Hot-Pierced & Cold-Rolled Seamless Stainless Steel Coil Tube

Product Overview

The Seamless Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. represents a premium-grade tubing solution produced through a traditional and time-proven seamless manufacturing methodology. This product combines the structural integrity of hot-pierced seamless tube with the dimensional precision and surface finish quality achieved through subsequent cold rolling. The result is a high-performance coil tube offering an exceptionally wide wall thickness range, making it suitable for demanding industrial applications where weld-free construction is mandatory.

Unlike welded alternatives, this seamless coil tube eliminates the inherent weld seam vulnerability, delivering superior pressure containment, corrosion resistance, and mechanical reliability. The coil configuration provides operational convenience for downstream fabricators, allowing continuous feed through forming, bending, and machining equipment without the need for frequent tube changeovers.

Material & Properties

Available Grades

Mechanical Properties

Surface Finish Options

Specifications

Parameter Specification
Product Type Seamless Stainless Steel Coil Tube
Manufacturing Process Hot Piercing + Cold Rolling
Outer Diameter (OD) 6.0 – 219.0 mm (0.24" – 8.62")
Wall Thickness 0.5 – 12.0 mm (0.020" – 0.472")
Single Tube Length ≤ 30 m (≤ 98.4 ft) per piece
Coil Length Custom (assembled via TIG butt welding of individual lengths)
OD Tolerance ±0.10 mm to ±0.50 mm (per ASTM A213 / A269)
Wall Thickness Tolerance ±10% (standard) or ±5% (precision)
Deliveries Coil on spool / Straight lengths
Coil Inner Diameter 500 mm / 600 mm / 800 mm (19.7" / 23.6" / 31.5")
Applicable Standards ASTM A213, A269, A778; EN 10216-5; GB/T 14976
End Treatment Plain / Beveled / Threaded / Custom
Packaging Wooden pallet, export-standard moisture-proof wrapping

Manufacturing Process

Step 1: Billet Preparation

High-purity stainless steel ingots or continuously cast billets are selected based on the target grade composition. Each billet undergoes rigorous incoming inspection including chemical analysis (OES/Light Emission Spectroscopy) and visual examination to ensure conformance to specified alloy chemistry.

Step 2: Hot Piercing

The billet is heated to a controlled temperature of 1,100–1,250°C (2,012–2,282°F) in an induction or gas-fired furnace. The heated billet is then pierced using a mandrel-driven piercing mill to form a seamless hollow shell. This process creates a weld-free tube body, ensuring uniform microstructure throughout the cross-section without the grain-boundary discontinuities associated with welded seams.

Step 3: Hot Rolling / Elongation

The pierced tube shell is further elongated through hot rolling or plug mill operations to achieve the intermediate OD and wall thickness required for the subsequent cold working stage. This step refines the tube geometry while maintaining the seamless integrity established during piercing.

Step 4: Annealing & Pickling

The hot-rolled tube is subjected to solution annealing in a protective atmosphere (argon or endothermic gas) to restore full austenitic microstructure, relieve residual stresses, and homogenize the alloy. Following annealing, the tube surface is pickled and descaled to remove oxide scale, resulting in a clean, corrosion-resistant surface.

Step 5: Cold Rolling (Cold Reduction)

The annealed tube passes through a series of cold-rolling mills where it is reduced to the final OD and wall thickness dimensions. Cold rolling provides:

Step 6: Final Annealing (Optional)

Where ductility restoration is required for downstream forming operations, the cold-rolled tube undergoes a final solution anneal to return to the full annealed (soft) condition, achieving maximum formability.

Step 7: Coil Assembly & Welding

Since individual seamless tube lengths are limited to a maximum of 30 m (98.4 ft), longer coil lengths are achieved through precision TIG (Gas Tungsten Arc) butt welding of individual tube pieces. Each weld joint undergoes 100% visual inspection and, where specified, penetrant testing (PT) or dye penetrant inspection to ensure weld integrity. The welded coil is then wound onto a steel spool to the required coil length and configuration.

Step 8: Final Inspection & Testing

Every coil tube batch undergoes comprehensive quality assurance including:

Applications

Heat Exchangers & Boilers

The seamless construction and wide wall thickness range make this coil tube ideal for shell-and-tube heat exchangers, condensers, evaporators, and boiler tubes where pressure integrity and thermal cycling resistance are critical.

Petrochemical & Oil/Gas

Used in refinery heat exchangers, distillation columns, heat tracing systems, and process piping where resistance to sour service and elevated pressures demands weld-free construction.

Food & Beverage Processing

Compliant with FDA and 3-A sanitary standards, this coil tube is employed in pasteurizers, homogenizers, brewing systems, and food-grade hygienic piping where CIP (Clean-in-Place) capability is essential.

Pharmaceutical & Medical

Electropolished or sanitary-grade versions are used in bioreactors, CIP/SIP systems, medical gas distribution, and pharmaceutical process equipment requiring high purity and corrosion resistance.

Power Generation

Utilized in superheater tubes, economizers, and feedwater systems in both conventional and nuclear power plants, where reliable long-term performance under extreme thermal gradients is paramount.

Automotive & Aerospace

Employed in exhaust systems, turbocharger manifolds, fuel lines, and hydraulic systems where high-temperature resistance and fatigue performance are required.

Construction & Architectural

Used in structural applications, decorative railings, elevator guide rails, and building facades where both mechanical strength and aesthetic surface quality are valued.

Quality Certifications & Standards

Management System Certifications

Product & Industry Certifications

Testing & Inspection Protocols

Unique Selling Points

Weld-Free Construction: The seamless hot-piercing process eliminates the weld seam entirely, providing superior pressure containment and eliminating the primary failure point present in welded tubing — critical for high-pressure and safety-critical applications.

Exceptional Wall Thickness Range: From ultra-thin walls of 0.5 mm (0.020") to heavy walls of 12.0 mm (0.472"), this product line covers an unprecedented range in a single seamless coil tube offering, providing design flexibility unmatched by conventional seamless straight-length products.

Coil Convenience with Seamless Integrity: Customers benefit from the operational efficiency of coil delivery — continuous processing, reduced handling, and minimized material waste — while retaining the full structural advantages of seamless tube. Individual 30 m lengths are precision TIG-welded to form continuous coils with full weld traceability.

Precision Cold-Rolled Dimensions: The final cold-rolling stage delivers tolerances up to ±0.10 mm on OD, ensuring excellent fit-up in heat exchanger tube sheets and minimizing reaming or finishing operations downstream.

Comprehensive Quality Assurance: Every production lot undergoes multi-stage inspection from raw material through final coil assembly, backed by internationally recognized certifications and full documentation traceability.

Technical Note

Important: Individual seamless tube lengths are limited to a maximum of 30 m (98.4 ft) due to the inherent constraints of the hot-piercing and cold-rolling production process. For coil lengths exceeding 30 m, individual tube pieces are joined via precision TIG butt welding. All weld joints are 100% inspected for quality and documented in the accompanying Mill Test Report. Customers requiring true single-length seamless coil (without weld joints) should consult with our engineering team regarding alternative supply configurations or accept the standard welded-coil specification with full traceability.