Stainless Steel Coil Tube (盘管 / Coiltube)

1. Product Overview

The Stainless Steel Coil Tube, also known as Coiltube, is a continuously formed tubular product manufactured in a coiled configuration for efficient transportation, storage, and downstream processing. This product is supplied by Wenzhou Jixing Metal Materials Co., Ltd. (Product Catalog No. 1699) and is classified under the technical documentation and study materials series for metallurgical and pipe engineering professionals.

Unlike seamless or welded straight lengths of stainless steel tubing, coil tubes are produced through a continuous forming process that yields long, unbroken lengths wound into compact coils. This format is particularly advantageous for applications requiring large quantities of tubing with minimal joint points, as it eliminates the need for field welding between straight segments and reduces material waste significantly.

The coiltube product line encompasses both cold-drawn (Cold Drawn / Cold Worked) and hot-rolled annealed configurations, with wall thicknesses ranging from ultra-thin gauge to heavy-duty industrial specifications. The product is designed to conform to international standards including ASTM A213/A213M (Standard Specification for Seamless Ferritic and Austenitic Cr-Fe, Cr-Ni, and Cr-Ni-Ti Alloy Tubing for High-Temperature Service), ASTM A312/A312M (Standard Specification for Austenitic Stainless Steel Welded, Seamless and Welded Autoclave Fittings), EN 10217 (Heat-Resistant Stainless Steel Tubes), and GB/T 12771 (Chinese National Standard for Welded Stainless Steel Tubes for General Purposes).

2. Material Composition & Mechanical Properties

Stainless steel coil tubes are available in a wide range of austenitic, ferritic, and duplex alloy grades. The most commonly supplied grades for coil tube applications include:

2.1 Common Alloy Grades

2.2 Typical Chemical Composition (ASTM A213)

Grade C Mn P S Si Cr Ni Mo Other
304 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 0.75 18.00–20.00 8.00–10.50 — N ≤ 0.10
304L ≤ 0.03 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 0.75 18.00–20.00 8.00–11.00 — N ≤ 0.10
316 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 0.75 16.00–18.00 10.00–14.00 2.00–3.00 N ≤ 0.10
316L ≤ 0.03 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 0.75 16.00–18.00 10.00–14.00 2.00–3.00 N ≤ 0.10
321 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 0.75 17.00–19.00 9.00–12.00 — 5Ti–6Al × C
310S ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.50 24.00–26.00 19.00–22.00 — N ≤ 0.10

2.3 Mechanical Properties (Annealed Condition, ASTM A213)

Grade Tensile Strength (MPa) Yield Strength (0.2% RM, MPa) Elongation (%) Hardness (HRB max)
304 / 304L ≥ 515 ≥ 205 ≥ 40 92
316 / 316L ≥ 515 ≥ 205 ≥ 40 92
321 ≥ 515 ≥ 205 ≥ 40 92
310S ≥ 515 ≥ 205 ≥ 40 92
430 ≥ 450 ≥ 205 ≥ 25 92

2.4 Corrosion Resistance Characteristics

3. Dimensional Specifications

Parameter Range / Specification Standard Reference
Outer Diameter (OD) 3.0 mm – 508.0 mm (1/8" – 20") ASTM A213 / EN 10216-5
Wall Thickness (WT) 0.3 mm – 50.0 mm (0.012" – 2.0") ASTM A213 / EN 10216-5
Coil Length (per coil) 10 m – 100 m (typical); up to 200 m for specialized orders Manufacturer specification
Coil Weight 0.5 tonnes – 5.0 tonnes per coil Manufacturer specification
OD Tolerance (≤ 50 mm OD) ± 0.5 mm or ± 1.0%, whichever is greater ASTM A213
OD Tolerance (> 50 mm OD) ± 1.0 mm or ± 1.0%, whichever is greater ASTM A213
Wall Thickness Tolerance ± 10% (standard); ± 5% (tight tolerance on request) ASTM A213 / EN 10216-5
Inside Diameter (ID) Tolerance ± 10% (standard); ± 5% (tight tolerance on request) ASTM A213
Surface Finish No. 1 (Hot-rolled Annealed), 2B (Cold-rolled Bright Annealed), BA (Bright Annealed), No. 4 (Brushed), HL (Hairline), Mirror (8K) ASTM A480 / EN 10088
End Condition Plain cut, beveled, threaded (BSP/NPT/UNF), or per customer drawing Per customer specification
Minimum Bend Radius 3D (cold bending); 1.5D (with mandrel) Industry practice

4. Manufacturing Process

The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and surface quality. The following outlines the principal process steps:

4.1 Raw Material Preparation

High-purity stainless steel ingots or continuous casting slabs are produced via the AOD (Argon Oxygen Decarburization) or ESR (Electroslag Remelting) processes. AOD is the industry standard for austenitic grades, enabling precise control of carbon and nitrogen content to achieve the required "L" (low-carbon) specifications. Raw material chemistry is verified through Optical Emission Spectrometry (OES) and Inductively Coupled Plasma (ICP) analysis prior to rolling.

4.2 Hot Rolling / Hot Forming

Slabs are reheated to temperatures between 1100°C and 1200°C and hot-rolled into strip or hot-formed directly into tubular shapes. The hot rolling process establishes the initial geometry and breaks down the cast microstructure. For coil tube production, the hot-rolled strip is typically coiled at a finishing temperature above the Ar3 (A3) temperature to prevent the formation of martensite.

4.3 Pickling and Descaling

Hot-rolled coils are subjected to acid pick