- Joined
- Sep 9, 2003
- Messages
- 2,361
Dan, actual normalizing that meets the classic industrial definition, need only be done once. This is due to the nature of the heating and what it is designed to do. A proper normalizing heat is done at a much higher heat than almost any other heat treatment (1600F-1800F), in order to put everything into solution so that on cooling you will have even conditions throughout. This will only refine grain in the sense that it will make recrystallize things to an even size throughout and my even mean a larger size, but at this point even size is more important than what that size is. Unequal grain size can become problematic in subsequent heat treatments.
Stock removal does not mess with things all that much and that steel is pretty much the same as it was from the mill, but forging has all those countless things to go wrong associated with it. Uneven grain sizes due to dynamic recrystallization, and drastically different cooling rates (ever notice how dark the spot between the hammer and the anvil is compared the rest of the blade), cycling in at who knows what temperature in order to accomplish the shaping. With all of this not only grain size be all over the map, but segregation could be as well. The banding that too many smiths are in awe of as a super thing is actually viewed as a terrible thing that every other tool making industry goes to great lengths to avoid, and for good reason. There is an easy fix for all of these things- one good normalizing heat.
But yes there are downsides to every heat, if you dont have good control you could overshoot even the normalizing range and at worse possibly burn the steel or make things too coarse to fix in one heat. But within the normalizing range you still have to deal with oxidation, decarburization and the like. So the least heats to accomplish your goal is most often the best. If you did everything right on the first full normalizing heat there should be no reason for a second or a third. Now move onto the next heats in the cycle.
That first high heat sets things up for the follow ups where you will grains and carbides, equalize any stress factors and eventually leave the steel ready for your bench finishing work. The next should be to just critical and then an air cool. It is here where you could throw in other heats to just critical and quench if you are concerned about grain size. The last heat is for final refinement and even for annealing purposes if you would like to avoid the overnight vermiculite thing, and if you threw a quench or two in before this the annealing and carbide refinement will be quite efficient.
Please dont misread anything I say about grain size, it is important for overall matrix strength. Many smiths confuse grains and carbides, the key to taking an ultra-fine edge and holding it is much more reliant on carbide size than n grain size. If you have really fine grain size but huge blocky carbides edge forming, and even retention, will still be miserable, but the blade could bend just fine.
, with all the mechanisms built into modern steel to control grain size, you really have to consistently overheat to grow grain. And even if you do it can be quickly fixed with proper normalizing. All the paranoia in bladesmithing over grain size really kind of tells one how out of control most of our temperatures really are. And the whole low temp forging phenomenon says quite a bit about this as well. When teaching a class, it only takes a couple of students to overheat steel the first day for me to spend a week constantly telling the class to get it hotter before hammering!
I will be trying to get the Houghton Quench K for my 1095, but for now I gotta make due with what I have. There is also something I kinda like about using a natural oil though too and perhaps more primitive "tribal" ways. I may also give brine a try... Thank you for the most informative posts.
. The O.P. didn't ask one of those all too general "how do I make a knife" type of questions, and although I have typed these answers more times than many people have lit a forge, the fact that he came here with specific questions, about specific materials I felt deserved my efforts to type it again. I was only giving him credit for the courtesy of providing the specific data to easily answer his question.
Sorry if it sounded like I was taking it out on you. I have an incredible amount of respect for you. I hear so much of this "canola's not a real quenchant, you need a real quenchant to make real knives." It is so discouraging to me as a beginner to hear that if I don't have everything just perfect or just so that my knives will be poor quality or inferior. There are so many variables, so many things to consider. As a beginner I am told that I should only buy the best belt grinder or the best anvil, or this specific quench oil. No matter which steel I choose, seems there is no way I can make a truly good knife unless I have a specially temperature controlled furnace to go with all the other stuff as well. It seems it never ends... I guess I'm just getting discouraged.
jeez are we going to meet behind the school at 3:30 or are people just going to grow up! The proof is in the performance? No it is not! If one guys blade out-cuts on rope or 2X4s the other will ask for cinder blocks in favor of his edge geometry, and when one doesnt come out on top in cutting, the other guys knife will be junk because it cant easily bend in a vice. We cant even agree on what a knife is supposed to do, how the heck can we be in lock step on how they should be made?