Answers

• 
  What is SUS304 material?

  SUS304 is an austenitic stainless steel according to the Japanese Industrial Standard (JIS), corresponding to the American ASTM standard 304 stainless steel (UNS S30400) and the Chinese national standard 06Cr19Ni10.
  
  1. The chemical composition of SUS304 is characterized by low carbon and high chromium and nickel content, specifically:
  Carbon (C): ≤0.08%
  Chromium (Cr): 17.00-19.00%
  Nickel (Ni): 8.00-10.50%
  Manganese (Mn): ≤2.00%
  Silicon (Si): ≤1.00%
  Phosphorus (P): ≤0.045%
  Sulfur (S): ≤0.030%.
  
  2. Key elements and their roles:
  Chromium: Forms a dense chromium oxide (Cr₂O₃) protective film, resisting oxidation and corrosion.
  
  Nickel: Stabilizes the austenitic structure, improving low-temperature toughness and acid and alkali resistance.
  
  Low-carbon design: Reduces intergranular corrosion tendency and optimizes weldability.
  
  3. Physical Properties
  Density: 7.93 g/cm³
  Melting point: 1398-1454°C
  Thermal conductivity: 16.3 W/(m·K) (at 100°C)
  Coefficient of thermal expansion: 17.2×10⁻⁶/°C (0-100°C)
  Resistivity: 0.73×10⁻⁶Ω·m (at 20°C)
  Magnetic properties: Non-magnetic (annealed state), may develop weak magnetism after cold working.
  
  4. Mechanical Properties
  SUS304 in the annealed state exhibits the following typical mechanical properties:
  Tensile strength (σb): 520-1035 MPa
  Yield strength (σ0.2): ≥205 MPa
  Elongation (δ5): ≥40%
  Hardness: ≤187 HB (Britner hardness)
  Impact toughness: Excellent low-temperature toughness (maintains good ductility even at -196°C).
  Work hardening characteristics: Cold working can significantly improve strength (e.g., hardness can reach HRB 92 after cold rolling).

  
  
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  What is the nickel content of stainless steel?

  304 stainless steel contains approximately 10% nickel, specifically between 8% and 10.5%.
  The national standard for 304 stainless steel requires a nickel content of at least 8%.
  Nickel is a major alloying element in austenitic stainless steel. Its main function is to strengthen and stabilize austenite, resulting in a fully austenitic structure. This gives the steel a good balance of strength, plasticity, and toughness, as well as excellent hot and cold workability, while also improving the thermodynamic stability of austenitic stainless steel.
  The addition of nickel to austenitic stainless steel and the increase in nickel content lead to increased thermodynamic stability. Therefore, austenitic stainless steel exhibits better rust resistance and resistance to oxidizing media. Furthermore, with increasing nickel content, its resistance to reducing media is further improved. It is worth noting that nickel is also one of the few important elements that enhances the resistance of austenitic stainless steel to transgranular stress corrosion in many media.

  
  
• 
  What is the maximum thickness of cold-rolled steel sheet?

  The thickness of cold-rolled steel sheet is not a fixed value, but rather determined by specific needs and applications.
  In the market, the thickness of cold-rolled steel sheet generally does not exceed 6mm. This is due to both market demand and the limitations of the rolling process. Generally, the thickness range of cold-rolled steel sheet can be between 0.1mm and 8mm. Cold-rolled steel sheet is made from hot-rolled steel coils through cold continuous rolling, annealing, and pickling, resulting in reduced plasticity and increased hardness.
  However, this range is not absolute. In reality, the maximum thickness of cold-rolled steel sheet can be greater, but this usually depends on production processes and equipment capabilities, as well as market demand.