Rockwell Hardness Test

MaterialsScience2000
26 Jan 201302:29

Summary

TLDRThis video explains the Rockwell hardness test, specifically using scale C. The test measures the permanent depth of indentation made by a diamond cone indentor under a specific force. Initially, a minor force of 10 kiloponds is applied, followed by a major force of 140 kiloponds, for a total of 150 kiloponds. The depth of indentation is measured after removing the major force, and the Rockwell hardness (HRC) is calculated using this value. The process is demonstrated using a gear wheel, with modern machines automating the test. The gear wheel in this example has a hardness of 55 HRC.

Takeaways

  • 🛠️ The Rockwell hardness test measures the permanent depth of indentation caused by a hard indenter under a specific test force.
  • 💎 For the Rockwell hardness test scale C, a conical diamond indenter is used to measure hardness.
  • 🔧 The test consists of three steps: applying a minor force, increasing the force to a major level, and measuring the permanent depth of indentation after reducing the force.
  • 📏 In step one, a minor force of 10 kiloponds is applied, setting the reference depth for measurement.
  • ⚙️ In step two, the test force is increased by 140 kiloponds, resulting in a total force of 150 kiloponds on the indenter.
  • ⏳ The major force is held for a certain time before being removed, while the minor force remains applied.
  • 📐 The permanent increase in the depth of indentation is measured to calculate the Rockwell hardness.
  • 📊 The Rockwell hardness (HRC) is calculated as HRC = 0.2 - permanent depth of indentation (e) * 500.
  • 🖥️ Modern Rockwell hardness testing machines are often fully automated, making them widely used in automated production lines.
  • ⚙️ In the example given, the hardness of a gear wheel was measured at 55 HRC, as shown on the machine's display.

Q & A

  • What is the basic principle of the Rockwell hardness test?

    -The basic principle of the Rockwell hardness test is to measure the permanent depth of indentation of a hard indentor, such as a diamond cone, under a test force.

  • What type of indentor is used in the Rockwell hardness test scale C?

    -In the Rockwell hardness test scale C (HRC), a diamond cone with a rounded tip is used as the indentor.

  • What is the minor force applied in the first step of the Rockwell hardness test?

    -The minor force applied in the first step of the Rockwell hardness test is 10 kiloponds.

  • How is the reference point established in the Rockwell hardness test?

    -The reference point is established by pressing the diamond cone onto the surface of the test piece with a minor force of 10 kiloponds, measuring the initial depth of indentation.

  • What happens in the second step of the Rockwell hardness test?

    -In the second step, the test force is increased by 140 kiloponds, resulting in a total force of 150 kiloponds acting on the indentor, and this force is held for a certain time.

  • What happens after the major force is removed in the Rockwell hardness test?

    -After the major force is removed, the minor force remains in place, and the permanent increase in the depth of indentation is measured.

  • How is Rockwell hardness (HRC) calculated?

    -Rockwell hardness HRC is calculated using the formula: HRC = 0.2 - (permanent depth of indentation in millimeters) × 500.

  • What tool is used to measure the depth of indentation during the test?

    -A microscope is used to focus on the surface of the test piece and measure the depth of indentation.

  • Why is the Rockwell hardness test commonly used in automated production lines?

    -The Rockwell hardness test is often used in automated production lines because modern testing machines can perform the test fully automatically, ensuring efficiency and accuracy.

  • What was the Rockwell hardness result for the gear wheel tested in the video?

    -The Rockwell hardness of the gear wheel tested in the video was 55 HRC.

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Rockwell testmaterial hardnessgear testingdiamond coneHRC scaleindustrial testingindentation testautomated machinesmetal qualitymanufacturing process
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