Charpy Impact Test: Example

The example shown is from the set of experiments I used to illustrate the equivalence of hardness and yield strength; this link leads to the actual paper
Here is the set of data:
Charpy impact energy and yield strength
Example of Charpy impact energy measurements.
The specimen was a "high-strength low-alloy" steels; the yield strength curve (YS) obtained by tensile testing is also shown for comparison.
We have three series of tests with 8 specimens per series to get statistically significant data. After "tempering", meaning holding the samples at the temperatures indicated for 1 hour and then let them cool to room temperature, Charpy impact tests were done at the three temperatures indicated.
What we see is:
  • The steel is always more brittle at lower testing temperatures.
  • Tempering around 500 oC (932 oF) produces very brittle steel. At -85 oC (- 121 oF) the steel is brittle like glass
  • Tempering at other temperatures is better with respect to brittleness. High-temperature tempering produces steel quite ductile at room temperature (25 oC) and below.
  • Unfortunately - but expected - the yield strength or hardness shows opposite behavior. It is highest for brittle steel.
  • The best compromise between brittleness and hardness is found for tempering at 600 oC (1112 oF). I'm sure you see why.
There are many more examples for Charpy impact energy measurements in a science module in chapter 9

With frame With frame as PDF

go to 3.2.2 The Charpy Impact Test

go to Overview of Major Steels

go to Ductile to Brittle Transition or Cold Shortness

go to Overview of Major Steels

go to Yield Strength and Hardness

© H. Föll (Iron, Steel and Swords script)