What is a seamless steel pipe?

What is a seamless steel pipe?

A seamless steel pipe is a type of steel pipe without any welding seams, manufactured by processing steel billets through heating, perforation, stretching, or rolling.  This process ensures that seamless steel pipes have no welding joints or seams, maintaining excellent mechanical properties and uniform internal structure.  Due to their high strength, corrosion resistance, and pressure resistance, seamless steel pipes are widely used in various industrial and engineering fields, such as pipelines for fluid transportation, pressure vessels, mechanical parts, and structural supports in construction.

Manufacturing processes of seamless steel pipes
Hot rolling process: Steel billets are heated to high temperatures and processed into hollow shells using a piercing machine, followed by multiple rolling or drawing processes to form the final shape.  This process is suitable for large-diameter and thick-walled pipes.
Cold rolling or cold drawing process: Hot-rolled hollow shells are further processed at room temperature to improve surface quality and dimensional precision.  This process is ideal for producing pipes with high precision, good surface quality, and small diameters.
Other processes: Processes such as sizing and heat treatment are used to further improve the performance of the steel pipes.

Common types of seamless steel pipes

By material:
Carbon steel seamless pipes: Examples include Q235, 20#, 45#.
Alloy seamless pipes: Examples include 15CrMo, 12Cr1MoV, suitable for high-temperature and high-pressure environments.
Stainless steel seamless pipes: Examples include 304, 316L, which feature excellent corrosion resistance.
By application:
Pipes for fluid transportation: Used for transporting water, oil, natural gas, and other fluids.
Structural pipes: Used in construction structures and as mechanical components.
Boiler pipes: Used in boilers and heat exchangers under high-temperature and high-pressure conditions.
Petroleum cracking pipes: Used in cracking equipment in petrochemical facilities.
By manufacturing process:
Hot-rolled seamless pipes
Cold-rolled or cold-drawn seamless pipes

Main characteristics of seamless steel pipes
Seamless steel pipes are made by piercing and rolling steel billets, avoiding stress concentration and weaknesses associated with welding seams.
With uniform pipe walls and no seams, seamless steel pipes can withstand high temperatures and pressures.
Seamless steel pipes inherently resist corrosion, especially alloy and stainless steel seamless pipes, which can be used in harsh corrosive environments.
Seamless steel pipes produced through cold-drawing or cold-rolling processes offer high surface quality and dimensional accuracy.

Applications of seamless steel pipes
Oil and gas industry: Used for transporting crude oil, natural gas, and refined petroleum products.
Boilers and heat exchangers: Used to transport steam or water under high-temperature and high-pressure conditions.
Mechanical manufacturing: Used to manufacture mechanical parts such as automotive bearings, drive shafts, and drill rods.
Construction and engineering: Used as high-strength support materials.
Chemical and power industries: Used in equipment pipelines for corrosive environments.

Read more: How to choose seamless steel pipe and welded steel pipe? or The use of seamless pipe industry