Rockwell Hardness Tester Demonstration

Introduction

• Demonstrated by Iris
• Used to test the hardness of metals in the lab

Rockwell Scale Variations

• B Variation:
  • Uses a ball-shaped indenter
  • Involves a 100 kilonewton preload
  • Suitable for softer materials
• C Variation:
  • Uses a cone-shaped diamond indenter
  • Involves a 150 kilonewton preload
  • Suitable for harder materials

Demonstration of B Scale

• Material: Brass
• Procedure:
  1. Place the brass on the platen
  2. Use the hand wheel to raise the platen until it touches the indenter
  3. Watch the dial closely for needle movement
  4. Continue turning the hand wheel until the small dial moves toward the red dot
  5. Align the zero on the outside scale with the vertical needle
  6. Push the handle away to apply load and observe the needle rotation
  7. Unload by bringing the lever towards oneself
  8. Take reading using the red B scale; example: 67
  9. Unload the specimen by turning the wheel counterclockwise

Metal Heating and Cooling

• Purpose: To demonstrate different cooling methods after heating metals
• Heating: Metals heated in a furnace
• Cooling Methods:
  • Quench Cooling:
    • Fastest cooling method
    • Stops diffusion
  • Air Cooling:
    • Medium speed
    • Diffusion continues while cooling
  • Furnace Cooling:
    • Slowest cooling
    • Maximum diffusion due to insulation

Work Hardening Metal

• Objective: To test hardness after work hardening
• Procedure:
  1. Check initial thickness of the metal sample
  2. Use a roller to work the metal
  3. Check thickness after each roll
  4. Continue until thickness is reduced by 5%
  5. Use the hardness tester to check hardness changes
• Rolling Tips:
  • Open rollers enough to grab the sample
  • Use the smooth side of the rollers
  • Alternate rolling directions to prevent curvature
  • Reduction by 5% achieved after three rolls
  • Hardness increases with each pass through the rollers