Case Hardening 101 - Heat Treatment Oversimplified

Artisan Makes・2 minutes read

Case hardening involves heat treating metal to create a hard exterior and a soft interior, commonly used for parts like gears. Carburizing is a method for case hardening that involves exposing low carbon steel to high temperatures in a carbon-rich environment to create a high carbon case for heat treatment.

Insights

  • Case hardening involves treating metal to create a hard outer layer while keeping the interior soft, ideal for parts like gears needing surface wear resistance and core toughness, often using low carbon steel.
  • Carburizing is a prevalent method for case hardening, exposing steel to a carbon-rich environment at high temperatures, with pack hardening being a cost-effective option for home workshops, emphasizing the importance of testing and tempering for optimal results.

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Recent questions

  • What is case hardening?

    Case hardening involves heat treating a softer metal to create a hard exterior while maintaining a soft interior, combining the best qualities of both types of metal.

  • How is case hardening done at home?

    The most efficient method for case hardening at home is pack hardening, involving sealing the part in a box with crushed charcoal and heating it in a forge for several hours.

  • Why is testing crucial before case hardening?

    Testing is crucial before case hardening to determine the best approach, with variables like time, temperature, and carbon content affecting the outcome.

  • What is carburizing in case hardening?

    Carburizing involves exposing low carbon steel to a carbon-rich environment at high temperatures to create a high carbon case for heat treatment.

  • Why is tempering recommended after case hardening?

    Tempering after case hardening is recommended to reduce the risk of cracking, with a low temperature temper sufficient for case hardened parts.

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Summary

00:00

"Case Hardening: Enhancing Metal Strength and Durability"

  • Case hardening involves heat treating a softer metal to create a hard exterior while maintaining a soft interior, combining the best qualities of both types of metal.
  • Case hardening is commonly used for parts like gears to provide wear resistance on the surface while maintaining toughness in the core.
  • It is also a cost-effective alternative to using high carbon steel, with many cheap hand files being case hardened low carbon steel.
  • Various methods exist for case hardening, with carburizing being a common method accessible for home workshops.
  • Carburizing involves exposing low carbon steel to a carbon-rich environment at high temperatures to create a high carbon case for heat treatment.
  • Material availability influences the choice of case hardening over purchasing tool steel, especially in regions where tool steel is not readily available.
  • The most efficient method for case hardening at home is pack hardening, involving sealing the part in a box with crushed charcoal and heating it in a forge for several hours.
  • Testing is crucial before case hardening to determine the best approach, with variables like time, temperature, and carbon content affecting the outcome.
  • The depth of the high carbon case depends on time and temperature, with a general rule suggesting a depth of 0.1 millimeters per hour.
  • Tempering after case hardening is recommended to reduce the risk of cracking, with a low temperature temper sufficient for case hardened parts.

15:59

Enhanced case hardening with sodium carbonate

  • Added 5% sodium carbonate by weight to charcoal, resulting in a deeper case hardening effect after an hour of testing compared to normal charcoal, enhancing the formation of hard martensite in steel, improving results and saving time in the case hardening process.
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