Stainless Steel Coil Tube in Quarter Hard (1/4H) Condition
Product Overview
The Quarter Hard (1/4H) Stainless Steel Coil Tube is a precision-engineered cold-worked tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product occupies a critical position in the mechanical property spectrum of stainless steel tubing, delivering an optimal balance between tensile strength and formability. The 1/4H temper is achieved through controlled cold working of annealed (soft) coil tubing, resulting in a material that offers significantly improved strength over the fully annealed condition while retaining excellent bending and deep-drawing capabilities.
Designed for applications that demand moderate strength without sacrificing workability, this coil tube product is supplied in continuous coil form to maximize manufacturing efficiency, minimize material waste, and accommodate high-volume automated processing lines.
Unique Selling Points
- Optimized Strength-to-Formability Ratio: The 1/4H temper provides approximately 25–40% higher yield strength compared to the fully annealed (1/2H or soft) condition while maintaining elongation of ≥30%, making it ideal for forming operations that require both structural integrity and dimensional accuracy.
- Consistent Mechanical Properties: Hardness maintained within a tight range of HV 180–220 ensures uniform performance across the entire coil length, reducing variability in downstream fabrication.
- High Coil Efficiency: Supplied in continuous coil configuration to support automated processing, reduce joint welds, and minimize material waste in high-volume production environments.
- Superior Surface Finish: Cold-working preserves the original surface quality of the base coil, delivering a clean, uniform finish suitable for direct use in food-grade, medical, and decorative applications.
- Multi-Grade Availability: Available in 304, 304L, 316, 316L, 321, 310S, and other common austenitic stainless steel grades to meet diverse corrosion resistance and performance requirements.
Material & Properties
Material Grades
The Quarter Hard coil tube is available in a comprehensive range of austenitic and duplex stainless steel grades, including but not limited to:
- 304 / 304L (UNS S30400 / S30403)
- 316 / 316L (UNS S31600 / S31603)
- 321 (UNS S32100)
- 310S (UNS S31008)
- 2205 Duplex (UNS S32205)
- Custom grades upon request
Mechanical Properties (1/4H Condition)
- Vickers Hardness: HV 180–220
- Elongation at Break: ≥30%
- Yield Strength (Typical, 304 grade): 240–320 MPa (35–46 ksi)
- Tensile Strength (Typical, 304 grade): 520–620 MPa (75–90 ksi)
Chemical Composition (304 Grade Reference)
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| C | — | 0.08 |
| S | — | 0.03 |
| P | — | 0.045 |
| Cr | 18.0 | 20.0 |
| Ni | 8.0 | 10.5 |
| Mn | — | 2.0 |
| Si | — | 1.0 |
| N | — | 0.10 |
Corrosion Resistance
The austenitic stainless steel composition provides excellent resistance to atmospheric corrosion, mild acids, and alkaline solutions. 316/316L grades offer superior resistance to chloride-induced pitting and crevice corrosion due to the presence of 2–3% molybdenum. The cold-worked 1/4H condition does not materially degrade the corrosion performance of the base alloy.
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (Continuous Coil) |
| Mechanical Condition | Quarter Hard (1/4H) — Light Cold Work |
| Outer Diameter | Φ3.0 mm – Φ200.0 mm (Φ0.118" – Φ7.874") |
| Wall Thickness | 0.2 mm – 6.0 mm (0.008" – 0.236") |
| Hardness | HV 180–220 |
| Elongation | ≥30% |
| Coil Inner Diameter | Φ100 mm – Φ300 mm (Φ3.94" – Φ11.81") |
| Coil Outer Diameter | Φ400 mm – Φ1200 mm (Φ15.75" – Φ47.24") |
| Coil Length | 200 m – 5000 m (656 ft – 16,404 ft) per coil |
| Surface Finish | Bright Annealed (BA), 2B, No.4, Hairline, Mirror |
| Manufacturing Method | Seamless (Capillary) or Welded (ERW/AW) |
| Standards | ASTM A511, ASTM A554, EN 10217, GB/T 12771, JIS G3446 |
| End Condition | Plain, Beveled, or Threaded (upon request) |
| Strut Length (Cut Lengths) | Custom cut-to-length available upon request |
Manufacturing Process
The production of Quarter Hard (1/4H) Stainless Steel Coil Tube involves a precisely controlled multi-stage process:
- Raw Material Selection: High-purity stainless steel coil strip is sourced from certified mills, with incoming inspection verifying chemical composition and mechanical properties.
- Coil Forming: The flat strip is precisely formed into a tubular shape using either the seamless capillary method (for seamless products) or the ERW/AW welding method (for welded products). For seamless tubes, a capillary die is drawn through the strip under controlled pressure to create a watertight weld seam.
- Full Annealing: The formed coil tube undergoes a full annealing cycle at 1050–1150°C (1922–2092°F) followed by controlled cooling (air or water quench) to achieve the fully soft (annealed) condition with a uniform austenitic grain structure.
- Pickling and Descaling: The annealed tube is subjected to acid pickling (typically nitric/hydrofluoric acid blend) to remove oxide scale, restoring the corrosion-resistant passive film and achieving the desired surface finish.
- Light Cold Working (1/4H Tempering): The annealed coil tube passes through a calibrated cold reduction line, where it is drawn through a series of precision-diameter rollers to achieve approximately 25–35% cold reduction. This controlled deformation work-hardens the material to the target 1/4H condition (HV 180–220) while preserving ≥30% elongation.
- Dimensional Verification: Each coil undergoes inline and offline dimensional inspection using ultrasonic thickness gauges, laser diameter sensors, and automated hardness testing.
- Final Inspection and Packaging: Tubes pass through eddy current flaw detection, visual surface inspection, and mechanical property sampling. Approved coils are wrapped in protective packaging and labeled with full traceability documentation.
Applications
The unique combination of moderate strength and excellent formability makes the 1/4H Quarter Hard coil tube suitable for a wide range of industrial applications:
- Automotive Industry: Fuel lines, brake lines, air conditioning tubing, exhaust system components, and structural tubing requiring moderate strength with good bendability.
- Appliance Manufacturing: Refrigerator evaporator tubes, washing machine structural frames, oven components, and dishwasher racks requiring corrosion resistance and forming capability.
- Medical Devices: Endoscope tubing, surgical instrument shafts, prosthetic components, and diagnostic equipment housings where moderate strength and excellent surface finish are required.
- Furniture and Decorative Applications: Tubular furniture frames, handrails, balustrades, and architectural decorative elements that demand dimensional stability and aesthetic surface quality.
- Food Processing Equipment: Conveyor system tubing, food-grade piping, and processing equipment components requiring corrosion resistance with moderate forming requirements.
- Electronics and Precision Engineering: Enclosure tubing, heat sinks, connector housings, and precision components requiring consistent mechanical properties.
- Energy Sector: Solar panel mounting frames, battery housing components, and wind turbine structural elements.
- Deep Drawing and Bending Applications: Any fabrication process requiring a material that can be bent, flanged, or formed without cracking while maintaining adequate structural strength.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications to ensure product excellence:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- ISO 45001 — Occupational Health and Safety Management System
- EN 10204 — Type 3.1 Material Test Certificates available upon request
- Mill Test Reports (MTR) — Full chemical and mechanical analysis provided with each shipment
- Third-Party Inspection — Available from SGS, BV, TUV, or other accredited inspection bodies
- Compliance with International Standards: ASTM, EN, JIS, GB, and DIN standards
Quality Commitment: Every coil of Quarter Hard (1/4H) Stainless Steel Tube produced by Wenzhou Jixing Metal Materials Co., Ltd. undergoes 100% dimensional inspection, batch mechanical property testing, and full traceability documentation. The company's state-of-the-art cold working equipment and in-house quality control laboratories ensure that every product meets the specified HV 180–220 hardness range and ≥30% elongation requirement with full consistency across coil lengths.
Ordering Information
Customers are advised to specify the following when placing orders:
- Stainless steel grade (e.g., 304, 316L, 321, 2205)
- Outer diameter and wall thickness (in mm or inches)
- Required coil length and coil dimensions (ID/OD)
- Surface finish preference (BA, 2B, No.4, Mirror, etc.)
- Manufacturing method (Seamless or Welded)
- End condition and any custom cutting requirements
- Applicable standard and certification requirements
For technical inquiries, custom specifications, or bulk order quotations, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Custom mill specifications and non-standard dimensions are available upon request subject to minimum order quantities.