When people talk about a "nose", that is refering to a curved line on a diagram that looks somewhat like a "nose" sticking out. The diagram in mention here, shows that the temperature of the steel when it is fully austenized, for 1095, is 1475 degrees. Most steels go non-magnetic WELL below that temp, so your magnet is only an indicator that you are approaching the necessary temp. Go another color change ABOVE non-magnetic to be sure you have achieved austenite.
To turn that austenite into martensite, 1095 needs to get from 1475 to below about 1000 degrees in about 1 second. It's not how long you have to get it into the quench, but how long your quenching media has to get the steel below the temperature that will turn the steel into another form, called Banite,which is a condition of steel that is somewhat harder than the normalized condition of steel - Pearlite - but softer than the fully hardened condition of steel that knife makers are looking for - Martensite! In 1095, and some other steels, you only have one second to drop the temp below 1000 degrees.
That's why there is so much attention on using the proper quenching method. Some steels need to get over this "nose" in only 1 second, whereas other steels have as much times as 4-6 seconds before they turn into other formations that Martensite. So, different oils extract heat at different RATES to match the alloy content of the particular steel! For instance, if you used the oil for the "fast" steels on say 5160, or O1, it would cool them TOO FAST and they would probably crack. So, those steels use a "medium" speed oil - an oil that extracts heat at a slower rate.
Conversely, if you use a medium speed oil on a "fast" steel, requiring only one second to get to 1000 degrees from around 1500, the blade won't harden becasue the oil is too slow! that oil is designed to extract heat slowly instead of fast. Now that steel converted to something other than your desired formation of Martensite.
That is why some steels are always recommended as a "beginner" steel, like 5160, O1 and 1084. Their "nose" isn't all that fast! You can quench them in almost anything from used motor oil, or mineral oil, etc. and the ability of these is sufficient to achieve martensite because those steels have 4-6 secionds to get below around 1000 degrees!
When you get into other stuff like W1 and W2 and 1095 and the like, you are either quenching in FAST oils, which you must buy at high $$$$, or are quenching in water and/or brine, which can have a high failure rate (cracking!) without MUCH experience.
Wow! That's hard to type first thing in the morning.
Topic: 1095 (Read 1130 times)
