Stainless Steel Half-Hard (1/2H) Coil Tube — Moderate Cold Work Condition
Wenzhou Jixing Metal Materials Co., Ltd. presents its premium-grade Stainless Steel Coil Tube in Half-Hard (1/2H) condition, engineered through controlled moderate cold working to deliver an optimal balance of mechanical strength, pressure resistance, and formability. This product line (Product No. 49) represents a critical intermediate temper state between the annealed (soft) and fully cold-worked (hard) conditions, making it the preferred choice for applications demanding enhanced structural integrity without sacrificing workability.
Product Overview
The Half-Hard (1/2H) stainless steel coil tube is produced by subjecting the base material to a precisely calibrated degree of cold rolling and cold drawing, achieving a controlled level of strain hardening. Unlike fully annealed coils that prioritize maximum formability at the expense of strength, or fully hardened coils that resist deformation, the 1/2H condition occupies the strategic midpoint — offering significantly elevated pressure resistance while retaining sufficient ductility for downstream forming operations such as bending, flanging, and expansion.
This product is supplied in continuous coil form, enabling high-volume, seamless integration into automated tube processing lines including cut-to-length, hydraulic bending, and precision stamping operations.
Material & Mechanical Properties
The moderate cold work treatment imparts a well-defined microstructural refinement, resulting in measurable improvements in hardness, yield strength, and fatigue resistance compared to the annealed (1M/soft) condition. The key mechanical characteristics are summarized below:
Key Performance Indicators
- Hardness (Vickers): HV 220–280 — representing a substantial increase over the annealed baseline (typically HV 150–200), providing superior resistance to indentation, wear, and internal pressure loads.
- Elongation at Break: ≥ 20% — ensuring adequate ductility for forming operations while maintaining structural integrity under stress.
- Pressure Resistance: Significantly improved over soft condition; the elevated yield strength directly translates to higher burst pressure ratings, making this grade ideal for pressurized fluid and gas conveying systems.
- Bending Behavior: Bending requires a larger minimum bend radius compared to the annealed condition. The increased strain hardening reduces the material's capacity for tight-radius deformation, necessitating careful planning of bend radii to avoid cracking or wall thinning at the bend apex.
Specifications
| Parameter | Specification | Notes |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) | Continuous coil supply |
| Product No. | 49 | Wenzhou Jixing catalog reference |
| Temper / Mechanical Condition | Half-Hard (1/2H) | Moderate cold work |
| Hardness (Vickers) | HV 220 – 280 | Verified per ISO 6507 |
| Elongation at Break | ≥ 20% | Minimum guaranteed value |
| Pressure Resistance | Enhanced vs. annealed condition | Higher burst pressure rating |
| Minimum Bend Radius | Larger than annealed (1M) condition | Plan for increased bend radius |
| Primary Cold Work Degree | Moderate (intermediate) | Controlled strain hardening |
| Supply Form | Coil (continuous length) | Suitable for automated processing |
| Typical Grades Available | SUS304, SUS316, SUS321, SUS316L, and custom alloys | Subject to order specification |
Manufacturing Process
The production of Half-Hard (1/2H) stainless steel coil tube follows a rigorous multi-stage manufacturing sequence designed to achieve precise control over mechanical properties:
- Slab Casting & Billet Production: High-purity stainless steel ingots are produced via EAF or AOD melting, with strict control over carbon, sulfur, and trace element content to ensure metallurgical consistency.
- Hot Rolling & Hot Finishing: Billets are hot rolled into seamless tube blanks or hollow bars, followed by hot finishing to achieve approximate dimensions and relieve gross casting stresses.
- Initial Annealing: The hot-rolled material undergoes a solution annealing cycle to fully soften the structure, establishing a uniform starting microstructure for subsequent cold working.
- Pilger Rolling / Cold Drawing: The annealed tube blanks are cold drawn through precision-die tooling to achieve final dimensional tolerances. The degree of reduction is carefully controlled to target the 1/2H temper — a moderate level of plastic deformation that introduces dislocation density and grain elongation without reaching the limits of full cold work.
- Intermediate Annealing (Controlled): A partial or controlled annealing step may be applied to stabilize the microstructure at the target hardness range (HV 220–280), preventing over-hardening while ensuring uniform property distribution along the coil length.
- Coiling & Winding: The finished tube is wound onto precision coils with controlled tension to prevent ovality, kinking, or surface damage during storage and transport.
- Final Inspection & Certification: Each coil undergoes comprehensive quality verification including dimensional checks, hardness testing, tensile testing, and surface inspection before shipment.
Applications
The Half-Hard (1/2H) condition is selected in engineering applications where the design demands a stronger, pressure-resistant tube that still permits moderate forming operations. Typical application areas include:
- Pressurized Fluid Systems: Hydraulic lines, pneumatic tubing, fuel delivery lines, and high-pressure gas transfer systems where elevated burst pressure ratings are critical.
- Automotive & Transportation: Brake lines, fuel injection tubing, and exhaust system components requiring a balance of fatigue resistance and formability for bend forming.
- Medical & Pharmaceutical Equipment: Tubing for autoclavable medical devices, sterilization chambers, and fluid delivery systems where moderate hardness provides dimensional stability under repeated thermal cycling.
- Food Processing & Dairy Equipment: CIP (Clean-in-Place) systems, pasteurization lines, and hygienic transfer tubing where enhanced pressure resistance ensures leak-free operation.
- Industrial Heat Exchangers & Cooling Systems: Intermediate-pressure heat exchanger tubes and refrigeration coils requiring improved mechanical properties over the annealed condition.
- Structural & Mechanical Components: Tubular structural elements, spring-like components, and precision-machined parts where the 1/2H condition provides a favorable strength-to-formability ratio.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and adheres to internationally recognized standards for stainless steel tube production:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and traceability.
- ISO 3834 — Quality requirements for welding, applicable where tubes are supplied for welded assemblies.
- ASTM / ASME Standards: Material and mechanical property compliance with ASTM A213, ASTM A269, and applicable ASME codes.
- EN / DIN Standards: Conformity with European standards including EN 10216, EN 10217, and DIN 18900 series for cold-drawn stainless steel tubing.
- JIS Standards: Compliance with Japanese Industrial Standards (JIS G3446, JIS G3459) for austenitic stainless steel tube.
- Mill Test Certificates (MTC): Each coil is accompanied by a comprehensive mill test certificate documenting chemical composition, mechanical properties (hardness, tensile strength, elongation), and heat traceability.
- Non-Destructive Testing (NDT): Available upon request — including eddy current testing, ultrasonic testing, and hydrostatic pressure testing for leak integrity verification.
Unique Selling Points
Optimized Strength-to-Formability Ratio: The 1/2H condition delivers approximately 40–60% higher hardness than the annealed state while retaining ≥20% elongation, making it the ideal engineering compromise for pressure-rated applications that still require downstream forming.
- Enhanced Pressure Resistance: The moderate cold work directly increases yield strength and burst pressure, reducing the risk of tube failure under operational loads and extending service life in pressurized systems.
- Predictable Mechanical Behavior: The tightly controlled HV 220–280 hardness window ensures consistent performance across the entire coil length, enabling reliable engineering calculations and design confidence.
- Continuous Coil Supply: Delivered in coil form for seamless integration into high-speed automated processing lines, minimizing waste and maximizing throughput compared to straight-length tube supply.
- Full Traceability & Certification: Every coil is backed by complete mill documentation, enabling compliance with stringent regulatory and industry-specific quality requirements.
- Customizable Grades & Dimensions: Wenzhou Jixing offers a broad range of stainless steel grades and dimensional configurations to meet specific project requirements, from standard austenitic alloys to specialized duplex and super-austenitic grades.
For detailed quotation, dimensional specifications, or custom order requirements, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Our engineering team is available to provide application-specific guidance on selecting the optimal temper condition and grade for your project.