THE LAB:
• Impact testing of two materials to find ductile to brittle transition temperatures.
THE SAMPLES
Charpy test specimens of low carbon steel (1018) and 304 stainless steel
THE EQUIPMENT
• Impact Tester.
• Safety Glasses.
• Tongs
• Temperature baths of temperatures listed below.
THE PROCEDURE
1. Wear safety glasses and instruct all observers to do the same and keep their distance.
2. Label all specimens on each side of the notch prior to placing into temperature baths.
3. Place two of each specimen in the following temperature baths for 15 minutes:
- Dry Ice (-108.4 °F)
- Ice water (32 °F)
- Boiling Water (212 °F)
4. Lift arm to the right of the fixture and lock it in place, place the safety latch (one person should be designated to check that safety latch is securely on every time).
5. Move dial indicator to the 264 ft-lb mark (one person should be designated this task).
6. While arm is in upper position, place specimen centrally in fixture ready for testing (grove should be facing away from arm), within 5 seconds of removing from the bath.
7. Release arm (while keeping your distance) allowing it to swing and fracture specimen.
8. Record dial indicator reading.
9. Collect fractured specimen.
THE REPORT:
Your company is making a new component. The component is expected to operate at sub zero temperatures. Your task is to determine which (if any) of these materials are suitable at least as a first screening. The material should have an impact energy more than 40 ft-lb at temperatures between 32 and -108.4 oF
Your report (no more than five pages) should include (but not limited to) the following:
• A table of your results (with impact energies in Joules)
• A plot of impact energy vs. temperature.
• The composition and relevant reported properties for the specimens provided, you can also find out which one is magnetic.
• Discuss your results, explaining the inherent reasons behind the difference between the impact energies of the specimens tested if any.
• Determine which material (s) satisfies the requirement of the acceptable impact toughness at subzero temperatures.
• Give your final recommendation based on your findings.