Stainless steel pipes: the "corrosion-resistant backbone" of industrial fluid transportation

As the core material of modern industrial pipeline systems, stainless steel pipes have built a safe and reliable fluid transportation network in the fields of petrochemicals, food and medicine, energy and environmental protection with their excellent corrosion resistance, high strength and hygiene. From medical injection tubes with a diameter of 6mm to cross-sea water pipes with a diameter of 2000mm, stainless steel pipes achieve "zero leakage" operation in harsh environments through precise alloy design and process control, becoming an indispensable pipeline solution in the field of high-end manufacturing.
1. Definition and classification system of stainless steel pipes
Definition: Stainless steel pipes refer to steel pipes that are resistant to corrosion by media such as air, water, acid, alkali, and salt. Their corrosion resistance comes from the chromium-rich passivation film (Cr content ≥10.5%) formed on the surface. According to GB/T 14976-2012 standard, stainless steel pipes are divided into seamless pipes and welded pipes according to the production process, and are divided into categories such as fluid transportation, boiler heat exchange, and mechanical structure according to their uses. The corrosion resistance and strength can be optimized by adding alloy elements such as nickel, molybdenum, and titanium.
Production process:
Seamless steel pipe: perforation + cold rolling / cold drawing, uniform wall thickness, used in high-pressure scenarios (such as boiler tubes);
Welded steel pipe: hot-rolled coil welding, including ERW (resistance welding), TIG (argon arc welding), SAW (submerged arc welding);
Composite steel pipe: stainless steel and carbon steel / copper composite, such as carbon steel composite pipe lined with 316L, to reduce costs.
Structural form:
Round pipe: diameter 6-2000mm, accounting for more than 90% of the output, used for fluid transportation;
Square and rectangular pipe: 10×10-500×500mm, used for building structures;
Special-shaped pipe: ellipse, triangle, etc., used for special equipment;
Corrugated pipe: axial / transverse corrugation, used for compensators and soft connections.
2. Production process and key technological breakthroughs
Full process analysis
Smelting and pipe casting:
Electric arc furnace (EAF) + refining outside the furnace (AOD/VOD): When producing 316L stainless steel pipes, the AOD furnace reduces the carbon content to ≤0.03% by blowing argon oxygen mixed gas to avoid intergranular corrosion;
Continuous casting technology: Use protective slag continuous casting to produce rough pipes below φ100mm, with a pulling speed of 1-2m/min and a surface quality of Ra≤12.5μm.
Forming and welding:
Seamless pipe forming:
Piercing: Φ100mm or less rough pipes are perforated by two-roller oblique rolling, and the rough pipe wall thickness tolerance is ±10%;
Cold rolling: Multi-roller cold rolling mill produces φ6-159mm pipes, with a wall thickness accuracy of ±0.05mm;
Welded pipe welding:
TIG welding: 304 stainless steel thin pipes (wall thickness ≤2mm) are pulsed TIG welding, and the weld height is ≤0.5mm;
Laser welding: 2205 duplex steel pipes (wall thickness 3-10mm) are fiber laser welded, with a speed of 10m/min and a heat affected zone ≤0.1mm.
Surface treatment technology:
Passivation treatment: nitric acid + hydrofluoric acid solution passivation, forming a 2-3nm thick Cr₂O₃ film to improve corrosion resistance;
Electrolytic polishing: voltage 15-25V, time 5-10 minutes, surface roughness Ra≤0.2μm, used for food pipelines;
Chromium-free coating: silane-titanium salt composite coating, salt spray resistance test (1000 hours) no rust, in compliance with EU REACH regulations.
Cutting-edge technology cases
Hot extrusion seamless pipe: Taigang Group uses a 125MN extruder to produce Φ426×50mm 310S stainless steel thick-walled pipes for 1200℃ high-temperature furnace pipes, filling the domestic gap;
Digital welded pipe production line: The intelligent welded pipe line deployed by Baowu Group uses AI vision to detect weld defects, with a detection speed of 50m/min and an accuracy rate of 99.2%;
3D printed stainless steel pipe: The 316L stainless steel special-shaped pipe developed by Xi'an Polylite is printed using SLM technology with a wall thickness tolerance of ±0.1mm, and is used for complex aviation pipelines.
3. Performance advantages and engineering applications
Petrochemical and energy fields
Oil refining equipment:
316L stainless steel pipe (Φ168×8mm) for atmospheric and vacuum distillation tower, resistant to corrosion of sulfur-containing crude oil (H₂S≤1000ppm), with a service life of more than 10 years;
310S stainless steel pipe (Φ108×10mm) for ethylene cracking furnace, resistant to high-temperature oxidation at 1100℃, with a wall thickness reduction rate of ≤10%/year.
Natural gas transportation:
2507 duplex stainless steel pipe (Φ89×6mm) for shale gas fields, resistant to Cl- corrosion (Cl-≤50000ppm), and resistant to CO₂ stress corrosion cracking;
304L stainless steel cryogenic pipe (Φ57×3mm) for LNG receiving station, with an impact energy ≥34J at -196℃ and no brittle cracking.
Food, medicine and hygiene
Food processing:
Mengniu Dairy uses 316L stainless steel pipes (Φ38×2mm) for aseptic filling lines, with electrolytic polishing of the inner wall (Ra≤0.4μm), which complies with FDA certification and avoids food residues;
304 stainless steel pipes (Φ60×3mm) for beer brewing, which are cleaned by CIP (80℃ hot water + 3% NaOH), and the microbial contamination rate is ≤10CFU/m².
Pharmaceutical manufacturing:
316LVM stainless steel pipes (Φ12×1.5mm) for vaccine production lines, with low vanadium content (V≤0.1%), and biocompatibility certified by ISO 10993;
316L stainless steel bright annealed pipes (Φ25×2mm) for pharmaceutical water systems, with inner surface roughness Ra≤0.2μm, which meet GMP standards.
Construction and water treatment fields
High-end buildings:
Beijing Daxing International Airport terminal uses 2205 duplex stainless steel pipes (Φ114×4mm), which are resistant to typhoons (wind speed ≥60m/s) and marine climate erosion, with a service life of 50 years;
Dubai Burj Khalifa water supply and drainage system uses 304 stainless steel pipes (Φ200×6mm), which are passivated and rust-free in tropical climates.
Water treatment projects:
Shanghai Qingcaosha Reservoir water pipes use 316L stainless steel pipes (Φ1600×12mm), which are resistant to chloride ion corrosion (Cl-≤200ppm) and have a water flow rate of 200,000 m³/day;
Sewage treatment plants use 430 stainless steel pipes (Φ219×8mm), which are resistant to acid and alkali corrosion (pH=5-9), and the sludge conveying pressure is ≤1.6MPa.
Aerospace and nuclear industry
Aerospace engines:
17-4PH stainless steel pipe (Φ8×1mm) for C919 engine fuel pipe, aging treatment (480℃×4h), σb≥1000MPa, resistant to 300℃ high temperature;
304 stainless steel thin-walled pipe (Φ6×0.8mm) for drone hydraulic system, bursting pressure ≥35MPa, meeting flight vibration requirements.
Nuclear industry:
316LN stainless steel U-shaped pipe (Φ19.05×1.09mm) for nuclear power plant steam generator, passed 100% eddy current flaw detection, radiation dose ≥10^5 Gy;
254SMO super stainless steel pipe (Φ50×5mm) for nuclear waste treatment, resistant to concentrated nitric acid (65% HNO₃) corrosion, working temperature ≤120℃.
IV. Market dynamics and technological trends
Global industry status
Capacity distribution: In 2024, the global stainless steel pipe production will be about 18 million tons, of which China will account for 58% (Jiangsu, Zhejiang and Guangdong are the main production areas), followed by Europe (15%), Japan (10%) and the United States (8%);
Price dynamics: The average price of 304 stainless steel welded pipe (Φ57×3mm) in 2024 is about US$3,200/ton, which is 12% higher than that in 2023 due to the LME nickel price (US$18,000-25,000/ton);
Import and export pattern: China exports about 3 million tons of stainless steel pipes annually, mainly to Southeast Asia (accounting for 40%), and imports about 500,000 tons, mainly high-end seamless pipes (such as JIS G 3463 boiler pipes imported from Japan, which are 40% higher than domestic ones).
Technology development direction
Green and low-carbon production:
Electric arc furnace short process: Use scrap steel + photovoltaic power to produce stainless steel pipes, and reduce CO₂ emissions per ton of steel from 8 tons to 3 tons (such as Tsingshan Group's Indonesian base);
Hydrogen-based reduction: The hydrogen-based vertical furnace developed by Taigang Group to smelt stainless steel pipes, using green hydrogen to replace coke to achieve "zero-carbon steelmaking";
Low-temperature rolling: 850℃ low-temperature rolling is used for 430 stainless steel pipes, reducing energy consumption by 15%, while refining the grain to level 8.
High-performance innovation:
Super duplex stainless steel pipe: 2507 steel pipe σb ≥ 700MPa, pitting resistance equivalent PREN ≥ 40, used for deep-sea oil and gas (water depth ≥ 3000m);
Antibacterial stainless steel pipe: 304Cu pipe with 0.8% copper added, killing rate of E. coli ≥ 99%, used for hospital water supply and drainage;
Memory alloy steel pipe: Ni-Ti stainless steel pipe has shape memory function, used for automatic compensation of pipeline, compensation amount up to 10% of pipe diameter.
Intelligent manufacturing:
Digital twin welded pipe: Establish a digital twin model of the welding process, predict the temperature field of the weld, and control the welding deformation to ≤ 0.1mm/m;
5G + intelligent detection: The 5G intelligent detection line deployed by Chalco Luotong uses ultrasonic phased array + AI recognition, with a detection speed of 100m/min;
Blockchain traceability: Apply blockchain technology to stainless steel pipes for nuclear power, trace the entire process from steelmaking to installation, and meet HAF certification requirements.
Functionalized surface engineering:
Self-cleaning stainless steel pipe: 316L pipe coated with TiO₂ photocatalytic coating, with an efficiency of ≥90% in degrading organic matter under ultraviolet light, used for sewage treatment;
Anti-scaling stainless steel pipe: 2205 pipe with micro-grooves laser-etched on the surface, with a 70% reduction in scale adhesion, used for heat exchangers;
Superconducting stainless steel pipe: 304 pipe with Nb-Ti alloy coating, superconducting at 4.2K, used for particle accelerators.
V. Selection Guide and Maintenance Points
Selection Decision Factors
Medium Corrosiveness:
Seawater/Chlorine-containing medium: Select 316L, 2205 duplex steel pipe;
Concentrated nitric acid: Select 310S, 254SMO steel pipe;
Food/Medicine: Select 316L, 316LVM steel pipe, with a surface roughness Ra≤0.8μm.
Pressure and temperature:
High-pressure scenario (≥10MPa): select seamless steel pipe, such as 304 seamless pipe (Φ108×12mm);
High temperature (≥600℃): select 310S, 314 steel pipe;
Low temperature (-196℃): select 304L, 316L steel pipe, impact energy ≥34J.
Connection method:
Compression connection: DN15-DN100, select 304 stainless steel thin-walled pipe (wall thickness 0.8-2.0mm);
Welding connection: high-pressure large-diameter, select 2205 duplex steel pipe, use TIG welding + back protection;
Threaded connection: DN15-DN50, select 316 stainless steel pipe, thread accuracy 6g/6H.
Storage and maintenance technology
Rust-proof storage:
Indoor storage: stacking in the air, humidity ≤60% RH, avoid contact with carbon steel;
Open-air storage: covered with waterproof canvas, the bottom is raised 300mm, and both ends of the steel pipe are sealed to prevent dust;
Maritime protection: the surface of the steel pipe is coated with dry anti-rust oil, wrapped with moisture-proof paper, and VCI gas phase anti-rust bags are placed in the container.
Daily maintenance:
Cleaning and maintenance: wipe with neutral detergent (pH6-8), avoid using steel wool to damage the passivation film;
Weld maintenance: check the corrosion of the weld every year, and local rust can be polished with sandpaper (grain size 240#) and then re-passivated;
Pressure test: industrial pipelines are subjected to water pressure test every 3 years (test pressure 1.5 times working pressure), and the pressure is maintained for 30 minutes without leakage.
Special environment maintenance:
Marine engineering: Use high-pressure water (pressure ≥10MPa) to flush the steel pipe surface every six months to remove marine organisms;
Chemical equipment: Regularly perform eddy current detection to monitor the thinning of the pipe wall and replace it when the remaining wall thickness is ≤80%;
Medical pipelines: Perform online passivation treatment every quarter and use 2% nitric acid solution for 2 hours to ensure the cleanliness of the inner surface.

Stainless steel pipes play a key role as the "vascular system" in the global industrial system with their excellent corrosion resistance and reliability. From deep-sea oil and gas extraction to vaccine production, from super high-rise buildings to particle accelerators, stainless steel pipes continue to break through environmental limits through continuous material innovation and process innovation, providing safety guarantees for high-end manufacturing. With the deep integration of green manufacturing and intelligent technology, stainless steel pipes will show more possibilities in the era of carbon neutrality and digitalization, and become an important cornerstone to support future industrial civilization.