broken blade

[bowfishjim]

flat spring steel profile to shape heated to non magnetic quenched and oil tempered three times at 350 in oven polishing blade blade snap hand polishing what went wrong?

[jmccustomknives]

The 350 deg temper was the first problem.  Spring steel (5160?) should be around 400 (straw yellow on a knife that size).  Also look at the break.  Does it look like sandpaper (sandpaper like, got it too hot) or satin like?  Are there any black inclusions that would mean you had a crack.  These sometime don't show up until final polish. 

Did you forge it?  Follow good forge theory? 

There's a lot that can go wrong.  My first big blade I did something like that, ended the same way.  Failure is a crule teacher, but she gets the leason across. :(

[bowfishjim]

there was a black spot at the top probably were the crack started.The Gran structure looks pretty smooth except for one black spot at the top.

[jmccustomknives]

So either the crack most likely was already there (can happen with used springs) or occured during forgine (too cool?) or a deep hammer mark that created a stress riser.

[bowfishjim]

Thanks for the info. Back to the drawing board.

[Steve Sells]

he never did really tell us what the steel was, Spring steel is not a steel ID,   but if its revcovered scrap could have been pre existing stress cracks in that steel.  We may never know...

[bowfishjim]

I am using flat coil spring used on a fork lift to help the ram lift up.it is new.don't know what spring steel it is thow. I am heating it in the forge to straighten.then I leve it in the forge till cool.then cut and profile. Heat till non magnetic.quench in used motor oil then temper at 450 for 1 hour 3times. Tried this today and 1 more crack after 1st temper?

[Steve Sells]

get a dif steel.  2 for 2 seems like maybe a badly stressed chuck of steel there.

[jmccustomknives]

get a dif steel.  2 for 2 seems like maybe a badly stressed chuck of steel there.

I'll agree, somethings going on there.  Can't say I've ever played with springs from a lift.  It could be anything.  If you must, find some late model truck springs.  They'll be 5160 (or a version there of).  It would be much better to buy some new steel that way you know what you are dealing with.  Too bad you aren't closer, I've got so many springs floating around here I feel like Fred Sanford.

[Rich Hale]

So we do not know if it is the material or the process...Order some new high carbon steel from a knife supplier and heat treat it as they direct...to the letter. Don't change anything..It will not cost you much at all..Think of it this way: you should have been able to sell two finished knives now and you are at ground zero. Since you are close try Sheridan Knife supply and see if she has some 1084, Get a three foot bar of the thickness and width she has that you are alright with. And again go with the heat treat info she supplies or from a website for that steel. Not a process that you find on a forum where you do not know who placed it there or How it really worked out for them.

If you would like my help pm me. 

[bowfishjim]

I am going to try 1 more time with this steel.just because I have a lot of it.I will try heating the oil a little more. If that does not work I will just use it for other blacksmith products .and order some known steel.thanks for the help and info on Sheridan.

[VaughnT]

This is why nobody recommends you use mystery metal for making knives.  It could be anything and all the time spent on making blades only to have them snap...  

 

The upside is that the allow will be a lot stronger than mild steel even if it's not hardened and tempered.  That will come in real handy around the shop.

[homeshow]

Bowfishjim is there a place to send a sample to be tested? It may or may not be worth it price wise. Once you know what it is then finding the proper heat treat should be doable.

Balancing price savings verses your time used is a difficult balance. I have a friend who got a lot of free 5160. Problem is It's 3/8" X 8" X 8'. Cutting into manageable pieces with a torch and grinding the slag off takes a lot of time. Buying 5160 in the size he needs only costs about $3.50 per blade.

Of course you can't put a price on fun! I hope you have fun with it.

[bowfishjim]

I think it has something to do with the /straightening process.I tried a different way last night. I cut the coils first.then heated and Left In forge over night. The steel looks better/more solid color. Just have to try and see. At this point I'm not looking to sell knife's /just for fun.maybe if I can turn out a good product I will sell in the future. Thanks for the feedback.all

[bowfishjim]

I tried This steal one more time .and one more crack . I was not heating up the oil enough. then I turned out this little neck knife .turned out okay shaved hair, has a little flex to the blade.I did this really quick.

[metal99]

Could it be an air hardening steel maybe?

[jmccustomknives]

I'm thinking his problem is heat related.  Trying to move carbon steel at too low or too high can cause cracking.  Probably not an air hardening, those steels aren't normally used in springs. 

If you are trying to straiten in one heat, slow down and do it in several.

[metal99]

That's most likely the problem or perhaps not properly normalizing and then quenching a little hotter then it should be. I lost a couple forging a from W1 that way.

[homeshow]

I'm thinking his problem is heat related. Trying to move carbon steel at too low or too high can cause cracking. Probably not an air hardening, those steels aren't normally used in springs.
If you are trying to straiten in one heat, slow down and do it in several.

I agree. Also a cold breeze thru my shop when I am moving a freshly quenched blade into the oven could be a problem. In my shop during final quench the forge, quenching oil, and toaster oven are only a few feet from one another. That's why I like 75 ft extension cords. The rest of the time the oil is covered and in a corner.