What is SMLS in piping?
SMLS Pipe & Tube Meaning: SMLS is the abbreviation of "Seamless", which specifically refers to seamless steel pipe in the field of pipelines. SMLS pipe is a weld-free pipe produced by hot rolling, cold rolling, cold drawing or extrusion. Its manufacturing process is to perforate the solid steel billet, then roll or stretch it into shape, and the overall structure is continuous without any welding seams. It has the characteristics of high strength and wide applicability, and is often used in high pressure, high temperature or high precision scenes.
Features of SMLS pipe:
1. Seamless structure
The overall structure of seamless pipe is continuous during production, without weld joints, avoiding strength weaknesses, leakage risks and corrosion hazards caused by welds.
2. High pressure bearing capacity
Due to the seamless design, its structure is more compact, so it has better strength and pressure resistance. The bursting pressure is 30%~50% higher than that of the same specification welded pipe, with outstanding pressure bearing capacity, suitable for high temperature and high pressure environment.
3. High dimensional accuracy
The tolerance of cold rolled/cold drawn pipe can reach ±0.05mm (such as precision pipe for hydraulic cylinder barrel).
4. Pure materials
The inner wall is smooth, with low roughness, no welding impurities, and low fluid resistance, which is suitable for high-purity medium transportation (such as semiconductor ultrapure water, pharmaceutical gas).
5. Corrosion resistance
SMLS pipelines can be made of corrosion-resistant materials such as stainless steel and alloy steel, which are suitable for acid, alkali and other chemical media environments and can be used for a long time in harsh environments.
Carbon steel is easy to rust, and the surface needs additional galvanizing or coating treatment to increase service life.
6. Mechanical properties
The grain structure is continuous, the toughness is good, the tensile/compressive/torsion performance is consistent, the bending radius can be as small as 3D (conventional welded pipes need ≥5D to avoid weld cracking), and the fatigue life can reach more than 10⁷ times, which is suitable for dynamic load environments (such as mechanical transmission shafts).
7. Processing characteristics
It can be conveniently cut, bent, flared and other processing operations, and is suitable for machinery manufacturing, shipbuilding and other fields.
8. Wide range of applications
SMLS pipes are widely used in petrochemical, electric power, water conservancy and other industrial fields due to their excellent performance, such as chemical pipelines, steam pipes, etc., which ensure safe transportation and have a long service life.
SMLS pipe manufacturing process:
The production process of seamless steel pipes is complex and has high technical requirements. It mainly adopts hot rolling or cold rolling/drawing technology:
1. Billet preparation: Select high-quality billets, and the chemical composition and physical properties must meet the standards.
2. Heating: The billet is heated to about 1200°C to soften it for subsequent processing.
3. Perforation: A hollow billet is formed by oblique rolling perforation or pressure perforation.
4.
Hot rolling: Continuous rolling and forming by rollers at high temperature, suitable for large-diameter and thick-walled pipes.
5. Cold rolling/
Cold drawing: Processing at room temperature to improve surface finish and dimensional accuracy. Produce small-diameter, high-precision, thin-walled pipes.
Both processes do not require welding steps, avoiding structural defects that may be caused by welds, thereby ensuring the overall uniformity of the material.
6. Sizing and reducing: adjust the outer diameter and wall thickness of the steel pipe to the standard size.
7. Cooling: stabilize the organizational structure and performance through a cooling bed or water cooling system.
8. Straightening: The straightening machine eliminates bending deformation and ensures straightness.
9. Cutting and heat treatment: Cut the length according to the demand, and perform heat treatment (such as normalizing, quenching) to improve the performance when necessary.
10. Surface treatment: sandblasting and pickling to remove oxide scale, some need coating or plating.
11. Inspection: strictly inspect the size, non-destructive testing (ultrasonic, eddy current) and physical and chemical properties.
Application of SMLS pipe:
1. Energy transportation field: SMLS steel pipe is often used in oil, natural gas pipelines, oil well casings, etc. because it can withstand high pressure environment and has excellent corrosion resistance.
2. Machinery manufacturing industry: Precision parts such as hydraulic cylinders and bearing sleeves rely on the dimensional stability and mechanical strength of seamless steel pipes.
3. Automobile and aviation fields: key components such as transmission shafts and landing gears use their lightweight and fatigue resistance.
4. Chemical and power equipment: In the manufacture of high-temperature reactors, acid-resistant pipes, boiler heat exchangers, and steam pipes, seamless steel pipes can withstand high temperatures and chemical media erosion.
Advantages compared to traditional ordinary steel pipes:
1. Structural integrity: The weld-free design eliminates weak links, and the compressive strength is increased by more than 30% compared to welded steel pipes.
2. High safety factor: Suitable for extreme working conditions, such as deep-sea oil and gas extraction or supercritical thermal power generation units.
3. Long service life: The uniform metal streamline structure significantly enhances the resistance to stress corrosion.
4. Processing adaptability: The mechanical properties can be adjusted through heat treatment to meet the special requirements of hardness and toughness in different industries.
At present, SMLS steel pipes have formed a complete standard system, including international general specifications such as
API 5L (line pipes) and
ASTM A106 (high temperature service), which further promotes its popularization and application in the global industrial field. For non-critical scenarios (such as low-pressure drainage), welded steel pipes are a more economical alternative.
In short, SMLS steel pipes have become core materials in the fields of energy, chemical industry, machinery, etc. due to their advantages such as no welds, high strength and pressure resistance, and high purity. When selecting a model, it is necessary to comprehensively consider the four factors of pressure, temperature, medium, and cost, and strictly follow industry standards.
Read more: API 5L Seamless Line Pipe or SMLS Pipe vs ERW Pipe Cost
