The Fundamental Differences Between ERW and CEW
Introduction: Two Core Technologies in Electric Resistance Welded Steel Pipes
Within the broad category of electric resistance welded steel pipes, Electric Resistance Welding (ERW) and Continuous Electric Welding (CEW) are two distinct technologies that serve different industrial needs. For Hebei Huayang Steel Pipe Co., Ltd.-a leading producer of electric resistance welded steel pipes-understanding these differences is critical to delivering tailored solutions: ERW pipes (its core product) dominate medium-to-large diameter, medium-pressure scenarios, while CEW pipes cater to small-diameter, light-duty applications.
To establish the technical context: what is erw pipe? It is an electric resistance welded steel pipe formed by medium-frequency resistance heat (1kHz-3kHz) to fuse steel plate edges, with erw pipe meaning emphasizing mass production efficiency and uniform weld quality. Both ERW and CEW differ from hfw steel pipes-another premium electric resistance welded steel pipe variant where hfw meaning refers to High-Frequency Welding (300kHz-500kHz) for high-pressure precision. This article explores the fundamental differences between ERW and CEW, with a focus on Huayang's production practice and real-world application cases.
Definition and Welding Principles: The Core Distinction
The most fundamental difference between ERW and CEW lies in their welding principles-how heat is generated, applied, and integrated with the pipe-forming process.
ERW: Medium-Frequency Resistance Welding for Versatility
Technical Principle of ERW
ERW relies on medium-frequency alternating current (1kHz-3kHz) and direct electrode contact to generate heat, with a two-step forming-welding process:
Heating Mechanism: Copper electrodes press against the edges of a flattened steel coil (pre-formed into a cylindrical shape via multi-rolls). Electrical resistance at the edge interface heats the steel to 1300℃-1400℃, melting the material into a molten state;
Fusion Process: Downstream squeeze rolls apply 2MPa-3MPa pressure to fuse the molten edges, forming a longitudinal weld. Unlike CEW, ERW separates forming and welding into sequential steps, allowing flexible adjustment for different pipe diameters.
At Huayang's ERW production line, this principle is optimized for Φ20mm-Φ630mm pipes. For example, its Φ48×3.5mm ERW scaffolding pipes use 2kHz current and 2.5MPa squeeze pressure, achieving a weld fusion rate of ≥98%-a key reason for their 0.3% defect rate, far below the industry average of 1.2%.
Huayang's ERW Process Features
Huayang enhances ERW performance with three core optimizations:
Multi-Roll Gradient Forming: 7-10 sets of precision rolls shape the steel strip into a cylinder with ovality ≤0.5%, ensuring the weld seam is centered (±0.1mm for Φ114×4.5mm ASTM A53 pipes);
Closed-Loop Parameter Control: A PLC system adjusts current (800A-1200A) and pressure in real time based on strip thickness. For thick-walled Φ273×10mm Schedule 80 pipes, current is increased to 1200A to ensure full edge melting;
Post-Weld Deburring: Mechanical cutters remove inner and outer weld beads, reducing height to ≤0.1mm-critical for fitting compatibility in the 2024 Baoding Affordable Housing water supply project.
CEW: High-Frequency Continuous Welding for Small Diameters
Technical Principle of CEW
CEW uses high-frequency current (10kHz-50kHz) and induction heating, with a fully integrated forming-welding process:
Heating Mechanism: An induction coil (no direct electrode contact) generates a magnetic field around the steel strip as it is continuously formed into a cylinder. Eddy currents induced in the strip edges heat the material to melting point, avoiding electrode wear;
Continuous Fusion: Forming and welding occur simultaneously, with line speeds up to 80m/min. This integration limits CEW to small diameters (≤20mm), as larger sizes struggle with forming precision.
Huayang's CEW line specializes in Φ6mm-Φ20mm pipes. For example, its Φ10×1.2mm CEW automotive brake lines use 30kHz induction heating and 1.8MPa pressure, achieving weld strength ≥90% of the base metal-sufficient for 0.8MPa operating pressure.
Huayang's CEW Process Features
To address CEW's small-diameter focus, Huayang implements precision-focused optimizations:
Micro-Forming Rolls: 4-6 sets of miniaturized rolls (diameter ≤50mm) ensure wall thickness tolerance ±0.05mm for Φ8×1mm medical instrument pipes;
Induction Coil Positioning: A servo system maintains the coil 0.5mm-1mm from the strip edge, reducing temperature variation to ±20℃-preventing under-welding in thin walls;
Online Thickness Monitoring: Laser gauges (accuracy ±0.001mm) check dimensions every 100mm, adjusting rolls automatically to keep deviations within limits.
Key Technical Parameters: Performance and Precision Differences
ERW and CEW differ significantly in technical parameters like weld quality, dimensional accuracy, and production efficiency-directly influencing their application scope.
Weld Quality: Strength and Integrity
ERW: Balanced Strength for Medium Pressure
Weld Strength: Huayang's ERW pipes have weld tensile strength 90%-95% of the base metal. For Φ88.9×4.55mm ASTM A53 pipes, weld strength averages 420MPa, meeting medium-pressure (≤2.0MPa) requirements;
Defect Control: 100% ultrasonic flaw detection (UT) detects defects ≥0.5mm, resulting in a leakage rate ≤0.1%. The 2024 Hebei Machinery Factory's ERW compressed air pipes had zero weld failures in 6 months.
CEW: Moderate Strength for Light Duty
Weld Strength: CEW weld strength is 85%-90% of the base metal. Huayang's Φ10×1.2mm CEW pipes (Q235 steel) have weld strength of 340MPa-360MPa, suitable for ≤0.8MPa scenarios;
Defect Risk: CEW's thin walls increase porosity risk (0.3%-0.5% without optimization). Huayang adds argon purging to reduce porosity to ≤0.2% for medical-grade CEW pipes.
Dimensional Precision: Diameter and Tolerance
ERW: Consistency for Medium-Large Sizes
Diameter Range: Φ20mm-Φ630mm, with outer diameter (OD) tolerance ±0.1mm (e.g., Φ100×6.02mm Schedule 40 pipes), exceeding ASTM A53's ±0.79mm standard;
Ovality: ≤0.5% (≤0.3% for Φ159×7mm drainage pipes), ensuring even pressure distribution.
CEW: Precision for Small Diameters
Diameter Range: Φ6mm-Φ20mm, with OD tolerance ±0.05mm (critical for Φ8×1mm medical fittings);
Ovality: ≤0.3% for ≤15mm diameters, but ≥0.8% for >15mm-why Huayang limits CEW to small sizes.
Production Efficiency: Speed and Cost
ERW: Mass Production Advantage
Line Speed: 15m/min-45m/min, with daily output of 500 tons for Φ48×3.5mm pipes-30% higher than seamless pipes;
Cost: 4,200 yuan/ton for Φ48×3.5mm ERW pipes, 15% lower than CEW for similar diameters, thanks to lower energy use.
CEW: Speed for Niche Needs
Line Speed: 40m/min-80m/min, but limited to small batches (daily output 100 tons for Φ10×1.2mm pipes);
Cost: 3,800 yuan/ton for Φ10×1.2mm CEW pipes, but higher per-unit cost for larger diameters due to low yield.
Application Scenarios: Clear Boundaries in Practice
Huayang's project experience highlights how ERW and CEW serve distinct markets, with no significant overlap in their optimal use cases.
ERW: Dominating Civil and Medium-Pressure Industrial Use
Civil Construction
Scaffolding: Φ48×3.5mm ERW pipes (ASTM A36) are Huayang's top-seller, with 50,000 tons annual sales. The 2024 Guangzhou CBD Skyscraper used 3,000 tons, withstanding 200kg/m loads;
Water Supply: Φ25×2.77mm-Φ114×4.5mm ERW pipes (ASTM A53) in the 2024 Baoding Affordable Housing Project have a 50-year design life and ≤0.1% leakage rate.
Industrial Lines
Compressed Air: Φ80×5.49mm-Φ159×7mm ERW pipes (ASTM A53 Grade B) in the 2024 Hebei Machinery Factory maintain 1.0MPa pressure with ±0.02MPa fluctuation;
Coolant Circulation: Φ114×4.5mm-Φ273×10mm ERW pipes (ASTM A36) in the 2024 Tangshan Machine Tool Factory ensure 20L/min flow to prevent overheating.
CEW: Specialized in Small-Diameter, Light-Duty Scenarios
Automotive and Precision Machinery
Brake Lines: Φ6×1mm-Φ10×1.2mm CEW pipes (Q235) supply the 2024 Hebei Automobile Parts Factory, meeting ISO 4038 standards for 0.8MPa brake fluid;
Medical Instrument Tubing: Φ8×1mm CEW pipes (electro-polished Ra ≤0.8μm) are used in Beijing medical equipment, with OD tolerance ±0.05mm ensuring fitting compatibility.
Indoor Light-Duty Piping
Air Vents: Φ15×1.5mm-Φ20×2mm CEW pipes in the 2024 Handan Office Building reduce ceiling support costs by 30% due to lightweight design (≤0.5kg/m);
Appliance Tubing: Φ6×1mm-Φ10×1mm CEW pipes for Guangdong water heaters, with thin walls (≤1mm) lowering material costs.
Conclusion: Complementary, Not Competitive
ERW and CEW are complementary technologies within the electric resistance welded steel pipe family, each optimized for distinct needs. ERW's medium-frequency welding, versatile diameter range, and balanced strength make it the workhorse of civil infrastructure and medium-pressure industry. CEW's high-frequency continuous welding excels in small-diameter, precision-focused light-duty scenarios.
For Huayang, mastering both technologies allows it to cover a broad market: from large-scale scaffolding projects (ERW) to miniaturized medical tubing (CEW). Importantly, neither replaces hfw steel pipes-which use high-frequency induction welding for high-pressure critical applications-further expanding Huayang's electric resistance welded steel pipe portfolio.
By aligning ERW and CEW with customer needs, Huayang delivers cost-effective, high-quality solutions that reinforce its position as a one-stop supplier of electric resistance welded steel pipes for global markets.
