Makio Posted January 5, 2022 Share Posted January 5, 2022 (edited) 3 days in rust acid removal I believe fosforic and this is happening on 4 blades some are broken in half but before acid bath nothing to be seen xxx??? Edited January 6, 2022 by Mod30 Language Quote Link to comment Share on other sites More sharing options...
Frazer Posted January 5, 2022 Share Posted January 5, 2022 You may want to edit the title of your thread before the mods do it for you... Etching will show cracks and delaminations. This happens with damascus sometimes as well. My guess is there is more surface area so the etchant oxidizes and/or eats away at the walls of the very small crack, both darkening it and making it wider. It kind of looks like quench cracking.. I'm guessing these were hardened before etching? Quote Link to comment Share on other sites More sharing options...
Makio Posted January 5, 2022 Author Share Posted January 5, 2022 (edited) Yes hardened it was from leaf springs Hardened of leaf springs in salty water cause olil didn't work Edited January 6, 2022 by Mod30 Excessive quoting Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 6, 2022 Share Posted January 6, 2022 Were they tempered as well as hardened? Hardened but untempered blades can self destruct upon being left alone. Is the spring steel new or was it used? Heavily used springs can have micro cracking in them due to fatigue---why we want to use the newest springs possible and NEVER springs found broken on the side of the road. Quote Link to comment Share on other sites More sharing options...
Frazer Posted January 6, 2022 Share Posted January 6, 2022 Salty water is a very aggressive quench for spring steel (usually 5160 or 9160 or something similar). What TP said is also very true. Steel should be tempered immediately after quenching. I generally try to start tempering before it even reaches room temperature. I've had tools and one knife crack on me because I let them sit around before tempering. In extreme cases they will break into pieces, but I've never seen that happen myself. What kind of oil did you use? Did you preheat the oil? P.S. No need to quote me if my post is the one just before. No hard feelings, just a friendly reminder. Read This First Quote Link to comment Share on other sites More sharing options...
Makio Posted January 6, 2022 Author Share Posted January 6, 2022 (edited) Overused car springs from 80 or 90's Not tempered here are other one more severe line in whole blade length but it's new steel 65mn disk for agro machine This is harrow disk new not used 65 MN steel but look Edited January 6, 2022 by Mod30 Excessive quoting Quote Link to comment Share on other sites More sharing options...
Frazer Posted January 6, 2022 Share Posted January 6, 2022 See TP's and my statements RE tempering immediately. This applies to new and used stock. Quote Link to comment Share on other sites More sharing options...
velegski Posted January 6, 2022 Share Posted January 6, 2022 Just my 2 cents worth. Listen to TP and Frazier comments on getting blades into tempering as quickly as possible. Ive seen those cracks before with 5160 in low salt or water quenches.. However I suspect that your cracks might be cause by 3 areas. 1. Using a unknown steel.. without running tests before you made something. Car springs are made from several steels throughout the world.. Each require different treatments.. Making small test samples and testing them in different quench mediums might take time but saves having to remake at least 4 blades. 2.Forging the blade when steel when too cold can cause unseen cracks. 3.Quench medium. You mentioned an oil but didn't say what type. A warmed canola oil will work. A tractor hydraulic oil or Atf works ((stinks and harmful to lungs, wear personal protective device and lots of ventilation), a professional heat treat oil is better, the oil may require warming to lower viscosity. Better luck next time! Quote Link to comment Share on other sites More sharing options...
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