Definition of seamless pipe and welded pipe:
Seamless steel pipe (SMLS) means that there are no seams. It is a uniform hollow steel pipe made of round steel billets that are heated and perforated. During this process, the billet is stretched and rotated, ultimately forming a seamless circular pipe.
Welded steel pipes are made of steel plates or strips that are crimped and then welded. A weld will be formed at the weld. Compared with welded steel pipes, seamless steel pipes have a uniform and compact internal structure, higher strength, toughness and pressure resistance, and are widely used in various fields.
How do I know if my pipe is welded or seamless?
1) Appearance features
Seamless steel pipe: a. Smooth surface: The surface of seamless steel pipe has no obvious unevenness, burrs, cracks and other defects;
b. Uniform cross-section: The seamless steel pipe has a circular cross-section, uniform diameter, and consistent thickness;
c. No oxide scale: There are no signs of rust, oxide scale, etc. on the surface of the seamless steel pipe.
Welded steel pipes have certain welds or melt marks inside or outside the steel pipe, which usually leave traces of welding and slag particles, and the surface of the steel pipe is relatively rough.
2) Detection means
In addition to visual observation, seamless steel pipes can also be effectively identified through the following detection methods:
1. Hand feeling detection
Compared with welded steel pipes, seamless steel pipes are smoother, have no edges, burrs, etc., and have a more even feel.
2. Internal defect detection
Internal defects of seamless steel pipes, such as inclusions, bubbles, cracks, etc., are usually detected through ultrasonic testing or radiographic flaw detection.
3. Magnetic detection
The seamless steel pipe material is relatively pure and has good magnetic permeability. Under the action of a magnetic field, it will produce obvious magnetization phenomenon. It can be detected by a magnetic flaw detector or a hand-held magnet.
4. Pull out test
The pull test is to fix both ends of the steel pipe, and then pull the middle part to observe whether cracks appear in the steel pipe. Seamless steel pipes usually do not show obvious deformation and cracks after a pull-out test. Welded steel pipes are prone to cracks at the welded joints.
5. Stress test
Pressure testing is a method of hydrostatically testing steel pipes. The steel pipe is usually filled with water and a certain pressure is applied to detect whether there is water leakage in the steel pipe. Seamless steel pipes can usually withstand higher pressures and are less prone to leaks. Welded steel pipes often leak at the welded joints.
Application differences:
Seamless steel pipes have better overall performance and no defects such as welds inside, so they are usually used in high-pressure, high-temperature and important mechanical equipment in chemical, petroleum, metallurgy, pharmaceutical, food and other industries. Seamless steel pipes can not only be used in civil fields such as construction and subways, but are also widely used in industrial fields such as oil, natural gas, chemicals, and electric power. They carry important energy transportation and delivery tasks, so the quality and performance of seamless steel pipes must be strictly controlled, and this is where the production process plays an important role.
Due to the presence of welds inside, welded steel pipes have relatively poor strength and sealing properties, and are prone to problems such as cracking and water leakage during use. They are suitable for some low-pressure and low-temperature occasions, such as construction, bridges and other fields, and are often used. Used in water supply pipes, drainage pipes, air conditioning pipes, automobile manufacturing, steel structures, etc.
Things to note when purchasing carbon steel seamless pipes:
1. Material quality
When purchasing
carbon steel seamless pipes, the first thing you should pay attention to is the material quality. The material quality of seamless steel pipes has a great impact on the use effect and service life. You should choose manufacturers whose production materials are of reliable quality to avoid poor performance or short service life due to material problems.
2. Specifications and standards
Secondly, when purchasing carbon steel seamless steel pipes, you also need to pay attention to its specifications and standards. Different projects have different requirements for seamless steel pipes, so when purchasing, it is also necessary to select appropriate specifications and standards based on project requirements. In construction projects, commonly used seamless steel pipe standards include
ASTM A106,
ASTM A53, API 5L, etc. You should choose the appropriate standard according to your needs.
3. Manufacturer credibility
Choosing a manufacturer with good reputation and complete after-sales service can avoid many purchasing risks. Before purchasing, you should understand the manufacturer's production capacity, quality control, after-sales service, etc., and confirm that the purchased seamless steel pipe is produced by a regular manufacturer and meets the quality requirements.
4. Dimensional deviation
You also need to pay attention to the dimensional deviation of carbon steel seamless steel pipes when purchasing. During the production process, the length, outer diameter and other dimensions of seamless steel pipes are prone to deviations. Therefore, the dimensions should be strictly controlled when purchasing to avoid quality problems caused by dimensional deviations.
5. Unqualified material
Finally, when purchasing, you need to pay attention to whether the material is qualified. The material of seamless steel pipe has a crucial impact on its use effect and lifespan. Seamless steel pipes produced by manufacturers with quality inspection certification and reliable production materials should be selected to avoid purchasing unqualified seamless steel pipes, which will affect the normal progress and use effects of the project.
