dickb Posted July 12, 2009 Share Posted July 12, 2009 I am relatively new to forging and/or heat treating. I am getting cracks in the finished forging. I am using pieces of automotive coil springs about 5/8 diameter, and working on a coal forge and am working the piece at cherry red. I allow the piece to cool down till it's just barely showing any color and then quench in water, a little at a time. What I mean is that I plunge about two inches into the water and then in and out of the water a little less and/or a little more than the two inches until it's black. Then I polish of the tip with a carbarundum stone and watch the tempering colors as they progress down the piece toward the cold end. When the cooler end reaches straw color I plunge the whole piece into the water . What should I do to avoid these cracks. I understand that oil is a preferred quenchant but I am working as a guest at another person's forge and he doesn't want to use oil. Thanks Dick B Thanks Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted July 12, 2009 Share Posted July 12, 2009 Avoid water Quote Link to comment Share on other sites More sharing options...
arftist Posted July 12, 2009 Share Posted July 12, 2009 If you can't use oil, at least heat the water. You can heat it by contiualy heating and cooling a good size piece of iron. Also be sure to not let your metal get to cold when you are working it. Quote Link to comment Share on other sites More sharing options...
Dave Hammer Posted July 12, 2009 Share Posted July 12, 2009 Why are you quenching it? That is probably what is leading to the visible cracks. Just forge it, lay it aside and let it cool naturally. Quote Link to comment Share on other sites More sharing options...
matt87 Posted July 12, 2009 Share Posted July 12, 2009 Dick, could you please explain to us your entire heat-treating routine? It may be that you're not being explicit but it seems like you're missing several key steps. Exactly what effect are you trying to achieve? What item/object are you trying to make? More detail will help us generate a more pertinent response. Remember that used springs could will have existing but invisibly small cracks in the steel and the shock of quenching may make them expand. Quote Link to comment Share on other sites More sharing options...
divermike Posted July 13, 2009 Share Posted July 13, 2009 another thought, when you burn the metal, it tends to crack as well. Quote Link to comment Share on other sites More sharing options...
BlackSmithBear Posted July 13, 2009 Share Posted July 13, 2009 Dickb, Your hardening process seems pretty good...try heating the water(quenching other pieces of metal first, to getit hot). I think your main problem is your tempering! You should NOT quench after getting your "color"!!! Let it air cool. Bear Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 13, 2009 Share Posted July 13, 2009 (edited) If you have a oil hardening steel, water can kill it, period. as for tempering/quench, WSB2 may not understand that it is needed to stop over-heating the tempering portion. And dont forget that used springs may already have had the cracks from prior use. Edited July 13, 2009 by steve sells Quote Link to comment Share on other sites More sharing options...
short swing Posted July 13, 2009 Share Posted July 13, 2009 Could it be your letting it cool to much and you are still hammering?? Quote Link to comment Share on other sites More sharing options...
dickb Posted July 13, 2009 Author Share Posted July 13, 2009 Why are you quenching it? That is probably what is leading to the visible cracks. Just forge it, lay it aside and let it cool naturally. I am making some tools including a center punch, a chisel, and some hardy tools, so they have to be hardened. Quote Link to comment Share on other sites More sharing options...
dickb Posted July 13, 2009 Author Share Posted July 13, 2009 Dick, could you please explain to us your entire heat-treating routine? It may be that you're not being explicit but it seems like you're missing several key steps. Exactly what effect are you trying to achieve? What item/object are you trying to make? More detail will help us generate a more pertinent response. Remember that used springs could will have existing but invisibly small cracks in the steel and the shock of quenching may make them expand. I am making some tools including a center punch, a chisel, and some hardy tools, so they have to be hardened. I am forging at around cherry red and quenching as follows : After forging to the desired shape I let the work cool down till it just about stops glowing. Then I plunge the part that I want to harden about two inches into water. I repeatedly put it into and out of the water but I am careful NOT to plunge to exactly the same depth. I am trying to avoid a sharp line between the hardened portion and the softer portion. I continue this till the first two inches are black. The I quickly scrape the first three inches so I can see the bare steel. I watch the tempering colors flow down toward the cool end and when the cool end gets to straw color quench the whole tool till it's cool enough to handle without gloves. Quote Link to comment Share on other sites More sharing options...
matt87 Posted July 13, 2009 Share Posted July 13, 2009 I am making some tools including a center punch, a chisel, and some hardy tools, so they have to be hardened. I am forging at around cherry red and quenching as follows : After forging to the desired shape I let the work cool down till it just about stops glowing. Then I plunge the part that I want to harden about two inches into water. I repeatedly put it into and out of the water but I am careful NOT to plunge to exactly the same depth. I am trying to avoid a sharp line between the hardened portion and the softer portion. I continue this till the first two inches are black. The I quickly scrape the first three inches so I can see the bare steel. I watch the tempering colors flow down toward the cool end and when the cool end gets to straw color quench the whole tool till it's cool enough to handle without gloves. Yup there's your problem, your HT process is missing a few steps. After forging you want to normalise or preferably anneal the tool. Then heat it past the eutectic point (roughly when it become non-magnetic, a red colour) and quench it. The tool is then 'dead hard' (as hard as it can ever be). You then temper it from cold to the colour you need. Do you know what type of steel you're using? Tempering to a somewhat specific hardness in an unknown material by oxide colour is a shot in the dark. There is a blueprint which goes into a lot of detail on heat-treating and several threads and 'sticky' threads which are a bit more 'beginner friendly'. Hot-work tools like hot-cutters don't really need to be hardened; they are harder then hot iron even annealed and lose temper too easily anyway. Normalising is usually sufficient, and of course safer than an incorrectly tempered tool. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 15, 2009 Share Posted July 15, 2009 (edited) After forging to the desired shape I let the work cool down till it just about stops glowing. Then I plunge the part that I want to harden about two inches into water. I repeatedly put it into and out of the water but I am careful NOT to plunge to exactly the same depth. I am trying to avoid a sharp line between the hardened portion and the softer portion. I continue this till the first two inches are black. When you want to harden, heat to above non magnetic, then plunge into the oil. By allowing it to cool so far first, you have lost the quench window, and that is why it is not getting hard. The interrupted quench at the end is nice for small tools, but you are jumping in and missing a few things. Edited July 15, 2009 by steve sells Quote Link to comment Share on other sites More sharing options...
Awalker Posted July 16, 2009 Share Posted July 16, 2009 Water quench is fine for coil spring. You are likely just working it too cold. Get it nice and orange before you hammer on it. No need to anneal it before you harden it either as when it is orange it is as soft as it is going to get, save it is molten. Get it orange, work it, make sure it is non magnetic, quench it fully in water, stick the non tool end in the forge until you get straw then quench it again. I have found that when making tools from coil springs that I just quench teh first time and do not temper. They tend to stay better and I have had no breakage, at all, using this method. Your usage may vary! As far as the "eutectic point" is concerned for steel there isn't one as steel is not that type of alloy. When thinking of eutictic metals think of solder, it is solid until it turns liquid, there is no slushy state. so the eutectic point is the point that it melts. Steel has an extended plastic state, followed by a slushy state followed by a liquid state. I think what the previous poster was trying to indicate by using the word eutectic was in fact non magnetic. Just keep a big welders magnet by your forge to tell you when it is the right temperature for hardening. Quote Link to comment Share on other sites More sharing options...
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