Which one is the fast and result in brittle form;water,air or oil quenching?

Question

it is an academic question and Ä° could not find the answer in a clear form in url.

Answer 1

Water quenching typically cools down metal faster than oil quenching, which is conducted at higher temperature. Hence the metal will be harder and more brittle.  

Answer 2

ofcourse water quenching. Heat carring capasity of water is sauperior, so cold water quenching is fast, compare to air and oil  

Answer 3

In order of speed, water is the fastest, followed by oil and then air.  Steels are made to be quenched in a particular medium (quenchant).  Most spring steels, for example, can only be quenched in oil, water would be far to severe and be likely to cause quench cracks and air would fail to harden them at all.  Also, many steel grades can not be allowed to cool to ambient temperature before entering the tempering furnace, they must be transfered from quench to temper at around 100 - 150C to avoid cracks from forming.

Answer 4

Water quenching is fast but, usually results in a hard and brittle steel.