Material specification vs. material grade - how do they relate? 15

[2muchcoffee]

We are a spring manufacturer. We made springs to a customer’s drawing but they are rejecting them. Their complaint is that we used the wrong material. Their drawing calls out “Music wire per QQ-W-470, spring temper, UNS G-10800, .0220 ± .0004 dia.”

We ordered - and used - music wire per ASTM A228 (replacement for QQ-W-470) which defines the material’s chemical composition. But as pointed out by our customer, the chemical composition of UNS G-10800 is different from the chemical composition prescribed in ASTM A228, as follows:

ASTM A228
Carbon: 0.70 - 1.00%
Manganese: 0.20 - 0.70%
Phosphorous, max: 0.025%
Sulfur, max: 0.03%
Silicon: 0.10 - 0.30%

UNS G-10800
Carbon: 0.75 - 0.88%
Manganese: 0.60 - 0.90%
Phosphorous, max: 0.04%
Sulfur, max: 0.05%
Silicon : "as required"

I’m trying to understand what, to me, is an apparent contradiction. That is, how can they specify music wire to material spec QQ-W-470 (now ASTM A228) that defines the material’s chemical composition limits, while simultaneously specifying it to a UNS category that sets contradictory chemical composition limits?

I’m missing a critical element of understanding here and I don’t know what it is, or who to go to for a clear explanation, or even how to frame a relevant question.

Any ideas or help?

 

[2muchcoffee]

Yep! We're doing that too. This job was the latest from an annual multi-ship PO that was reviewed and quoted last year. Since then we have tightened up our review process due to other in-house audit findings, and are much better at finding, questioning and documenting this sort of thing. We know we have areas that need improvement and are doing so. Customer also knows this. As for scrutiny, they have already ramped up their scrutiny on every level due to new higher-level corporate program improvement. And you know what flows downhill, right? ;-)

 

[redpicker]

Just want to comment that there really is nothing contradictory in the drawing callout. It is possible that the material will meet both requirements, and this is probably what the "new guard" is expecting you to provide. While is it possible that the application does not actually require the restricted Mn content of the UNS specification, as a supplier, you do not know this and it would be wrong for you to just assume they don't understand what they have specified. Perhaps they have knowledge that the lower Mn contents do not perform as well in their applications.

As far as ordering material goes, you can say "Material per ASTM 228 excpet chemistry must be per UNS G-10800".

Of course, it could be possible that things have gotten confused over the years. Do you have access to the QQ-W-470 specification that was active when the original drawing was produced? If you can get a copy, it may be useful to see if the chemical composition listed in the old specification matches what is now in the current ASTM A228. Is it possible that the old QQ-W-470 spec was loose on chemical composition and that the UNS callout was needed to insure the correct material was used? Obviously, when the QQ-W-470 was discontinued the drawing should have been revised to reflect the active specifications, but that didn't happen. All you can do now is to try to get the customer to use current specifications.

Regardless, you will have to negotiate with your customer to resolve this situation to your customer's satisfaction.

rp

 

[2muchcoffee]

Yes, I do have a copy of the original QQ-W-470 spec. The ASSIST website is an invaluable resource for MIL specs and FED specs, and it's all FREE!

Interestingly, the chemistry is very slightly different between the old QQ-W-470 spec and the current ASTM A228 spec, most noticeably for Manganese (old was 0.20% - 0.60%, new is 0.20% - 0.70%). So with the old QQ-W-470 spec there was no Manganese overlap to the UNS chemistry (which is Mn 0.060% - 0.90%), but the newer ASTM spec provides wiggle room (some overlap) for Mn.

I was hoping there might be someone in this forum with mill experience to explain how the two material callouts relate to each other (QQ-W-470 vs. UNS G-10800), and what would our PO need to look like in order to receive compliant material? So far our material suppliers have not provided such expertise.

 

[salmon2]

I will suggest to contact your customer to confirm that they really need QQ-W-470 plus 1080 because the 0.6~0.7 Mn is a bit tight and it can possbily drive up your price to get raw material.

But on the other hand, a range like 0.6~0.9 of 1080 is not the range that steel mills absolutly need to produce 1080. If they pay attention, they can control Mn in that range all day long. I had experience to order mill runs for many years and I can say that the variance of Mn is small within a batch of different heats.

1080 is a plain carbon steel and the only alloying element is Mn. If the steel mill is BOF, they can control it easier than a EAF mill as they have to literally add in Mn to a level versus EAF that they have to balance their different scraps to get the tight range for Mn. So possibly you have to pay a surcharge if you insist on 0.6~0.7 of Mn.

 

[2muchcoffee]

I've just learned that our customer has submitted an ECR to change the drawing material callout to ASTM A228 and remove the UNS G-10800 designation. All of a sudden it's a non-issue, nor our fault.

Hmmm...

Of course, we still have process issues to remediate, but those are already pretty much resolved. In the end, everyone is better and smarter.