321/347 Seamless Stainless Steel EGR Cooler Coil Tube
Product Overview
The EGR Cooler Coil Tube is a high-performance seamless stainless steel tube engineered specifically for Exhaust Gas Recirculation (EGR) cooler systems in automotive and heavy-duty transportation applications. Operating under the most demanding conditions in the exhaust system—combining extreme thermal cycling, aggressive condensation acid corrosion, and sustained mechanical vibration—this coil tube delivers exceptional durability and reliability. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a critical component in modern emission control technology, enabling vehicles to meet increasingly stringent emission standards while maintaining long-term operational integrity.
Material & Properties
EGR cooler systems expose tubing to a uniquely hostile environment where exhaust gas temperatures range from 600°C to 800°C, condensation acids (including sulfuric and nitric acids formed from SOx and NOx in the presence of moisture) attack the inner and outer tube surfaces, and continuous engine vibration induces cyclic mechanical stress. To address these combined challenges, only the highest-grade austenitic stainless steels are specified:
- Type 321 (UNS S32100) — Titanium-stabilized austenitic stainless steel offering superior resistance to intergranular corrosion and excellent thermal stability at elevated temperatures. The titanium addition prevents chromium carbide precipitation during heat exposure, ensuring sustained mechanical and corrosion resistance throughout the service life.
- Type 347 (UNS S34700) — Niobium-stabilized austenitic stainless steel providing enhanced creep resistance and stress-rupture strength at high temperatures, making it ideal for applications subject to prolonged thermal loading combined with mechanical vibration.
Both alloys are supplied in seamless form to eliminate weld-induced microstructural weaknesses, ensuring uniform metallurgical properties throughout the tube cross-section. The seamless construction is critical for withstanding the dual assault of thermal fatigue and condensation acid corrosion without premature failure.
Specifications
| Parameter | Specification |
|---|---|
| Material Grades | ASTM A269 Type 321 / Type 347 |
| Tube Type | Seamless Coil Tube |
| Maximum Operating Temperature | 600°C – 800°C (continuous) |
| Corrosion Environment | Condensation acid (H2SO4, HNO3) + high-temperature oxidizing atmosphere |
| Mechanical Environment | Continuous vibration (engine-mounted application) |
| Outer Diameter Range | Customized per OEM requirements (typically 6 mm – 14 mm) |
| Wall Thickness | Customized (typically 0.5 mm – 1.5 mm) |
| Coil Form | Continuous coil, customizable coil diameter |
| Surface Finish | Pickled & passivated (BA finish available on request) |
| Applicable Standards | ASTM A269, ASTM A270, GB/T 14976 |
| Delivery Condition | Annealed, fully stress-relieved |
Manufacturing Process
The production of EGR Cooler Coil Tubes follows a rigorous, multi-stage manufacturing process to ensure every tube meets the demanding performance requirements of automotive exhaust applications:
- Raw Material Selection — Certified 321 or 347 stainless steel billets/slabs sourced from reputable mills with full traceability and chemical composition verification.
- Hot Rolling / Hot Extrusion — Initial forming of seamless tubes to approximate dimensions, ensuring full grain flow and uniform microstructure.
- Cold Drawing / Cold Pilgering — Precision sizing to achieve exact dimensional tolerances required for EGR cooler tube-in-tube or tube-in-shell configurations.
- Heat Treatment (Annealing) — Solution annealing at 1050°C–1150°C followed by controlled cooling to restore full austenitic microstructure and relieve residual stresses.
- Pickling & Passivation — Removal of surface oxide scales and formation of a protective chromium oxide passivation layer for enhanced corrosion resistance.
- Coiling — Precision coiling to specified coil diameter and pitch, ensuring uniform geometry without introducing work hardening or distortion.
- Quality Inspection — Full-spectrum inspection including chemical analysis, mechanical testing, dimensional verification, and surface quality assessment.
Applications
This EGR Cooler Coil Tube is specifically designed for the following automotive and transportation applications:
- EGR Coolers — Primary application in cooled Exhaust Gas Recirculation systems for diesel and gasoline engines, where the coil tube serves as the gas-side or coolant-side heat exchange element.
- Heavy-Duty Diesel Engines — Commercial vehicles, trucks, buses, and industrial engines requiring high-temperature exhaust gas cooling to reduce NOx emissions.
- Passenger Vehicle EGR Systems — Modern turbocharged gasoline and diesel passenger vehicles meeting Euro 6 / China VI emission standards.
- Off-Highway Applications — Construction equipment, agricultural machinery, and marine engines with EGR emission control requirements.
- Aftertreatment System Integration — Upstream components of SCR and DPF systems where precise exhaust gas temperature management is critical.
Quality Certifications & Validation
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system to ensure every batch of EGR Cooler Coil Tubes meets the rigorous demands of automotive OEMs and Tier-1 suppliers:
- ISO 9001:2015 — Quality Management System certification ensuring consistent manufacturing processes and continuous improvement.
- IATF 16949 — Automotive-specific quality management system certification demonstrating capability to serve automotive supply chains.
- Thermal Fatigue Testing — All production batches undergo validated thermal cycling tests simulating real-world exhaust temperature fluctuations (600°C–800°C) to verify long-term fatigue resistance and structural integrity.
- Condensation Acid Corrosion Testing — Dual validation against aggressive condensation acid environments, including simulated spray and immersion tests replicating sulfuric and nitric acid exposure at elevated temperatures.
- Full Material Traceability — Mill certificates, chemical analysis reports, and mechanical test data provided with every shipment.
Key Differentiator: Unlike general-purpose stainless steel coil tubes, this product is specifically validated through dual testing protocols—thermal fatigue AND condensation acid corrosion—ensuring proven performance in the most demanding EGR cooler environments. The seamless construction eliminates potential failure points, while the 321/347 alloy selection provides the optimal balance of high-temperature strength, oxidation resistance, and acid corrosion resistance required for next-generation emission control systems.