Historical Introduction, Q345B Seamless Steel Pipe: The history of the development of seamless steel pipes in China started with the production of the first seamless steel pipe. These pipes are manufactured by piercing ingots or solid tube blanks to form a rough tube, which is then processed through hot rolling, cold rolling, or cold drawing. The specifications of seamless steel pipes are indicated by the outer diameter * wall thickness in millimeters, such as Q345C seamless steel pipes. Seamless steel pipes are categorized into two main types: hot-rolled and cold-rolled (drawn) seamless steel pipes.
Hot-rolled seamless steel pipes include general-purpose pipes, low and medium-pressure boiler pipes, high-pressure boiler pipes, alloy pipes, stainless steel pipes, oil cracking pipes, geological pipes, and other types of pipes. Cold-rolled (drawn) seamless steel pipes not only cover general-purpose pipes, low and medium-pressure boiler pipes, high-pressure boiler pipes, alloy pipes, stainless steel pipes, oil cracking pipes, and other pipes but also include carbon thin-walled pipes, alloy thin-walled pipes, stainless thin-walled pipes, and shaped pipes.
The outer diameter of hot-rolled seamless pipes is generally greater than 32mm, with a wall thickness ranging from 2.5mm to 75mm, such as 16MnDG low-temperature pipes, which mainly come from the American market. The outer diameter of cold-rolled seamless pipes can reach up to 6mm, with a wall thickness that can be as thin as 0.25mm. For thin-walled pipes, the outer diameter can reach 5mm with a wall thickness less than 0.25mm. Cold-rolling provides higher dimensional accuracy compared to hot-rolling.
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