F304
F304 alloy material is a typical austenitic stainless steel, and its technical specifications and performance characteristics can be comprehensively analyzed through the following dimensions:
I. Standards and brand system
- Core Standards: F304 mainly relies on the ASTM A182/A182M – 2018 standard, which specifically regulates forged or rolled stainless steel flanges, pipe fittings, and valve components for high temperatures. In addition, in the field of tubes, F304 also complies with ASTM A312 (Seamless and Welded Austenitic Stainless Steel Tubes) and ASTM A276 (Stainless Steel Bars and Shapes) standards.
- International Code Correspondence:
- United States: UNS S30400
- Europe: EN 1.4301
- Japan: JIS SUS304
- China: Old grade 0Cr18Ni9, new national standard 06Cr19Ni10
II. chemical composition
The alloy composition design of F304 aims to balance corrosion resistance and processability. The typical chemical composition is as follows:
- Main elements: Chromium (Cr) 18.0 – 20.0%, nickel (Ni) 8.0 – 11.0%, forming a stable austenitic structure and endowing excellent corrosion resistance.
- Secondary elements: Carbon (C) ≤ 0.08% (controlling the risk of intergranular corrosion), manganese (Mn) ≤ 2.00%, silicon (Si) ≤ 1.00%, phosphorus (P) ≤ 0.045%, sulfur (S) ≤ 0.030%.
- Trace elements: Nitrogen (N) ≤ 0.10% (some standards allow addition to improve strength, such as F304N).
III. Mechanical performance parameters
According to the ASTM A182 standard, the typical room – temperature mechanical properties of F304 are as follows:
- Tensile strength: ≥515 MPa
- Yield strength: ≥205 MPa
- Elongation: ≥30% (gage length 50 mm)
- Hardness: ≤217 HB (Brinell hardness)
Its elastic modulus is approximately 193 GPa, density is 7.93 g/cm³, and thermal expansion coefficient is 17.3 μm/m·°C at 0 – 100°C. These properties enable it to have good cold – working and welding adaptability while maintaining structural strength.
IV. Heat Treatment Process
- Solution Treatment:
- Temperature: 1010 – 1150°C (adjusted according to specific products; for example, cold – rolled plates usually adopt 1050 – 1150°C).
- Cooling method: Rapid water cooling to ensure sufficient dissolution of carbides, obtain a single austenitic structure, and improve corrosion resistance.
- Application scenarios: Basic treatment for all F304 products, especially suitable for stress relief after welding.
- Stabilization Treatment (Optional):
- Temperature: 850 – 900°C (only used for components that need long – term high – temperature service).
- Function: Promote the combination of titanium or niobium with carbon to prevent intergranular corrosion (this process is more common in stabilized stainless steels such as 321 and 347).
V. Main application fields
With the comprehensive advantages of corrosion resistance, heat resistance, and easy processability, F304 is widely used in the following fields:
- Industrial Equipment:
- Chemical reaction kettles, heat exchangers (resistant to nitric acid and organic acid corrosion).
- Storage tanks and pipelines in the food and beverage industry (complying with hygiene standards).
- Construction and Decoration:
- Curtain walls, railings (resistant to atmospheric corrosion).
- Kitchen countertops, sinks (resistant to daily chemicals).
- Energy and Environmental Protection:
- Non – critical components of nuclear power plants (such as pipeline systems).
- Water treatment equipment (resistant to chloride ion corrosion).
- Mechanical Manufacturing:
- Pump and valve components (ASTM A182 F304 butt – welded flanges).
- Medical devices (such as surgical instrument frames).
- Transportation:
- Ship deck equipment (resistant to seawater corrosion).
- Auto exhaust system components (resistant to high – temperature oxidation).
VI. Special Variants and Precautions
- F304L: Low – carbon version (C ≤ 0.03%), with better resistance to intergranular corrosion, suitable for components that cannot undergo heat treatment after welding.
- F304N: Contains nitrogen (0.10 – 0.16%), with improved strength (tensile strength ≥ 550 MPa), used for high – load structural parts.
- Corrosion environment adaptation: In environments with chloride ion concentration > 200 ppm, it is recommended to upgrade to 316 stainless steel; strong reducing acids (such as hydrochloric acid) require the use of nickel – based alloys.
From the above multi – dimensional analysis, it can be seen that as the most commonly used austenitic stainless steel, F304 has its standardized system, composition design and performance proven by long – term engineering practice. While taking into account economy and reliability, it has become a benchmark material for cross – industry applications.