Tubbe Posted June 14, 2011 Share Posted June 14, 2011 Hi, I recently bought an old trip hammer. It's in pretty good condition but I'm currently reworking the dies. The bottom die went through the milling machine with no problem. However the upper die is super hard and I really need to anneal it before it goes near any machine. Well thats easy, but then what? I don't know what steel it's made of. How do I heat treat it? This is my plan... Heat, and let it soak for a good while in the forge to non magnetic, then quench in oil. Then I plan to temper it in the oven in stages, to check how hard it gets. First stage 200 deg c (~400 F) and then increase to 250 (~500 F) and so on... This type of die is attached to the hammer head with a round 1 1/2" (40mm) shank. Should I temper the shank even more with a torch maybe? Any ideas or thoughts? Quote Link to comment Share on other sites More sharing options...
macbruce Posted June 14, 2011 Share Posted June 14, 2011 Looks like the situation is well in hand to me.......B) Quote Link to comment Share on other sites More sharing options...
fciron Posted June 15, 2011 Share Posted June 15, 2011 Sounds to me like you should be giving advice rather than asking for it. Your procedure has both a high chance of success and a proper amount of caution. Quote Link to comment Share on other sites More sharing options...
ciladog Posted June 15, 2011 Share Posted June 15, 2011 Hi, I recently bought an old trip hammer. It's in pretty good condition but I'm currently reworking the dies. The bottom die went through the milling machine with no problem. However the upper die is super hard and I really need to anneal it before it goes near any machine. Well thats easy, but then what? I don't know what steel it's made of. How do I heat treat it? This is my plan... Heat, and let it soak for a good while in the forge to non magnetic, then quench in oil. Then I plan to temper it in the oven in stages, to check how hard it gets. First stage 200 deg c (~400 F) and then increase to 250 (~500 F) and so on... This type of die is attached to the hammer head with a round 1 1/2" (40mm) shank. Should I temper the shank even more with a torch maybe? Any ideas or thoughts? When doing multiple tempers it is my experience that the first temper is at the highest temp and decresses on subsequent tempers. Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 15, 2011 Author Share Posted June 15, 2011 When doing multiple tempers it is my experience that the first temper is at the highest temp and decresses on subsequent tempers. ok? There may be applications where you gain from the multiple tempers... but for me I don't want to go too soft from the beginning. When I somehow find the right hardness maybe another pass of tempering at a lower temperature may be in place. Another thing! I have never hardened a piece of this size. Is there a good rule of thumb on how much quench fluid one need for a specific size of object? I have a feeling the bucket I have will heat up real quick... Quote Link to comment Share on other sites More sharing options...
pkrankow Posted June 15, 2011 Share Posted June 15, 2011 One gallon per pound is a good estimate for tank quenching. (8.3 liter/kg) My question is : do you have any means to determine what material was used, then look up the specifications on that material? Phil Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 15, 2011 Author Share Posted June 15, 2011 One gallon per pound is a good estimate for tank quenching. (8.3 liter/kg) Woho, that's allot, but probably needed.My question is : do you have any means to determine what material was used, then look up the specifications on that material? Nope, that's the main problem... I can make a qualified guess among the types of steel used for dies and average somehow, I guess. Quote Link to comment Share on other sites More sharing options...
fciron Posted June 15, 2011 Share Posted June 15, 2011 When doing multiple tempers it is my experience that the first temper is at the highest temp and decresses on subsequent tempers. I don't think Tubbe is doing a multiple temper process. I believe he intends to take the piece out and test it every couple hundred degrees and then stop when it is as soft as he wants it. So it's really only a single temper. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 15, 2011 Share Posted June 15, 2011 Right, when you are experimenting to find the proper temper you do it exactly the way you suggested: start low and increment till happy with it. When you *know* the temperature to start with; decreasing temps are often used for multiple cycles. You may want to increment at a lower rate, say 25 degC rather than 50 and watch out for any decarb layer from the hardening process making a "false soft" when you test. Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 15, 2011 Author Share Posted June 15, 2011 You may want to increment at a lower rate, say 25 degC rather than 50 and watch out for any decarb layer Fair enough, will increase in smaller steps. How thick would a decarb layer be from a reasonable heat? Could it be a real problem? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 15, 2011 Share Posted June 15, 2011 Thickness is dependent on time, temperature and forge atmosphere (reducing vs oxidizing). Usually not a big problem but as you are working with stuff the size of hammer dies the 1 hour per 2.54 cm of thickness can make it a bit more of an issue. Generally just cleaning the die up well after hardening will take care of most of it. If you really worry allot a small amount to be abrasively removed after hardening Quote Link to comment Share on other sites More sharing options...
pkrankow Posted June 15, 2011 Share Posted June 15, 2011 Thickness is dependent on time, temperature and forge atmosphere (reducing vs oxidizing). Usually not a big problem but as you are working with stuff the size of hammer dies the 1 hour per 2.54 cm of thickness can make it a bit more of an issue. Generally just cleaning the die up well after hardening will take care of most of it. If you really worry allot a small amount to be abrasively removed after hardening A stainless steel foil bag can help with decarb. It will prevent scale and keep the system isolated. A little bit of cloth or paper can suck up your extra free oxygen. Phil Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 15, 2011 Author Share Posted June 15, 2011 the 1 hour per 2.54 cm of thickness can make it a bit more of an issue Sorry, I don't quite follow you , can you explain more... Are you talking about the annealing process here? I know there are several ways to do oxygen isolation when annealing for several hours, but surely when doing the hardening we are talking minutes of heat, right? After the annealing I will mill the working faces, so thats no problem I think. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted June 15, 2011 Share Posted June 15, 2011 Many hardening specifications call for a soak at temperature to insure that the carbon and carbides all dissolve prior to quench. 1 hour per inch of thickness is common, but you should look up the specifications and heat treat instructions for your best guesses and decide for yourself. Phil Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 15, 2011 Share Posted June 15, 2011 What he said! For knifemaking heating for hardening is just a few minutes---for low alloy steel, for the high alloys stuff where you need to dissolve a lot of weird carbides it can run longer... For big chunks an hour of heating per 2.54 in thickness is more the norm. Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 16, 2011 Author Share Posted June 16, 2011 Ok, yes you are right, I wasn't quite aware of all the procedures. Gone through some of the tool steel specs. and most of them advice for 20-30 min of soaking at hardening temperature when the tool is warmed through. And during heating it should be protected.... Several of the tool steels requires preheating in stages, also. I assume the specs are designed for optimum results. I hope one can get a way with a ok result even not following the specs to 100%. Starting to think this is impossible to do right in the coal forge. A gas forge may work better but have none. Is there any practical way of protecting the steel when heating in a coal forge?? On the other hand, it's no intricate engine part or anything I am hardening... maybe a light grinding is all it needs to remove any decarb layer right after the quench. Thanks for your input! Quote Link to comment Share on other sites More sharing options...
ciladog Posted June 16, 2011 Share Posted June 16, 2011 Tubbe, How do you plan on evaluating the hardness of the dies at each temper step? Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 16, 2011 Author Share Posted June 16, 2011 How do you plan on evaluating the hardness of the dies at each temper step? Well... not the most scientific method but I am going to use the old file trick, and try to compare the hardness against the lower die. The most important thing is probably not to get the die too hard. A bit too soft is better than too hard in my mind. Quote Link to comment Share on other sites More sharing options...
knots Posted June 16, 2011 Share Posted June 16, 2011 Hi, I recently bought an old trip hammer. It's in pretty good condition but I'm currently reworking the dies. The bottom die went through the milling machine with no problem. However the upper die is super hard and I really need to anneal it before it goes near any machine. Well thats easy, but then what? I don't know what steel it's made of. How do I heat treat it? This is my plan... Heat, and let it soak for a good while in the forge to non magnetic, then quench in oil. Then I plan to temper it in the oven in stages, to check how hard it gets. First stage 200 deg c (~400 F) and then increase to 250 (~500 F) and so on... This type of die is attached to the hammer head with a round 1 1/2" (40mm) shank. Should I temper the shank even more with a torch maybe? Any ideas or thoughts? One possible problem that I see is that the cylindrical mounting lobe appears to be ground to size. With heat soaking, scaling is likely to effect the size of that lobe. Maybe that is not a problem. It could be that the mounting tolerances are not critical. You might consider finishing the hard one by grinding, rather than milling, to avoid changing the fit. Quote Link to comment Share on other sites More sharing options...
ciladog Posted June 16, 2011 Share Posted June 16, 2011 I’ve gone back and looked at the pic of the dies. Have you checked to see if the hardness of the tenon is the same as the die? I would guess that it is much softer maybe not hardened at all. I would think that a hardened tenon would give rise to a stress riser. I would anneal and then only harden and temper the bottom few inches of the die. Perhaps that is why one die machined well and the other will not. Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 16, 2011 Author Share Posted June 16, 2011 With heat soaking, scaling is likely to effect the size of that lobe Yes I know, but I don't think it's critical. Even the rehardening process can change the dimensions somewhat to my understanding.Have you checked to see if the hardness of the tenon is the same as the die Yep, it's not at all that hard as the working end. Hmm... I think it's problematic to only harden the lower part. Can't really tell how I would do that actually, and I also think that could induce more stress than necessary on the tool. I will however temper back the tenon/shank at a later stage. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted June 16, 2011 Share Posted June 16, 2011 In a gas or electric oven I would recommend stainless steel foil wrap to prevent scale and decarb. Because solid fuel can be a problem with physical manipulation you can use a pipe, tube, or box to contain the part in the foil, then heat the box. The box will get hot and radiate to the part. This is not a new technique, and is described in older texts. In the older texts it is often limited to descriptions of hardening and tempering smaller items like springs. There is also lead or salt baths, but these have a level of added safety requirements. OTOH this may be an excellent excuse to buy or build a heat treating oven. http://www.bladeforums.com/forums/showthread.php/573671-Heat-Treat-Oven-Build http://sbgswordforum.proboards.com/index.cgi?board=forgetools&action=display&thread=5863 Have you called up any local heat treat companies? If you are lucky you may find someone who is willing to barter for this work. Phil Quote Link to comment Share on other sites More sharing options...
Tubbe Posted June 19, 2011 Author Share Posted June 19, 2011 It's done! Annealed, milled, grinded and filed. Then slowly heated in the forge to non magnetic. I tried to let it soak at non magnetic temperature for about 15 min, while constantly rotating and shuffling coke above it. Quenched in oil, then put in the kitchen oven at 200c for 2 hours. Evaluated the hardness - really hard. Continued in the oven and increased to 280c (purple-blue) a last run for 2 hours. Now it feels quite like the other die, but it's tricky to tell really. Hmm, do you think the tempering is enough? Hand hammers can be tempered to some ware near blue, right? I haven't done any special tempering for the tenon, unsure if it's really needed. I protected the tenon with steel wool during annealing and hardening, and I think it helped against scaling somewhat. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted June 19, 2011 Share Posted June 19, 2011 Looks good. You can temper to the same temperature again if you feel unsure about the tempering. Phil Quote Link to comment Share on other sites More sharing options...
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