spring steel

[scarecrow55]

can I refer you to my 3 questions here?

http://www.eng-tips.com/viewthread.cfm?qid=132056&page=1

thanks

 

[redpicker]

(Mechanical) 18 Aug 05 5:14
I have a very old torsion bar that has been analysed as being nearly eqiv to British 925A60. It falls within the spec except my shaft has the addition of .15 Ni.
Is this a common matl. for torsion bars?
Can anyone suggest an eqiverlent, also a website with eqivl. metals
Thanks

I forgot to add. The shaft is marked on the end with an arrow. Is it usual to refit torsion shafts the same way after stripping and why. Do they get "prestressed"

Also I notice from a lot of spring steels there is no nickel, why's that?

I am not familar with either Brittish spec's or torsion bar materials, but I'll give it my best shot.

0.15% Ni is usually considered residual. Unless otherwise restricted, Ni is typically held to residual limits of 0.25% for AISI steels. Another way to put this is that with no mention of the Ni content, a maximum limit of 0.25% Ni is permissible for AISI steels. I would suspect the Brittish steel specifications would have similar limits.

As far as what effect the 0.15% Ni would have on the spring, it would have very little effect at this concentration. A slight increase in hardenability and toughness (generally, both good things for a spring application), but even that effect would not be very noticable.

As to why Nickel is not used in spring steel compositons, I would guess that it isn't cost effective. Nickel is expensive. I believe spring steels are typically higher carbon, so with an effective amount of Nickel, you could run into a retained austenite problem that would require extra processing (cryogenic) to address. But, that is just a guess as springs aren't really my area of expertise.

 

[swall]

My company makes both springs and torsion bars. With spring wire, you normally are talking cross sections less than .5", so you don't need much alloy to fully harden. Many oil tempered spring wire grades are just carbon steel. Torsion bars, generally being larger section sizes, need to be alloy steel to fully harden up. We've used 4340 and its 300M variant.

 

[adyonel]

Ni is not important now. My suggestion is A401 SAE, or W1.7102.