Stainless steel plate: the "corrosion-resistant pioneer" among metal materials

As an indispensable metal material in modern industry and life, stainless steel plate plays a key role in many fields with its excellent corrosion resistance, aesthetics and high strength. From curtain wall decoration of high-rise buildings to precision medical equipment, from kitchen utensils to aerospace equipment, the application of stainless steel plate covers all aspects of human production and life.
1. Definition and core characteristics of stainless steel plate
Definition: Stainless steel plate refers to a steel plate that is resistant to corrosion by weak corrosive media such as air, steam, and water, and chemically corrosive media such as acids, alkalis, and salts. Its corrosion resistance mainly comes from the chromium-rich oxide film (passivation film) formed on the surface. According to GB/T 20878-2007 standard, the chromium content of stainless steel is at least 10.5%, and most grades also add alloy elements such as nickel, molybdenum, and titanium to optimize performance.
Core characteristics analysis
Corrosion resistance mechanism: Chromium elements will generate a layer of Cr₂O₃ passivation film about 2-3nm thick in an oxidizing environment. This film has self-repairing ability. When the surface is slightly scratched, it can be regenerated in an oxygen-containing medium. For example, in seawater environment, the addition of molybdenum to 316L stainless steel can enhance the resistance of the passivation film to chloride ions.
Diversity of mechanical properties:
Austenitic stainless steel (such as 304) has good plasticity and toughness, with an elongation of more than 40%, suitable for deep drawing;
Martensitic stainless steel (such as 420) can reach a hardness of more than HRC50 after heat treatment, and is often used in tool manufacturing;
Ferritic stainless steel (such as 430) has high strength and low thermal expansion coefficient, suitable for high temperature environment.
Difference in physical properties: Compared with carbon steel, the thermal conductivity of stainless steel is about 1/3 of that of carbon steel (such as 16W/m・K for 304 stainless steel and 45W/m・K for Q235 carbon steel), and the linear expansion coefficient is higher, which requires special attention in the design of high-temperature equipment.
2. Production process and key technologies
Integrated production process
Metallurgy:
Electric arc furnace (EAF) + external refining (AOD/VOD) process is used. For example, when producing 316L stainless steel, the AOD furnace accurately controls the carbon content to ≤0.03% by blowing argon oxygen mixed gas to avoid intergranular corrosion;
High-end stainless steel (such as 316LN for nuclear power) needs to use vacuum induction furnace (VIM) + electroslag remelting (ESR) to reduce the inclusion content to ≤5μm.
Rolling process:
Hot rolling: The steel billet is heated to 1100-1250℃ and rolled into a plate with a thickness of 1.2-200mm through rough rolling and finishing rolling mills. For example, the 4300mm wide and thick plate rolling mill of Taigang can produce stainless steel plates with a width of 4.1m;
Cold rolling: After annealing and pickling, the hot-rolled coil is rolled to a thickness of 0.1-3mm on a cold rolling mill. For example, the 20-roller Sendzimir rolling mill of Baowu Group can produce ultra-thin stainless steel foil with a thickness of 0.05mm.
Key technologies for surface treatment:
Passivation treatment: Remove free iron on the surface through nitric acid + hydrofluoric acid solution to form a complete passivation film and improve corrosion resistance;
Chromium-free passivation: In response to environmental protection requirements, develop alternative processes such as silane treatment and titanium salt passivation. For example, the chromium-free passivation technology developed by Japan's JFE has passed ISO 12944 certification;
Nano coating: Deposit TiO₂ nanolayer on the surface of stainless steel to achieve self-cleaning function (photocatalytic decomposition of organic matter), which is used for building exterior wall panels.
3. Typical application areas and cases
Architectural decoration field
Landmark building application: The terminal building of Beijing Daxing International Airport uses 304 stainless steel honeycomb panel ceiling with a total area of ​​more than 100,000 square meters, and fluorocarbon spraying is used to enhance weather resistance; the facade of Shanghai Tower uses 2205 duplex stainless steel decorative strips to resist typhoons and marine climate erosion.
Innovative application: The exterior wall of the Guggenheim Museum in Bilbao, Spain uses titanium-stainless steel composite panels, and the curved surface is achieved through a special welding process, and the annual maintenance cost is reduced by 70% compared with traditional materials.
Food and medical industry
Food processing equipment: Mengniu Dairy's aseptic filling line uses 316L stainless steel plates with a surface roughness of Ra≤0.8μm, which complies with FDA certification and prevents food residues from breeding bacteria;
Medical implants: 316LVM stainless steel (low vanadium and molybdenum) is used to manufacture artificial joints. Its biocompatibility is certified by ISO 10993, with a fatigue strength of ≥500MPa and a service life of more than 20 years.
Industrial and energy fields
Petrochemical: The ethylene cracking furnace pipelines in the Jubail Petrochemical Park in Saudi Arabia use 310S stainless steel plates (temperature resistance of 1200℃), and the replacement cycle is extended from 1 year to 5 years compared to carbon steel pipelines;
New energy: CATL's battery shell uses 430 ferritic stainless steel plates, which are airtight through laser welding (leakage rate ≤10⁻⁹Pa・m³/s), and the cost is 30% lower than that of aluminum alloy shells.
Transportation field
Rail transportation: CRRC Qingdao Sifang's subway cars use 304 stainless steel plates, which can reduce the weight of the whole vehicle by 15% through modular design, and are rust-free in the salt spray test (5,000 hours);
Shipbuilding: The bow outer plate of China's first polar research icebreaker "Xuelong 2" uses 6mm thick 316L stainless steel, which can withstand low temperatures of -40℃ and ice impact.
IV. Market dynamics and technology trends
Global market structure
Capacity distribution: In 2024, the global stainless steel plate output will be about 52 million tons, of which China will account for 56% (TISCO, Tsingshan, and Baowu are the top three), Europe (ArcelorMittal) and Japan (JFE, Nippon Steel) will account for 18% and 12% respectively;
Price trend: The average price of 304 stainless steel plate (1.0mm12192438mm) in 2024 is about US$2,200/ton, which is affected by the fluctuation of nickel prices (LME nickel price range is US$18,000-25,000/ton), an increase of 12% compared with 2023.
Technology development trend
Low-carbon production:
The hydrogen-based vertical furnace (H2-FER) technology developed by Tsingshan Group uses green hydrogen to replace coke to smelt stainless steel, reducing CO₂ emissions per ton of steel from 2.5 tons to 0.3 tons;
The European acierinova project develops arc furnace + CCUS (carbon capture) technology, aiming to achieve carbon neutrality in stainless steel plate production.
Functional innovation:
Antibacterial stainless steel: 304Cu stainless steel with 0.8% copper added has a killing rate of ≥99% for Escherichia coli and Staphylococcus aureus, and is used for hospital handrails;
Self-lubricating stainless steel: The surface is laser-etched with micro-grooves and embedded with molybdenum disulfide, and the friction coefficient is reduced from 0.6 to 0.2, which is used for oil-free bearings.
Circular economy application:
The "infinite cycle stainless steel" developed by Japan's NSSC makes scrapped stainless steel plates 100% recyclable through composition design without performance degradation, and has been used in home appliance panels;
China Baowu has established a closed-loop system of stainless steel plate recycling-sorting-smelting, and the nickel recovery rate of recycled stainless steel plates has reached 99.3%.
V. Purchase and maintenance guide
Key selection factors
Environmental adaptability: 316L (chloride ion resistance) is selected for seaside buildings, 310S (oxidation resistance) is used for high-temperature furnaces, and 304 (no precipitation) is selected for food equipment;
Processing performance: 304 (r value ≥ 1.8) is selected for deep drawing parts, and 420F (sulfur is added to improve cutting performance) is selected for cutting parts;
Cost balance: 430 (price is about 60% of 304) is selected for ordinary decoration, and 2205 duplex steel (strength is twice that of 304) is selected for high-end equipment.
Maintenance technical points
Daily cleaning: Wipe with a neutral detergent (pH 6-8), avoid using steel wool to damage the passivation film;
Special environment maintenance: Rinse with 5% citric acid solution every quarter in the marine environment to remove salt spray deposits; passivation treatment is performed every year in industrial acid rain areas;
Repair process: Local scratches can be repaired by electrolytic polishing (voltage 15-20V, time 3-5 minutes), and deep corrosion needs to be polished to a metallic luster before re-passivation.