Answers

• 
  What is P20 material?

  P20 is a pre-hardened plastic mold steel, corresponding to the Chinese national standard 3Cr2Mo and the German standard 1.2311.
  
  P20 contains alloying elements such as chromium and molybdenum, has a uniform microstructure, well-controlled impurities, stable machining performance, reasonable tool wear, and good surface finish. It is suitable for making structural parts such as cavities, cores, and mold frames. Upon arrival, it can be directly milled, ground, drilled, and EDM machined without additional quenching and tempering, shortening the mold making cycle and reducing precision issues caused by heat treatment deformation.
  
  Its polishing performance meets the requirements of most plastic exterior parts, adapting to the surface standards of molds for household appliance housings, automotive interiors, and daily necessities. It can also undergo nitriding treatment to improve wear resistance.

  
  
• 
  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%.

  
  
• 
  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).