Alberta Boilers Safety Association (ABSA) Practice Test

What is the result of case hardening low carbon steel?

1. A high carbon inner core and low carbon outer surface

2. A low carbon inner core and high carbon outer surface

3. A low carbon inner core and low carbon outer surface

4. A high carbon inner core and high carbon outer surface

The correct answer is: A low carbon inner core and high carbon outer surface

When low carbon steel undergoes case hardening, a process commonly used to improve its wear resistance and hardness on the surface while maintaining toughness in the inner core, the correct outcome is indeed a high carbon outer surface and a low carbon inner core. The case hardening process involves introducing carbon into the surface layer of the steel, which is typically performed using methods such as carburizing. During this treatment, the outer layer absorbs carbon and transforms microstructurally, increasing its hardness and strength. This selective hardening allows the inner core, which initially has a low carbon content, to remain tough and ductile. This combination is particularly beneficial for components that need a hard surface to resist wear but must also be able to withstand impact or stress without fracturing. Thus, the process successfully achieves the desired properties of high hardness at the surface due to the increased carbon content, while the core retains its original low carbon properties that provide structural integrity.