When we purchase steel pipes, we often come into contact with two products, ERW steel pipes and seamless steel pipes, which are widely used in our lives. So, what's the difference between the two? How to choose?
Seamless steel pipes generally use perforation and rolling processes. Seamless steel pipes are characterized by no welds in the pipe and have high strength, toughness and corrosion resistance.
ERW steel pipes have good toughness and reliability and are suitable for transporting low-pressure liquids and gases such as oil and natural gas. ERW steel pipes are also widely used in manufacturing machines, constructing buildings, etc.
Seamless steel pipe: The limit of wall thickness control accuracy is 0.9mm.
Seamless steel pipe: The hot-rolled forming process is used. The raw material composition, cooling conditions, and cooling conditions of the rolls have a large impact on the outer diameter of the steel pipe. Therefore, it is difficult to control the outer diameter accurately and the fluctuation range is large.
The tensile properties of seamless steel pipes and ERW steel pipes meet API standards, but the strength of seamless steel pipes is generally at the upper limit and the plasticity is at the lower limit. In comparison, the strength of ERW steel pipes is at its best and the plasticity index is 33.3% higher than the standard. The reason is that the performance of the raw material and hot-rolled strip of ERW steel pipe is guaranteed by means of micro-alloying smelting, refining outside the furnace, and controlled cold and controlled rolling; seamless steel pipes mainly rely on means of increasing carbon content, which is difficult to ensure strength and plastic Reasonable match.
There are also differences in the application scenarios of ERW steel pipes and seamless steel pipes.
Seamless steel pipes are mainly used in transportation pipelines and equipment under high pressure, high temperature and special environments. Specifically, seamless steel pipes are widely used in petroleum, natural gas, chemical industry, electric power, aerospace, pharmaceutical and other fields. In some special industries, such as the nuclear energy industry, seamless steel pipes are an indispensable material.
Tips: ERW welded pipe is formed by rolling strip and welding the seam, with tighter dimensional tolerances and less weight. The weld seam is heat treated after welding that no untempered martensite remains, and the weld flash can be removed from both inner and outer surfaces. ASTM A53 ERW steel pipe is a typical carbon steel pipe. It is largely used to convey fluids at low / medium pressures such as oil, gas, steam, water, air and also for mechanical applications.
The pros and cons of seamless pipe:
Seamless pipes are manufactured out of a solid block of steel and do not have any weld seam, which may represent a weak area (subject to corrosion, erosion and, general failure)
Seamless pipes have more predictable and precise shapes, in terms of roundness and ovality, compared to welded pipes.
The main disadvantage of seamless pipes is that their cost per ton is higher than the cost of ERW pipes of the same size and grade (Seamless vs ERW pipe compete in the range 2 to 20 inches)
Delivery times may be longer, as there are fewer manufacturers of seamless pipes than welded pipes (lower entry barriers exists for weldedpipes vs. seamless pipes)
Seamless pipes may have an inconsistent wall thickness across their length, indeed the general tolerance is +/- 12.5%
The major "defect" attributed to welded pipes is that the presence of a weld seam constitutes a weakness factor. Whereas this may have been true in the past, this is becoming less and less true with the advances of the welding technologies in the last ten years.
1. High-risk working conditions, high pressure & high temperature, corrosion resistance and high safety requirements → Seamless Steel Pipe
2. Civil general use, low-pressure transmission, structural materials and limited budget → ERW Steel Pipe
3. For sufficient budget, long-term service life and low maintenance demand, seamless pipe is preferred; for short-term projects and conventional applications, ERW pipe is the better choice.
Q1: What is a seamless steel pipe?
A1: Seamless steel pipe is a steel pipe without weld seams made from solid steel ingots/bills through processes such as piercing, hot rolling/cold rolling, etc. The overall structure is formed in one piece and there are no weak points in the weld seams.
Q2: What is ERW steel pipe?
A2: ERW steel pipe is a steel pipe made by rolling steel plates/coils into pipe blanks and then welding the joints together using high-frequency resistance welding. There is a weld seam on the pipe body.
Q3: What is the most fundamental difference between the two?
A3: The core difference lies in the manufacturing process and weld structure:
Seamless pipe: No weld seams, integrally formed, with uniform strength distribution.
ERW pipe: Contains weld seams; the performance of the weld area is its weak point (requiring compensation through heat treatment/flaw detection).
Q4: What are the differences in size and specifications between the two?
A4: Seamless pipe: Suitable for small to medium diameter and thick-walled specifications; large diameter/thin-walled specifications are costly and have long delivery cycles.
ERW pipe: Capable of stable production of large diameter, thin-walled, and long-length pipes with high dimensional accuracy and fast batch delivery.
