Carbon steel pipe: the core carrier of industrial fluid transportation and structural support

Carbon steel pipe is a tubular product made of carbon steel (carbon content 0.02%-2.11%) through rolling, welding or forging. With its high strength, low cost and easy processing, it has become the core material for conveying fluids (water, oil, gas, etc.) and bearing structures, and is widely used in the entire industrial chain such as energy, construction, and machinery.
1. Classification and core characteristics of carbon steel pipes
The classification of carbon steel pipes needs to be combined with production processes and usage scenarios. Different categories have significant differences in performance, cost and adaptability.
1. Classification by production process
This is the most core classification method, which directly determines the accuracy, strength and applicable scenarios of the pipe:

Seamless carbon steel pipe:
No welding is required. The solid steel billet is perforated into a pipe through hot rolling or cold processing. There is no seam, high overall strength, good dimensional accuracy, and can withstand high pressure (up to 100MPa or more).
Hot-rolled seamless pipe: The billet is heated and then punched by a piercer and rolled by a tube rolling mill. The wall thickness is relatively thick (usually 3-120mm), and it is used for high-pressure pipelines (such as oil transportation main pipelines) and mechanical structural parts (such as machine tool spindles).
Cold-drawn/cold-rolled seamless pipe: The hot-rolled pipe is further cold-processed, with thin wall thickness (0.2-30mm), smooth surface, and small tolerance (±0.1mm). It is used for precision machinery (such as hydraulic pipelines, automobile transmission shafts), and high-pressure instrument pipelines.
Welded carbon steel pipe: It is made of steel plate or steel strip as raw material, and is welded after curling and forming. It has high production efficiency and low cost (20%-30% lower than seamless pipes of the same specification), but the overall strength is slightly inferior to seamless pipes.
Straight seam welded pipe: The steel plate is curled and straight seam welded (high-frequency welding or submerged arc welding). The length is limited by the width of the steel plate (usually 6-12m), and it is suitable for low-pressure transportation (such as tap water pipelines and low-pressure gas pipelines).
Spiral welded pipe: The steel strip is welded after spiral curling, and the length can be extended indefinitely (as required), the weld stress is dispersed, and the pressure resistance is better than that of straight seam welded pipe, which is used for medium and low pressure long-distance transportation (such as urban centralized heating pipelines and sewage treatment pipes).
2. Classification by use and performance
Carbon steel pipe for transportation: Focus on fluid sealing and corrosion resistance (internal and external anti-corrosion treatment is required, such as galvanizing and epoxy coating), used for water, gas, oil, steam, etc. For example, municipal tap water pipelines mostly use spiral welded carbon steel pipes (low cost + long-distance adaptation).
Structural carbon steel pipe: Emphasize strength and toughness, used for building steel structures (such as trusses, support columns), mechanical frames (such as equipment bases), bridge pile foundations, etc. For example, thick-walled seamless carbon steel pipes (strong load-bearing capacity) are often used for steel structure columns of large factories.
Carbon steel pipe for high pressure: high-strength carbon steel (such as Q345, Q460) is used, and the pressure resistance is improved through quenching and tempering heat treatment. It is used for high-pressure boilers, hydraulic systems, oil and gas well casings, etc. For example, seamless carbon steel pipes for deep wells in oil fields need to withstand formation pressures above 100MPa.
Summary of core characteristics
Strength advantage: The tensile strength can reach 300-1000MPa (depending on the material and process), can withstand high pressure and heavy load, and is suitable for industrial-grade scenarios.
Controllable cost: The price of raw materials (carbon steel) is lower than that of alloy steel pipes and stainless steel pipes, the production process is simple (especially welded pipes), and the cost performance is outstanding.
Flexible processing: It can be cut, welded, bent, and threaded, and is suitable for complex installation environments (such as pipeline bends and branches).
Limitations: Poor corrosion resistance (easy to rust), and it is necessary to expand the application scenarios through anti-corrosion treatment such as coating (galvanizing, painting), lining (plastic, rubber), etc.; insufficient low-temperature toughness, and carbon steel pipes with optimized low-temperature toughness (such as Q355ND) are required in extremely cold areas.
2. Carbon steel pipe production technology and innovation
The production technology of carbon steel pipes revolves around improving performance, reducing costs, and enhancing corrosion resistance. In recent years, there have been significant breakthroughs in process optimization and intelligence.
1. Core production process
Seamless pipe production:
The key process is "blank heating → perforation (perforating solid billets into hollow rough tubes) → tube rolling (adjusting wall thickness and outer diameter) → sizing (precisely controlling size) → heat treatment (optimizing performance)". Among them, the perforation process (such as oblique rolling perforation) determines the quality of the rough tube, and the use of continuous rolling mills (such as MPM continuous rolling mills) in the tube rolling process can improve production efficiency and dimensional accuracy (outer diameter tolerance ≤±0.5%).
Welded pipe production:
The core is welding quality control. High-frequency induction welding is commonly used for straight seam welded pipes (with fast welding speed, up to 100m/min). The seam is heated by electric current to a molten state and extruded to ensure the strength of the weld. Spiral welded pipes are mostly made of submerged arc welding (with deep weld penetration and high strength). The spiral angle needs to be controlled (usually 30°-70°) to balance the force and production efficiency.
2. Technical innovation direction
High performance:
Develop low-alloy high-strength carbon steel (such as Q460, Q690), refine the grains by adding alloying elements such as manganese, vanadium, and niobium, and improve the strength of the pipe (tensile strength is increased from 400MPa to more than 800MPa), while maintaining good toughness, and replace some seamless steel pipes for high-pressure scenarios (such as shale gas extraction pipelines).
Anti-corrosion technology upgrade:
Coating innovation: Promote three-layer PE anti-corrosion coating (bottom layer epoxy powder + middle layer adhesive + outer layer polyethylene), which is resistant to soil corrosion and impact, and has a service life of more than 50 years (suitable for buried oil pipelines); develop nano-composite coating (adding graphene) to improve scratch resistance and chemical resistance.
Surface treatment optimization: Use chromium-free passivation (replacing traditional chromate passivation), zinc-nickel alloy plating (corrosion resistance is 3-5 times that of galvanizing), and adapt to environmental protection requirements (such as EU REACH regulations).
Intelligent production:
Online detection: Through ultrasonic flaw detection (detecting internal defects), eddy current detection (detecting surface cracks), and laser diameter measurement (real-time monitoring of outer diameter size), ensure the quality of each meter of pipe; AI visual system identifies weld appearance defects (such as undercuts and incomplete penetration) and automatically adjusts welding parameters.
Digital twin: Build a digital model of the entire process from billet to finished product, simulate the impact of different process parameters on pipe performance, optimize parameters such as rolling temperature and welding current, and reduce trial and error costs (a steel plant reduced the scrap rate by 15% after application).
3. Core application areas of carbon steel pipes
Carbon steel pipes cover many fields of industry and people's livelihood due to their performance adaptability and cost advantages, and are the "main force" of transportation and structural support.
1. Energy and chemical industry (accounting for more than 40%)
Oil and gas transportation: long-distance oil/gas pipelines (such as some branches of the West-East Gas Transmission Project use spiral welded carbon steel pipes with a diameter of 1219mm), high-pressure oil and gas well casings (use seamless carbon steel pipes to withstand high pressure and corrosion in the formation).
Chemical and electric power: raw material transportation pipelines of chemical plants (such as steam and cooling water), boiler pipes and steam pipelines of thermal power plants (need to be resistant to high temperature and high pressure, and use seamless carbon steel pipes after quenching and tempering).
2. Construction and municipal engineering
Structural support: columns and beams of steel structure buildings (such as large stadiums use seamless carbon steel pipes to build trusses to reduce deadweight), bridge pile foundations and guardrails (use anti-corrosion treated welded pipes to adapt to outdoor environments).
Municipal transportation: tap water pipes (DN100-DN2000 spiral welded pipes), city gas medium and low pressure pipes (straight seam welded pipes + anti-corrosion coatings), rainwater/sewage discharge pipes (spiral welded pipes, inner wall coated with cement mortar for anti-corrosion).
3. Machinery and transportation
Machinery manufacturing: spindles of machine tools, hydraulic system pipes (cold-drawn seamless pipes with high dimensional accuracy), hydraulic oil pipes of construction machinery (high-strength seamless pipes, withstanding pressures above 30MPa).
Transportation: automobile drive shafts (seamless carbon steel pipes, requiring high strength and toughness), ship deck pipes, engine room pipes (use galvanized carbon steel pipes to prevent seawater corrosion), railway freight car brake pipes (resistant to vibration and low temperature).
4. Application in special scenarios
Agriculture and irrigation: farmland irrigation pipes (thin-walled welded pipes, low cost and easy to install), water supply branches of sprinkler equipment (galvanized to prevent rust).
Mining and metallurgy: tailings transportation pipelines in mines (thick-walled welded pipes, wear-resistant treatment), steam pipelines in metallurgical plants (seamless pipes, high temperature resistance).
IV. Industry trends and challenges of carbon steel pipes
The carbon steel pipe industry is significantly affected by raw material prices, environmental protection policies, and downstream demand. It currently presents the characteristics of "structural upgrading, green transformation, and regional differentiation".
1. Market driving factors
Infrastructure and energy demand: Global urbanization (such as Southeast Asia and Africa) drives the demand for municipal pipelines and steel structures; oil and gas extraction (especially shale gas and deep-sea oil and gas) drives the demand for high-pressure seamless pipes; new energy projects (such as hydrogen energy transportation pipelines, which require low-alloy high-strength carbon steel pipes) become new growth points.
Substitution and upgrading: Replacement of concrete pipes in some areas (such as municipal drainage, carbon steel pipes are fast to install and have a long life), plastic pipes (such as high-pressure scenarios, carbon steel pipes have obvious advantages in temperature and pressure resistance); upgrading of low-end welded pipes to high-end (such as anti-corrosion coated welded pipes replacing ordinary black pipes).
2. Core challenges
Raw material fluctuations: The price of carbon steel raw materials (iron ore, scrap steel) is greatly affected by international supply and demand (such as the price of iron ore rose by 20% in 2024, pushing up the cost of carbon steel pipes), and the profits of small and medium-sized enterprises are under pressure.
Environmental pressure: The heat treatment and coating links in the production process emit waste gas (such as VOCs), and stricter environmental regulations (such as China's "dual carbon" policy and EU carbon tariffs) force companies to upgrade environmental protection equipment (such as RTO incineration treatment of VOCs), and short-term costs rise.
Competition and homogenization: There is an overcapacity of mid- and low-end welded pipes (such as straight seam welded pipes below DN500), and the price war is fierce; high-end seamless pipes (such as high-pressure boiler pipes) rely on imported technology, and the localization rate needs to be improved.
3. Future development direction
High-end and customized: Focus on high-pressure, low-temperature, and corrosion-resistant scenarios, develop special carbon steel pipes (such as seamless pipes for low temperatures of -60℃ and anti-sulfur pipes for shale gas development); provide "pipe + anti-corrosion + connection" integrated solutions (such as customizing prefabricated pipeline systems with flanges and elbows for customers).
Green production: Promote short-process steelmaking (using scrap steel + electric arc furnace to reduce carbon emissions by more than 60%); use green electricity (photovoltaic, wind power) to drive rolling and welding links; develop recyclable carbon steel pipes (coatings are easy to peel off and pipes can be remelted for use).
Intelligent and service-oriented: Realize the full life cycle traceability of pipes through the Internet of Things (raw materials - production - installation - maintenance); establish an online selection platform (recommend pipe models and anti-corrosion solutions based on customer pressure, medium, and environment) to improve service efficiency.
Optimize regional layout: Set up factories in demand-concentrated areas (such as Southeast Asia) to avoid trade barriers (such as anti-dumping duties); close to raw material production areas (such as North China and India) to reduce logistics costs.

As the "blood vessels" and "skeleton" of industry, the development level of carbon steel pipe directly reflects the degree of industrialization of a country. In the future, driven by technological innovation and policies, carbon steel pipe will transform from "general products" to "high performance, high added value, and green", and continue to support the upgrading of core industries such as energy, infrastructure, and machinery.
</think># Carbon steel pipe: "blood vessels" and "skeleton" of the industrial system

Carbon steel pipe is a tubular product made of carbon steel as raw material (carbon content 0.02%-2.11%) through rolling, welding or forging. With its high strength, low cost, and easy processing, it has become the core material for conveying fluids (water, oil, gas, etc.) and bearing structures. It is widely used in the entire industrial chain such as energy, construction, and machinery. It is the "blood vessels" (transportation) and "skeleton" (support) of modern industry.
1. Classification and core characteristics of carbon steel pipes
The classification of carbon steel pipes needs to be combined with production processes and application scenarios. Different categories have significant differences in performance, cost and adaptability, supporting their flexible application in multiple fields.
1. Classification by production process
This is the most core classification method, which directly determines the structural integrity and applicable pressure level of the pipe:
Seamless carbon steel pipe:
Seamless, made by "solid billet heating → perforation into hollow rough tube → rolling tube to adjust size → heat treatment to optimize performance", with high overall strength and good pressure resistance (can withstand 10-100MPa pressure), but the production process is complex and the cost is high.
Hot-rolled seamless pipe: thicker wall thickness (3-120mm), used in high-pressure scenarios (such as oil and gas well casing, high-pressure boiler tube), such as shale gas exploitation using seamless pipes need to withstand high formation pressure and corrosion.
Cold drawn / cold rolled seamless pipe: thin wall thickness (0.2-30mm), smooth surface, high dimensional accuracy (tolerance ±0.1mm), used for precision machinery (such as hydraulic pipelines, instrument pipelines), such as automobile hydraulic system pipelines require cold drawn seamless pipes to ensure sealing performance.
Welded carbon steel pipe:
It is made of steel plate/steel strip after curling and welding the seam. It has high production efficiency and low cost (20%-30% lower than seamless pipes of the same specification), but the overall strength is slightly inferior, suitable for medium and low pressure scenarios.
Straight seam welded pipe: The seam is straight, and the length is limited by the width of the steel plate (6-12m). It is used for low-pressure transportation (such as tap water pipelines, low-pressure gas pipelines). For example, most gas branches in residential areas are straight seam welded pipes.
Spiral welded pipe: The steel strip is spirally curled and welded, and the length can be customized as needed (up to 120m). The weld is stressed and has better pressure resistance than straight seam welded pipes. It is used for long-distance transportation (such as urban centralized heating pipelines and oil pipelines).
2. Classification by use and performance
Carbon steel pipe for transportation: Focus on sealing and corrosion resistance (anti-corrosion treatment is required), used for water, gas, oil, etc. For example, municipal tap water pipelines often use DN500-DN2000 spiral welded pipes (low cost + long-distance adaptation).
Carbon steel pipe for structure: Emphasis on strength and toughness, used for building steel structure (such as truss, column), bridge pile foundation, such as large factory buildings use seamless carbon steel pipe to build load-bearing columns, reduce deadweight and good earthquake resistance.
Carbon steel pipe for high pressure: using low alloy high strength carbon steel (such as Q460, Q690), tempering heat treatment to improve performance, used for high pressure boilers, hydraulic systems, such as oil field deep well anti-sulfur seamless pipe can withstand pressure above 100MPa.
Core characteristics summary
Strength advantage: tensile strength 300-1000MPa (depending on the material), can withstand high pressure, heavy load, suitable for industrial-grade scenes.
Cost controllable: the raw material is carbon steel, the production process is simple (especially welded pipe), the cost performance is far better than stainless steel pipe and alloy steel pipe.
Flexible processing: can be cut, welded, bent, threaded, adapted to complex installation environment (such as pipeline turns, branches).
Limitations: Poor corrosion resistance (easy to rust), requiring anti-corrosion treatment such as galvanizing and epoxy coating; insufficient low-temperature toughness, and low-temperature special steel (such as Q355ND) is required in extremely cold areas.
2. Carbon steel pipe production technology and innovation
Carbon steel pipe production technology has made breakthroughs around "improving performance, enhancing corrosion resistance, and intelligence", and the process has been significantly optimized in recent years.
1. Core production process
Seamless pipe production:
The key lies in the perforation and pipe rolling links. Oblique perforation will make the solid billet into a hollow rough tube. The continuous rolling unit (such as MPM continuous rolling mill) accurately controls the wall thickness and outer diameter, and the dimensional accuracy reaches the outer diameter tolerance ≤±0.5%. Heat treatment (such as normalizing and tempering) can optimize toughness. For example, the impact energy of high-pressure seamless pipes after tempering is ≥34J.
Welded pipe production:
Welding quality is the core. High-frequency induction welding (speed up to 100m/min) is used for straight seam welded pipes, and submerged arc welding (deep weld penetration and high strength) is mostly used for spiral welded pipes. The welding current and extrusion volume must be controlled to ensure that the weld strength is ≥ 80% of the parent material.
2. Technical innovation direction
High performance: Adding alloy elements such as manganese and vanadium to develop low-alloy highHigh-strength pipes (such as Q690), with tensile strength increased to more than 800MPa, can replace some seamless pipes for high-pressure scenarios (such as shale gas pipelines).
Anti-corrosion upgrade: Promote three-layer PE anti-corrosion coating (soil corrosion resistance, life span of more than 50 years), zinc-nickel alloy plating (corrosion resistance is 3-5 times that of galvanizing), and adapt to environmental protection requirements (such as chromium-free passivation replacing traditional processes).
Intelligent production: Online ultrasonic flaw detection to detect internal defects, laser diameter measurement to monitor dimensions in real time, AI algorithm to optimize rolling parameters, and reduce scrap rate by more than 15%; digital twins simulate the life of pipes in different environments and optimize the formula.
3. Typical application areas of carbon steel pipes
Carbon steel pipes penetrate multiple industries and are "rigidly needed" materials for industry.
1. Energy and chemical industry
Oil and gas transportation: spiral welded pipes (three-layer PE anti-corrosion) for long-distance oil/gas trunk lines, and high-pressure seamless pipes for oil and gas well casings (sulfur and high temperature resistance).
Chemical industry and power: raw material transportation pipes for chemical plants (anti-corrosion welded pipes), steam pipes for thermal power plants (seamless pipes, resistant to high temperatures above 450°C).
2. Construction and municipal administration
Structural support: seamless pipes are used to build steel structure trusses in stadiums and airport terminals, and anti-corrosion welded pipes are used for bridge pile foundations (adapted to outdoor environments).
Municipal transportation: tap water pipes (spiral welded pipes), medium and low pressure gas pipes (straight seam welded pipes), rainwater/sewage pipes (welded pipes with cement mortar applied to the inner wall for anti-corrosion).
3. Machinery and transportation
Machinery manufacturing: machine tool spindles (cold-drawn seamless pipes, high precision), hydraulic oil pipes for engineering machinery (high-strength seamless pipes, bearing pressure above 30MPa).
Transportation: automobile transmission shafts (seamless pipes, good strength and toughness), ship deck pipelines (galvanized welded pipes to prevent seawater corrosion).
IV. Industry trends and challenges
The carbon steel pipe industry is driven by raw materials, environmental protection, and demand, showing a trend of "structural upgrading and green transformation".
1. Driving factors
Infrastructure and energy demand: Global urbanization drives the demand for municipal pipelines and steel structures; energy projects such as oil, gas, and hydrogen energy drive the demand for high-pressure pipes, such as low-alloy carbon steel pipes for hydrogen transportation, which has become a new growth point.
Substitution upgrade: Replace concrete pipes (fast installation) and plastic pipes (high-pressure scenarios), and upgrade low-end welded pipes to high-end anti-corrosion.
2. Core challenges
Raw material fluctuations: Iron ore and scrap steel prices affect costs, and small and medium-sized enterprises are under pressure on profits.
Environmental pressure: VOCs are emitted in coating and heat treatment links, and environmental protection equipment upgrades increase costs.
Homogeneous competition: There is an overcapacity of mid- and low-end welded pipes, and high-end seamless pipes rely on imported technology.
3. Future direction
High-end: Develop high-pressure, low-temperature, and sulfur-resistant special pipes, such as -60℃ low-temperature seamless pipes and pipes for shale gas development.
Green production: Promote short-process steelmaking (scrap steel + electric arc furnace) to reduce carbon, use green electricity to drive production, and establish an old pipe recycling system.
Intelligent service: full life cycle traceability, online selection platform provides "pipe + anti-corrosion + connection" solutions.