Re: Spring Pivots

[Steve Simmons]

Are the forward pivot mounts for the leaf springs hardened steel, heat treated, or anything special? I'm about to get a frame acid dipped, and hardened steel needs special care during the process to avoid hydrogen embrittlement. I already have the rears removed but since the fronts are such a pain to deal with I'd like to leave them in place if possible. So I'd like to know what to tell the stripper he will be dealing with. Or would I be better off removing them?

[doug fromtheframeup.com]

Steve,

To confirm it sounds like you are asking about the front pivot shackle pin for rear spring. These are just standard steel. You are correct on the pain . They have a horizontal pin to remove and then are threaded in place. Avoid removal at all cost, only if unserviceable.

Regards,

Doug Pelton

From The Frame Up
4064 E. Presidio St. #104
Mesa, AZ 85215
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[Steve Simmons]

Yes, that's the one. I'd really like to avoid removing it. Thanks for the metallurgy confirmation. I'll just have them dunk it with the frame without worry.

[Bill Hyatt]

Steve,

It is easy to determine the hardness of ferrous metals by a simple spark using a grinder to generate spark. See: http://www.machinetoolrecyclers.com/spark-test.html A more definite test would be a Rockwell or Brinell hardness test. https://www.reference.com/article/metho ... dpArticles

Hydrogen Embrittlement cannot occur if dipping solution does not contain hydrogen elements to be absorbed into metal at raised temps. Both acid and caustic cleaning dips can contain hydrogen atoms.

Bill
TC 4926
Odessa, Fl.

Steels

If steel is exposed to hydrogen at high temperatures, hydrogen will diffuse into the alloy and combine with carbon to form tiny pockets of methane at internal surfaces like grain boundaries and voids. This methane does not diffuse out of the metal, and collects in the voids at high pressure and initiates cracks in the steel. This selective leaching process is known as hydrogen attack, or high temperature hydrogen attack, and leads to decarburization of the steel and loss of strength and ductility.

Steel with an ultimate tensile strength of less than 1000 MPa (~145,000 psi) or hardness of less than 32 HRC is not generally considered susceptible to hydrogen embrittlement. As an example of severe hydrogen embrittlement, the elongation at failure of 17-4PH precipitation hardened stainless steel was measured to drop from 17% to only 1.7% when smooth specimens were exposed to high-pressure hydrogen.

As the strength of steels increases, the susceptibility to hydrogen embrittlement increases. In high-strength steels, anything above a hardness of HRC 32 may be susceptible to early hydrogen cracking after plating processes that introduce hydrogen. They may also experience long-term failures anytime from weeks to decades after being placed in service due to accumulation of hydrogen over time from cathodic protection and other sources. Numerous failures have been reported in the hardness range from HRC 32-36 and more above; therefore, parts in this range should be checked during quality control to ensure they are not susceptible.

[Clive Sherriff]

Bill, This will not tell you the hardness of a steel. The "Spark Test" will give you an indication of the composition of the steel, eg primarily of a high or low carbon content.. With certain wheels some indication of other element content can be implied from spark colour too. Ultimately the hardness will depend on the heat treatment the steel receives. CliveOxford, UK,. mmmmmmmmmmmmmmmmmmmmm

[Bill Hyatt]

Hi Clive,

I think we are talking semantics here. One can indeed easily tell the composition & thus difference between carbide, HSS, non HSS steel, cast iron, and other grades of steel. However each will also display different patterns and colors of sparks before and after heat treatment. Useful in determining if desired hardness has been achieved.

As I mentioned, there are more definitive hardness tests

-Bill