Elmarginalo Posted June 13, 2014 Share Posted June 13, 2014 I got my hands on some O1 tool steel, and I was planning to try forging a knife out of it. Now I've been browsing the forum for a while, and have read the stickies etc about heat treatment. I'm still wondering about a few things: - Forging takes place in bright red to yellow heat, which is above the critical point (non magnetic) as I understand (since critical point is a deep red). Does this mean grain size grows while forging? How bad is this? - Can grain size be reduced by annealing or normalizing? As I understand it, you heat up the steel to critical temp and then let it cool slowly in forge/sand/ashes/... or in the air. I've read in some sources this is hard to do for O1 steel. I've read some sources that say it can air harden while normalizing, or that the grains can still grow while annealing. Anyone with any hands on experience with O1 got any tips for this? I've read a lot of different explanations for this, so this has me quite confused... - Is thermal cycling basicly normalizing multiple times? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted June 13, 2014 Share Posted June 13, 2014 grain will grow when heated, hammering will fracture most of them into smaller grains. The real effective work to reduce the grain size is the thermal cycling from above to below criticle a few times forcing the reformation of the grains, without allowing them to grow much. O1 likes to air harden. I advise never setting it to rest on the anvil wile working, or on any other large heat sink. I lost a few blades that way before I was smart enough to figure that out. I make 1/8 diameter holes at end of tang for hanging to drip dry after hardening. That same tiny hole works well to hang for anealingg or just cooling off also. Quote Link to comment Share on other sites More sharing options...
Dan C Posted June 13, 2014 Share Posted June 13, 2014 Hi Steve, I'm confused "hammering will fracture most of them into smaller grains". Isn't that the same as edge packing which is considered obsolete? Granted your next sentence says what is really effective in reducing grain size is the normalizing multiple times. Quote Link to comment Share on other sites More sharing options...
bigfootnampa Posted June 13, 2014 Share Posted June 13, 2014 Dan; NO it is NOT the same as edge packing! When a piece is heated and then forged the forging process is continuously interrupting the grain formation... effectively preventing dangerous grain growth! When a piece is repeatedly heated and forged very little, or not at all... the potential for grain growth is VERY HIGH!!! If you practice forging vigorously with each heat, you will rarely have much grain growth to worry about. Lots of beginners forge so tentatively or ineffectively that grain growth gets out of control and their metal becomes severely weakened. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted June 13, 2014 Share Posted June 13, 2014 Hi Steve, I'm confused "hammering will fracture most of them into smaller grains". Isn't that the same as edge packing which is considered obsolete? Granted your next sentence says what is really effective in reducing grain size is the normalizing multiple times.The so called "edge packing" is really only planishing, the iron martix does not compress or pack. The action has good results in making sure the grains are small, and the surface is smoother, but in no way does it do what we used to think it was doing for our blades.We do not need to be fully normalizing, I said cycling. It does not need to cool much, we just need to cycle from above AC3 to below the transformation temperature, a black heat is usually plenty cool, then reheat it again. Quote Link to comment Share on other sites More sharing options...
Dan C Posted June 13, 2014 Share Posted June 13, 2014 Thank you both for clarifying, I wasn't aware that forging itself interrupted the grain growth. I typically normalize 1-2 times as Steve suggested above. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted June 14, 2014 Share Posted June 14, 2014 Describing colors can be very confusing when forging or heat treating steel for knife making.If you are in the sunshine and see a yellow color...or red or etc..that will be a very different steel heat than if you were in a dark shade area or in the evening or night...Try thagt for your self.....If yu use non magnetic as a simple shopt test you can at least get a baseline for that tmeperatures color in the light you are forging in. I put a long magnet across the face of my anvil with a third or more hanging off the side nearest the forge...I get some color on the steel, pull and see if it sticks to magnet....if not...back in the forge and retest as often as I need to see what color it is when the magnet first does not attrack the steel...In that light youi now have a color to go by...when yuo get a brighter color than that you can start being wary of grain growth...it alos give yu a starting point for a color for first normalizubg round. There is even more in the stickies and knife making lessons for you to review if you wish. Quote Link to comment Share on other sites More sharing options...
Elmarginalo Posted June 15, 2014 Author Share Posted June 15, 2014 Thanks for the tips & input, I'll give it a try tomorrow evening :-) Quote Link to comment Share on other sites More sharing options...
Rick Marchand Posted June 18, 2014 Share Posted June 18, 2014 Don't worry about grain size when you are forging... just make sure it stays HOT when you're moving metal. As long as you don't create fractures, normalizing will fix all the "wrong" you've done during the forging process. YOU NEED TO NORMALIZE AFTER FORGING. Start your normalizing at 1650F to make sure everything gets into solution. Then use lower heats during subsequent cycle to refine grain and not undo what we are trying to accomplish. In between cycles the steel only needs to form another structure from which to renucleate... when it becomes magnetic again, you're there! Then you can ramp back up for the next cycle. Here is a good starting regime that will work for most carbon steels... - Heat to 1650F, cool to magnetic. - Heat to 1525F, cool to magnetic. - Heat to 1475F, Quench in warm oil. Medium speed(for O1) if you have it... canola if you don't. - Heat to 1300F (make sure you don't go non-magnetic) and cool to black. Repeat 2-3 times and quench in oil on the last. Yes, you end your last normalization cycle with a hardening quench. You don't have to, but I recommend it. If you choose not to, at least quench from black to avoid coarse pearlite and other unwanted structures. That last 1300F bit is a sub-critical anneal(or at least a redneck version of it.) Proper spheroidizing would be best but for those without the equipment, this does the trick. Now, you have dead-soft annealed steel all set up for a great final quench. For O1, without a controlled kiln, I would forgo any attempt to soak and just heat it to 1500F and quench. Rick Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted June 18, 2014 Share Posted June 18, 2014 Rick I suspect from his post that he does not have the equipment to tell him what the temps of his steel are..Which is why I suggested a magnet for a simple way of determining a starting point...For the other folks that read this that can measure steel temps in those ranges your information will be handy. Quote Link to comment Share on other sites More sharing options...
mitch4ging Posted June 18, 2014 Share Posted June 18, 2014 Rick, Rich, et al, Great information for whatever your setup. Thanks for posting. Quote Link to comment Share on other sites More sharing options...
Elmarginalo Posted June 23, 2014 Author Share Posted June 23, 2014 Once again thanks for all the input guys! Like Rich says: I don't have any equipment to read temperatures etc, so I use a magnet. I tried normalizing this weekend trying to relieve stresses. I know now what color the critical point is at by testing it with my magnet. I'm using a coal forge, these were the main problems I encountered: - First problem I had was overheating, parts were getting too hot, so basicly what I did was let the coals die out a little then heat the blade slowly. Took me a lot of time to heat it nice and even and don't let it overheat. Any tips for this? or is this the way you all do it? - The main problem I encountered was getting an even heat:Is there anyone here who is doing his heat treating in a coal forge? I can't seem to get an even heat all over the blade: either the blade itself is heating or the handle, but I can't seem to get them both hot at the same time... any tricks for this? I tried making my fire bigger, and then it got better but I can't seem to get it big enough to heat the blade and the handle. I was wondering if I only quench the blade if it's ok to normalize the blade only, but I guess I can answer this one myself: there's a stress difference between the blade and the handle that will cause problems, am I correct? Quote Link to comment Share on other sites More sharing options...
Elmarginalo Posted June 25, 2014 Author Share Posted June 25, 2014 After some googling I came out on this vid: I love the idea, going to give it a try as soon as I get my hands on an iron pipe. Quote Link to comment Share on other sites More sharing options...
gearhartironwerks Posted June 26, 2014 Share Posted June 26, 2014 To me, and I defer to Rich and Steve who have done more O1 than me, but from my experience, overheating can be a major culprit. O1 holds a great edge, but close attention should be applied to forging/ht. It also rusts easily. I made one for a fisherman who loves and dislikes it, but he still wants me to sharpen it on occasion. Says it's the best and ugliest blade he's ever had. What can I say...something has to give. Kind of like life. John Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted June 26, 2014 Share Posted June 26, 2014 I would like to add a generat statement of most higher alloys need to be kept close to recomended forging temps. Forging either too hot or too cold ruins them fast. Quote Link to comment Share on other sites More sharing options...
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