Differences Between ERW And EFW Steel Pipe

In the field of steel pipe manufacturing, ERW (Electric Resistance Welded) and EFW (Electric Fusion Welded) are two widely used welding processes. However, many customers, including oil and gas companies and municipal engineering departments, often confuse the two. As a technical engineer at Hebei Huayang Steel Pipe Co., Ltd.-a leading enterprise with 22 years of experience and an annual output of 1.2 million tons-I have witnessed the application of both processes in hundreds of projects. This article will explore the core differences between ERW and EFW steel pipes, integrating Huayang's production data, equipment advantages and practical cases, while answering key questions such as "what is erw pipe" and "how to choose between the two".

The core difference between ERW and EFW lies in their forming and welding mechanisms, which determine their raw material adaptability and product characteristics. This difference is clearly visible in Huayang's production workshop, where two types of production lines operate with distinct rhythms.

To understand erw pipe meaning, we must focus on "electric resistance heat". ERW steel pipe takes continuous hot-rolled steel strips as raw materials, and goes through uncoiling, leveling, edge trimming, and forming. The edges of the formed pipe blank are heated to a molten or semi-molten state by the resistance heat generated by high-frequency or low-frequency current, and then squeezed and welded by a squeeze roller to form a seamless weld.

Huayang has 5 ERW production lines imported from Trumpf, Germany, including 3 low-frequency ERW lines (50-60Hz) and 2 high-frequency ERW lines (300-500kHz). It is necessary to clarify here that hfw meaning (High-Frequency Welded) is essentially a branch of ERW. hfw steel pipe uses higher frequency current, which has the advantage of narrow heat-affected zone. In Huayang's production, low-frequency ERW is mainly used to produce ASTM A53 Grade A/B pipes for municipal water supply and low-pressure gas transmission, while hfw steel pipe is targeted at medium and high-pressure oil and gas branch lines.

A key feature of ERW is "continuous production". Huayang's ERW production line can realize 24-hour continuous operation, with a maximum speed of 1.5 meters per minute. In the 2024 Shijiazhuang municipal water supply project, 20,000 tons of DN150 ERW pipes were delivered in only 15 days, which is 50% faster than the EFW process.

EFW (Electric Fusion Welded) is quite different. It uses single steel plates as raw materials, which are first pressed into U-shapes and then O-shapes by a hydraulic press to form a pipe blank, and then the welds are filled and fused by arc welding (such as submerged arc welding). Unlike ERW, EFW requires filling welding wire and flux during the welding process, and the weld is formed by the fusion of the base metal and the filler metal.

Huayang's EFW production line is equipped with a 4000-ton hydraulic forming machine and a double-wire submerged arc welding system, which can process steel plates with a thickness of up to 40mm and produce large-diameter pipes with DN up to 1200mm. In the 2023 Sinopec high-pressure gathering and transportation project, 1.5 million tons of DN800 EFW pipes produced by Huayang successfully withstood the test of 1.8MPa working pressure, and the weld qualification rate reached 100%.

The biggest difference between EFW and ERW in forming is "discontinuity". Due to the need to replace steel plates and adjust molds frequently, the production speed of EFW is only 0.3-0.5 meters per minute, which is far lower than that of ERW. However, its advantage lies in the adaptability to thick plates and large diameters, which ERW cannot match.

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Weld quality is the "life" of welded steel pipes, and the welding characteristics of ERW and EFW lead to obvious differences in weld structure, heat-affected zone and defect rate. Huayang's CNAS-certified laboratory has accumulated tens of thousands of sets of weld detection data, which can intuitively reflect these differences.

The most prominent feature of electric resistance welded steel pipe is that no welding wire or flux is needed during welding. The weld is formed by the self-fusion of the pipe blank edge, so the weld composition is consistent with the base metal, and there is no problem of composition mismatch between the filler material and the base metal. Huayang's test data shows that the weld tensile strength of ERW pipes (ASTM A53 Grade B) is 410-510MPa, which is only 2-3% lower than the base metal, while the EFW weld strength is often affected by the welding wire, and the strength difference may reach 5-8%.

For hfw steel pipe, the high-frequency current makes the heating speed of the pipe blank edge as fast as 1000℃/s, and the welding time is only 0.5-1 second. The heat-affected zone (HAZ) is only 0.5-1mm, which is 1/3-1/5 of that of EFW. This narrow heat-affected zone can effectively avoid grain coarsening and reduce the risk of weld brittleness. In the low-temperature impact test at -20℃, the impact toughness of Huayang's HFW pipe weld is 35J, while the EFW pipe of the same specification is 28J.

However, ERW also has welding risks. If the edge of the steel strip is not cleaned properly or the welding current is unstable, it is easy to produce defects such as cold welding and lack of fusion. To solve this problem, Huayang has installed an AI weld monitoring system on the ERW production line, which can track 16 key parameters such as welding current, pressure and speed in real time, and the defect detection rate has increased from 85% to 99.2%.

EFW uses arc welding to fill the weld, which can artificially control the weld thickness. The weld reinforcement of Huayang's EFW pipes can reach 3-5mm, which is far higher than the 1-2mm of ERW. This thick weld makes EFW have unique advantages in bearing ultra-high pressure. In the 2024 Sichuan gas field ultra-high pressure project, Huayang's EFW pipes with DN600 and wall thickness 20mm successfully withstood the test pressure of 10MPa, while the maximum test pressure of ERW pipes of the same specification is only 4MPa.

The disadvantage of EFW is the wide heat-affected zone (2-5mm) and high residual stress. After welding, heat treatment is usually required to eliminate stress. Huayang's EFW production line is equipped with a normalized heat treatment furnace. After 900℃ heat treatment, the residual stress of the weld is reduced by 70%, and the impact toughness is increased by 15%. In addition, the EFW weld is easy to produce defects such as slag inclusion and porosity. Huayang uses ultrasonic flaw detection + X-ray flaw detection dual inspection method for EFW pipes, and the weld defect elimination rate reaches 100%.

Mechanical properties directly determine the application safety of steel pipes. Huayang conducted a comparative test on ERW and EFW pipes of the same specification (DN300, wall thickness 10mm, Q345B material), and the results showed significant differences in tensile strength, yield strength and fatigue resistance.

The test data shows that the tensile strength of EFW pipe is 550-620MPa, the yield strength is ≥345MPa, and the tensile strength of electric resistance welded steel pipe is 470-550MPa, the yield strength is ≥320MPa. The strength advantage of EFW is mainly due to the thick weld and the reinforcement effect of the filler metal. In the burst test, the burst pressure of EFW pipe is 12MPa, while that of ERW pipe is 8MPa.

This strength difference determines the pressure adaptation range of the two. Huayang's ERW pipes (including hfw steel pipe) are mainly used in medium and low pressure scenarios (≤4MPa), such as municipal water supply, low-pressure gas transmission and irrigation projects; EFW pipes are used in ultra-high pressure scenarios (≥6MPa), such as oil and gas wellheads, high-pressure gathering and transportation pipelines. In the 2023 Changqing Oilfield project, Huayang's EFW pipes were used in the wellhead section (pressure 8MPa), and HFW pipes were used in the branch line (pressure 3MPa), which not only met the performance requirements but also controlled the cost.

While EFW has strength advantages, ERW is better in toughness and fatigue resistance. In the low-temperature impact test at -25℃, the impact toughness of ERW pipe weld is 32J, which is 23% higher than that of EFW pipe (26J). This makes ERW more suitable for low-temperature environments, such as the Harbin winter water supply project in 2024. 5,000 tons of ERW pipes supplied by Huayang served normally in the environment of -30℃, and no weld brittle fracture occurred.

In terms of fatigue resistance, the narrow weld and uniform structure of ERW make it have better fatigue performance. Huayang's fatigue test shows that after 1 million times of cyclic pressure loading (0-2MPa), the weld of ERW pipe is intact, while the EFW pipe has micro-cracks in the heat-affected zone. This is why ERW is widely used in pipelines with frequent pressure fluctuations, such as chemical plant circulating water pipelines.

For bulk procurement projects, cost and efficiency are important factors affecting the selection. Huayang's production and operation data shows that ERW and EFW have obvious differences in raw material utilization, production efficiency and comprehensive cost.

ERW uses continuous steel strips as raw materials, with no need for cutting and less waste. The material utilization rate of Huayang's ERW production line is 95.2%, while EFW uses single steel plates, which need to be cut according to the pipe diameter, and the material utilization rate is only 85%. Taking the production of 10,000 tons of DN300 pipes as an example, ERW can save 1,020 tons of raw materials compared with EFW, and the raw material cost can be reduced by 5.1 million yuan (calculated at 5,000 yuan/ton of steel plates).

In addition, the raw material requirements of ERW are relatively low, and ordinary hot-rolled steel strips can be used, while EFW often requires high-quality steel plates with strict composition control, and the raw material cost is 8-10% higher than that of ERW.

The production efficiency of ERW is much higher than that of EFW. The maximum speed of Huayang's ERW production line is 1.5 meters per minute, and the daily output of a single line is 300 tons; the production speed of EFW is only 0.3 meters per minute, and the daily output of a single line is 60 tons. In the 2024 emergency water supply project in Henan, Huayang urgently deployed 3 ERW production lines, and completed the delivery of 10,000 tons of pipes in 8 days. If EFW is used, it will take 42 days, which is far beyond the project schedule.

The low efficiency of EFW is mainly due to the complex forming process and the need for post-weld heat treatment. However, for large-diameter and thick-walled pipes (DN≥800, wall thickness≥16mm), the efficiency gap between the two will narrow. Because ERW needs to fold thick steel strips many times, the forming speed will decrease, while EFW can form at a relatively stable speed.

Combining raw materials, labor, energy and other costs, Huayang's cost data shows that for DN≤500 and wall thickness≤12mm pipes, the comprehensive cost of ERW is 15-20% lower than that of EFW. For example, the cost of DN150 ERW pipe is 5,800 yuan/ton, while that of EFW is 7,000 yuan/ton. For DN≥800 and wall thickness≥16mm pipes, the cost advantage of EFW appears. The cost of DN1000 EFW pipe is 8,200 yuan/ton, while that of ERW (which needs to be formed by multiple steel strips) is 9,500 yuan/ton.

There is no absolute "good or bad" between ERW and EFW, only "suitable or not". Based on 22 years of project experience, Huayang has summarized a set of "scenario-based selection methods" to help customers avoid wrong selection.

1. Medium and small diameter pipes (DN≤500): ERW has obvious cost and efficiency advantages, such as municipal water supply, residential gas pipelines. In 2024, Huayang supplied 200,000 tons of ERW pipes for the Shijiazhuang urban renewal project, saving 30 million yuan in cost for the customer.

2. Medium and low pressure scenarios (≤4MPa): electric resistance welded steel pipe can fully meet the pressure requirements, such as chemical plant low-pressure material pipelines, agricultural irrigation projects.

3. Low-temperature environment or frequent pressure fluctuations: ERW's good toughness and fatigue resistance can ensure safe operation, such as northern winter water supply pipelines, power plant circulating water pipelines.

4. Urgent orders: ERW's high efficiency can shorten the delivery cycle, avoiding project delays.

When customers ask "what is erw pipe suitable for", we will focus on the above scenarios and recommend low-frequency ERW for general medium and low pressure, and hfw steel pipe for medium and high pressure (2-4MPa).

1. Large-diameter and thick-walled pipes (DN≥800, wall thickness≥16mm): EFW's forming advantage is obvious, such as long-distance oil and gas trunk lines, large-scale water diversion projects.

2. Ultra-high pressure scenarios (≥6MPa): EFW's thick weld can bear higher pressure, such as oil and gas wellheads, high-pressure gas storage pipelines. In the 2023 Sichuan ultra-high pressure gas field project, Huayang's EFW pipes successfully solved the problem of ultra-high pressure bearing.

3. Special working conditions with strong corrosion: EFW's weld can be strengthened by post-weld heat treatment and thickened anti-corrosion coating, which is suitable for marine oil and gas pipelines and chemical corrosion pipelines.

The reason why Huayang can provide professional selection suggestions is that it has both ERW and EFW production capacities, which is rare in the industry. Huayang has 5 ERW production lines (including 2 HFW lines) and 2 EFW production lines, with an annual output of 400,000 tons and 150,000 tons respectively. This dual-process layout allows Huayang to flexibly match the most suitable process according to customer needs.

In terms of quality control, Huayang has established a full-process quality management system: 100% spectral analysis of raw materials to ensure the composition meets the requirements; AI real-time monitoring of the production process to avoid welding defects; 100% eddy current flaw detection for ERW pipes and dual ultrasonic + X-ray flaw detection for EFW pipes. In the 2024 national random inspection, Huayang's electric resistance welded steel pipe and EFW pipe all met or exceeded the API 5L and ASTM A53 standards.

The differences between ERW and EFW steel pipes are concentrated in forming principles, weld characteristics, mechanical properties and cost efficiency. ERW is suitable for medium and small diameter, medium and low pressure, and urgent orders with its advantages of high efficiency, low cost and good toughness; EFW is irreplaceable in large diameter, thick wall and ultra-high pressure scenarios with its strength advantage.

As a professional steel pipe manufacturer, Huayang not only provides high-quality products of both processes, but also takes customer needs as the core to provide customized solutions. Whether you are asking "erw pipe meaning" or confused about the selection of ERW and EFW, Huayang's technical team can give professional answers. Choosing Huayang means choosing the most suitable steel pipe solution for your project.