Stainless Steel Coil Tube — Light Cold Worked (1/4H) Condition
Wenzhou Jixing Metal Materials Co., Ltd. offers premium-grade stainless steel coil tubes supplied in the Light Cold Worked (1/4H) mechanical condition. This product line is engineered to deliver an optimal balance between mechanical strength and formability, making it the ideal choice for applications that demand reliable bending performance without compromising structural integrity.
Product Overview
The 1/4H (Quarter-Hard) condition represents a controlled degree of cold working applied to the stainless steel coil tube after the initial annealing process. Unlike fully annealed (soft) tube, which offers maximum formability but lower strength, or fully hard (1H) tube, which provides maximum strength but limited bendability, the 1/4H condition strikes a precise engineering compromise. The partial cold reduction introduces dislocation density and grain refinement sufficient to elevate yield strength while preserving ductility and elongation characteristics necessary for complex forming operations.
This product is particularly valued in industries where post-manufacture bending, coiling, and shaping operations are required — ensuring that the tube maintains dimensional accuracy and surface quality throughout subsequent fabrication stages.
Material & Properties
Mechanical Characteristics
- Vickers Hardness (HV): 180–220 — indicating a controlled intermediate hardness level that provides resistance to wear and indentation while remaining formable.
- Elongation at Break (A): ≥30% — demonstrating excellent ductility, allowing the tube to undergo significant plastic deformation before fracture.
- Yield Strength: Moderately elevated above fully annealed condition, providing improved load-bearing capacity for structural and pressure-retaining applications.
- Bendability: Superior bending performance with minimal risk of cracking or wall thinning at bend radii, suitable for cold bending, U-bend, and spiral coil forming.
Key Selling Points
- Optimized Strength-to-Ductility Ratio: The 1/4H condition delivers approximately 25–35% higher yield strength compared to the fully annealed (01) condition, while retaining over 30% elongation — a unique combination difficult to achieve with other mechanical conditions.
- Excellent Formability: Ideal for secondary forming processes including cold bending, flanging, and coiling without the need for intermediate re-annealing.
- Dimensional Stability: Reduced springback compared to fully annealed tube, resulting in tighter dimensional tolerances after bending operations.
- Surface Integrity: The controlled cold working process maintains a smooth, defect-free surface suitable for high-quality downstream applications.
Specifications
| Parameter | Specification |
|---|---|
| Mechanical Condition | Light Cold Worked (1/4H / Quarter-Hard) |
| Vickers Hardness (HV) | 180 – 220 |
| Elongation (A) | ≥ 30% |
| Product Form | Coil Tube (Continuous Coil) |
| Manufacturing Method | Seamless or Welded (per customer requirement) |
| Available Grades | 304, 304L, 316, 316L, 321, 310S, Duplex 2205, and custom grades |
| Surface Finish | 2B, BA, No.4, Mirror (8K), Hairline, Custom |
| Applicable Standards | ASTM A213, ASTM A269, ASME SA-213, ASME SA-269, EN 10216-5, GB/T 14976 |
| Quality Certification | ISO 9001, PED (EU Pressure Equipment Directive), EN 10204 3.1 |
Manufacturing Process
The production of Light Cold Worked (1/4H) stainless steel coil tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage process to ensure consistent mechanical properties and dimensional accuracy:
- Raw Material Selection: High-purity stainless steel billets or wire rods are procured from certified suppliers with full chemical composition traceability.
- Piercing & Extrusion / Welding: Seamless tubes are produced via hot piercing and extrusion, or welded tubes are manufactured through ERW (Electric Resistance Welding) or TIG (Tungsten Inert Gas) processes.
- Full Annealing: The tube is heated to the appropriate solution-annealing temperature (typically 1010–1150°C depending on grade) and cooled to achieve a fully recrystallized, soft structure.
- Precision Sizing & Cold Reduction: The annealed tube undergoes a controlled cold drawing or cold rolling reduction — approximately 25–35% cross-sectional area reduction — to achieve the 1/4H mechanical condition.
- Coiling & Winding: The formed tube is coiled onto mandrels at precise tensions to maintain uniform coil geometry and prevent deformation.
- Surface Treatment & Finishing: Pickling, passivation, and surface finishing (polishing, grinding) are applied to achieve the required surface quality and corrosion resistance.
- Quality Inspection: Every batch undergoes hardness testing (HV), tensile testing (elongation verification), dimensional measurement, hydrostatic or pneumatic pressure testing, and visual/eddy current inspection.
Applications
The Light Cold Worked (1/4H) stainless steel coil tube is widely utilized across multiple industries due to its unique combination of strength and formability:
- Heat Exchangers & Refrigeration: U-tube and spiral coil applications in condensers, evaporators, and refrigeration systems where tubes must be bent into complex geometries.
- Automotive & Transportation: Exhaust system components, fuel lines, and structural tubing requiring post-fabrication bending.
- Medical Equipment: Surgical instrument tubing, endoscopy guide tubes, and dialysis components requiring precise forming and high surface quality.
- Food & Beverage Processing: Hygienic piping systems, mixing equipment, and CIP (Clean-in-Place) compatible tubing.
- Oil & Gas / Chemical Processing: Instrumentation tubing, pressure relief lines, and chemical transfer systems requiring corrosion resistance and moderate mechanical strength.
- Electronics & Appliances: Compressor tubing, heat sink coils, and appliance structural components.
- Architecture & Decoration: Handrail tubing, decorative coil elements, and structural applications requiring aesthetic surface finishes.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing excellence.
- EN 10204 3.1 — Full inspection certificates provided with each shipment, including mill test reports, chemical analysis, and mechanical property verification.
- PED (Pressure Equipment Directive 2014/68/EU) — Compliance for pressure-containing applications within the European Economic Area.
- ASME / ASTM Compliance — Products manufactured to meet North American standards for pressure vessels and piping.
- Material Traceability: Full heat number tracking from raw material through final product delivery.
Why Choose the 1/4H Condition? When your application requires the tube to be bent, coiled, or formed after delivery — yet still demands reliable mechanical strength — the Light Cold Worked (1/4H) condition from Wenzhou Jixing Metal Materials Co., Ltd. provides the engineering advantage that fully annealed or fully hardened conditions cannot. With HV 180–220 hardness and ≥30% elongation, this product eliminates the need for intermediate re-annealing cycles, reducing manufacturing time and cost while ensuring superior final product quality.