Charpy Impact Testing small hardware items

[lurks]

I am currently working on a project involving hardware ranging between 1/4" and 5/16" diameter. One of the requirements is that these items must have a minimum energy absorption of 20J @ -20C per ASTM A370 (10 mm X 10 mm sample). From what I can find the smallest sample size specified in ASTM A370 is 5 mm X 5 mm and there is no correction factor for energy absorption. It may be possible to machine the smaller specimen out of the 5/16" material but not the 1/4", what would the solution be to verify that these items meet the customer's requirements?

Thanks in advance,

Lurks

 

[TVP]

When you say hardware, do you mean threaded fasteners or something else? Essentially, I would test a version of the raw material using a 5 x 5 or 10 x 10 specimen. If the hardware item is 1/4", get a piece of the raw material that is larger than 1/4".

 

[lurks]

Yes, these items are threaded fasteners with an upset head (carriage or hex). Typically the raw material is not even large enough to test. It starts as a round bar that is slightly larger, drawn down to the pitch diameter of the threads and then upset and threaded. Also, there is a post process heat treat that gives these items the strength necessary to meet the energy absorption requirements of A370.

Thanks,

Lurks

 

[TVP]

The initial hot-rolled wire rod or bar is subsequently cold-drawn into wire to manufacture the fasteners. I suggest obtaining a sample of the hot-rolled wire rod or bar, not the cold drawn wire, and then heat treat this sample to mimic the finished fastener microstructure. Machine the specimen out of the hardened sample.

 

[redpicker]

You really need to go back to your customer and let them know that you cannot meet their requirement. While TVP's suggestion is a good alternative you can offer as a substitute (provided that you can obtain a large enough sample), even with that suggestion, you are not testing in the same condition as the final product. Only the party that is making the requirement (ie, the customer) can decide if that will meet their needs.

It sounds as if the customer is applying a specification to a product (small diameter fasteners) that it was not intended to cover. You probably can meet all the other requirements, but since the specificaiton was not intended to cover this small diameter, it does not say what to do in these circumstances.

rp

 

[EdStainless]

What people usually do is require testing of the actual parts, and then they develop an appropriate toughness limit based on the real parts. No, this can't be done theoretically, real testing is what is needed.
It sounds like they tried to go cookie cutter and forgot to consider the part size.

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Plymouth Tube

 

[Screwman1]

I agree with Ed. Typical customer who slaps a spec onto a part without actually reading it. You need to do any testing using a specimen machined from an actual finished part, I would not attempt to correlate results from a non headed part, the processing is too different.
It is unusual to see that requirement on a part with that small of a thread size. I wonder what the application is that will require those properties.

 

[lurks]

First off, thank you all for the intelligent responses.

These products are for a Canadian customer that puts the same Charpy impact requirements on all of the products that they receive from us.

Thanks,

Lurks

 

[Metaljon]

Yes Canadian that explains everything.

 

[redpicker]

These products are for a Canadian customer that puts the same Charpy impact requirements on all of the products that they receive from us.

Then, by all means, you need to go back to them for guidance. In all likelihood, they do not understand the issue. If you do not bring it to their attention, they will assume that you are meeting their requirements, with no qualifications or exceptions. If a problem should arise with the material, they will be able to claim that they had no idea that these products could not be tested to meet the requriements they put on the product, so they could not have prevented the problem. They could, however, go back on you, saying that you obviously did know this bit of information and neglected to inform them.

rp

 

[Guest102023]

Blame Canada!

Sounds like a clerk with a BA was put in charge of handling technical specifications.