The Difference Between ERW and EFW Pipe
Clarifying Core Concepts: ERW and EFW Pipe Definitions
To accurately distinguish between ERW and EFW pipes, we first need to clarify their basic definitions-this includes understanding what is erw pipe, erw pipe meaning, and the unique characteristics of EFW (Electric Fusion Welded) pipes. For Hebei Huayang Steel Pipe Co., Ltd., which specializes in electric resistance welded steel pipes (including ERW and hfw steel pipes), mastering these concept differences is the foundation for guiding customers to choose the right product.
What is ERW Pipe? Understanding ERW Pipe Meaning and Its Variants
ERW stands for Electric Resistance Welding, and erw pipe meaning refers to a type of electric resistance welded steel pipe manufactured by using the resistance heat generated when an electric current passes through the contact surface of steel workpieces to fuse the edges of the pipe blank, then applying pressure to form a firm weld. Unlike seamless pipes (made by piercing steel billets), ERW pipes are formed by welding steel plates or coils, with high production efficiency and relatively low cost.
At Huayang, ERW technology has two main application forms:
Ordinary ERW pipes: Using low-frequency or medium-frequency current (50Hz-3kHz) for welding, suitable for low-pressure scenarios such as urban water supply and construction scaffolding. Huayang's ordinary ERW pipe production line covers diameters from 21.3mm to 630mm and wall thicknesses from 2mm to 16mm, with an annual output of over 30,000 tons.
HFW steel pipes: A high-performance variant of ERW technology, hfw meaning is High-Frequency Welding (using 300kHz-500kHz high-frequency current). The high-frequency current induces eddy currents on the steel surface, concentrating heat on the pipe blank edge to achieve rapid, uniform welding. Huayang's hfw steel pipe production line adopts German SMS high-frequency welding machines, with weld strength reaching 95% of the base metal, suitable for high-pressure scenarios such as oil and gas transportation.
It is important to emphasize that both ordinary ERW pipes and hfw steel pipes belong to electric resistance welded steel pipes-they share the core principle of resistance heat welding but differ in current frequency and application scenarios.
What is EFW Pipe? Definition and Technical Characteristics
EFW (Electric Fusion Welded) pipes, also known as Submerged Arc Welded (SAW) pipes, are a type of welded steel pipe manufactured by using an electric arc as the heat source to melt the base metal and welding wire, with the arc and molten pool protected by a granular flux layer. Unlike ERW pipes (which rely on resistance heat), EFW pipes use arc heat for welding-this difference in heat source leads to significant differences in their manufacturing process, performance, and application.
EFW pipes are mainly divided into two types:
Longitudinal EFW pipes: The steel plate is rolled into a cylindrical pipe blank, and the weld is parallel to the pipe axis. This type is similar to ERW pipes in shape but uses submerged arc welding instead of resistance welding.
Spiral EFW pipes: The steel coil is rolled into a spiral pipe blank at a certain angle, and the weld is spiral-shaped. This type has better structural stability and is suitable for large-diameter, thick-walled pipes.
Huayang does not produce EFW pipes (focusing on electric resistance welded steel pipes), but the company's sales and technical teams are familiar with EFW pipe characteristics-this allows them to provide customers with professional comparisons and recommendations based on project needs. For example, when a customer inquires about large-diameter (≥800mm) pipes for long-distance water transmission, Huayang's team will explain the advantages of spiral EFW pipes (such as better pressure resistance for large diameters) while introducing the applicable scenarios of hfw steel pipes (more cost-effective for diameters ≤630mm).
Manufacturing Process Comparison: ERW vs. EFW Pipe
The core difference between ERW and EFW pipes lies in their manufacturing processes-from raw material processing to welding technology, each link has obvious distinctions. These differences directly affect the pipes' production efficiency, cost, and performance. Below, we take Huayang's ERW pipe production process as a reference and compare it with the mainstream EFW pipe manufacturing process.
Raw Material Requirements and Pretreatment
ERW Pipe Raw Materials (Huayang's Standards)
Electric resistance welded steel pipes (including ERW and hfw steel pipes) have strict requirements for raw material chemical composition and surface quality, as resistance welding requires good electrical conductivity and weldability of the steel. Huayang mainly uses hot-rolled low-carbon or medium-carbon steel coils (Q195-Q345) for ERW pipes, with the following key indicators:
Carbon content: ≤0.25% (ensures good weldability, avoiding brittle welds);
Manganese content: 0.30%-1.60% (enhances steel strength without affecting welding);
Sulfur and phosphorus content: ≤0.035% (reduces weld defects such as inclusions);
Surface quality: No cracks, rust, or pits (Huayang's raw material inspection rejects coils with surface defects exceeding 0.5mm in depth).
Before production, the steel coils undergo uncoiling, leveling, and edge trimming-Huayang uses a 12-roller leveler to ensure the steel plate flatness (deviation ≤0.1mm/m) and a precision edge trimmer to cut the plate edge into a V-shape (angle 30°-45°), which is conducive to subsequent welding.
EFW Pipe Raw Materials
EFW pipes (especially spiral EFW pipes) mainly use hot-rolled steel coils or steel plates with higher carbon content (Q235-Q460), as arc welding can handle higher-strength steel. The raw material requirements for EFW pipes are relatively loose compared to ERW pipes:
Carbon content: ≤0.45% (arc welding can melt high-carbon steel, but requires preheating to avoid cracks);
Surface quality: Allowable minor rust (the flux layer during welding can cover minor surface defects);
Plate thickness: EFW pipes are more suitable for thick-walled pipes (wall thickness ≥8mm), while ERW pipes (especially ordinary ERW) are more suitable for thin-walled pipes (wall thickness ≤12mm).
The pretreatment of EFW pipe raw materials mainly includes uncoiling (for coils) and plate cutting (for steel plates), with no strict edge trimming required-this simplifies the pretreatment process but may affect weld uniformity.
Forming Process: Rolling Methods and Precision
ERW Pipe Forming (Huayang's Multi-Roll Gradient Process)
ERW pipe forming requires high precision to ensure the pipe blank edge alignment (critical for resistance welding). Huayang adopts a "multi-roll gradient forming process" for electric resistance welded steel pipes:
Pre-forming stage: 4-6 sets of horizontal rolls gradually bend the steel plate into a U-shape, with roll pressure adjusted from 5kN to 15kN according to plate thickness;
Intermediate forming stage: 3-4 sets of vertical rolls further shape the U-shaped plate into a semi-circular shape, ensuring the edge gap is ≤0.5mm;
Final forming stage: 2-3 sets of combined rolls (horizontal + vertical) form the semi-circular plate into a cylindrical pipe blank, with ovality controlled at ≤0.5% (e.g., Φ325mm pipes have an ovality ≤1.6mm).
This multi-roll forming process ensures high dimensional precision of ERW pipes-Huayang's hfw steel pipes have an outer diameter deviation of ±0.1mm and wall thickness deviation of ±0.05mm, meeting the high-pressure transportation standard.
EFW Pipe Forming
EFW pipe forming is relatively simple, with two main methods:
Longitudinal EFW forming: The steel plate is rolled into a cylinder using a single set of forming rolls, with edge alignment relying on manual adjustment-this leads to low precision (ovality ≥1%) and is only suitable for low-pressure scenarios.
Spiral EFW forming: The steel coil is rolled into a spiral pipe blank using a spiral forming machine, with the forming angle (usually 30°-60°) determined by the pipe diameter. Spiral forming has higher precision than longitudinal forming (ovality ≤0.8%) but is still lower than ERW forming.
The low forming precision of EFW pipes means they are not suitable for scenarios requiring strict dimensional accuracy (such as precision fluid transportation), while ERW pipes (especially Huayang's hfw steel pipes) are the first choice for such scenarios.
Welding Process: Heat Source, Speed, and Quality
ERW Pipe Welding (Resistance Heat: Ordinary ERW vs. HFW)
The welding process is the core difference between ERW and EFW pipes. ERW pipes use resistance heat, with two main forms at Huayang:
Ordinary ERW welding: Uses medium-frequency current (1kHz-3kHz), with welding speed of 10-20m/min. The welding station consists of two copper electrodes that clamp the pipe blank and pass current-resistance heat melts the edge, and an extrusion roll applies pressure (2MPa-5MPa) to form a weld. Huayang's ordinary ERW pipes have a weld strength of 85%-90% of the base metal, suitable for low-pressure water supply.
HFW welding: Uses high-frequency current (300kHz-500kHz), with welding speed of 30-60m/min (3 times faster than ordinary ERW). The high-frequency current is induced by an induction coil (no direct contact with the pipe blank), concentrating heat on the edge (heating width ≤2mm) to achieve rapid welding. Huayang's hfw steel pipes undergo post-weld annealing (heating to 650℃-700℃) to eliminate internal stress, with weld strength reaching 95% of the base metal-this allows them to withstand a hydrostatic pressure of 12MPa, meeting the oil and gas transportation standard.
A key advantage of ERW welding is no need for welding wire or flux-this simplifies the process, reduces costs, and avoids flux residue (which can cause pipe corrosion).
EFW Pipe Welding (Arc Heat: Submerged Arc Welding)
EFW pipes use submerged arc welding (SAW), which relies on an electric arc between the welding wire and the pipe blank as the heat source. The welding process has the following characteristics:
Heat source: Arc heat has a high temperature (≥3000℃), which can melt thick-walled steel (wall thickness up to 100mm) but has slow heating speed (welding speed of 1-5m/min, 1/10 of HFW speed).
Welding materials: Requires welding wire (matching the base metal composition) and granular flux (to protect the arc and molten pool from air contamination). The flux needs to be cleaned after welding, increasing the process complexity.
Weld quality: The weld of EFW pipes is thicker (weld height ≥3mm) and has good toughness, but may have internal defects such as slag inclusion or porosity (requires X-ray flaw detection to eliminate).
Compared with ERW welding, EFW welding has lower efficiency and higher costs-this is why EFW pipes are usually more expensive than electric resistance welded steel pipes of the same specification.
Post-Welding Treatment: Inspection and Finishing
ERW Pipe Post-Welding Treatment (Huayang's Strict Standards)
Huayang conducts comprehensive post-welding treatment for electric resistance welded steel pipes to ensure quality:
Weld trimming: Uses a mechanical trimmer to remove excess weld beads (weld height ≤0.5mm), ensuring the pipe surface is smooth.
Heat treatment: Ordinary ERW pipes undergo stress relief annealing (550℃-600℃), while hfw steel pipes undergo full annealing (700℃-750℃) to refine grains and improve toughness.
Quality inspection: Includes three key links:
Ultrasonic flaw detection: Scans the weld 360° to detect internal defects (sensitivity ≥0.5mm);
Hydrostatic pressure test: Tests at 1.5 times the rated pressure for 10 minutes (e.g., hfw steel pipes for gas transportation are tested at 12MPa);
Mechanical property test: Samples are taken for tensile, impact, and bending tests (Huayang's hfw steel pipes have a tensile strength of ≥480MPa and impact toughness of ≥60J/cm² at -40℃).
EFW Pipe Post-Welding Treatment
EFW pipe post-welding treatment focuses on weld cleaning and defect repair:
Flux cleaning: Uses a brush or air jet to remove residual flux from the weld surface-this step is critical, as leftover flux can cause corrosion.
Heat treatment: Thick-walled EFW pipes (wall thickness ≥20mm) require post-weld heat treatment (600℃-650℃) to reduce internal stress, while thin-walled EFW pipes often skip this step to save costs.
Quality inspection: Mainly relies on X-ray flaw detection to check for internal defects, but rarely conducts hydrostatic pressure tests (due to high cost for large-diameter pipes). This means EFW pipes may have hidden leakage risks in high-pressure scenarios.
Performance Comparison: ERW vs. EFW Pipe
The differences in manufacturing processes lead to significant performance gaps between ERW and EFW pipes-including strength, toughness, corrosion resistance, and pressure resistance. These performance differences determine their applicable scenarios. Below, we compare the key performance indicators using Huayang's ERW pipes (ordinary and hfw steel pipes) and mainstream EFW pipes as examples.
Strength and Toughness: Weld and Base Metal Consistency
ERW Pipe Strength (Huayang's Test Data)
Electric resistance welded steel pipes have good strength consistency between the weld and base metal, especially hfw steel pipes:
Ordinary ERW pipes: Tensile strength of the base metal is 335MPa-410MPa, and the weld tensile strength is 85%-90% of the base metal (285MPa-369MPa). Huayang's ordinary ERW pipes for scaffolding can withstand a vertical load of 200kg/m without deformation.
HFW steel pipes: After annealing, the weld tensile strength reaches 95% of the base metal (456MPa-480MPa for Q345 steel), and the yield strength is ≥400MPa. In Huayang's impact test, hfw steel pipes have an impact toughness of ≥60J/cm² at -40℃-this means they can resist brittle cracking in low-temperature environments (such as northern winter oil transportation).
The high strength of hfw steel pipes is due to the high-frequency welding process, which refines the weld grains and reduces internal defects.
EFW Pipe Strength
EFW pipes have high weld toughness but lower strength consistency:
Tensile strength: The base metal tensile strength is 345MPa-460MPa, and the weld tensile strength is 75%-85% of the base metal (259MPa-391MPa)-lower than ERW pipes.
Toughness: The weld of EFW pipes has good toughness (impact toughness ≥50J/cm² at 0℃) due to the arc welding's slow cooling rate, but it decreases significantly at low temperatures (≤30J/cm² at -20℃), making them unsuitable for low-temperature scenarios.
The lower strength of EFW pipe welds is because the arc heat causes coarse weld grains-even with heat treatment, it is difficult to achieve the grain refinement effect of HFW welding.
Corrosion Resistance: Weld Surface and Internal Cleanliness
ERW Pipe Corrosion Resistance (Huayang's Surface Treatment)
ERW pipes have good corrosion resistance due to the clean weld and optional surface treatment:
Weld cleanliness: ERW welding uses no flux or welding wire, so there is no residue on the weld surface-this avoids corrosion caused by flux reactions with water or air.
Surface treatment: Huayang provides galvanizing, epoxy coating, or 3PE anti-corrosion treatment for electric resistance welded steel pipes. For example, galvanized ERW pipes have a zinc coating thickness of 80-120μm, with a service life of ≥15 years in humid environments (such as rural irrigation canals).
Huayang's hfw steel pipes for marine oil transportation undergo 3PE anti-corrosion treatment (epoxy powder + adhesive + polyethylene), which can resist seawater corrosion for ≥20 years-this is comparable to EFW pipes' corrosion resistance.
EFW Pipe Corrosion Resistance
EFW pipes have lower corrosion resistance due to potential flux residue:
Flux residue: Even with cleaning, EFW pipes may have tiny flux particles embedded in the weld-these particles are hygroscopic and will react with water or air over time, causing localized corrosion (rust spots) on the weld surface. In a 2024 field test, spiral EFW pipes used in a rural irrigation canal showed obvious weld corrosion after 8 years, while Huayang's galvanized ERW pipes in the same project remained intact.
Surface treatment limitations: EFW pipes' thick welds make it difficult to apply uniform anti-corrosion coatings (such as 3PE). The coating on the weld surface is often thinner than the pipe body, becoming a "corrosion weak point"-this is why EFW pipes are rarely used in marine or high-humidity environments.
Pressure Resistance: Suitable for Low-Pressure vs. High-Pressure Scenarios
ERW Pipe Pressure Resistance (Huayang's High-Pressure Advantage)
Electric resistance welded steel pipes, especially hfw steel pipes, have excellent pressure resistance due to high weld quality and dimensional precision:
Ordinary ERW pipes: Suitable for low-pressure scenarios (working pressure ≤2MPa), such as urban water supply (water pressure usually 0.4MPa-0.6MPa) and indoor gas pipelines (gas pressure ≤3kPa). Huayang's ordinary ERW pipes undergo a 1.2MPa hydrostatic pressure test before delivery, ensuring no leakage.
HFW steel pipes: The high-frequency welding process and post-weld annealing make them suitable for high-pressure scenarios (working pressure ≤10MPa). Huayang's Φ325×10mm hfw steel pipes can withstand a long-term working pressure of 8MPa, meeting the national standard for natural gas long-distance transportation (GB 9711). In the 2023 Shanxi-Beijing Natural Gas Pipeline Project, these pipes operated continuously for 12 months without pressure drop or leakage.
EFW Pipe Pressure Resistance
EFW pipes' pressure resistance is limited by weld defects and low precision:
Longitudinal EFW pipes: Due to low forming precision and unstable weld quality, their maximum working pressure is ≤1.5MPa-only suitable for low-pressure fluid transportation (such as factory cooling water with pressure ≤1MPa).
Spiral EFW pipes: Spiral welds distribute pressure more evenly than longitudinal welds, so their maximum working pressure can reach 4MPa-suitable for medium-pressure scenarios such as urban heating pipelines (working pressure 1.2MPa-2MPa). However, spiral EFW pipes cannot meet high-pressure requirements (≥6MPa) because their welds have a higher risk of slag inclusion, which will expand under high pressure and cause leakage.
Application Scenario Comparison: ERW vs. EFW Pipe
The performance differences between ERW and EFW pipes determine their distinct application scenarios. Hebei Huayang Steel Pipe Co., Ltd. often uses this comparison to guide customers in product selection, ensuring each project uses the most cost-effective pipe.
ERW Pipe Application Scenarios (Huayang's Main Markets)
Civil and Low-Pressure Industrial Scenarios
Urban water supply and drainage: Huayang's ordinary ERW pipes (Φ114×4.5mm to Φ273×8mm) are widely used in residential area water supply networks. In the 2024 Shijiazhuang Residential Water Supply Renovation Project, 5,000 tons of these pipes were supplied-their low cost (30% cheaper than EFW pipes) and easy installation (light weight, easy cutting) reduced the project's total cost by 15%.
Construction scaffolding and decoration: Φ48×3.5mm ordinary ERW pipes are the standard for construction scaffolding. Huayang's pipes have uniform wall thickness (deviation ≤0.05mm), ensuring stable load-bearing (each meter can bear 200kg). In the 2023 Baoding Commercial Building Project, 2,500 tons of these pipes were used to build scaffolding for 50,000㎡ construction area.
Indoor gas and fluid pipelines: Huayang's ERW pipes with epoxy coating are used in indoor gas pipelines-their smooth inner wall (roughness ≤Ra6.3μm) reduces gas flow resistance, and the coating prevents internal corrosion. In the 2024 Tangshan Residential Gas Pipeline Project, 1,800 tons of these pipes were installed, passing the national gas safety inspection.
High-Pressure Industrial Scenarios
Huayang's hfw steel pipes are the core product for high-pressure scenarios:
Oil and gas transportation: Φ219×8mm to Φ630×12mm hfw steel pipes are used in onshore and offshore oil pipelines. In the 2023 Bohai Bay Offshore Oil Field Project, 3,000 tons of Huayang's hfw steel pipes (with 3PE anti-corrosion treatment) were laid-they withstood seawater corrosion and 8MPa working pressure, meeting the oil field's 20-year service life requirement.
High-pressure steam pipelines: hfw steel pipes with heat-resistant steel material (Q345R) are used in thermal power plants' high-pressure steam pipelines (working temperature ≤450℃, pressure ≤6MPa). Huayang's 2024 supply to a Cangzhou thermal power plant included 800 tons of such pipes, which operated stably during the winter heating season.
EFW Pipe Application Scenarios
EFW pipes are mainly used in large-diameter, medium-low pressure scenarios where ERW pipes' specifications are limited:
Large-diameter water transmission pipelines: When the pipe diameter exceeds 800mm (such as cross-river water pipelines), spiral EFW pipes are the only choice-their spiral forming process can produce large-diameter pipes (up to 3000mm) that ERW technology cannot match. For example, the 2024 Zhengzhou Yellow River Water Diversion Project used Φ1200×12mm spiral EFW pipes.
Low-pressure industrial exhaust pipelines: Longitudinal EFW pipes (Φ500×6mm to Φ800×8mm) are used in factory exhaust systems (working pressure ≤0.5MPa). Their low cost and large diameter make them suitable for conveying low-pressure exhaust gas, but they require regular weld inspection to prevent corrosion leakage.
Conclusion: Choosing the Right Pipe Based on Demand-Huayang's Professional Guidance
The difference between ERW and EFW pipes is not a "good or bad" distinction, but a "suitable or not" match for specific scenarios. For Hebei Huayang Steel Pipe Co., Ltd. and its customers, understanding these differences is the key to optimizing project costs and ensuring operational safety.
From the perspective of electric resistance welded steel pipes (ERW), their advantages lie in high production efficiency, low cost, and excellent performance in low-to-high pressure scenarios (especially hfw steel pipes for high pressure). Huayang's ERW product line-covering ordinary pipes for civil use and hfw steel pipes for high-pressure industry-can meet 80% of the market's steel pipe needs. For example, urban water supply, construction scaffolding, and oil/gas transportation projects all benefit from ERW pipes' precision and cost-effectiveness.
EFW pipes, on the other hand, have unique value in large-diameter (≥800mm) medium-low pressure scenarios-their spiral forming process fills the gap where ERW technology cannot produce large-diameter pipes. However, their low corrosion resistance, low pressure resistance, and high cost make them unsuitable for most civil and high-pressure industrial projects.
Huayang's role is not only to produce high-quality electric resistance welded steel pipes but also to provide customers with professional selection guidance:
When a customer needs pipes for high-pressure oil/gas transportation or low-cost civil projects, Huayang recommends hfw steel pipes or ordinary ERW pipes, explaining erw pipe meaning and hfw meaning to help them understand the technical advantages;
When a customer needs large-diameter pipes for medium-pressure water transmission, Huayang will objectively introduce the advantages of spiral EFW pipes while reminding them of corrosion prevention and maintenance requirements.
In the future, as ERW technology continues to develop (such as Huayang's R&D of hfw steel pipes with diameters up to 800mm), the application scope of electric resistance welded steel pipes will further expand. But no matter how the market changes, the core principle of "choosing the right pipe based on scenario needs" will remain unchanged-and Huayang will continue to be a reliable partner for customers in this process, providing both high-quality products and professional technical support.
