SMLS pipe is a steel tube made from a solid round billet. The billet is heated and pierced to form a hollow shape, without any welding seam on the body of the pipe.Because there is no weld, the structure is more uniform and stable. That’s why seamless pipes are often used in places where pressure, temperature, or safety requirements are higher.Typical applications include oil and gas pipelines, boilers, hydraulic systems, and general industrial piping.
Seamless Pipe Meaning
In simple terms, a seamless pipe is a pipe without a welded joint.Unlike welded pipe, which is formed by rolling steel plate and welding the seam, seamless pipe is formed from a solid piece of steel. After piercing and rolling, it becomes a hollow tube.This difference in manufacturing is what gives seamless pipe its strength advantage in many engineering applications.
Types of Seamless Pipe
Seamless pipes are usually divided by how they are produced.
Hot-rolled seamless pipe
Made at high temperature. It is suitable for larger diameters and general industrial use.
Cold-drawn or cold-rolled pipe
Processed at room temperature after hot rolling. It has better accuracy and smoother surface, often used in mechanical or precision applications.
Fast forming speed, high productivity, no damage to the coating, and profiles can be made into various shapes to adapt to different use conditions. The cold rolling process can cause large plastic deformation of steel, thereby increasing the yield point of steel. 2. The cold rolling process can destroy the casting structure of the steel ingot, refine the grains of the steel, eliminate organizational defects, make the steel structure dense, and improve the mechanical properties of the steel. This improvement is mainly reflected in the rolling direction, and to a certain extent, the steel is no longer an isotropic body. The bubbles, cracks, shrinkage holes, etc. formed during casting can be repaired under high temperature and high pressure.
Seamless pipes are available in the following specifications: ASTM A53, A106, A252, A333, A335, A501, A523, A589, API 5L and API 5CT. The most common seamless pipe is A106B. End treatments of seamless pipes include beveled or square cut flat ends. Seamless carbon steel pipes are available in black, bare, galvanized or epoxy coatings. Steel pipes are usually available in lengths of 21 feet. It is also available in single random lengths (SRL) ranging from 17 feet to 24 feet. Double random lengths (DRL) refer to pipes with a length of at least 37 feet to 44 feet.
Hot Rolled vs Cold Rolled Seamless Pipe
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Feature
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Hot Rolled
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Cold Rolled
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Diameter
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Larger (>32 mm)
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Smaller (<6 mm typical)
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Precision
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Moderate
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High
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Surface Finish
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Rougher
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Smoother
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Strength
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Good
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Higher yield strength after processing
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Cost
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Lower
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Higher
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Seamless pipe weight calculation formula
The weight per meter of seamless steel pipe is W=0.02466*S(DS).
Symbol meaning: D=outer diameter, S=wall thickness.
For example, for a seamless steel pipe with an outer diameter of 60mm and a wall thickness of 4mm, calculate the weight per meter.
Solution: Weight per square meter = 0.02466*4*(60-4)=5.52Kg.
The theoretical weight calculation formula for seamless steel pipes is W=0.0246615(DS)*SW.
Seamless steel pipes have a hollow cross-section and are widely used as pipelines for conveying fluids, such as pipelines for conveying oil, natural gas, coal gas, water and certain solid materials. For most seamless steel pipe manufacturers in China, the maximum outer diameter of the original seamless pipe they produce is 20 inches, 508 mm. Due to equipment limitations, it is usually less than 16 inches, 406.4 mm. If customers want to purchase seamless steel pipes larger than the above size, they need to undergo hot expansion. But usually the quality of such hot-expanded seamless steel pipes cannot be compared with the original seamless steel pipes. In contrast, welded steel pipes do not have these limitations and range in size from 1-1/2 inches (48.3 mm) to 100 inches (2540 mm).
FAQ of SMLS pipe
1. Is seamless pipe better than welded pipe?
Not always. Seamless pipes are better for high-pressure and critical applications, while welded pipes are more cost-effective for general use.
2. Do seamless pipes rust?
Yes, carbon steel seamless pipes can rust if not protected. Coatings such as galvanizing or epoxy are commonly used.
3. Why are seamless pipes more expensive?
Because the manufacturing process is more complex and requires higher-quality raw materials.
4. What is the most common seamless pipe grade?
ASTM A106 Grade B is widely used for high-temperature and pressure applications.
Conclusion
Seamless steel pipes offer high strength, durability, and reliability, making them essential in industries where performance and safety are critical.Choosing the right type—hot rolled or cold rolled—depends on your application, required precision, and budget.
Baowi-steel is a manufacturer of seamless steel pipes in China. We are committed to providing high-quality products and services. If you need them, you can leave a message for inquiry.
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