Chem Posted August 20, 2017 Share Posted August 20, 2017 Sorry if this was covered, if it is I couldn't find it. I was recently given a coil spring. He said it was from Toyota tundra. Having worked with spring steel, I was confident I could make some nice knines. I hot cut a small price to test the steel. Problem is that I can't get this spring to harden. File bites easily I to it. I first quenched in oil, twice. Thinking it may be .your oil, I got new oil. Still too soft. Finally I tried a brine ( salt water) quench with the same results. Has anyone worked with coil springs? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 20, 2017 Share Posted August 20, 2017 Yes and they have hardened nicely HOWEVER a manufacturer can change the alloy they use 3 times a day if that suits them! I have run into a low alloy strain hardened leaf spring before that could not be quench hardened and had to be discarded from my possibles pile. If your hardening temps were correct; it looks like that one is similar and is just rod stock for other projects not needing hardening. GREAT JOB testing before you threw away your time and effort. Go get a different coil spring and most likely it will do fine for a knife. (test first!)\ And since that is a fairly modern spring I will be more on guard in the future! Quote Link to comment Share on other sites More sharing options...
JHCC Posted August 20, 2017 Share Posted August 20, 2017 Welcome aboard, @Chem! I see this is your first post, so why don't you head over to the Introduce Yourself section and let us know who you are -- just make sure to READ THIS FIRST! Quote Link to comment Share on other sites More sharing options...
Frosty Posted August 20, 2017 Share Posted August 20, 2017 Welcome aboard Chem, glad to have you. If you'll put your general location in the header you might be surprised how many of the gang live within visiting distance. Yeah, you collected one of the new alloys alright. Springs are supposed to be springy not hard and with modern alloys they can find alloys that don't harden. They are also a lot less likely to work harden and break from metal fatigue. I wouldn't toss the spring but I'd put it somewhere I wouldn't mistake it for a hardenable steel, maybe mark it with spray paint to be sure. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
TwistedCustoms Posted August 20, 2017 Share Posted August 20, 2017 I have not yet used an automotive coil spring that wouldn't oil harden but the proof is in the results. If it got WAY too hot during forging and burned out too much carbon or it just wasn't hot enough to quench it is possible. As long as you have those bases covered it may just be some alloy that wont work with simple steel/low alloy heat treat methods. Coil springs are usually something 5160 ish, no way to know what alloy they really are but using heat treat data for 5160 is usually a good place to start. I have found coil springs to be very forgiving to work with and easy to temper from Rc 52 to 58 just by watching the colors run. If you want to put a little more time into it you might try cutting out a small section from further into the coil and giving it another go. If you get the same results then toss it and start with new steel. How does it move under the hammer during initial forging compaired to say mild steel, or another known alloy. does it move like butter or do you have to pound it to move it a little? Good luck! Quote Link to comment Share on other sites More sharing options...
jlpservicesinc Posted August 21, 2017 Share Posted August 21, 2017 did you do a notch and break test? or just a file test? Some of the steels just don't get as hard as a true 5160 or 52100 so the file feels sticky.. But it is still hard.. If you do a notch and break test it will for sure show you the error of the ways.. Also some of the springs are decarbed on the outside so there is less likely hood of a spring failure from fracturing.. Flatten out 5", notch every half inch, take a full yellow heat at the end and have your last notch just before transition temperature (1500F or less) then harden the whole 5".. give it a file test, and then snap off each segment and look to see if there is a nice clean, small grain in the broken off part.. You'll notice that at the high heat sections 2400 down to about 1800 the grain gets smaller with the lower temps.. Post back results. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted August 22, 2017 Share Posted August 22, 2017 I second jlp's recommendation. I had a similar result as you with some coil spring. However, it did actually harden as was proven when I tried to take a small warp out cold. It snapped cleanly and then I discovered that only a relatively shallow layer didn't harden. Yours may or may not be the same as mine, but it's worth exploring. Here's what I made from that particular coil spring: https://www.iforgeiron.com/topic/48558-first-dagger/ Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.