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[ASK] Permissible Deviation of Material Elongation

[ASK] Permissible Deviation of Material Elongation

[ASK] Permissible Deviation of Material Elongation

(OP)
Hello guys,

I am working on a project relating with material specification. Usually i am checking conformance between our material specification and mill certificate that supplied.
But often i found, in mill certificate for elongation of material having discrepancy with our material spec, but the deviation is very little in my personal, 2%-5%.

My question, is there any regulation that regulating permissible deviation of elongation of material ? so i may argue if there is auditing and auditor ask us why we accept mill certificate that has elongation not meet with minimum requirement of our material spec ?

RE: [ASK] Permissible Deviation of Material Elongation

The contract states the requirement. If you are failing to enforce your contract that's a bad sign. It was entirely up to your company to make an exception in the contract; but your company paid for conforming material that it did not get.

RE: [ASK] Permissible Deviation of Material Elongation

(OP)
Mr Dave, So as your said, there is no normative standard that regulated about permissible deviation of material elongation ? just up to us ?

RE: [ASK] Permissible Deviation of Material Elongation

Am I reading this correctly? You regularly have certs from the mill with %Elongation values 2-5% less than the requirement?

When you say 2-5% does that mean the %E reported is 17% and it should be 22% or do you mean the requirement is 22% and it is 21%. Either could be expressed as 5% low.

When you order a material to a standard, either an industry standard like ASTM or your own company standard, the supplier should send you product that meets all the requirements of that standard. If they have material that does not meet the standard they can ask for a deviation for that lot and you have the ability to determine if that deviation is acceptable for your application. There is no standard acceptable deviation from the requirements as reported on the mil certs.

Bob

RE: [ASK] Permissible Deviation of Material Elongation

In the ASTM/ASME world, the requirements and permitted deviations are clearly defined. Look not only in the applicable standard/specification, but in the parent standard that is referenced therein. For example, A516 PV plate references A20.
Customer specifications may further restrict the limits.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: [ASK] Permissible Deviation of Material Elongation

(OP)

Quote (ironic metallurgist)

In the ASTM/ASME world, the requirements and permitted deviations are clearly defined. Look not only in the applicable standard/specification, but in the parent standard that is referenced therein. For example, A516 PV plate references A20.
Customer specifications may further restrict the limits.

In my case, material we accepted is for alloy steel 41XX, which we used ASTM A29 and ASTM A434, then what is the parent of these standard sir if i may know ?

RE: [ASK] Permissible Deviation of Material Elongation

You're right, I don't think my comment about parent documents applies to SAE alloys in ASTM space (most of which I do not reference frequently - I reside in the pressure vessel and structural worlds).
However the essential point still applies: the information you seek is all found in the ASTM specifications and tech spec (if there is one).
Addressing the technical question, 2-5% deviation in elongation is a very large discrepancy, one that no Code would permit. I know I certainly would not, because it indicates that something went wrong in the manufacture.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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