Grade Substitution (lower grade shipped than ordered)
The mill certificate matches your spec, but the steel shipped is a cheaper, lower grade — S235 for S355, 201 for 304, Q195 for Q235, A36 for A572.
How the scam works
- 1.Contract and MTC both state the correct, higher grade.
- 2.The supplier produces or sources a visually identical lower grade.
- 3.The certificate is genuine-looking but issued for a different (lower) batch.
- 4.The substitution surfaces only on PMI or mechanical testing — sometimes after a failure.
Red flags to watch for
- Price sits below the realistic cost of the specified grade.
- Supplier claims 'minor composition variation within tolerance' if questioned.
- Heat numbers on the MTC cannot be traced to the shipped batch.
- Resistance to mandatory arrival testing or third-party PMI.
How to protect yourself
- Mandate PMI and mechanical testing on arrival for grade-sensitive steel.
- Cross-check heat numbers and chemistry against the named mill.
- Write clear grade, tolerance and rejection terms into the contract.
- For structural/stainless, never skip independent verification to save cost.
In depth
Grade substitution supplies a lower, cheaper grade against a certificate for a higher one — Q235 sold as S355, or 201 stainless sold as 304. The substitution is invisible to the eye and survives a casual fabrication check, so it typically surfaces only when the part underperforms or fails in service. In load-bearing or corrosive applications that is a safety issue, not merely a commercial one.
Because the certificate and a supplier-chosen sample can both be genuine while the bulk load is not, the metal itself must be tested. Require PMI on the shipped lot tied to the certificate heat numbers, escalate to laboratory chemistry for safety-critical material, and write clear grade-rejection rights into the contract so you have both evidence and a remedy.
Related reading
Frequently asked questions
- What is steel grade substitution?
- The supplier ships a cheaper, lower grade than the one you ordered — for example S235 instead of S355, 201 instead of 304 stainless, or A36 instead of A572. The mill certificate often looks correct because it is issued for a different, lower batch.
- How do I detect grade substitution?
- Mandate PMI (Positive Material Identification) and mechanical testing on arrival for grade-sensitive steel, cross-check heat numbers and chemistry with the named mill, and write clear grade, tolerance and rejection terms into the contract.
Real cases
304 that held no nickel
A food-equipment maker ordered 304 stainless. The MTC and a sample PMI showed 304, but the shipped pipe tested as 201 — a lower-cost stainless with far less corrosion resistance.
Automotive coil that cracked
An auto-parts maker ordered a deep-drawing CRC grade. The MTC from a 'major mill' showed the right spec, but testing revealed commercial-quality CRC unsuitable for stamping; the certificate number was recycled.
Chrome paint on carbon steel
A kitchen-equipment maker ordered 304 stainless. The shipped material was ordinary carbon steel with a thin chrome-like surface treatment; PMI showed 0% nickel — not stainless at all.
Bridge steel two grades too low
A contractor ordered ASTM A572 Grade 50 for a highway bridge. Shipped steel tested as A36 — two grades lower and unsafe for the loads. The MTC was fabricated with untraceable heat numbers.
Worried this is happening to you?
Run your supplier through the structured verification checklist.