Air hardening steel?

It is, I believe, that air hardening steels may harden with such because of their forgiving curve and that that does not preclude faster means of quenching. I would like being able to oil quench my air hardening steels but with foil wrap it just does not work out well. I am of the school, for our purposes, the faster to quench and the quicker the quench the better and therefore, if air the faster the air movement about the steel surface the better. I have now converted to plate quenching my air hardening steels and believe I am getting better blades than with forced air quench. At any rate, for our purposes I do not recommend STILL air quenching.

RL
 
can you go in to detail about the benifits of oil quenching air hardening steels? I thought the whole idea was to use air?
 
Brian according to Uddeholm explaination of HTing tool steels, oil quenching gives you a better hardness. Here's a quote, "If the steel is quenched sufficiently rapid in the hardening process, the carbon atoms do not have time to reposition themselves to allow the re-forming of ferrite from austenite, ie. as in annealing. Instead, they are fixed in positions where they really do not have enough room, and the result is high microstresses that can be defined as increased hardness." The same goes for plate quenching with forced air, so both ways work. The bottom line is to cool it quickly. The only problem with oil is the risk of quench cracking and distortion.
Scott
 
Yea I like to forge D2. It has a small heat window and you cannot heat to many times. I edge quench in oil and have great results. Guess I like the mess and the flaming oil but that' just me. I'll try the plate thing some day but for now this works.
If you can figure how to forge D2 it makes some of the other stuff seem easy....Not that it is...just seems that way.
Try this link for some aluminum: http://www.industrialmetalsales.com/Aluminum_Flat_Bar_6061_Large.html

Larry
 
Plate quenching works by conduction, which is much faster than convective cooling.

The forced air (only a convective process, no matter how cold or fast the air flow is) will not affect the quench rates enough to make any difference at all. The convective cooling is a surface effect, while the conductive cooling works by more or less uniform heat flow from the body of steel to the Al. The rate that matters is how fast the whole piece of steel gets into the Martensite field.

Brian, another thing about faster quenching is controlling the size of carbides that reform as the quench goes on. This can be important (in my opinion) in a steel like D2 where there is a large amount of Carbon. The carbides form by diffusive recrystallization, while the Martensite transition is a diffusionless shear process. The faster you can lock up the structure, the better. That is why I follow Uddeholm's advice and cryo immediately after the quench gets down to room temp.
 
what about a plate and oil quench together?
 
When you guys plate quench, how many blades are you able to do? What I mean is when I oil quench I have two quench tanks set up so I usually do two blades at a time. With the plate set up, how do you manage HTing more then one blade?
Scott
 
When really up against the clock I have done as Mete described above but I just feel better doing my blades one at a time in the furnace. Takes longer but I sleep better.

RL
 
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