Bent High Strength Steel A325 and Hydrogen Embrittlement

[MechAnalyst2112]

I need a high strength u-bolt of 3/4" rod dia and 4-1/2" inner diameter. I planned on using A325 rod with rolled threads, and then bend to correct inner diameter. The part will also be galvanized.

However, another engineer metioned that this would result in hydrogen embrittlement due to the stress after bending in the high strength steel.

If this is true, can anyone suggest a method/process to get a high-strength steel u-bolt without getting the hydrogen embrittlement issue????

 

[metengr]

A 325 u-bolts are a common item, plain or galvanized. Have you shopped around for a supplier? If not, and you are custom making for your application, the strength level is really not high enough to have a service-induced hydrogen embrittlment problem.

 

[MechAnalyst2112]

I did do a little shopping around, but didn't find and off-the-shelf high strength u-bolt. Vendor suggestions?

The initial concern wasn't due to service loads, it was due to the initial bending of the steel.

 

[metengr]

There should be no hydrogen embrittlement issues from cold forming based on the strength level of the A 325 steel. Use Google and shop around for suppliers of A 325 U-bolts in the diameter and inner bend radius you need.

 

[unclesyd]

I think you will find what you need at Portland Bolt. These are very good people to deal with.

http://www.portlandbolt.com/products/bent/

 

[TVP]

metengr,

My understanding of the OP is that the purchased item (A325 bolt w rolled threads) would be subsequently bent into a U-bolt configuration. This could possibly strain harden the part locally in excess of 320 HV which is the usual limit given for hydrogen embrittlement susceptibility.

 

[metengr]

TVP;
Possibly. There are other factors that should be considered like the service environment. Personally, I rather doubt this is a real concern for this material in service given the bend radius. One approach could be to warm form the u-bend, e.g. apply general heat but remain below the original tempering temperature to form the bend. This approach would reduce susceptibility to HE.

 

[MechAnalyst2112]

Thanks for the feedback.

The service environment will be outdoors exposed to the weather and elements for many years. It will also be under a constant load.