Heating after twisting cold

[yves]

I bent some hooks 1/8" x 1/2" flat at 90 degrees, cold. In use, some of them broke, just snapped.

 

Does it make sense to heat after bending cold to "normalize", relieve the stresses cold bending produces?

 

Can this unhealthy cold bent steel be heated to health?

 

Thanks

[jmccustomknives]

Long and short, if the steel has already has stress fractures from being worked cold no amount of normalizing will help.  The damage has already been done.

[yves]

Thanks jmccustomknives. Loud and clear and confirms my doubts.

[HWooldridge]

You could normalize prior to bending cold. HR steel can have hard spots running along the bar that will fracture when bending cold.

[yves]

HWooldridge,

 

Thank you. I only did this once for a set of hooks for my booth when I go at fairs and such. A few snapped. The other reason I asked was because I planned on giving extra movement to small flat bars forged in the shape of long leafs bendind in the wind. 

 

From the answers I get here, I'll heat the flats.

 

What I liked about twisting cold was that you have the same "heat" all along the bar/twist and that I did not have to light the forge. I got the idea of twisting cold in Schwartzkof when he explains that to forge gate hooks, " a skilled worker will make the twist cold first". That's on page 61.

 

I'll take no chances and heat the bars.

 

Again thanks.

[Gergely]

Just asking:

Isn't bending and twisting different kinds of operations? I can twist a bar cold, just did it today with MI, but the same material might crack if I try to bend it 90 degrees.

But I'm not familiar with the book you quoted and also may have misunderstood the whole thing.

 

Greetings

 

Gergely

[yves]

The steel snapped when I bent it 90 degrees. I was worried if I twisted it that something might happen.

 

In fact, I understand that if I bend 90 degrees or whatever I'm looking for trouble. If I twist a bar lightly, nothing would happen.

[BIGGUNDOCTOR]

What alloy are you using? When I had my shop we needed to make some 1/2" dia. u-bolts for a project. We got some chrome moly IIRC from a local welding shop. Tried bending them hot, and they cracked. Bent some cold,and they came out perfect.

How did you bend them? Did they have sharp corners that may have a stress riser from a nick? How much weight was on them? How much movement-springiness did they have in use? They may have failed from fatigue.

More info is needed to come to the root cause of failure.

[yves]

Biggundoctor,

 

The steel used was cheap (but new) mild steel flat bar 1/8" x 1/2".

 

I bent them in the vise with a hammer. The corners were sharp (some still are). There were no nicks except the center punch mark in the middle of the bar.

 

There was virtualy no weight on them, maybe 3 pounds. 

 

Like I said when I started the thread, my worry is about the stress I would put on 1/4" x 1/2" flat bar with a long half twist. I have a commission for a balustrade and I want to be on the safe side when I give some movement to a long "leaf blade" much like those of cattails when the steel is cold.

 

Having has the steel snap on me in what I now see as extreme conditions (90º bent, sharp), I was worried that in the long run, something might happen to the long blades because of the strresses cold twisting (not bending) would have built up in the steel.