Answers

• 
  National Standard Tolerances for Stainless Steel Thickness？

  Thin Plates (Below 0.5mm): For these extremely thin stainless steel plates, the allowable thickness deviation is relatively small, within ±0.08mm. This requires manufacturers to strictly control the thickness during manufacturing to ensure product precision and stability.
  
  Thin Plates (0.5mm to 1mm): The allowable thickness deviation for this type of thin plate is slightly larger than that for plates below 0.5mm, within ±0.10mm. Although the deviation range is wider, high manufacturing precision is still required to meet market demands.
  
  Medium Plates (1mm to 2mm): For this type of medium-thickness stainless steel plate, the allowable thickness deviation is ±0.12mm. This standard ensures product quality while also considering production efficiency and cost control.
  
  Thick Plates (Greater than 2mm): For stainless steel plates thicker than 2mm, the allowable deviation range is relatively larger, within ±0.15mm. This is mainly because as the thickness increases, the difficulty and uncertainty in the manufacturing process also increase accordingly.
  
  For hot-rolled or cold-drawn (rolled) stainless steel seamless pipes, the permissible deviation of their wall thickness is usually within ±12.5%.

  
  
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  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?

  The nickel content of 304 stainless steel is typically between 8% and 10.5%, which is within the range specified by international standards. Nickel's role is to make the stainless steel more corrosion-resistant while maintaining the material's high-temperature strength and machinability. If the nickel content is below 8%, the material's corrosion resistance will be significantly reduced.

  
  

  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.