Lower quenching temperatures create microstructures that demonstrate a greater elasticity, with smaller and less brittle connections forming between microstructures. 12) Martensite is a high-carbon steel formed from the rapid cooling of austenite in a process that does not allow carbon to diffuse out of the heated metal. Tempered Martensite has reduced hardness but increased toughness, and the metal is partially decomposed into ferrite and cementite by the tempering process.

13) Yes; there are some limited applications where the brittleness of quench-hardened steel will not pose a significant barrier to use. In most applications, however, tempering is required after quench hardening in order to reduce brittleness and increase the toughness of the steel.

14) Furnace: All heat shields must be in place, and the area in and around the furnace must be kept clear of all dust, debris, and other equipment. Ventilation paths must be substantial and remain free from blockages, and indicators in the area should clearly show when the furnace is on. Izod Impact Testing Machine: Ensure safety is on the pendulum arm whenever first...

Ensure safety is on before proceeding with any other work (until experimentation). Wear safety glasses and avoid placing any clothing or body parts in the potential pinch area at all times. All participants/observers must remain at a safe distance from the machine until the pendulum has been brought to a full stop by application of the break.
15) Tempered brittleness is brittleness observed in many carbon alloy steels following the tempering process. Essentially, the crystal structures that form in the tempering process have fracture planes that become more susceptible to certain stresses, and other means of treating the tempered steel is necessary to overcome this brittleness while retaining the positive effects of the tempering.

16) Straw: 200-241

Brown/Purple: 250-280

Blue/Grey: 300-530

Slight Red/Red: 590-760

Orange Red/Orange Yellow: 871-982

Yellow: 1038+

Reference

Askeland, T. & Phule, P. (2006). The science and engineering of materials. Ontario:

Cengage.