Carbon steel pipes: pressure-resistant and durable, serving as the core of conveying and structural systems across multiple industries.

Carbon steel pipe is a tubular metal product made from carbon steel plates or coils through processes such as bending, welding, and seamless rolling. It is one of the most commonly used piping materials in industrial production. It retains the core advantages of carbon steel—high cost-effectiveness, high strength, and ease of processing—while also possessing good pressure-bearing capacity and toughness. It is widely used in fluid transportation, structural support, and machinery manufacturing, from small household gas pipelines to large petrochemical pipelines and bridge steel structures, playing an irreplaceable role and becoming the "blood vessels" connecting industrial production and daily life.

I. Core Definition and Compositional Characteristics of Carbon Steel Pipe The core composition of carbon steel pipe is consistent with that of carbon steel plates and coils, based on iron and carbon. The carbon content is controlled between 0.0218% and 2.11%, containing small amounts of impurities such as silicon, manganese, sulfur, and phosphorus. It does not actively add alloying elements such as chromium, nickel, and molybdenum, distinguishing it from alloy steel pipes. Its performance is primarily determined by carbon content: lower carbon content results in better plasticity and toughness, making it easier to weld and process; higher carbon content leads to greater hardness, strength, and pressure resistance, but at the expense of reduced plasticity and toughness.

Compared to pipes made of other materials, carbon steel pipes offer the core advantages of high cost-effectiveness, excellent pressure resistance, and strong adaptability. They can meet the general transportation needs under normal temperature and pressure, and through heat treatment optimization, can be adapted to complex industrial scenarios such as high pressure and medium temperature. Furthermore, the mature processing technology allows for the manufacture of pipes in various specifications and shapes to meet specific requirements, making them highly practical.

II. Main Classifications of Carbon Steel Pipes: By Process and Application
The classification of carbon steel pipes is mainly based on processing technology and application scenarios. Different categories exhibit significant differences in structure and performance. Accurate matching based on actual application is crucial for selection to avoid resource waste or usage risks.

(I) Classification by Processing Technology: The Core Difference Between Seamless and Welded Pipes

This is the most fundamental classification method for carbon steel pipes. The processing technology directly determines their pressure-bearing capacity, sealing performance, and applicable scenarios, and is also the primary reference for industrial selection:

- Seamless Carbon Steel Pipes: Made by directly piercing and rolling round steel billets, the pipes have no welded joints, resulting in high overall strength, good sealing performance, and strong pressure-bearing capacity. They are suitable for high-pressure, high-temperature, and mildly corrosive fluid transportation scenarios, such as oil and natural gas pipelines, boiler tubes, and high-pressure hydraulic pipelines. Common grades include 20#, 45#, and Q345, with a wide range of specifications. Different diameters and wall thicknesses can be customized according to requirements.

- Welded Carbon Steel Pipes: Made from carbon steel coils or plates, bent and formed, and then welded using processes such as submerged arc welding and high-frequency welding. The pipes have one or more weld seams. Its cost is lower than seamless carbon steel pipes, and its processing efficiency is high. It is suitable for ordinary fluid transportation and structural support under normal temperature and pressure, such as water pipes, gas pipes, factory ventilation ducts, and steel structure support pipes. Common grades include Q195 and Q235.

(II) Classification by Carbon Content: Adapting to Different Performance Requirements

Similar to carbon steel coils and plates, carbon steel pipes are also divided into three categories according to carbon content. The performance differences determine their different application scenarios:

- Low-carbon steel pipes: Carbon content ≤0.25%, excellent plasticity and toughness, easy to weld and process, good sealing performance, mainly used for ordinary fluid transportation (such as water and gas), low-pressure pipelines, and structural support. This is the most widely used category.

- Medium-carbon steel pipes: Carbon content 0.25%～0.6%, balancing strength and toughness, with better pressure-bearing capacity than low-carbon steel pipes. Hardness can be increased through heat treatment. They are mostly used in mechanical manufacturing for drive shafts, high-pressure hydraulic pipes, and medium-pressure fluid transportation pipelines. - High-carbon steel pipes: Carbon content > 0.6%, high hardness and wear resistance, but poor plasticity and toughness, difficult to weld. Mainly used in the manufacture of tools, molds, high-pressure wear-resistant pipelines, and other special applications; their use is relatively niche.

(III) Classification by Application: Precisely Adapting to Industry Needs
Based on different application scenarios, carbon steel pipes can be divided into carbon steel pipes for transportation, carbon steel pipes for structure, and carbon steel pipes for machinery. Carbon steel pipes for transportation are mainly used for transporting fluids such as water, gas, oil, and chemical media; carbon steel pipes for structure are used for steel structure support such as bridges, factories, and supports; carbon steel pipes for machinery are used for manufacturing mechanical parts, drive shafts, hydraulic pipes, etc. III. Core Applications and Precautions for Using Carbon Steel Pipes Carbon steel pipes are used in industrial production, infrastructure construction, and daily life. Core applications include: petrochemicals (crude oil and natural gas pipelines, chemical reaction pipelines), municipal engineering (water supply, gas, and heat transmission pipelines), building construction (steel structure support, ventilation ducts), machinery manufacturing (drive shafts, hydraulic pipes, machine tool accessories), and power engineering (boiler pipes, cable protection pipes), serving as a fundamental material supporting the normal operation of various industries.

When using carbon steel pipes, three key points must be noted to avoid affecting their service life and safety: First, proper anti-corrosion treatment is essential. Carbon steel is prone to oxidation and rust, especially in humid and corrosive environments. Protection methods such as applying anti-corrosion paint, galvanizing, and spraying anti-corrosion coatings are necessary to extend their service life. Second, strict matching of pressure requirements is crucial. Select carbon steel pipes of the appropriate specifications and grade based on the pressure and temperature of the transported medium to avoid overpressure use that could lead to pipe rupture. Third, standardized installation and maintenance are vital. Appropriate welding processes must be selected to ensure weld quality. Regular inspections during use are necessary to promptly address rust, damage, and other issues, ensuring safe operation.

As a pressure-resistant, durable, and cost-effective piping material, carbon steel pipes have always maintained a core position in the piping market thanks to mature processing technology and wide applicability. With the upgrading of industrial technology, the corrosion resistance and pressure-bearing capacity of carbon steel pipes are continuously optimized, enabling them to continue to adapt to more high-end industrial scenarios and provide a solid guarantee for the stable development of various industries.