (±2° tolerance) | ASTM A213 / GB/T 12771 |
| Test Method | End-face rolling/flanging using a calibrated mandrel or beading tool | ASTM E140 / GB/T 14976 |
| Acceptance Criteria | No cracks, splits, or visible surface defects on the formed flange | Manufacturer Specification |
| Sample Preparation | Tubes cut to test length; ends cleaned and free of burrs | — |
| Testing Temperature | Ambient (room temperature, 18°C–28°C) | — |
| Sampling Frequency | Per heat lot or per shift batch (minimum 3 samples per lot) | — |
3.2 Coil Tube Dimensional Specifications
| Specification | Range |
|---|---|
| Outer Diameter (OD) | 6 mm – 168 mm |
| Wall Thickness | 0.5 mm – 12.0 mm |
| Coil Inner Diameter | 102 mm – 305 mm (4" – 12") |
| Coil Length | Up to 200 m (custom lengths available) |
| Surface Finish | 2B, BA, No.1 Pickled & Oiled, Custom Polished |
| Weld Seam Type | Continuous Welded (ERW/ODW/IDW) or Seamless |
4. Manufacturing Process
4.1 Production Workflow
- Coil Uncoiling & Straightening: Stainless steel strip or coil is uncoiled and fed through a straightening line to achieve the required flatness tolerance.
- Forming & Welding: The flat strip is roll-formed into a tubular shape. For welded tubes, an automated resistance or orbital welding process is applied; for seamless tubes, hot/cold rolling methods are used.
- Heat Treatment: Solution annealing (1050°C–1150°C) followed by rapid quenching to restore full austenitic structure and maximize ductility.
- Pickling & Passivation: Acid pickling removes oxide scale; passivation forms a protective chromium oxide film on the surface.
- Coiling: The finished tube is wound into coils of the specified diameter for shipment.
- End Processing: Tube ends are cut and prepared for the 90° flange beading inspection.
4.2 Flange Beading Test Procedure
- Sample Selection: Extract representative samples from each production lot at defined intervals along the coil length.
- End Preparation: Cut tube ends square; remove burrs and cutting marks using abrasive or mechanical methods.
- Fixture Setup: Mount the tube sample on a calibrated flanging/beading fixture with the mandrel positioned for 90° deformation.
- Forming Operation: Apply controlled force to roll the tube end outward to a 90° angle, forming a complete flange bead around the tube circumference.
- Visual & Dimensional Inspection: Examine the formed flange for cracks, splits, folds, or surface irregularities under magnification (minimum 10×). Measure the flange angle for conformance to the 90° specification.
- Documentation: Record results including pass/fail status, any observed defects, and sample identification for traceability.
4.3 Process Control Points
- Residual Stress Management: Coiling and straightening introduce residual stresses that may compromise end-face ductility; controlled tension levels during coiling minimize this risk.
- Grain Size Control: Solution annealing parameters are optimized to achieve fine, uniform grain structure (ASTM Grain Size 5–8) for superior formability.
- Surface Condition: Surface roughness (Ra ≤ 0.4 μm for BA finish) is maintained to prevent stress concentration initiation sites during flanging.
5. Applications
5.1 Primary Application Areas
- Piping System Connections: Tubes passing the 90° flange beading test are qualified for use in flanged, beaded, or rolled-end connections in process piping systems.
- Heat Exchanger Fabrication: Coil tubes used in shell-and-tube heat exchangers require verified end-formability for tube sheet attachment.
- Automotive Exhaust Systems: Stainless steel coil tubes for exhaust manifolds and catalytic converter housings where beaded joints are employed.
- Food & Pharmaceutical Equipment: Sanitary process piping requiring flanged connections with verified material integrity at the joint.
- Construction & Architecture: Structural and decorative stainless steel tube applications where end-forming is part of assembly.
- Chemical Processing: Corrosive service piping systems utilizing flange beading connections for leak-tight joints.
5.2 Why the 90° Flange Beading Test Matters
The 90° flange beading test is a direct simulation of the most demanding end-forming operation encountered in tube assembly. A tube that passes this test at room temperature demonstrates sufficient ductility, edge quality, and microstructural soundness to perform reliably in all less-severe forming applications. It is the definitive quality gate for flange-connection-compatible stainless steel coil tubes.
6. Quality Certifications & Compliance
6.1 Applicable Standards
| Standard | Description |
|---|---|
| ASTM A213 / A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| ASTM A554 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Heat Exchangers |
| ASTM E140 | Standard Practice for Visual Reference Methods for Examination of Welds |
| GB/T 12771 | Stainless Steel Tubes for Fluid Transport (Chinese National Standard) |
| GB/T 14976 | Heat Exchanger and Condenser Tubes (Chinese National Standard) |
| EN 10216-5 | Non-alloy, Heat Resistant and Stainless Steel Tubes for Technical Use |
| ISO 3506 | Stainless Steel Bars, Rods and Sections |
6.2 Quality Management System Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — European Conformity for pressure equipment (PED 2014/68/EU)
- ASME — American Society of Mechanical Engineers stamp (where applicable)
- Mill Test Certificates (MTC) — EN 10204 Type 3.1 for each shipment
6.3 Testing & Inspection Protocols
- Hydrostatic Testing: All tubes hydro-tested at 2–4× working pressure per ASTM A213 requirements.
- Chemical Analysis: Spectrometric verification of chemical composition per lot.
- Microstructural Examination: Grain size and phase composition verification via optical microscopy.
- Mechanical Testing: Tensile strength, yield strength, and elongation per ASTM A370.
- Flange Beading Test: 90° end flanging inspection as described herein, performed per production lot.
- Surface Inspection: Visual and magnetic particle inspection (MPI) for surface defects.
7. Unique Selling Points
- Guaranteed Formability: Every coil tube lot undergoes 90° flange beading verification, ensuring zero cracking or splitting at tube ends — a critical differentiator for applications requiring rolled-end or flanged connections.
- Full Traceability: Each coil is accompanied by a comprehensive Mill Test Certificate documenting flanging test results, chemical analysis, and mechanical properties for complete supply chain traceability.
- Wide Grade Availability: From standard 304/316L to super-austenitic and duplex grades, all materials are qualified through the same rigorous flanging inspection protocol.
- Process-Verified Quality: The 90° flange beading test directly simulates real-world connection fabrication, providing end-users with confidence that purchased tubes will perform in actual assembly conditions.
- Custom Specifications: Wenzhou Jixing Metal Materials offers tailored coil dimensions, surface finishes, and test protocols to meet specific customer application requirements.
8. Conclusion
The 90° Flange Beading Test represents the most stringent and application-relevant formability assessment for stainless steel coil tubes. By ensuring that tube ends can be formed to a full 90° angle without any cracking, splitting, or surface degradation, Wenzhou Jixing Metal Materials Co., Ltd. provides customers with a verifiable guarantee of end-face ductility and edge quality. This inspection is not merely a quality check — it is a process capability validation that directly correlates to the tube's performance in flanged connection fabrication, making it an indispensable element of the company's quality assurance framework.