TeH_Chach Posted February 1, 2019 Share Posted February 1, 2019 Hey everyone, I've searched the heat treating thread for about 20 mins now and i'm having a hard time finding info on the proper heat treat for s7 hot punches. I made a slitting chisel a few weeks back out of 3/4 s7 round stock. I like the look of the curved working end, so that's how i forged it. I normalized it twice and heated the steel to a brightish orange and let it air cool. Drew a dark straw temper for the working end. It worked great for a few minutes then snap, the chisel broke right in the center. (it was about 6 inches long). Any tips for the heat treatment of s7 would be much appreciated. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted February 2, 2019 Share Posted February 2, 2019 Why S7 for a hot working tool? Quote Link to comment Share on other sites More sharing options...
Stash Posted February 2, 2019 Share Posted February 2, 2019 Looking at the heat treating app, re normalizing, it says do not normalize. The app is available for free to your phone or device. I believe info on the app is above, in the HT stickies. Steve Quote Link to comment Share on other sites More sharing options...
TeH_Chach Posted February 3, 2019 Author Share Posted February 3, 2019 I misspoke when I made the post. s7 air hardens so I guess it would be hard for it to normalize. On 2/2/2019 at 3:19 PM, BIGGUNDOCTOR said: Why S7 for a hot working tool? I've seen different smiths sell hot working tools made out of s7, and i can get drops for cheap lol Do you have another steel you would recommend? If you do could you include the heat treatment method that you find works best for you? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 3, 2019 Share Posted February 3, 2019 S7 :and H13 are both alloys used for a lot of blacksmithing hotwork tools as it has high hot hardness and so doesn't upset when used for tooling that gets driven into hot steel like slitting chisels and punches. (and both can be heat treated by blacksmith methods) My favorite hot chisel is made from S-1 as I was given some and my favorite slitting chisel I forged from H13 which was a learning experience, as is working any alloy new to you... Quote Link to comment Share on other sites More sharing options...
IronAlchemy Posted February 3, 2019 Share Posted February 3, 2019 Like Thomas says, S7 works great for hot working tools especially for something like slitting where the tool can get very hot. It is also really good for tools used cold when the edge is left at a hard temper. All my chasing tools are S7 for example. S7 generally heat treats easily because of the air hardening. As mentioned, it does not normalize. It needs to be heated to 1750F (typically described as cherry). When heating from cold for forging or heat treatment, don't heat it too fast. Heat it gradually or it can develop cracks from that. Folks preferences vary but I like to harden the whole tool as you did since the struck end will mushroom if left fully annealed. I think it most likely that the problem you had was that you only tempered the cutting edge whereas you hardened the whole tool. This left everything but the edge fully hardened and brittle. Also when you temper S7, it takes a quite high temperature to reduce the hardness. I temper the struck end to at least 1000F which is about where you just see color in the metal which would leave it near Rc 50 which is still pretty hard. Straw color is typically about 450F in carbon steels which would leave your edge at ~Rc 55. That said, alloy steels do not exhibit the same temper colors as carbon steel. I have dozens of S7 tools forged without heat treating in an oven and have yet to have a failure so it is generally pretty forgiving. Quote Link to comment Share on other sites More sharing options...
TeH_Chach Posted February 3, 2019 Author Share Posted February 3, 2019 9 hours ago, IronAlchemy said: I have dozens of S7 tools forged without heat treating in an oven and have yet to have a failure so it is generally pretty forgiving. So it will work fine if i just let it air harden and i can let her rip? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 4, 2019 Share Posted February 4, 2019 Did you not read the section of his post where he describes tempering tools after hardening them? Quote Link to comment Share on other sites More sharing options...
TeH_Chach Posted February 6, 2019 Author Share Posted February 6, 2019 I did, thank you Thomas. @IronAlchemy Do you just use a torch to get that 1000 degree temper? set it in the forge checked colors frequently? Quote Link to comment Share on other sites More sharing options...
IronAlchemy Posted February 15, 2019 Share Posted February 15, 2019 Usually I use the forge (gas or coal) to heat the struck end but it makes no difference how you do it. Torch does work fine. Quote Link to comment Share on other sites More sharing options...
Cavpilot2k Posted February 20, 2019 Share Posted February 20, 2019 I'm a novice, but I made a similar rounded slit chisel out of 3/4" round. I nearly ruined it when I oil quenched it before finding out that S7 was air hardening (ever since I check first lol- rookie mistake). Fortunately I didn't use it because it would have almost certainly broken, possibly spectacularly. So I re-heated it and air cooled it then tempered to straw and the thing has been like a rock. Used many times now for all sorts of hot work and not the slightest sign of edge deformation or dulling. I LOVE this chisel, and so will you most likely if you get the HT right. I plan to make another just like it with a straight edge. Here are some pics, because folks here like pics. Quote Link to comment Share on other sites More sharing options...
anvil Posted February 24, 2019 Share Posted February 24, 2019 On 2/20/2019 at 11:25 AM, Cavpilot2k said: Here are some pics, because folks here like pics. Nice job! Quote Link to comment Share on other sites More sharing options...
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