Stainless Steel Coil Tube — Theoretical Weight Settlement with Agreed Tolerance (理计+磅差约定)
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司) manufactures and supplies precision stainless steel coil tubes (盘管, Coil Tube) engineered for industrial piping, heat exchanger assemblies, and fluid transport systems. This product line is distinguished by its Theoretical Weight Settlement with Agreed Tolerance pricing methodology (理计+磅差约定), which establishes a transparent, efficient, and equitable commercial framework that balances operational simplicity with contractual fairness for both suppliers and purchasers.
The coil tube product itself is produced from high-grade austenitic and duplex stainless steel alloys, wound into continuous coils for downstream processing including straightening, cutting, welding, and forming. The pricing model ensures that settlement is primarily based on theoretical weight (理论重量, calculated from cross-sectional dimensions and length), while incorporating a mutually agreed allowable deviation tolerance (允许偏差范围) to account for manufacturing variances.
Material & Properties
Stainless steel coil tubes offered under this product line are fabricated from premium-grade stainless steel grades compliant with international standards including ASTM (American Society for Testing and Materials), EN (European Norms), JIS (Japanese Industrial Standards), and GB/T (Chinese National Standards).
- Common Grades: 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 310S (UNS S31008), 904L (UNS N08904), Duplex 2205 (UNS S31803), Duplex 2507 (UNS S32750)
- Alloy Composition: Typically 18–25% Chromium (Cr), 8–22% Nickel (Ni), with trace amounts of Molybdenum (Mo), Titanium (Ti), Niobium (Nb), and Nitrogen (N) depending on grade
- Mechanical Properties: Tensile strength ranging from 515 MPa to 950 MPa; Yield strength from 205 MPa to 550 MPa; Elongation ≥ 40% (annealed condition)
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular corrosion in aggressive chemical, marine, and food-grade environments
- Temperature Range: Operational from cryogenic temperatures (−196°C / −320°F) up to 870°C (1598°F) for standard austenitic grades
- Surface Finish: Available in 2B (bright annealed), No. 4 (brushed), BA (bright annealed), and custom finishes with surface roughness Ra ≤ 0.4 μm
Specifications
The following table summarizes the dimensional and pricing specifications for the stainless steel coil tube product line:
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ3.0 mm – Φ50.8 mm (1/8" – 2") | ASTM A213 / A269 |
| Wall Thickness (WT) | 0.25 mm – 3.00 mm | ASTM A213 / A269 |
| Coil Inner Diameter (ID) | Φ100 mm – Φ400 mm | Manufacturer Specification |
| Coil Length per Piece | 50 m – 200 m (typical) | Customizable |
| Dimensional Tolerance | OD: ±0.05 mm to ±0.15 mm; WT: ±10% | ASTM A269 / EN 10216 |
| Settlement Method | Theoretical Weight (理计) with Agreed Tolerance (磅差约定) | Contractual Agreement |
| Allowable Weight Deviation | ±0.5% to ±1.5% (negotiable per order) | Contractual Agreement |
| Over-Tolerance Adjustment | Settled at Actual Weighed Weight (实重结算) | Contractual Agreement |
| Heat Treatment | Annealed (Solution Treated) + Pickled & Passivated | ASTM A213 |
| End Condition | Beveled, Flat, or Custom | Per Customer Requirement |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Inspection: Ingot or strip stock sourced from certified mills undergoes incoming inspection for chemical composition (via OES — Optical Emission Spectroscopy), mechanical properties, and surface quality.
- Hot Rolling / Cold Forming: Steel strip is fed through precision roll-forming dies to create the tubular geometry. Cold drawing is employed for thin-wall applications requiring tight tolerances.
- Welding (for welded tube): GTAW (Gas Tungsten Arc Welding) or SAW (Submerged Arc Welding) processes create the longitudinal weld seam, with internal gas shielding to prevent oxidation.
- Heat Treatment: Solution annealing at 1050°C–1150°C followed by controlled cooling restores full austenitic microstructure and eliminates residual stresses.
- Pickling & Passivation: Acid pickling removes oxide scale; subsequent passivation forms a protective chromium oxide film for enhanced corrosion resistance.
- Precision Coiling: Tubes are wound onto coils using automated coiling heads that control coil diameter, layer stacking, and end alignment to minimize handling damage.
- Quality Control & Testing: Each coil undergoes ED (Electromagnetic) testing for seam integrity, dimensional gauging, hydrostatic pressure testing, and surface inspection.
- Theoretical Weight Calculation & Tagging: Theoretical weight is computed from verified dimensions (OD × WT × Length × Density). Coils are tagged with calculated weight, actual weighed weight, and deviation percentage for settlement purposes.
- Packaging & Dispatch: Coils are wrapped in protective film, banded, and palletized for shipment with full documentation including MTC (Mill Test Certificate) and weight reconciliation reports.
Applications
Stainless steel coil tubes are utilized across a broad spectrum of industrial and commercial applications:
- Heat Exchangers & Boilers: Coil tubes serve as efficient heat transfer elements in condensers, evaporators, and radiators due to their high thermal conductivity and corrosion resistance.
- Food & Pharmaceutical Processing: Used in hygienic piping systems for beverage, dairy, and pharmaceutical production lines where sanitary standards (EHEDG — European Hygienic Engineering Design Group) are required.
- Chemical & Petrochemical Industry: Resistant to aggressive chemicals, acids, and alkalis in process piping, reactor internals, and distillation columns.
- Marine & Offshore Engineering: Deployed in shipbuilding, offshore platforms, and desalination systems where chloride-induced corrosion is a concern.
- Automotive & Aerospace: Used in exhaust systems, fuel lines, and hydraulic circuits requiring high-temperature and fatigue resistance.
- Medical Equipment: Employed in MRI machines, autoclaves, and surgical instrument manufacturing due to biocompatibility and weldability.
- Construction & Architectural: Structural tubing for handrails, decorative elements, and load-bearing components in high-rise and coastal construction.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system with the following certifications and compliance frameworks:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System Certification
- NADCAP (National Aerospace and Defense Contractors Accreditation Program) — for aerospace-grade product lines
- EN 10204 3.1 — Third-Party Inspection Certificate availability
- CE Marking — Compliance with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU)
- TÜV / SGS / BV — Third-party inspection and verification services available upon request
Unique Selling Points — Theoretical Weight Settlement with Agreed Tolerance (理计+磅差约定)
The pricing and settlement methodology employed for this product line represents a significant commercial advantage that distinguishes Wenzhou Jixing Metal Materials Co., Ltd. from competitors:
- Operational Efficiency: By settling on theoretical weight (calculated from precise dimensional measurements), the need for weighing every individual coil at the time of transaction is eliminated, streamlining logistics, reducing handling time, and accelerating order fulfillment cycles.
- Fairness & Transparency: The agreed tolerance band (typically ±0.5% to ±1.5%) provides a fair margin that accommodates normal manufacturing variation. If the actual weighed weight exceeds the agreed deviation, settlement is automatically adjusted to the actual weight (实重结算), ensuring that the purchaser is never disadvantaged by systematic over-delivery or under-delivery.
- Reduced Disputes: The pre-agreed tolerance framework minimizes post-delivery weight reconciliation disputes, as both parties have a clear, contractually defined mechanism for weight verification and adjustment.
- Cost Predictability: Theoretical weight is directly derivable from order specifications (OD, wall thickness, length, and alloy density), enabling purchasers to accurately forecast costs at the quotation stage without waiting for physical delivery and weighing.
- Traceability: Each coil is accompanied by a weight reconciliation document showing theoretical weight, actual weighed weight, deviation percentage, and settlement weight — providing full audit trail for quality and financial compliance.
- Industry-Aligned Practice: This methodology aligns with established international trade practices for metallic products (referencing ISO 4035 — Steel — Determination of mass per unit length), ensuring compatibility with global procurement standards.
Settlement Formula: If |Actual Weight − Theoretical Weight| / Theoretical Weight ≤ Agreed Tolerance, then Settlement Weight = Theoretical Weight. If deviation exceeds the agreed tolerance, Settlement Weight = Actual Weighed Weight (实重). This dual-condition approach guarantees efficiency within tolerance and fairness beyond tolerance.
This combination of premium material quality, precision manufacturing, comprehensive certification, and a commercially intelligent pricing framework makes Wenzhou Jixing Metal Materials Co., Ltd.'s stainless steel coil tube product a trusted choice for demanding industrial procurement applications worldwide.