Tri-Ply Circles
How to Read a Mill Test Certificate (MTC) for Tri-Ply Circles
An MTC is your material’s birth certificate. Most buyers file it unread - here is how to actually read one.
The 6 fields that matter
- Heat/lot number - must match the marking on your circles
- Chemical composition - Cr/Ni percentages confirm 304 vs 201
- Tensile & yield strength (MPa) - typical tri-ply: 345-370 tensile, 246-277 yield
- Elongation % - 40%+ means it will deep-draw without cracking
- Peel strength (N/mm) - bond quality per interface
- Standard referenced - ASTM A240 / EN / GB as applicable
Spotting a fake
- Heat number on the MTC doesn’t match circle markings
- Values identical across months of "different" lots (copy-paste)
- No lab name, signature or accreditation
- Refusal to share the underlying lab report
Make it contractual
Require MTC with every lot in your PO, with the right to third-party retest at the supplier’s cost if values are disputed.
Frequently asked questions
What is an MTC?
A Mill Test Certificate documents a material lot’s chemical and mechanical test results, traceable by heat number.
Should every lot have an MTC?
Yes - reputable suppliers issue one per production lot. No MTC = no traceability.
Have a cookware project in mind?
We manufacture triply cookware and supply tri-ply circles for OEM, private label and distribution. Tell us your specs - we reply with a quote.