Leafsprings heat treating ? -- myArmoury.com

Maurizio D'Angelo · Posted: Tue 29 Sep, 2009 1:55 pm Post subject:

Hello,
make a sword blade tempered already be a great job. Eek!

Work often special steels, also 5160.
These steels, steels with memory we call them for their ability to return to original form.
If I think of our heat treatment before, during and after work ... I am amazed by your passion. Happy

Bruno, if you want 5160 or a steel better, ask. Wink

Ciao
Mau

Maurizio D'Angelo · Posted: Tue 29 Sep, 2009 4:18 pm Post subject: Re: Leafsprings heat treating ?

Bruno Giordan · Posted: Thu 01 Oct, 2009 12:49 pm Post subject:

Ozsváth Árpád-István · Posted: Sun 04 Oct, 2009 1:31 am Post subject: Leafsprings heat treating ?

Maurizio, there's some misunderstanding. Leafspring is a already hardened to do what it was intended to do: absorbing shocks and not for good edge retention. Therefore the leafspring is too soft to hold a good edge. If you try to quench the whole blade to make a harder edge (50-55 HRC) it will become brittle as glass and will break apart at first impact. Somehow you can temper it, you must heat up to 200-300 centigrades, keeping it for hours than let it cool very slowly. It's difficult to achieve that for the edge it's much thinner and will heat up faster and therefore will loose it's hardness, not to mention bending and warping, problems that are hard to correct. That's for the "don't try this at home" section. Only a few experts can do proper heat treating.
If you look at hacksaw blades, you will notice that they are hardened only at a narrow, few millimeters section behind the teeth. To achieve this they use special induction heaters. Only that portion of the blade passes close to the the induction coil and are heated. That's differential hardening and would be ideal for leaf-spring swords resulting in a hard edge and leaving the original temper for the rest of the blade unmodified.
If you can only access such hardware...

Take a look at this:
http://www.youtube.com/watch?v=j5_zSrMN3s4

Maurizio D'Angelo · Posted: Sun 04 Oct, 2009 1:51 pm Post subject:

Ozsváth Árpád-István · Posted: Mon 05 Oct, 2009 11:27 pm Post subject: Leafsprings heat treating ?

Michael Pikula · Industry Professional

Your best bet might be to make 3 or 4 small trial blades from the steel and seeing if you can get a proper edge without any heat treat. If you don't, then heat treat each of your trial pieces a different way and destructively test them to see which process worked the best.

Apply what you learned to making your sword, and you should be on the right track.

Maurizio D'Angelo · Posted: Wed 07 Oct, 2009 9:46 am Post subject:

Ozsváth Árpád-István · Posted: Mon 08 Mar, 2010 11:17 pm Post subject:

I left my sword to rest sometime, I was busy with my family and my bayonet collection. But now as spring is coming I feel the urge to chop down some hostile bushes from horseback Big Grin

You convinced me about heat treating. I find my blade material too soft, unable to keep a good edge. Now I have a question about tempering, my concern is to have a decent, but not too brittle blade, because I want a functional sword, not just a wall-hanger. It has to take a lot of abuse without breaking.
Blacksmiths are used to heat-treat knives, they temper blades to a pale yellow or so, but swordblades build up a lot of stress therefore they must be a little softer. Can you tell me the right tempering color (or temperature). Well I still don't know the exact type of steel, it's just "somekinda' leafspring"...

Aleksei Sosnovski · Posted: Tue 09 Mar, 2010 12:04 am Post subject:

A LOT depends on the steel. Carbon steel should be tempered to purple or blue. Alloy steels may need to go beyound that. And once the steel becomes gray (after lighter blue) it is virtually impossible to tell the temperature by the color.

I would advise to quench your steel in oil (maybe even hot oil, try with a scrap piece before you attempt to quench a sword). The slower your steel cools down, the less likely it is to warp or crack.

Then test it with a file. If the file does not bite, the quench is successful (unless you overquenched the steel). If the file bites easily, then you've failed. If it does not bite but leaves some marks then you've got a slack quench. Test in several places, not just one. Remember that you cut with the tip of the blade, so the base of the blade may be much softer, it will not cause any problems.

If you partially failed (for example got a slack quench or there are softer spots on the half of the blade that is closer to the tang) I would not recommend to quench the blade again. If you've failed once, there are very few chances you will succeed next time with the same blade. It's more psychology than physics. Reattempt quenching only if you ended up with a totally soft blade. But before the second attempt thoroughly anneal the blade (well, you'd better do it before the first attempt too). And do not make the second attempt on the same day.

When you are sure that the blade was quenched successfully, you should temper it ASAP. In case of unknown steel I would recommend to temper to lighter blue (comes after concentrated blue which in turn comes after purple). Softer is always better than broken, you know. Well, if your steel gets a decent hardness when quenched in hot oil, you may be sure that you got some alloy steel. If it quenches in cold oil but does not quench in hot, then most likely you've got plain carbon steel. In the latter case you may decide to temper to purple color to get a harder blade (I would not recommend it though). If the blade was slack quenched then you may decide to temper to yellow or brown color because the blade is not that hard already. For carbon steels it is enough to heat the steel to the decided color and then let it cool down about 5 times (the more the better). But if you can hold it at required temperature for an hour or two, do so. And then repeat. Alloy steels take A LOT more time to temper (and leaf springs are usually made of alloy steels). Ideally you should keep it at the required temperature for 2 hours, let it cool down and then repeat. I never heat treated blades made from alloy steels myself so I cannot tell whether it will be enough to just heat it and then cool down 5 times like I did with carbon steel. Depends on particular steel, I guess.

I would advise to temper base of the blade and tang a little bit more then the rest of the blade to make them softer but more resilient. And of course the end of the tang should be annealed.

And finally, as my experience has shown, the blade should not be that hard to hold the edge against some bushes. So do not get discouraged if you don't get the ideal 50-52 HRC. 40 HRC will also make a good sword. You may need to sharpen it more often, but consider it as a good practice. Believe me, this experience will be very handy when you finally get a good valuable sword with hard blade.

Ozsváth Árpád-István · Posted: Tue 09 Mar, 2010 2:03 am Post subject:

Well, thanks a lot I will keep that in mind, I should contact someone who works in a heat-treatment facility, because I have no experience in doing that and absolute no equipment. I still have some work on the blade and I'll try to bring it to the final stage before heat treating and the final sharpening.