Carbon steel pipes are made from steel ingots or solid round steel that is perforated to make a rough pipe and then processed through
hot rolling, cold rolling, or cold drawing. Carbon steel pipes hold a significant position in the steel pipe industry. They are a common type of metal pipe made of carbon and iron, among other elements. Carbon steel pipes have good corrosion resistance, pressure-bearing capacity, and workability, making them widely used in many fields.
1.Classification of Carbon Steel Pipes
Carbon steel pipes are primarily classified by manufacturing process and application fields into two categories: hot-rolled and cold-rolled (cold-drawn).
1.1 Hot-Rolled Carbon Steel Pipes
Hot-rolled carbon steel pipes are subdivided by usage into general pipes, low to medium pressure boiler pipes, high-pressure boiler pipes, alloy pipes, stainless steel pipes, petroleum cracking pipes, geological pipes, and other special-purpose pipes. Their outer diameter is typically greater than 32mm, with a wall thickness range of 2.5-75mm, suitable for larger structural applications.
1.2 Cold-Rolled (Cold-Drawn) Carbon Steel Pipes
In addition to the aforementioned categories, cold-rolled (cold-drawn) carbon steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes, and shaped steel pipes. Cold-rolled seamless steel pipes have higher dimensional accuracy, with an outer diameter that can reach 6mm and a wall thickness as low as 0.25mm, making them particularly suitable for high-precision fields, such as thin-walled pipes and specially shaped pipes.
2.Differences Between Carbon Steel Pipes and Welded Steel Pipes
Carbon steel pipes are not welded steel pipes. The term "carbon steel pipe" refers to the material of the pipe being carbon steel, which also contains limited amounts of silicon, manganese, phosphorus, sulfur, and other impurities, as well as other trace residual elements. These carbon steel pipes are widely used in construction, bridges, railways, vehicles, ships, and various machinery manufacturing industries.
3.Manufacturing Materials of Carbon Steel Pipes
The manufacturing materials for general carbon steel pipes are diverse, including high-quality carbon structural steel such as 10, 20, 30, 35, and 45, as well as low alloy structural steel like 16Mn and 5MnV, or alloy steel such as 40Cr, 30CrMnSi, 45Mn2, and 40MnB. Low carbon steel grades 10 and 20 are used to manufacture fluid conveying pipelines, while medium carbon steel grades like 45 and 40Cr are used to make mechanical parts such as stressed components of automobiles and tractors. Strength and flattening tests are important indicators to ensure the performance of general carbon steel pipes. Hot-rolled steel pipes are typically delivered in a hot-rolled or heat-treated state, while cold-rolled pipes are delivered in a heat-treated state.
4.Categories and Characteristics of Carbon Steel Pipes
Carbon steel pipes can describe various metallic tubular products whose main alloying element is carbon, in the range of 0.12%-2% carbon. Besides elements like chromium, cobalt, molybdenum, nickel, niobium, titanium, and tungsten, carbon can be alloyed with vanadium and zirconium for specific effects. For example, A333 Grade 6 pipes, used in low-temperature applications, have higher tensile strength and impact properties compared to A106 Grade B pipes, which is achieved by adding more than 0.9% manganese (limited to 0.65% in A106 pipes).
Four Categories of Carbon Steel Pipes
Low Carbon Steel Pipes - Carbon content: 0.55%-1.05%
Medium Carbon Steel Pipes - Carbon content: 0.25%-0.6%
High Carbon Steel Pipes - Carbon content: 0.9%-2.5%
Ultra High Carbon Steel Pipes - Carbon content: 2.5%-3.0%
As carbon content increases, high carbon steel pipes become harder through quenching and tempering but lose ductility. High carbon steel pipes, if not heat-treated, may have poor weldability and low melting points. Large diameter pipes used for water transportation are generally made of carbon steel.
5.Manufacturing Methods of Carbon Steel Pipes
According to the manufacturing method, carbon steel pipes are divided into three different types:
Seamless Pipes - Pipes formed by pushing hot steel through a mold. The manufacturing range of carbon steel seamless pipes is 24-600NB. Despite the mechanical and time-consuming processes involved, making this the most expensive method, it is historically the most reliable method ever invented.
Welded Pipes - Pipes formed by wrapping a steel plate into a cylindrical shape and then welding the seam. These pipes are in high demand due to their lower cost. Depending on the required type, these pipes are welded in the following forms:
ERW: Electric Resistance Welded Pipe
EFW: Electric Fusion Welded Pipe
SSAW: Submerged Arc Welded Pipe
6.Methods for Rust Removal from the Inner Wall of Carbon Steel Pipes
6.1 Epoxy Powder Coating
Rust removal from the inner wall of carbon steel pipes cannot use electrostatic spraying as the inner wall surface is not easily charged. Instead, epoxy powder spraying can be used, or natural gas heating can be used, heating the pipe to above the powder melting temperature. During spraying, preheat the steel pipe placed on a rotating bracket, and the spray gun head can move along the axis.
6.2 Rust Remover
Rust removers are environmentally friendly and strong rust-removing agents composed of penetrants, rust-removing aids, and other materials. They can quickly clear and dissolve various heat exchanger equipment rust and deposits. Rust removers are safe and efficient for removing rust and have little to no corrosion on common metals like carbon steel and stainless steel. They also form a protective film to prevent rust effectively but should not be used when heated.
6.3 Steel Pipe Rust Removal Machine
Steel pipe rust removal machines clean the inner surface by shot blasting, effectively removing the surface oxide scale. The machine uses a high-efficiency powerful shot blaster to eject high-speed shot streams, removing sand, rust, welding slag, and other debris, achieving a finely polished surface. This improves the adhesion of the paint film to the steel surface, enhances the internal quality of the steel, and extends its service life.
7.Conclusion
As an important type of piping material, carbon steel pipes are widely used in construction, machinery manufacturing, fluid transportation, and other fields. Understanding their manufacturing processes, material selection, and rust removal methods can help in better selecting and using carbon steel pipes to meet various engineering needs.