Stainless Steel Coil Tube — Elongation (A%) Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for a wide range of industrial applications. The product is supplied in continuous coil form, enabling efficient downstream processing including straightening, cutting, bending, and forming. A critical metallurgical property governing the formability and structural reliability of this coil tube is the Elongation (A%) — a quantitative measure of the material's capacity for plastic deformation prior to fracture under uniaxial tensile loading.
2. Material & Properties
Stainless steel coil tubes are produced from austenitic and austenitic-ferritic (duplex) stainless steel grades conforming to international standards such as ASTM A554 (Standard Specification for Stainless Steel Tubular Products for General Application), EN 10217, and GB/T 12771. The base alloy chemistry typically includes chromium (Cr ≥ 17–25%), nickel (Ni ≥ 8–22%), and controlled levels of carbon (C ≤ 0.03%–0.10%), manganese (Mn), silicon (Si), and other trace elements to ensure optimal corrosion resistance, weldability, and mechanical integrity.
The Elongation at Break (A%) is defined as the percentage increase in gauge length of a standard tensile specimen between the original gauge length and the length at fracture, as determined per ASTM E8/E8M or ISO 6892-1. This property is a direct indicator of the material's plastic deformation capability — its ability to undergo permanent shape change without cracking or failure. Higher elongation values correlate with superior formability, which is essential for applications requiring deep drawing, cold bending, or complex geometric shaping.
3. Specifications
| Parameter | Specification | Test Standard |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Material Classification | Materials & Metallurgy — Metallurgical Indicators — Mechanical Properties | — |
| Key Property | Elongation at Break (A%) — Plastic Deformation Capability Indicator | ASTM E8/E8M; ISO 6892-1; GB/T 228.1 |
| Eligible Grades | 304, 304L, 316, 316L, 321, 310S, 430, 904L, 2205 (Duplex) | ASTM A554; EN 10217-1 |
| Supply Form | Continuous Coil (Coiltube) | — |
3.1 Elongation (A%) Requirements by Temper Condition
| Temper Condition | Designation | Minimum Elongation (A%) | Typical Application Context |
|---|---|---|---|
| Soft (Annealed) | Soft / SA | ≥ 40% | Deep drawing, cold forming, complex bending |
| Half-Hard | Half-Hard / Y2 | ≥ 25% | Moderate forming with enhanced spring-back resistance |
| Hard (Cold Worked) | Hard / Y3 | ≥ 15% | High-strength structural applications with limited forming |
3.2 Typical Dimensional Ranges
| Parameter | Range |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (customizable) |
| Wall Thickness | 0.15 mm – 2.0 mm |
| Coil Inner Diameter (ID) | 100 mm – 500 mm |
| Coil Length | Custom per order (typically 1,000 – 10,000 m) |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous, multi-stage process chain designed to ensure dimensional precision, metallurgical homogeneity, and controlled mechanical properties:
- Slitting & Leveling: Cold-rolled stainless steel strip is slit to the required width and leveled to eliminate coil set and ensure flatness within tolerance.
- Forming & Welding: The leveled strip is fed through a series of progressively reducing rolls in a cold-forming machine, which shapes the flat strip into a tube. A continuous TIG (Tungsten Inert Gas) welding process, typically using a high-purity argon shielding atmosphere, joins the seam. In-line weld inspection ensures seam integrity.
- Heat Treatment (Annealing): For soft temper (SA) coil tubes, the formed tube is subjected to solution annealing at 1050°C – 1150°C followed by controlled cooling (air cooling or pickling and passivation). This recrystallizes the cold-worked microstructure, restoring ductility and achieving elongation values ≥ 40%. For half-hard and hard temper conditions, the degree of cold work is controlled during the forming process to achieve the target mechanical properties without full recrystallization.
- Pickling & Passivation: The annealed tube undergoes acid pickling (typically a mixture of nitric and hydrofluoric acid) to remove the oxide scale, followed by passivation to establish a protective chromium oxide layer on the surface.
- Dimensional Inspection: In-line laser and ultrasonic gauges verify outer diameter, wall thickness, and ovality within specified tolerances (typically ±0.05 mm for OD and ±0.03 mm for wall thickness).
- Coiling & Packaging: The finished coil tube is wound onto a protective core, wrapped in VCI (Vapor Corrosion Inhibitor) paper, and packed in export-grade wooden crates or steel banding for shipment.
5. Applications
The selection of temper condition — and consequently the elongation (A%) value — is dictated by the end-use application requirements:
- Soft Temper (A% ≥ 40%): Ideal for applications requiring extensive cold forming, including automotive exhaust systems, appliance components, heat exchanger tubes, pharmaceutical equipment tubing, and decorative architectural elements where deep drawing and multi-axis bending are required.
- Half-Hard Temper (A% ≥ 25%): Suitable for applications demanding a balance between formability and dimensional stability, such as fuel lines, hydraulic tubing, food processing equipment, and medical device housings.
- Hard Temper (A% ≥ 15%): Employed in high-strength structural applications where minimal forming is required, including spring components, high-pressure fluid conveyance lines, aerospace structural tubing, and wear-resistant applications.
Additional application sectors include the chemical processing industry, oil and gas pipelines, power generation, semiconductor manufacturing, and marine engineering — all of which benefit from the corrosion resistance and mechanical versatility of stainless steel coil tubes.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring traceability and compliance across all production stages:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, inspection, and delivery processes.
- ISO 14001:2015 — Environmental Management System certification ensuring environmentally responsible manufacturing practices.
- EN 10204 3.1 — Material Test Reports (MTR) issued for each batch, documenting chemical composition, mechanical properties (including elongation), heat treatment records, and dimensional inspection data.
- Mill Test Certificates (MTC) — Full traceability from raw material heat number through to finished coil, including third-party laboratory verification where required.
- Compliance with ASTM, EN, and GB Standards — Products are manufactured and tested in accordance with applicable international and Chinese national standards.
7. Unique Selling Points
Controlled Elongation Across Temper Spectrum: The ability to deliver coil tubes with precisely controlled elongation values — ≥ 40% (soft), ≥ 25% (half-hard), and ≥ 15% (hard) — provides engineering flexibility unmatched by competitors limited to a single temper condition. This enables downstream fabricators to select the optimal mechanical property profile for their specific forming and performance requirements.
- Full Temper Range Availability: Single-source procurement of soft, half-hard, and hard temper coil tubes from a single manufacturer reduces supply chain complexity and ensures consistent material quality across temper grades.
- High Formability Assurance: Elongation values exceeding 40% in soft temper provide exceptional cold workability, minimizing crack risk during complex multi-step forming operations and reducing scrap rates in downstream manufacturing.
- Metallurgical Traceability: Every coil is accompanied by a full material test report with elongation data verified per ASTM E8/E8M, ensuring complete traceability from raw material through to the finished product.
- Customization Capability: Flexible ordering options for outer diameter, wall thickness, coil length, and temper condition allow tailored solutions for niche industrial applications.
The combination of rigorous metallurgical control, comprehensive testing protocols, and multi-temper product availability positions the Wenzhou Jixing Stainless Steel Coil Tube as a reliable, high-performance solution for demanding industrial applications where plastic deformation capability is a critical design parameter.