Seamless steel pipes (often shortened to SMLS pipes) are hollow steel tubes without any longitudinal or spiral weld seam, manufactured from solid steel billets via piercing, rolling, drawing or extrusion.

1. Manufacturing Process

• Billet Preparation: Solid round steel billet is heated to high temperature.
• Piercing: The hot billet is pierced by a mandrel to form a hollow shell.
• Rolling & Sizing: The hollow shell is rolled and stretched to precise diameter, wall thickness and length.
• Finishing: Heat treatment, straightening, inspection and cutting to final specs。

2. Key Features & Advantages

• No Weld Seam: Homogeneous structure, no weak points from welding。
• High Strength & Pressure Resistance: Withstands higher pressure, temperature and cyclic loads than welded pipes。
• Uniform Mechanical Properties: Consistent strength, toughness and ductility across the entire pipe。
• Superior Corrosion Resistance: No weld crevices for corrosion initiation。
• Reliability: Lower risk of leakage, cracking or failure under extreme conditions。

3. Common Materials & Types

• Carbon Steel: ASTM A106, A53; GB/T 8162, 8163 – general structural and fluid service。
• Alloy Steel: ASTM A335, P11/P12/P22; 15CrMo, 12Cr1MoV – high-temperature/pressure applications。
• Stainless Steel: ASTM A312, TP304/316 – corrosion-resistant environments。
• Others: Titanium, copper alloy – aerospace, marine and heat exchange。

4. Main Applications

• Oil & Gas: Drilling, casing, high-pressure transmission pipelines。
• Power Generation: Boiler tubes, superheater tubes, high-pressure steam lines。
• Petrochemical: Refining, cracking, high-temperature reactor pipes。
• Mechanical & Structural: Hydraulic cylinders, bearings, high-precision components。
• Construction & Infrastructure: High-rise building supports, bridge structures。

5. Size Range

• Outer Diameter: ~0.3mm to 650mm。
• Wall Thickness: Thin-wall to heavy-wall (customizable)。
• Length: Typically 6m–12m, or cut to required lengths。

6. Quality Standards

Chinese: GB/T 17395, GB/T 8162, GB/T 8163。

International: ASTM, ASME, API, DIN, EN, ISO。