Let me explain the differences and characteristics of seamless steel pipes and precision welded pipes.

14 Jul,2021

Let me explain the differences and characteristics of seamless steel pipes and precision welded pipes.

　　Let me explain the differences and characteristics of seamless steel pipes and precision welded pipes.

　　Precision welded tubes can be manufactured from any one of several alloys and metals, including carbon steel, stainless steel, molybdenum, tungsten, and others.

　　1. The difference between seamless steel pipes and precision welded pipes: Seamless steel pipes are manufactured by extruding and drawing raw material, whereas precision welded pipes are produced by rolling steel strip into shape and then welding it to form the pipe.

　　Seamless steel pipes offer a broader range of safety features and are therefore more expensive than precision‑welded pipes. Seamless pipes tend to be shorter in length, whereas precision‑welded pipes can be manufactured in long continuous lengths. Unless exposed to highly corrosive environments, seamless pipes generally do not exhibit signs of corrosion, while the weld zones in precision‑welded pipes are prone to corrosion due to perceived non‑uniformity, resulting in differences in ductility and corrosion resistance and greater dimensional variability. To address these issues, seamless steel pipes are engineered with superior corrosion resistance.

Precision welded pipe

　　2. Characteristics: Seamless steel pipes are widely used in engineering and construction projects. They are hollow steel tubes with a seamless joint, primarily employed for fluid‑transport pipelines. Compared with ordinary steel, they exhibit superior strength, excellent corrosion resistance, and good resistance to general corrosive environments.

　　It enables high-precision small‑batch production, with a small diameter, excellent weldability, and strong compressive strength. The steel tubes exhibit superior mechanical properties, dense microstructure, and enhanced performance in cross‑disciplinary applications. High‑precision cold‑drawn products deliver outstanding surface quality.

　　3. Mechanical Properties: The mechanical properties of seamless steel pipes are critical indicators that ensure the pipe’s ultimate in-service performance. These properties depend on the steel’s chemical composition and heat treatment. Standards specify tensile properties, including tensile strength, yield strength or yield point, elongation, and hardness, as required.

　　Characteristics of precision welded pipes:

　　1. Tensile strength

　　During tensile testing, the stress obtained by dividing the maximum force applied to stretch a material by its original cross-sectional area is called the tensile strength; it is said to represent the maximum load a material can withstand before failure due to tensile forces.

　　2. Yield Point

　　Among the phenomena observed in metallic materials, the stress at which a specimen continues to elongate without an increase in applied tensile force is called the yield point. When a drop in stress occurs, it is necessary to distinguish between the upper yield point and the lower yield point. The yield strength is expressed in units of N/mm² (MPa). At the yield point, the specimen experiences its maximum stress before the first abrupt decrease; the lower yield point corresponds to the minimum stress observed after the initial transient effects have subsided.

　　3. In a tensile test, to measure the elongation—defined as the increase in gauge length—the specimen is stretched until it fractures by a specified percentage of its original gauge length; this value is expressed as a percentage.

　　In a tensile test, the fracture ratio of the specimen is expressed as the percentage reduction in cross-sectional area, calculated as the ratio of the minimum cross-sectional diameter to the original cross-sectional area.

　　4. Hardness Testing

　　The resistance of a metallic material to indentation by a hard object is referred to as hardness. Depending on the testing method and application range, hardness is classified into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, and high‑temperature hardness; among these, Brinell, Rockwell, and Vickers hardness are commonly used for tubes.


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