Stainless Steel Coil Tube — Theoretical Weight Settlement with Tolerance Agreement (Coiltube Pricing Specification)
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) offered by Wenzhou Jixing Metal Materials Co., Ltd. is a continuous-length tubular product supplied in coiled form, designed for high-volume industrial and commercial applications. This product is procured under a Theoretical Weight Settlement with Tolerance Agreement (理计+磅差约定) pricing model, which represents a hybrid approach to trade settlement that balances operational efficiency with commercial fairness.
Under this settlement framework, the transaction is calculated based on the Theoretical Weight (Theoretical Weight, derived from the product's dimensional specifications and material density) rather than actual weighed mass. However, a mutually agreed Allowable Tolerance Range (磅差允许偏差范围) is established between the buyer and seller. If the actual weighed weight deviates beyond this tolerance threshold, the settlement is adjusted to reflect the Actual Weight (实重), ensuring equitable compensation for both parties.
Key Principle: Theoretical Weight Settlement with Tolerance Agreement — efficiency through standardized calculation, fairness through deviation-triggered adjustment.
2. Material & Properties
2.1 Common Grades
- Austenitic Stainless Steels: SUS304 (UNS S30400), SUS304L (UNS S30403), SUS316 (UNS S31600), SUS316L (UNS S31603), SUS321 (UNS S32100), SUS310S (UNS S31008)
- Duplex Stainless Steels: SUS31803 (UNS S31803), SUS32205 (UNS S32205)
- Other Grades: SUS201, SUS430, SUS409, and custom alloy compositions upon request
2.2 Mechanical Properties (Typical for SUS304)
- Tensile Strength: ≥ 520 MPa (75,400 psi)
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40%
- Density: 7.93 g/cm³ (used for theoretical weight calculation)
- Operating Temperature Range: −196 °C to +870 °C (in oxidizing atmospheres)
2.3 Corrosion Resistance
- Excellent resistance to atmospheric corrosion, mild acids, and organic compounds
- SUS316 variants offer superior resistance to pitting and crevice corrosion due to molybdenum (Mo) addition (2–3%)
- Non-magnetic in annealed condition (austenitic grades)
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 219.1 mm (1/8" – 8") | ASTM A554 / A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.3 mm – 6.0 mm | ASTM A554 / GB/T 12771 |
| Coil Length | Continuous (typically 100 m – 500 m per coil) | Manufacturer standard |
| Coil Weight (per coil) | 500 kg – 3,000 kg (typical) | Logistics-dependent |
| Surface Finish | BA (Bright Annealed), No.1 Pickled, 2B, 2D, Custom | ASTM A478 |
| End Condition | Plain end, Beveled end, Threaded (upon request) | — |
3.2 Pricing & Settlement Specification (Theoretical Weight + Tolerance Agreement)
| Settlement Parameter | Description | Typical Value |
|---|---|---|
| Settlement Basis | Theoretical Weight (理计) | Calculated from OD × WT × Length × Density |
| Allowable Tolerance (磅差) | Permitted deviation between theoretical and actual weight | ±0.5% to ±3% (negotiable, grade-dependent) |
| Within Tolerance | Settlement at theoretical weight — no adjustment | Actual weight within ±tolerance → billed at theoretical |
| Beyond Tolerance (Excess) | Settlement adjusted to actual weight (按实重调整) | Buyer pays for actual overage above tolerance |
| Beyond Tolerance (Shortage) | Settlement adjusted to actual weight (按实重调整) | Seller credits shortfall below tolerance |
| Verification Method | Third-party weighing at delivery or designated weighbridge | Sealed container / calibrated scale |
3.3 Theoretical Weight Calculation Formula
The theoretical weight per unit length is calculated as:
W = π × (D − t) × t × ρ
- W = Weight per meter (kg/m)
- D = Outer Diameter (mm)
- t = Wall Thickness (mm)
- ρ = Material Density (kg/mm³); for stainless steel ≈ 7.93 × 10⁻⁶ kg/mm³
4. Manufacturing Process
4.1 Production Flow
- Raw Material Preparation: Hot-rolled coil (HRC) or cold-rolled coil (CRC) strip of certified stainless steel grade is inspected for chemical composition and mechanical properties.
- Coiling / Forming: The strip is precision-formed into a tubular cross-section using a seamless coil tube mill (e.g., planetary roll or multi-stand forming system), achieving the target OD and wall thickness continuously.
- Welding (if applicable): For welded coil tube, the formed tube is longitudinally welded via TIG (Tungsten Inert Gas) or laser welding, followed by inline heat treatment.
- Heat Treatment / Annealing: Solution annealing (1050–1150 °C) followed by rapid cooling (air or water quench) to achieve the desired microstructure and corrosion resistance.
- Pickling & Passivation: Chemical treatment to remove scale, oxide films, and contaminants; passivation restores the passive chromium oxide layer for optimal corrosion protection.
- Surface Finishing: Mechanical polishing (if required) to achieve specified surface finish (BA, mirror, matte, etc.).
- Dimensional Inspection: Inline and offline measurement of OD, wall thickness, roundness, and straightness.
- Coiling & Packing: The finished tube is coiled at controlled tension, wrapped in protective film, and packed for shipment.
4.2 Quality Control Points
- Spectroscopic analysis (OES) for chemical composition verification at each heat
- Hydrostatic testing (per ASTM A530) to verify weld integrity and wall soundness
- Dimensional tolerance inspection per ASTM A554 (for seamless) or ASTM A795 (for welded)
- Surface quality inspection under controlled lighting conditions
- Final weighing at the shipping dock for settlement verification
5. Applications
- Automotive Industry: Exhaust systems, fuel lines, structural tubing for lightweight vehicle frames
- Petrochemical & Oil/Gas: Process piping, heat exchanger tubes, subsea flow lines
- Food & Beverage Processing: Hygienic piping, brewing equipment, dairy processing lines
- Medical Devices: Surgical instrument tubing, implant-grade components
- Architectural & Construction: Balustrades, structural supports, decorative cladding
- Electronics & Appliances: Heat exchangers, condenser tubes, gas appliance burners
- Energy Sector: Solar thermal absorber tubes, geothermal piping, nuclear-grade components
6. Quality Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management
- EN 10204 — Type 3.1 Material Test Certificates (MTC) available per shipment
- Mill Test Reports (MTR): Provided for every heat, including chemical analysis, mechanical test results, and dimensional compliance data
- Third-Party Inspection: Available upon request (SGS, BV, TUV, or equivalent)
- Material Traceability: Full heat number traceability from raw material to finished product
7. Unique Selling Points
- Efficient Settlement Mechanism: The theoretical weight basis eliminates the need for weighing every individual coil during normal operations, streamlining logistics and reducing administrative overhead while maintaining trade integrity through the tolerance safeguard.
- Fairness Assurance: The tolerance-agreement mechanism (磅差约定) ensures that significant deviations—whether overage or shortage—are compensated at actual weight, protecting both buyer and seller from asymmetric risk.
- High-Volume Supply Capability: Continuous coil format enables high throughput for downstream processing (cut-to-length, bending, stamping), minimizing material waste and production downtime.
- Customizable Specifications: Wide range of grades, dimensions, and surface finishes available to meet specific project requirements.
- Full Traceability & Certification: Every coil is backed by complete documentation, enabling compliance with the most stringent regulatory and quality standards.
- Competitive Pricing: Theoretical weight settlement typically results in more predictable and competitive pricing compared to strict actual-weight billing, particularly beneficial for large-scale procurement.
8. Order & Delivery Notes
- Minimum Order Quantity (MOQ): Negotiable; typically 1 metric ton or 1 coil (whichever is greater)
- Lead Time: 15–30 days from order confirmation (stock items available for immediate shipment)
- Packaging: Protective PE film wrapping, steel strapping, wooden pallet or bulk coil packaging; seaworthy packing available for export
- Settlement Clause (Standard): "Settlement shall be based on theoretical weight calculated from nominal dimensions and applicable material density. An allowable tolerance of ±[__]% shall be agreed upon. Should the actual weight deviate beyond this tolerance, settlement shall be adjusted to actual weighed weight."
- Dispute Resolution: In case of weight discrepancy disputes, a mutually agreed third-party weighbridge or inspection agency shall serve as the final arbiter.
Wenzhou Jixing Metal Materials Co., Ltd. — Delivering precision-engineered stainless steel coil tube solutions with transparent, efficient, and fair commercial practices that serve industrial partners worldwide.