Stainless Steel Coil Tube with TIG Autogenous Welding and Back-Side Argon Shielding
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for demanding applications requiring superior corrosion resistance, structural integrity, and seamless internal surfaces. This product is distinguished by its advanced TIG (Tungsten Inert Gas) autogenous welding process with back-side argon shielding, which ensures an oxidation-free, metallurgically sound weld joint free from any filler material contamination. This joining technique is critical for coil tube assemblies used in sanitary, pharmaceutical, food-grade, and chemical processing environments where even trace oxidation on the internal wall surface can compromise product purity and long-term durability.
Material & Properties
- Base Material: Austenitic stainless steel (304 / 304L / 316L), selected for excellent corrosion resistance and weldability
- Form: Coil tube (spiral wound), offering flexibility in installation and efficient space utilization
- Surface Finish: Internal surface maintained in a clean, passive state with no oxide discoloration — a direct indicator of successful argon shielding
- Key Performance Characteristic: Full preservation of the base material's corrosion resistance at the weld zone, achieved through the absence of filler metal and complete inert gas coverage
Specifications
| Parameter | Specification |
|---|---|
| Product Type | Stainless Steel Coil Tube (Welded Assembly) |
| Welding Process | TIG Autogenous Welding (No Filler Metal) |
| Shielding Gas | Pure Argon (Ar ≥ 99.99%) |
| Gas Flow Rate | 8–15 L/min |
| Back-Side Protection | Continuous Argon Purge on Root Side |
| Pre-Flush Requirement | Mandatory — purge prior to arc initiation |
| Post-Weld Condition | No internal oxidation, no blackening, no discoloration |
| Common Grades | SUS304, SUS304L, SUS316L |
| Weld Joint Type | Butt Weld (Autogenous) |
Manufacturing Process
1. Pre-Weld Preparation
Before welding commences, the joint area and the interior of the coil tube are thoroughly cleaned to remove all contaminants, including oil, moisture, and particulate matter. A pre-flushing procedure is executed using pure argon gas at a flow rate of 8–15 L/min to displace all atmospheric air from the interior of the tube. This step is non-negotiable — failure to pre-flush adequately allows oxygen and nitrogen to react with the molten weld pool, resulting in internal oxidation.
2. Back-Side Argon Shielding Setup
A dedicated argon purge system is positioned to deliver continuous, laminar flow of inert gas along the root side (interior surface) of the weld zone. This back-side shielding ensures that the molten weld root is fully protected from atmospheric contamination throughout the entire welding cycle. The flow rate is precisely controlled within the 8–15 L/min range to provide adequate coverage without causing turbulence that could entrain air.
3. TIG Autogenous Welding Execution
The welding is performed using a tungsten electrode with no filler rod (autogenous process). The absence of filler metal eliminates the risk of introducing foreign elements or impurities into the weld zone, preserving the chemical composition and corrosion resistance of the base material. The welder maintains consistent travel speed, amperage, and arc length to produce a uniform, smooth weld bead with full penetration.
4. Post-Weld Inspection
Upon completion, the internal weld surface is visually inspected. A silvery, clean weld appearance confirms successful argon protection. Any indication of internal oxidation, blackening, or dark discoloration signals that the shielding gas failed to protect the root side — this constitutes a critical quality failure, as it indicates that the corrosion resistance of the weld zone has been permanently compromised.
Critical Quality Indicator: Internal wall oxidation or blackening = protection failure = loss of corrosion resistance. Any coil tube exhibiting this condition must be rejected and reworked or replaced. This is the single most important visual acceptance criterion for this product.
Unique Selling Points
- Filler-Free Welding: Autogenous TIG welding preserves the exact chemical composition of the base stainless steel, ensuring homogeneous corrosion resistance throughout the entire tube assembly.
- Complete Internal Protection: The back-side argon shielding system guarantees a clean, oxide-free internal weld surface — essential for sanitary and high-purity applications.
- Process Discipline: Mandatory pre-flushing protocol and controlled gas flow rates (8–15 L/min) ensure consistent, repeatable weld quality across all production batches.
- Visual Quality Assurance: The weld appearance serves as an immediate, unambiguous quality indicator — any discoloration is easily detectable and triggers immediate corrective action.
- Enhanced Service Life: By eliminating oxidation at the weld zone, the product maintains full corrosion resistance throughout its operational lifespan, even in aggressive chemical environments.
Applications
- Pharmaceutical & Biotechnology: CIP/SIP systems, bioreactor connections, and sterile fluid transfer lines where internal surface cleanliness is paramount
- Food & Beverage Processing: Sanitary piping, heat exchanger coil assemblies, and product contact surfaces requiring hygienic-grade welds
- Chemical Processing: Transfer of aggressive chemicals where weld integrity and corrosion resistance are critical
- Semiconductor Manufacturing: Ultra-pure fluid delivery systems demanding zero-contamination weld joints
- Dairy & Brewing Industry: Process coil tubes subject to frequent cleaning cycles and corrosive cleaning agents
- Installation & Maintenance: Field-welded coil tube assemblies for connecting existing piping systems during retrofit or expansion projects
Quality Certifications & Standards
- Welding process compliant with ASME BPV Section IX and ISO 15614 qualified welding procedures
- Material certified to ASTM A213 / A269 (tubing) and ASTM A312 (welded pipe)
- Sanitary applications meet 3-A Sanitary Standards and EHEDG guidelines
- Weld quality verified through visual inspection (VT) per ASME Section V Article 1
- Internal surface condition assessed against ASTM A967 passivation requirements
- Production facility maintains ISO 9001:2015 quality management system certification
Wenzhou Jixing Metal Materials Co., Ltd. is committed to delivering coil tube products that meet the most stringent quality and performance requirements. The TIG autogenous welding with back-side argon shielding process represents our highest standard of weld integrity — ensuring that every coil tube delivered maintains uncompromised corrosion resistance and surface cleanliness throughout its service life.