Reported Nb out of spec 1

[MistaMojo]

Has any one had any experience with chemical composition of structural components being out of spec?
If so what recourse did you pursue?

 

[MintJulep]

Rather than asking random strangers on the internet if you should ask your engineer a question, why not just ask your engineer a question?

 

[redpicker]

If the composition limits that are out of spec are the Nb levels, what is being reported and what are the limits? Have you performed analysis on the components to verify what your reports are telling you?

 

[mrfailure]

From a test lab perspective, this happened time to time when I was testing for conformance for customers. You need to compare with the actual specification called out. Also note that your specification may call out a general specification for the component that will add allowable product tolerances beyond the spec called out i.e. your sample may conform for product analysis even if it originally was not within requirements.

 

[MistaMojo]

redpicker & mrfailure,
Thank you for the replies. Reported value is .009, spec limit is .008

We’ll send samples to an independent lab next week to get a clearer picture of what’s going on.

Thank you again.

 

[isoca]

In some cases it is acceptable a variation in product analysis (regarding the specified chemical composition). An example is the ASTM B880 for nickel alloys.

 

[EdStainless]

When you do your lab check it is a product analysis and there is an additional tolerance for that. Look it up.

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P.E. Metallurgy, consulting work welcomed

 

[bobjustbob]

Is the requirement in ASTM or is it a customer specific requirement? Either way, the first thing to to is to go back to your supplier and alert them that they have material out of spec. They need to determine where the error occurred to prevent it from happening again.

You need to determine if it is acceptable. If it is an ASTM standard then you need to look at your customers to see if it is acceptable to them. If it is your own specification requirement, you need to figure out if is a problem, you should have some reasoning behind the requirement and determine if the cost for you to use it is worth the time to have replacement material.

You can have an analysis done, however, that does not trump the material test report. There are product analysis ranges in ASTM standards because of possible uncertainties in the testing methods. You could come out in spec due to uncertainties in the tests, but you still need to ensure that if the part is at the reported CMTR level it will not cause a problem.

That being said, if the difference between 0.008 and 0.009% Niobium can cause a problem you need to tighten up those specs further.

 

[arunmrao]

In addition to excellent responses, I would also consider looking at the testing methods. If it is a OES, the calibration curves and samples, used for standardization.

Also please check for ASTM tolerance and note that there is a difference between melt or bath analysis and product analysis.