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Jerrod Miller

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Everything posted by Jerrod Miller

  1. Your best bet is probably just going to be normalizing. Heat it up past the austenite conversion (watch for decaslescence), then let it cool to black in still air. While you are at it you might as well do it 3 times. Should only take a few minutes per cycle (heating and cooling). Oh, and the forge would be best for that, but may be good to go with the propane torch. You don't need to do the whole thing all at once.
  2. Basically what they said, except that the Ms is when martensite starts forming upon cooling, which is usually around 400 F. Not going to do much good to quench from there. What Joshua meant was the austenitizing temp. But you knew that already. I'd also add that one may want to do a normalization cycle after mechanical stock removal (grinding or machining) if heavy work is done. Meaning really big /aggressive cuts, not just lots of material removed. If you use a file and remove half your starting stock, that is pretty gently and shouldn't need another cycle. But if you were to mill your bevels in one pass, that aggressive machining may have caused stresses in the metal. I would think this need is not very common, but if anyone is experiencing problems this may explain it a little.
  3. You could do that with the forge you have, just build up the walls with brick on that. Also, if you think propane is scary, liquid aluminum probably isn't for you. That stuff sticks to you.
  4. Those actually are lead, so there's that. <insert general lead warnings here> That said, I use that to cast bullets. That is mainly because it is fun, not because it is cost effective.
  5. Can we renumber these so Alan's points come before mine? Also, foundry101.com is a good source of info, if a bad (awkward) website.
  6. First, smelting is converting ore to metal. You're just looking at remelting. Second, I would recommend you try it with your forge fist, since you have it already. From there you can see what you like and don't like about it. Third, make sure you follow the instructions for your crucible pre-heating so you don't crack it.
  7. I did speak to our machinist today. He said 17-4PH isn't too bad if you you get the right feed and speed. Keep the chip load fairly light or you get work hardening effects.
  8. Normalize a couple times, then go for the sub-critical anneal. Heat to 1300 F or so. Do not go through the phase change. It is a very aggressive temper, which leaves a normalized piece pretty soft.
  9. I really shouldn't have used the term "hardened". Solution treated is the right wording. It was still a little early for me after a long weekend. I'll talk to our machinist tomorrow to get his thoughts on machining it, but we have no problems machining it that I am aware of. You're looking at having ferrite stringers in a martensite matrix. Better than having austenite, which gums things up!
  10. That is only if it is already hardened. Hardening 17-4PH is a solution treatment at 1025-1050 C (1875-1920 F) then oil quenched. After that you age at about 480 C (900 F) to get a hardness in the low 40s HRC.
  11. I just want to really clarify that as long as you aren't cracking the metal, and you are going to HT later, the HAZ isn't something to worry about. Unless you are doing stock removal, then you may run into hard spots that a normalization cycle will fix.
  12. If you are doing things by eye (rather than thermocouple), I'd highly recommend spending whatever time it takes to get good at seeing decalescence and recalescence. A similar chart to that is on the cover of my copy of the ASM Heat Treater's Guide, and I really wish those charts would go away. Your magnets are better off melted than being used for HT control. Control your ambient light in order to HT by eye. 1500 degree steel looks very different at high noon (on a sunny day), dusk, and pitch black night.
  13. The heat affected zone is just an area around the place that got welded or thermally cut, but was not actually welded or cut. I wouldn't really worry about it since you are going to HT after the cut. Some alloys may crack during a thermal cutting operation due to the rapid temperature change. For leaf springs I would image you would be very safe if you normalize, cut, normalize. And probably won't have problems if you do no normalizing (other than your usual amount after forging for grain refinement).
  14. Sadly, my Rockwell tester is down (both at work and at home). A local college that has an engineering or machining center may be able to run a test for you.
  15. Just to add a little info... It is most certainly stainless, as evidenced by the condition it is in, but also because it only takes about 13% (some say 12%) free chrome to make something "stainless". That is why the carbon is kept so low, to prevent chrome carbides from forming and taking up the chrome. And this is the website that I always reference for hardness conversion, though technically ASTM E140 would be a bit more "respectable".
  16. That is how all the cannons we do make will probably leave. The down side is that they just don't really fit in with what we do, so there is no way we'd be able to do them profitably enough to sell.
  17. Glad you are liking it! I'm going to try to get a couple more batches made, but there are some pretty big changes going on at the foundry and it is hard to get stuff made for side projects. I may have to work on creating a new patter for 1-off molds that I can make myself off in a corner. They are currently made 4 at a time (assuming that pattern still exists). We are changing our entire molding media to comply with OSHA requirements, and changing (adding) our ERP system. Things will be pretty nuts around here for a few months. I'd like to get these as a stock item we can sell. I also have a couple designs for shooting steel targets (gongs) that will take advantage of the casting process to add features not available in cut plate targets. I also have a golf-ball cannon on the to-do list, but I'm pretty sure we won't be selling those.
  18. For our purposes, retained austenite is always a bad thing, so it is always worth thinking about. The pedantic metallurgists will say there is never a practical way to achieve 100% martensite, but I think we can say anything over 99% conversion is fully martensitic. 1080 has a Ms at around 425 F, and M90 at around 275 F. I think it is pretty safe to say we are pretty much completely transformed by room temp. It is pretty much the same for 5160. As far as the steel is concerned, time at temperature in excess of a couple seconds doesn't do anything except allow for diffusion related processes: atomic movement (what we generally mean by diffusion), grain growth, and carbide dissolving are the big ones. Iron carbides dissolve remarkably quickly, others not so much (and all temperature dependent). The biggest benefit to holding for longer time (for simple steels) is the improved evenness of heat in the steel. But this is getting a bit off topic for this thread.
  19. Only thing I'd change is that the Cr is not much of a toughener, so much as making it more responsive to HT (changes austenitizing temp, martensite start temp, and pushes out the nose of the TTT curve). As far as beginner steels go, I would say 1080/1084, 80CrV2, and 5160 are the three best. A beginner isn't likely to be able to tell the difference in final product. It is a very small difference anyway.
  20. I have cropped and zoomed in on a section of Photo#2. I have put red circles around some (but certainly not all) of the carbides. The blue arrows are pointing to stuff that is the same color as the carbides, but is in fact not carbide. You can see that all of the carbides have a defined black edge to them; this is from the etching process. I tried to run it through the software (ImageJ) to have it automatically identify them, but the image quality is not good enough.
  21. I'm using picture titles, not order of pictures, just to be clear. Photo#3 is completely worthless. Not enough in focus and what is in focus isn't magnified nearly enough. Photo#2 isn't properly etched, but we can see where the carbides are, so at least there is that. Photo#4 has a better etch but it has a bit too much out of focus to be a ton of help. All three pictures aren't magnified as much as would be good to do a carbide fraction analysis. And really, we should be looking at the edge and the spine of a a single blade, to see if there are more carbides per area due to the processing.
  22. I'm not Alan, but yes, you can indeed auto-temper, but your martensite generally isn't starting to form much above your final temper temperature, and you aren't staying that hot too long anyway. But it is possible you won't see peak hardnesses. And generally Ms= martensite start, Mf = Martensite finish, and M90 is 90% completion. So what we are really shooting for is straightening between the nose of the curve and Ms.
  23. I think part of the problem here is a bit of a misunderstanding. First of all, I think we all need to agree on what we mean/think when the term "edge packing" is used. My understanding is that this has historically been used to describe "packing the atoms at the edge closer together", thus improving the quality of the edge. This is complete nonsense, and as such "edge packing" is not really a thing. As I understand what Sean is saying, his "edge packing" is not that at all. Sean is in fact mechanically refining the microstructure. The degree to which this is being done and the actual benefits of it are another matter, but I only want to make sure we're all talking apples to apples here. It is important to note that mechanical grain refinement is a thing, and its effects carry on to affect grain refinement through heat treat. Generally speaking, it is preferred by makers (here at least) to have consistent properties, so a triple normalization is used to ensure uniformity. He is also work hardening, but that is completely irrelevant as the hardening cycle is over-riding that work hardening. As I understand his description of what he is doing (and Sean, please do correct me if I am not properly describing what you are doing/saying; I'm not trying to put words in your mouth at all), he is working the steel along the edge while the metal is a mixture of ferrite and carbides. The ferrite is being squished out of the way between the carbides, thus there is a higher density of carbides along the edge. He then proceeds directly to a hardening heat treat cycle, presumably with tempering to follow. To really see what is going on with the microstructure, it would be best to be at least 2000x magnification (I like to use a 100x objective with 20x eye-piece/camera lens, etched with nital).
  24. Take these materials and try to make something specific (go in with a plan). Make tongs, or hooks, or anything specific, preferably something you can use. That way it doesn't feel like a waste while you practice. General blacksmithing techniques apply well to blade making. As long as you are having a good time, it is all good.
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