If your supplier uses the wrong steel grade or uncertified raw materials, you could be held accountable by your customer. I’ve been there—it caused delays, lost trust, and financial losses.
To ensure suppliers use certified raw materials, you must require Mill Test Reports (MTRs), traceability, and supplier audits. This layered approach protects your supply chain from non‑compliance and poor‑quality imports.
It’s not just about asking for a certificate. Let me walk you through how to verify raw material certification step by step—and avoid future headaches.
What certifications to request?
I once received a shipment of machined parts where the supplier simply said, “It’s the correct material.” No proof, no certificate. I had to send the parts for third-party testing, and they failed.
You should always ask for a Mill Test Report (MTR) to confirm chemical and mechanical properties, and a Certificate of Conformance (CoC) to validate compliance with customer specifications. Ideally, demand certification per EN 10204 Type 3.1 or 3.2 to ensure traceable, standards-compliant material.
Common Certifications for Custom Steel Parts
| Certificate Type | Purpose | Issued By | Key Standards |
|---|---|---|---|
| Mill Test Report (MTR) | Verifies chemical & mechanical properties | Raw material mill | ASTM, ASME, EN 10204 |
| Certificate of Conformance (CoC) | Confirms compliance with specs | Supplier or manufacturer | Customer-specified |
| EN 10204 3.1 | MTR verified by mill QA | Mill QA Department | EN standard |
| EN 10204 3.2 | Independent third-party verification | Mill & external inspector | EN standard |
MTRs must show batch or heat numbers, along with chemical composition and physical test results. Without these, there’s no proof the steel used matches the contract requirements. If you’re in aerospace or automotive sectors, you'll also need suppliers certified under AS9100 or IATF 16949.
How to verify material traceability?
One of my U.S. customers needed parts for a defense-related application. The supplier provided certificates, but none matched the actual batch codes on the product. We had to re-produce everything.
Always check that batch or heat numbers on the MTR match those on the final parts. Material traceability must link each part back to the original mill source. Refer to ISO traceability audit guidelines for best practices in traceability assurance.
Steps to Verify Traceability
- Request MTRs with heat numbers.
- Confirm each part or raw material label includes the heat number.
- Ensure labels, MTRs, and packing lists match.
- Cross-check production records from the supplier.
Traceability Contract Clauses
| Requirement | Description | Where to Apply |
|---|---|---|
| Heat number on part/packaging | Unique identifier linked to MTR | All shipments |
| Lot/batch number linkage | Tracks manufacturing date & source | Contract & invoice |
| Material source declaration | Declares raw material origin | Supplier agreement |
| Record retention clause | Supplier must keep records for X years | Purchase terms |
Traceability reduces risk by enabling root-cause identification and supports compliance with U.S. import regulations like SIMA or Section 232 administered by CBP.
Should raw material audits be done?
In the past, I avoided factory visits to cut costs. That was a mistake. When things went wrong, I had no visibility into their sourcing or quality systems.
Yes — supplier material audits help you verify procurement practices, ensure quality documentation exists, and assess how certified materials are stored separately from uncertified ones.
Types of Raw Material Audits
| Audit Type | What It Covers | Recommended For |
|---|---|---|
| On-site audit | Physical review of supplier documentation, sourcing, and QA | High-risk or large orders |
| Virtual audit | Remote review via video or document sharing | Moderate orders or tight budgets |
| Third-party audit | Independent verification | Aerospace, defense, regulated sectors |
Audit teams should check:
- Sourcing records and raw material invoices
- MTR record-keeping process
- Quality manual and ISO 9001 procedures
- Material rejection history
- Testing equipment calibration
How to handle material non-compliance?
We once received flanges that failed salt spray tests despite being labeled stainless steel. A lab test revealed carbon steel was used. The supplier denied responsibility.
When material non-compliance is found, file a Non-Conformance Report (NCR), require root cause analysis, and initiate corrective action. See industry-standard NCR handling practices for a structured approach.
Response Plan for Non-Compliance
| Action | Description | Timeline |
|---|---|---|
| Issue NCR | Document issue, attach photos, MTRs | Within 1 day of discovery |
| Request Root Cause Analysis | Ask supplier to investigate and report | Within 3 days |
| Review Corrective Action Plan | Ensure plan addresses root cause | Within 7 days |
| Enforce Warranty or Reject Clause | Rework or reject at supplier cost | As per contract |
Contract Recommendations:
- Warranty against non-certified materials
- Right to audit and test
- Liability for downtime
- Payment withholding until resolution
Also, randomly test shipments using spectrochemical analysis to catch counterfeit materials early.
Conclusion
Always ask for MTRs, verify traceability, audit suppliers, and prepare for non-compliance. Certified raw materials protect your product quality and your customer relationships.
Footnotes
[1] https://www.asminternational.org – Technical resource on Mill Test Reports and metal certification standards.
[2] https://www.iso.org – ISO definition and role of Certificate of Conformance in international supply chains.
[3] https://www.bsigroup.com – Official guide comparing EN 10204 Type 3.1 vs Type 3.2 certification.
[4] https://www.qualitymag.com/articles/96894 – Overview of AS9100 and IATF 16949 standards for supplier qualification.
[5] https://www.iso.org/news/ref2645.html – ISO guidance on material traceability and supply chain audits.
[6] https://asq.org/quality-resources/auditing – ASQ resource on supplier audits and quality verification procedures.
[7] https://www.qualitymag.com/articles/96927 – Standard procedures for issuing and resolving non-conformance reports (NCRs).
