Cold drawn spring steel properties 3

[corus]

Is it possible to determine the approximate yield strength of a cold drawn spring steel knowing only the UTS of the material or can it be determined from other factors such as hardness etc.?

 

[unclesyd]

Try this for properties of C/S sping material.

http://www.precisionsteel.com/intro3.cfm?Properties=True&Standard=1095

To calculate springs go to:

http://www.efunda.com/DesignStandards/springs/spring_calculators.cfm

 

[corus]

Thanks for the information unclesyd but the site data only mentions tensile psi, which is presumably the UTS. Would it be reasonable to assume that the yield stress is approximately the same as the UTS? Another source has said that the yield is 70% of the UTS but whether that applies to this type of material is another matter.

 

[unclesyd]

The numbers are the UTS. No the yield strength is not the UTS. The 70% number is a little high for most metals and I wouldn't use it unless I had actual physical test data of the material being used. The convention is to use 60-62% of the UTS as an approximation of the yield strength.

Having said all this, the yield strength of very strong metals can approach the UTS, that is a 70%-80% value may apply. Always use the numbers in producers data sheets or recognized handbooks. In the Precision Metals web site their numbers are very good for working with spring design.

This subject can get a little involved due to the terminology and at times somewhat technical definitions. There are some good inexpensive handbooks on metals and their properties available, they used to be free. Maybe someone will suggest one.

I hope this helps.

 

[NickE]

We use Hardened and tempered modified 420ss adn the yeild is roughly 76% of the tensile, w/ elong of ~4%. Spring steels are likely to have yeild to tenslie ratios like this.

nick

 

[TVP]

Depending on the amount of cold drawing, the yield to tensile ratio for a spring steel is likely to be in excess of 80%-- more like 90%. The standards and specifications for these materials are all based on ultimate tensile strength, so it is difficult to find yield data. I'll see if I can find some, and post again.

 

[corus]

Thanks all, and IVP. The properties are to be used in an analysis of forming the metal into a spring and the resulting residual stresses/strains that may occur once the material has yielded.

 

[TVP]

I went through some data that I have for spring steels. The yield-to-tensile ratio was as low as 80% for a carbon steel strip material (0.75 nominal carbon), and as high as 95% for some 17-7 PH stainless steel wire. A 1% carbon spring steel (heat treated strip) has a specified ratio of 85% minimum, but the range is usually higher, ~ 90%. Another data point-- fastener standards like ISO 898-1 specify a yield-to-tensile ratio of 90% for high strength bolts/studs.

 

[corus]

Thanks TVP. The information given is excellent. We may test a specimin to confirm the figures at some time in the future. I'll post the results later for anybody's reference.