From kitchen utensils to offshore platforms, and from medical devices to aerospace components, different scenarios have vastly different performance requirements for stainless steel, which is underpinned by the precise matching of its grades. The grading of stainless steel is closely related to its chemical composition, where adjustments in the content of elements such as chromium, nickel, molybdenum and carbon shape its diverse material properties. This article focuses on mainstream stainless steel grades, analyzing their core characteristics and typical applications by organizational structure classification, and reveals the underlying logic of material selection.
Austenitic Stainless Steel: The Versatile Performer’s Application Scope
Austenitic stainless steel dominates the market with its non-magnetic property, good weldability and corrosion resistance. Its core advantage lies in the synergistic effect of chromium-nickel alloy, and some grades further enhance performance by adding elements such as molybdenum and titanium. This type of stainless steel can be strengthened through cold working but does not undergo hardening through heat treatment, making it the most balanced category in terms of comprehensive performance.
As the “benchmark grade” of austenitic stainless steel, 304 (06Cr19Ni10) has a carbon content of ≤0.08%, chromium content of 18%-20%, and nickel content of 8%-10.5%, forming a stable chromium oxide protective film that performs excellently in atmospheric and weak acid-alkaline environments. It boasts outstanding processability and can be easily formed through thermal processing such as stamping and bending, thus widely penetrating into domestic and industrial scenarios: household tableware, thermos flasks, kitchen sinks, building railings, curtain walls, and food industry filling equipment and biscuit molds all take 304 as the first choice. More importantly, it meets food-grade safety standards, becoming the “access threshold” material for food-contacting equipment.
304L (022Cr19Ni10), the low-carbon version of 304, reduces the carbon content to ≤0.03%, with its core advantage being significantly improved intergranular corrosion resistance after welding. In structures requiring frequent welding such as chemical storage tanks and large pressure pipelines, ordinary 304 is prone to intergranular corrosion due to carbide precipitation in the weld heat-affected zone, while 304L can maintain corrosion resistance without subsequent heat treatment, thus becoming the core material for outdoor equipment in the petrochemical and coal industries.
The “upgrade secret” of 316 (06Cr17Ni12Mo2) lies in the addition of 2%-3% molybdenum, which significantly enhances its pitting corrosion and crevice corrosion resistance, especially greatly improving its resistance to chloride ion media. Seawater desalination equipment and ship parts in marine environments, dye and papermaking equipment in the chemical industry, and pharmaceutical reaction kettles in contact with organic acids all rely on the corrosion resistance of 316. Its low-carbon version, 316L (022Cr17Ni12Mo2), further optimizes corrosion resistance and weldability, making it irreplaceable in scenarios with strong corrosion and high cleanliness requirements such as injection production lines and offshore platforms.
Ferritic Stainless Steel: An Economical and Weather-Resistant Option
Ferritic stainless steel uses chromium as the main alloying element (content 10.5%-30%), contains no or little nickel, and has the characteristics of magnetism and low thermal expansion coefficient. Its cost is only 60%-80% of that of austenitic stainless steel, making it the preferred choice for cost-effective scenarios. Its shortcoming is poor low-temperature toughness, making it unsuitable for extremely low-temperature environments.
As the “national grade” of ferritic stainless steel, 430 (10Cr17) has a chromium content of about 16%, with excellent oxidation resistance and formability. Its surface can be polished or brushed to achieve a textured finish. Due to its moderate cost, it is widely used in scenarios with low corrosion requirements: home appliance casings, washing machine inner drums, kitchen stove panels, as well as external decorative materials and skirting boards in the construction field. Although its corrosion resistance is inferior to 304, its service life can reach decades in dry indoor environments, making it a model of balancing decorativeness and economy.
409L (00Cr11Ti) has significantly improved high-temperature corrosion resistance and strength due to the addition of titanium, and can maintain stable performance after welding without heat treatment. The automotive exhaust system is its core application scenario – the exhaust pipe is in a high-temperature environment of 400℃-800℃ and exposed to exhaust corrosion for a long time, and the heat resistance and corrosion resistance of 409L are perfectly matched. At the same time, its cost advantage makes it the standard choice for automobile manufacturers. In addition, it is also commonly used in welded structures such as containers and heat exchangers.
Martensitic Stainless Steel: The High-Strength “Hardening Pioneer”
Martensitic stainless steel has a relatively high carbon content (0.1%-1.0%) and chromium content of 12%-18%. Its hardness and strength can be significantly improved through quenching and tempering treatment, and it has obvious magnetism. However, its corrosion resistance is the weakest among the three basic categories, making it suitable for scenarios where strength is prioritized and the corrosion environment is mild.
410 (12Cr13) is the basic grade of martensitic stainless steel, with a carbon content of about 0.12%. Its hardness can reach HRC 40-45 after heat treatment, and it has excellent processability. Its applications are concentrated in the field of mechanical structures and daily-use cutlery: mechanical parts such as steam turbine blades, pump rods, bolts and nuts, as well as first-class tableware such as kitchen knives and scissors, all rely on its high-strength characteristics. In petroleum refining equipment, the strength of 410 is sufficient to withstand high-pressure working conditions, while the mild refining environment can avoid severe corrosion.
The carbon content of 420J2 (30Cr13) is increased to 0.3%, and its hardness can reach above HRC 50 after quenching, with significantly enhanced sharpness and wear resistance. It is the core material for high-end cutlery, such as scalpels, butchers’ knives and industrial scissors. At the same time, it is also used in small parts requiring wear resistance such as nozzles and valves. Its twin grade, 420J1 (13Cr-0.2C), has lower hardness but slightly better corrosion resistance, suitable for tableware such as knives and forks where moderate sharpness is required.
Special Stainless Steel: Customized Experts for Extreme Environments
For extreme scenarios such as marine engineering and aerospace, special stainless steel achieves breakthroughs in strength and corrosion resistance through composite organizational structures or precise alloy ratios, representing the highest technical level of stainless steel materials.
As a representative of duplex stainless steel, 2205 (S31803) combines the advantages of austenitic and ferritic structures: austenite provides good toughness and weldability, while ferrite endows high strength and stress corrosion resistance. Its tensile strength can reach more than 800MPa, which is twice that of ordinary 304. Its chloride ion corrosion resistance is comparable to 316L, and its cost is lower, making it widely used in high-corrosion and high-pressure scenarios such as offshore platforms, chemical reactors and seawater desalination reverse osmosis membrane modules.17-4PH (05Cr17Ni4Cu4Nb) belongs to precipitation hardening stainless steel. It can form copper-based precipitates through aging treatment, with a maximum hardness of HRC 45, while maintaining good corrosion resistance and weldability. Its lightweight and high-strength characteristics make it a favorite in the aerospace field, used in aircraft structural parts and engine components; in the medical field, it can be used to manufacture load-bearing implants; in mechanical manufacturing, it is used in high-strength shaft parts and molds.
