304 Stainless Steel: The Universal Standard Austenitic Stainless Steel

304 stainless steel is the most widely used austenitic stainless steel, belonging to the classic "18-8" series (18% chromium + 8% nickel). It forms a dense chromium oxide passivation film on the surface, which provides excellent corrosion resistance in most mild environments. With balanced mechanical properties and cost-effectiveness, it has become the benchmark for general-purpose stainless steel.

Core Parameters

Chemical Composition (wt%): C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=18.00-20.00, Ni=8.00-10.50, Fe=Balance

Mechanical Properties (Annealed): Tensile Strength ≥520MPa, Yield Strength ≥205MPa, Elongation ≥40%, Brinell Hardness ≤201HB

Service Temperature: -196℃ to 800℃ (continuous service; long-term service recommended ≤650℃)

Equivalent Grades: SUS304 (JIS), EN 1.4301 (EN), UNS S30400 (ASTM)

Performance Advantages: Excellent corrosion resistance in atmospheric, fresh water, and weak acid-base environments; high toughness even at low temperatures (-196℃), no brittle fracture; good cold forming and welding performance; non-magnetic (weak magnetic may occur after cold working); cost-effective, suitable for mass production applications.

Typical Applications: Architectural decoration (curtain walls, handrails), food processing equipment (tanks, conveyors), household appliances (sinks, oven inner walls), medical devices (non-implantable), general industrial pipelines, and chemical equipment for mild corrosion environments.

Practical Q&A

Q1: Why does 304 stainless steel rust in coastal areas? A1: Coastal salt mist contains high concentrations of chloride ions, which can penetrate and damage the passivation film. Without regular cleaning, local pitting corrosion may occur. For coastal applications, it is recommended to increase surface passivation treatment or directly select 316 stainless steel with better chloride ion resistance.

Q2: Can 304 stainless steel be used in high-temperature equipment? A2: It can be used at temperatures up to 800℃ for short periods, but long-term service at temperatures above 650℃ will reduce its oxidation resistance and mechanical strength. For high-temperature environments above 650℃, 304H or 309S with better high-temperature stability should be selected.

Q3: What factors affect the corrosion resistance of 304 stainless steel? A3: The core is the integrity of the passivation film. Physical damage (scratches, collisions), chemical erosion (strong acids, high-concentration chloride ions), and long-term accumulation of surface contaminants can damage the passivation film, leading to reduced corrosion resistance. Regular cleaning and maintenance can extend its service life.

Q4: Is 304 stainless steel suitable for cold working processes such as stamping? A4: Yes. It has excellent cold formability, and can withstand deep drawing, stamping, bending and other processes without cracking. It should be noted that after cold working, the material will be work-hardened, and if further processing is required, intermediate annealing (1050-1100℃, rapid cooling) should be performed to restore toughness.

Q5: What welding materials and processes are recommended for 304 stainless steel? A5: The preferred welding wire is ER308L, and the electrode is E308L-16, which can ensure the corrosion resistance and toughness of the weld. For TIG welding, the current should be controlled at 80-120A, and pure argon should be used for protection; for MIG welding, the current is 150-200A, and the welding speed should be kept stable to avoid excessive heat input.