ERW vs Seamless Stainless Steel Pipe: 6 Key Differences

What is the difference between ERW and Seamless stainless steel pipes?

Simply put: stainless steel pipes are a general term, and steel pipes are made of stainless steel materials. Seamless pipes and ERW pipes refer to the categories or production processes of stainless steel materials into pipes.

The difference between seamless pipes and ERW pipes:

Simply put, one has a weld and the other does not; in addition, the raw materials processed are different. Seamless pipes are made of stainless steel round bars by heating and perforating, and ERW pipes are made of stainless steel strips by rolling and then welding.

Welded pipes are divided into straight seam welded pipes and spiral welded pipes according to the shape of the welds. ERW refers to straight seam welded pipes.

ERW Stainless Steel Pipe vs Seamless Stainless Steel Pipe: 6 Key Differences

The main differences between ERW stainless steel pipes and Seamless stainless steel pipes are their raw materials, manufacturing processes, appearance, mechanical properties, cost-effectiveness, and application areas.

1. Raw materials

Seamless stainless steel pipes are made of solid round steel "billets", which are heated and pushed or pulled to form steel until the steel is formed into a hollow tube. Steel billets are purchased from well-known factories in China or abroad.

ERW stainless steel pipe is made of stainless steel strip or steel coil as raw material, through rolling and then welding.

‌2. Manufacturing process‌ 

ERW stainless steel pipe is made by resistance welding process, which involves rolling steel plate or steel strip continuously into a cylindrical shape, and then passing electric current to both ends to generate heat, so that the edges of the material melt and combine. In contrast, seamless stainless steel pipe is made by perforation and stretching method, without welds, so its production process is more complicated.

3. Appearance 

ERW (Electric resistance welding) pipe is made by rolling metal and then welding it longitudinally in its length. ERW stainless steel pipe has a weld seam, which is the key to its quality.

Seamless stainless steel pipe is made by perforating and extruding metal to the required length, without welds, which is due to their different production methods.

Therefore, in appearance, the cross section of ERW pipe has a welded joint, while the cross section of seamless pipe does not have any welded joints throughout its length.

4. Mechanical properties ‌

Since the weld of ERW stainless steel pipe is formed by melting the parent material of the steel strip body, its mechanical strength is generally better than that of general welded pipe. Seamless stainless steel pipe, due to its continuity and weld-free characteristics, shows better durability when handling fluid transmission at different temperatures and pressures. The pressure distribution on the wall of seamless steel pipe is more uniform, and it is not easy to break and leak.

5. ‌Cost-effectiveness ‌

The production cost of ERW stainless steel pipe is relatively low because it uses an efficient resistance welding process, while the production process of seamless stainless steel pipe is more complicated and the cost is relatively high.

6. Application 

ERW stainless steel pipe: Suitable for general industrial applications such as building decoration, food machinery, furniture, and heat exchangers, as well as medium and low pressure pipelines (working pressure ≤10MPa). Low cost, high efficiency, suitable for large-scale applications.

Seamless stainless steel pipe: Suitable for high-pressure pipelines in petrochemicals, boilers, nuclear power, hydraulic cylinders, and other applications requiring extremely high pressure resistance and reliability. No weld seams, continuous and uniform overall design, ensuring greater safety and reliability under high-pressure conditions.

Specification Range: 

Standard outer diameters for ERW stainless steel pipes are 1/2"~8" (approximately 13~203mm); standard outer diameters for seamless stainless steel pipes are 1/8"~24" (approximately 6~610mm). For large diameters, seamless pipes are extremely expensive, and LSAW welded pipes are typically used instead. Hunan Standard Steel Co., Ltd (HSCO) is one of China's leading manufacturers and exporters of ERW welded pipes and seamless stainless steel pipes: sales@hu-steel.com

Specifications Comparison Table:

The table below provides a detailed comparison of ERW stainless steel tubing and seamless stainless steel tubing across various dimensions, including raw materials, manufacturing process, specifications, pressure resistance, and cost. Please note: Carbon steel ERW tubing size can be up to 24 inches in length, but stainless steel ERW tubing, due to work hardening limitations, typically has a maximum length of only about 8 inches. Do not confuse them.

Comparison Dimensions	ERW Stainless Steel Pipe	Seamless Stainless Steel Pipe
Raw Materials	Stainless steel strip/coil	solid stainless steel round bar (bulk)
Manufacturing Process	Cold bending + resistance welding (with weld seam)	heated piercing + extrusion/stretching (without weld seam)
Appearance Characteristics	Longitudinal weld seam on pipe wall	seamless throughout
Standard Outer Diameter Range	1/2" ~ 8" (maximum approximately 10")	1/8" ~ 24" (large diameter uneconomical)
Wall Thickness Uniformity	Uniform, no eccentricity	possible wall thickness deviation
Weld Seam	Yes, equivalent to the base material after solution treatment	No
Pressure Resistance	Medium and low pressure (≤10MPa)	High pressure (up to 70MPa and above)
Corrosion Resistance (Standard Production)	Same as the base material (after solution treatment)	Consistent with the body, no risk of heat-affected zone
Production Cost	Low, high efficiency	High, complex process
Price	20-40% cheaper	More expensive
Optimal Applications	Building decoration, food machinery, medium and low pressure pipelines, heat exchangers	Petrochemical high-pressure pipelines, boilers, nuclear power, aerospace

ERW vs Seamless Stainless Steel Pipe – How to Choose?

Seamless stainless steel pipe is recommended if any of the following conditions are met:

● Working pressure > 10MPa
● Working temperature > 400°C or < -100°C
● Highly corrosive or high-purity media
● Project specifies the use of seamless pipe (e.g., certain pressure vessel specifications)

ERW stainless steel pipe is recommended if the following conditions are met:

● Working pressure ≤ 10MPa
● Normal or medium temperature environment
● Limited cost budget
● Large-volume purchase with delivery time requirements
● Structural or decorative applications (no special pressure requirements)

Frequently Asked Questions (FAQ):

Q1: Will the weld seams of ERW stainless steel pipe leak or crack?

A: No.
Qualified ERW welded pipes that have undergone solution annealing and passed ultrasonic/eddy current testing have weld seam strength comparable to the base material, ensuring safe and reliable use under rated pressure.

Q2: Is the corrosion resistance of ERW stainless steel pipe worse than that of seamless pipe?

A: The key is whether it has undergone solution treatment.
Untreated ERW welds have a risk of sensitization (chromium precipitation), resulting in decreased corrosion resistance. After solution annealing and pickling passivation, the corrosion resistance is basically the same as seamless pipe.

Q3: Why can't ERW stainless steel pipes be made to 24 inches?

A: Stainless steel undergoes severe work hardening during cold bending.
Large diameters (>8 inches) are difficult to form, have high springback, and high weld stress. Carbon steel ERW pipe can reach 24 inches, but the conventional maximum for stainless steel ERW pipe is only about 8 inches. For diameters exceeding this, it is recommended to use seamless pipes (SMLS) or LSAW welded pipes.

Q4: How much is the price difference?

A: For the same specifications, ERW stainless steel pipes are about 20-40% cheaper than seamless pipes. The larger the diameter and the thicker the wall, the more significant the price difference.

Q5: How to determine if a manufacturer is reliable?

A: Required documents include:
① Material certificate (MTC);
② Solution heat treatment report;
③ Non-destructive testing report (UT or ET);
④ Hydrostatic test report. Suppliers with all four documents are considered qualified.

Related articles: 

● 7 Things to Consider When Purchasing Stainless Steel ERW Pipes 

● 304 vs. 316 Stainless Steel: What's the Difference?

● Carbon Steel Tube vs Stainless Steel Tube