Answers

• 
  What is the hardness of hard cold rolled coil?

  Hard cold rolled coil is a semi-finished product made by continuously cold-rolling hot-rolled coil at room temperature after pickling to remove the oxide scale. Hard cold rolled coil typically has a hardness exceeding 90 HRB (Rockwell hardness) and has very poor machinability, requiring only simple, directional bends of less than 90 degrees (perpendicular to the coiling direction). Therefore, it is primarily used for parts requiring simple deformation or as feedstock for hot-dip galvanizing plants.
  
  Factors Affecting Hardness
  1. Material Composition:
  Every 0.1% increase in carbon content increases hardness by approximately 10 HV; alloying elements such as manganese and silicon also enhance the hardening effect.
  2. Rolling Process:
  Reduction: The greater the rolling reduction, the higher the hardness (for example, a 50% reduction yields a 15-20% increase in hardness compared to a 30% reduction).
  Annealing Temperature: The hardness of fully hardened (unannealed) cold-rolled coil can reach 180 HV, but after annealing at 700°C, it drops below 120 HV.

  
  
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  Silicon Content and Characteristics of Silicon Steel Sheets?

  Silicon steel sheets (also known as electrical steel) are silicon-containing soft magnetic alloys primarily composed of iron (Fe) and silicon (Si). The addition of silicon significantly increases the material's resistivity and reduces iron losses (hysteresis and eddy current losses) while maintaining good magnetic conductivity.
  
  Different silicon content directly affects the electromagnetic properties (such as iron loss and magnetic flux density) and mechanical properties (such as hardness and brittleness) of silicon steel sheets.
  
  1. Low-Silicon Steel (Silicon Content: 0.8%-3.2%)
  Features: Low silicon content, retains good ductility and toughness, and offers excellent machinability (such as stamping and shearing). Iron losses are relatively high, but saturation magnetic flux density (BS) is high (approximately 1.8-2.0 T). Applications: Primarily used in applications requiring high mechanical strength, such as small motors, relays, and speakers. Typical grades: DR series (hot-rolled low-silicon steels such as DR13 and DR14) in Chinese standards; some cold-rolled non-oriented silicon steels (such as DW470, with a silicon content of approximately 0.8% to 1.8%).
  
  2. Medium Silicon Steel (Silicon Content: 3.2% to 4.5%)
  Features: As the silicon content increases, resistivity further increases and iron loss decreases; however, brittleness begins to develop, making machining slightly more difficult; and the saturation magnetic flux density decreases slightly (approximately 1.7 to 1.9 T).
  Applications: Balancing iron loss and machinability, it is widely used in small and medium-sized transformers, industrial motors, etc.
  Typical grades: Cold-rolled non-oriented silicon steel (such as DW350 and DW540); some hot-rolled silicon steels (which have been gradually replaced by cold-rolled steel).
  
  3. High-Silicon Steel (Silicon Content: 4.5%-6.5%)
  Features: High silicon content, extremely high resistivity, and extremely low eddy current losses; however, it exhibits high hardness, significant brittleness (difficult to stamp), a significant decrease in saturation magnetic flux density (approximately 1.5-1.7 T), and temperature sensitivity (lower Curie temperature).
  Applications: Primarily used in high-frequency (e.g., above 10 kHz) or thin-profile equipment, such as high-frequency transformers, reactors, and magnetic heads. Some thin-gauge high-silicon steels produced through specialized processes (such as chemical vapor deposition (CVD)) can be used in flexible electronic devices.

  
  
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  How is TR11 corrosion-resistant?

  TR11 steel is a high-speed tool steel with excellent hardness and strength. It can be quenched to achieve even higher hardness levels. It also possesses high toughness, allowing it to withstand significant impact during operation and reduce the risk of tool breakage.
  
  TR11 high-speed steel utilizes a special formulation and heat treatment process to achieve exceptional corrosion resistance. It can withstand harsh environments such as moisture, acidity, and alkalinity, and is resistant to rust and corrosion. This characteristic makes TR11 widely used in the manufacture of metal machinery parts and cutting tools.
  
  In corrosive media such as acid mist and acidic solutions, a dense oxide film forms on the surface of TR11, effectively isolating the metal from the corrosive medium and providing corrosion protection. TR11's compact crystal structure offers high corrosion resistance, making it less susceptible to erosion by external factors.
  
  TR11 steel's corrosion resistance has made it an indispensable material in the manufacturing industry. Its corrosion resistance reduces wear and tear on machinery parts and extends their service life. The surface flatness of TR11 material is high, and it is not easy to crack and corrode, which ensures the stability of product quality. TR11 material has high hardness and wear resistance, and is suitable for manufacturing high-speed cutting tools, which improves processing efficiency.