metallurgy expert, please

It depends on the material.

Ideally, you would cold form from a spring steel.

I know how to heat treat all sorts of mets for harness, annealing, and so on, but I don't know how to impart springiness (or elasticity and resiliency) by heat treating.

Someone here might.

Matt

 

Not knowing the car, might it be easier to modify torsion bars off a similar car. Just a suggestion.

 

By chance a Chrysler Corp. produced (Chrysler, DeSoto, Dodge, Plymouth or Imperial) from the 1950's or 1960's ?

 

It really depends on the material used. You can buy spring steel (various alloys) either hardened or in a soft state.

If hardened and if you do not have annealing ovens working with precise temperature control, then you should try to bend the material in the cold. The bending radius should be more than 2x, better 3x, the diameter. Take care not to make any marks to the surface (pliers etc.) since these marks will promote fracture. Good luck that the material will not break during the bending process. Take this risk into regard and keep persons and your own hands, head etc. well away from directions into which parts may be propelled upon fracture.

A safe approach is to heat the material up (if not purchased in soft state already) for bending. Afterwards you will have to harden the whole device (quite large such spring) by annealing to around 850 °C and quenching in oil. After quenching you will have to anneal again at about 500 °C for some time (about 1 hour, e.g.). The exact temperatures and durations depend on the specific material used. This hardening process will require appropriate heating facilities, obviously ....

It will for sure be the best approach to look for a most similar spring and to adapt it to your car.

 

I'm not a Metallurgist, but I do have a good technical understanding of this topic.....

This is your best option if you are trying to make a torsion rod (spring) from scratch DIY.

Treating steel to a "spring" condition is far beyond what you can do yourself --- much more complex and involved than simply heat-treating or annealing. It typically requires many days of precisely controlled baking (sustained heating) and cooling cycles --- it cannot be done at your home or in your garage.

 

You would need to buy the rod in the hardened and tempered condition to start. Then to make it easier to bend you can heat it up only so much as it doesn't drop the hardness...say about 500 - 700F. If you go much higher you'll permanently soften the rod and it won't work as a spring very well.

After forming, it should be stress relieved around 600 - 700F depending on the grade. Then for best performance, have it bead blasted on the surface especially in the bends. This will put in compressive stress that will make it last longer.

The other path as others have said is to form it soft, but then you need to heat the whole piece above 1550 - 1650F and quench in heated oil (at least 150-170F, NOT cold!). Then temper the entire piece for an hour around 700F.

These temps are approximate and depend on the grade of rod you're using. Shoot me a PM if you want, I could talk spring metallurgy all day

 

It may be easier to go to a local scrap yard and buy the pieces.

 

Have you done this before?

500F is not much for most steels. It won't harden, anneal, or even get it more malleable for bending. 500F would be actually quite similar to cold forming the bends. Meaning it won't really help.

And to better answer your original question, cooling and quenching doesn't matter in this case.

Matt

 

Mitchell,

Note: the (torsion bar type) hood springs on my 330 2+2 were absent when I bought the car and totally unavailable, so I had to have them made. I was able to get the dimensions from the springs on the cars of two friends. I made drawings, then took the drawings to a spring maker about 90 miles away. He made me a prototype set which I installed to check the fit, then he made about 20 more sets most of which I will sell.

Firstly, you want an OTMB spring wire in the appropriate diameter. It comes already heat treated (OT=oil tempered). You will bend it, using generous radii, absolutely COLD. Do not heat-to-bend in any way. The finished spring will then be stress relieved, but otherwise, will not be further heat treated.

I would strongly urge you to find a spring maker near you. There must be at least a dozen on the left coast. They will have the forming equipment and the experience needed to make a proper part. Take the pieces of your broken spring to them and explain what you want. Have them make a prototype set. Then install them in the car and test operation. Also note any set they take after about a hundred cycles. If changes are needed tell that to your shop. Have them make ten or more sets. Pick the best set for your application and a spare set for future needs then sell the rest.

Tom (retired PE)

 

I'm surprised you can't get them as re-pop parts, most all GM stuff is still available. what yr? Also wouldn't be surprised if it's shared with a couple other models too.

classic industries may have what you're looking for. Sure beats trying to build them your self. here's a link to some resources I found on google. Hope it helps.
Part Sources

 

Nice...let us know how it goes. I suspect that's relatively soft steel from HD, it might yield pretty quick depending how high the stress is.