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The specialised skate shoes used in the sport of speed skating have hardened and tempered steel blades attached to the skate shoe - Leaving Cert Engineering - Question a - 2020
Question a
The specialised skate shoes used in the sport of speed skating have hardened and tempered steel blades attached to the skate shoe. (i) Describe the processes of har... show full transcript
Worked Solution & Example Answer:The specialised skate shoes used in the sport of speed skating have hardened and tempered steel blades attached to the skate shoe - Leaving Cert Engineering - Question a - 2020
Step 1
Describe the processes of hardening and tempering the steel blade.
Answer
Hardening involves heating the steel piece to a temperature that is 25°C - 50°C above the upper critical temperature (UCT) for hypoeutectoid steels (those with less than 0.83% carbon) and 25°C - 50°C above the lower critical temperature (LCT) for hypereutectoid steels (those with more than 0.83% carbon). After reaching the desired temperature, the steel is then rapidly cooled, or quenched, in water. This process increases the hardness of the steel by transforming its microstructure.
Tempering follows the hardening process, where the steel is heated to temperatures between 230°C and 350°C, though temperatures as high as 550°C can also be used for certain types of tempering. This process reduces brittleness while maintaining a good balance between hardness and toughness.
Step 2
Outline two reasons for tempering the steel blade of the skate.
Answer
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Tempering reduces some of the hardness and brittleness that remain in the steel after hardening, making the blade less prone to fracture during use.
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It increases the toughness of the steel, ensuring that the blade is not only hard but also suitable for the impact and stresses it may encounter while skating.