Gemma,
A few questions about the process overall:
- Do you perform any heat treatment on this material after stamping?
- Does the new supplier use a different melting/conversion practice than the previous suppliers did?
- Is the new supplier reputable (and/or located in a reputable country) such that you are confident that whatever capability testing they may have reported on the MTR is accurate?
- Has your stamping process (or any other relevant internal processes, such as test specimen location) changed at all?
My first inclination is to conclude that the higher levels of Si and Cu shouldn't hurt your strength; they are elevated but not terribly high and I agree with your assessment that if they were to do anything, it'd be to hurt ductility which you state has not occurred. The only strengthening element you're really lower in here is carbon (which is also going to be the most impactful one); the others like Nb/Cr/Ni/Mn are present in greater quantities than the historical heats although their impact on strength will depend on your heat treat condition.
Conclusion: provided that the only relevant variable to have changed is chemistry, I would conclude that the lower carbon content is responsible and I'd suggest that you specify a minimum of 0.06% for future heats (or whatever other number would be supported by other historical data you might have).
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Sean Piper
Product / Process Metallurgist
Ellwood Texas Forge Houston
Houston TX
(713) 434-5138
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Original Message:
Sent: 07-28-2021 05:43
From: Gemma Bertran
Subject: Steel Quality S550MC
Dear all,
We buy S550MC material to our cold stamping process, to obtain steel flat sheets with min Rm required of 25KN. Normally we buy material with 600 Rm min and it is enough to obtain our parts with the mechanical properties required. Nevertherless, we now have problems with a new supplier and we do not see where is the problem. I attach the chemical composition for your analysis. Is the different Si content detrimental? It is under the quality limit but higher than the material we normally use. Wich could be the Si role here?
Thanks a lot for your time.
Cert | Re | Rm | A% | C | Mn | P | S | Si | Al | Ni | Nb | V | Cr | Cu | N | Ti | Pb | Mo | Sn | B | Ceq | CET | CEV |
46260 | 556 | 627 | 25 | 0,061 | 0,790 | 0,007 | 0,003 | 0,010 | 0,040 | 0,040 | 0,048 | 0,010 | 0,020 | 0,020 | 0,005 | 0,060 | | | | 0,000 | 0,2 | 0,143 | 0,203 |
26776 | 622 | 662 | 10,2 | 0,063 | 1,230 | 0,017 | 0,001 | 0,024 | 0,035 | 0,000 | 0,052 | 0,002 | 0,000 | 0,000 | 0,000 | 0,001 | 0,000 | 0,000 | | 0,000 | | 0,186 | 0,268 |
46916 | 610 | 663 | 21,4 | 0,043 | 1,607 | 0,010 | 0,003 | 0,317 | 0,030 | 0,067 | 0,043 | 0,003 | 0,060 | 0,132 | 0,005 | 0,058 | | 0,012 | 0,010 | 0,000 | | 0,216 | 0,339 |
Gemma Bertran VidalConsultora Industrial
Mb. (+34) 646190321