Release time：2020-01-16 18:44 Browse：
Material Structure:
Grade 8.8 screws are typically made from medium carbon steel (e.g., 35# or 45# steel) and undergo quenching and tempering, resulting in a strong and tough core.
The surface is then treated with zinc plating (e.g., blue-white, yellow, or mechanical plating), which is mainly for corrosion resistance.
Effect of Zinc Plating:
The zinc coating itself is a soft metallic layer and does not increase surface hardness; it may slightly reduce the measured hardness due to its coverage.
Some additional surface treatments, like passivation or sealing, can further reduce the apparent surface hardness.
Testing Differences:
Surface hardness (e.g., Vickers HV or Rockwell superficial scale) can be affected by the coating.
Core hardness (e.g., Rockwell HRC) reflects the actual strength of the internal steel structure.
The surface hardness of 8.8 grade 72-hour zinc-plated extra-long screws is typically slightly lower than the core hardness, mainly due to the characteristics of the zinc coating process. However, this difference usually does not impact normal performance.
For improved surface wear resistance or hardness, alternative treatments like carburizing, phosphating, or Dacromet coating may be used instead of basic zinc plating.
