Must-Read for Shipbuilding Steel Plate Purchasing: How to Read an MTC (Mill Test Certificate)
Keywords: MTC interpretation, material certificate verification, shipyard quality control, classification society approval, steel plate acceptance
For shipyard QC personnel, verifying that each batch of marine steel plates matches its MTC (Mill Test Certificate) is the first and most critical step in ensuring the project passes class inspection. A compliant MTC is not just proof of steel quality; it is the core document reviewed by classification society surveyors.
This guide breaks down the key elements of an MTC and provides a field-ready checklist to help you quickly identify problematic certificates and avoid project delays caused by documentation issues.
What is an MTC and Why is it Critical?
An MTC is the quality assurance document issued by the steel mill, recording:
Security and authentication are crucial
Chemical composition (confirming compliance with class society rules)
Toughness at low temperatures
Mechanical properties (actual values for yield, tensile, elongation, impact, etc.)
Differences in corrosion resistance
Traceability information (heat number, batch number, plate number)
Endorsement (classification society surveyor stamp or approval number)
Key Elements of an MTC: Quick Reference Table
| Element | What to Look For | Common Issues | Example of Compliance |
|---|---|---|---|
| 1. Class Society Logo & Approval No. | Clear class society logo (CCS/ABS/LR/DNV) and Works Approval Number or surveyor authorization. | No logo; only "meets standard" wording without approval number. | "Approved by CCS – Works Approval No. XX-XXXX" + surveyor signature/electronic stamp. |
| 2. Heat Number & Batch Number | Unique identifiers for the batch: Heat No. and Batch No. | Missing heat number; mismatched with plate stamp. | Clearly printed: Heat No.: 2412-XXXX; Batch No.: 2025-001. |
| 3. Chemical Composition | Percentages of C, Si, Mn, P, S, etc. Must meet both minimum and maximum class society limits. | Element exceeds limit (e.g., S ≥ 0.035%); actual values not shown. | C: 0.17%, Si: 0.25%, Mn: 1.05%, P: 0.018%, S: 0.012%. |
| 4. Mechanical Properties | Actual values for yield strength, tensile strength, elongation, and impact energy (if required) vs. specified limits. | Actual below required; impact test missing when required. | Yield: 285 MPa (≥235); Tensile: 460 MPa (400-520); Elongation: 26% (≥22%). |
| 5. Dimensions & Quantity | Thickness, width, length, number of plates, and total weight of the batch. | Dimensions mismatch with physical plates; quantity discrepancy. | Thick: 12mm, Width: 2400mm, Length: 12000mm, Pcs: 15, Net Weight: 42.3 MT. |
| 6. Surveyor Stamp | Critical: Must have class society surveyor's signature or electronic stamp and date of witnessing. | Missing stamp; stamp from wrong society (e.g., LR stamp on CCS certificate). | CCS surveyor handwritten/electronic signature + stamp + date. |
| 7. Traceability Statement | Clear statement that "the material identified in this certificate matches the plates and complies with [class society] rules." | No traceability statement; vague wording. | "The above results are for the material identified, which complies with the requirements of CCS Rules for Materials and Welding." |
On-Site Verification: Three-Step QC Process
Step 1: Four-Point Document-to-Plate Match
When plates arrive, QC should perform these four checks during unloading:
| Check | Action | Pass Criteria |
|---|---|---|
| Heat Number | Compare the Heat No. on the MTC with the steel stamp on each plate (side or end). | Exact match; no omission or alteration. |
| Class Society Marking | Check each plate for clear class society stamp (e.g., CCS, ABS, LR, DNV). | Stamp is legible and matches the class society shown on the MTC. |
| Dimensions | Randomly measure thickness and width (minimum 10% of plates, at least 3 plates). | Measured values within MTC tolerance (typical thickness tolerance: -0.3/+0.5mm). |
| Quantity & ID | Count plates; verify unique plate number (if applicable) against MTC. | Quantity matches; plate numbers align with MTC list. |
Step 2: Data Validity Verification
Are chemical and mechanical values within specification?
Compare against the class society requirements in your purchase spec (e.g., CCS Grade A: C ≤ 0.21%, yield ≥ 235 MPa). Confirm all actual values are neither below minimum nor above maximum (some elements above max may not affect strength but can impact weldability).
Does impact testing meet requirements?
If the project requires low-temperature impact (e.g., CCS A requires 0°C longitudinal impact ≥ 27J), verify that the MTC shows impact test results and that the average of three specimens ≥ 27J, with no single value below 20J.
Step 3: Document Completeness Confirmation
Is the MTC an original or certified copy?
Most class societies require original hard copy with shipment (or a certified electronic version). Photocopies or non-certified scans are generally not accepted by surveyors.
Does the MTC have the mill's quality stamp?
A valid MTC must have the mill's official QA stamp and the signatory's name.
| Issue Type | Example | Risk Level | Recommended Action |
|---|---|---|---|
| Heat Number Mismatch | Heat No. on MTC differs from plate stamp. | Critical | Reject. Immediately contact supplier; demand correct MTC matching physical plates. |
| Missing Surveyor Stamp | MTC has mill stamp only, no class society surveyor signature/electronic stamp. | Critical | Reject. Such certificates will fail class inspection. Demand properly endorsed certificate. |
| Mechanical Properties Out of Spec | Yield or elongation below minimum required. | Critical | Reject. Request third-party retesting. If still non-conforming, return the batch. |
| Chemical Composition Out of Spec | P or S content exceeds class society limit. | Moderate | Depending on severity: if marginal, consult surveyor for possible acceptance; if clearly out of spec, reject. |
| Dimensions/Quantity Mismatch | Actual thickness or number of plates differs from MTC. | Moderate | Pause unloading; confirm actual shipping list with supplier; request corrected or supplementary MTC. |
| Impact Values Missing | Impact required but not shown on MTC. | Moderate | For standard Grade A with no low-temperature requirement, may be acceptable. For cold-service applications, must request impact report. |
| Blurry or Altered Document | Text unclear; alterations without countersignature; electronic stamp illegible. | Low-Moderate | Request clear original copy. Any alteration without stamp/initial is invalid. |
QC Personnel's MTC Checklist (Printable)
Use this checklist for every incoming batch:
Class Society Logo & Approval No.: Clear CCS/ABS/LR/DNV marking with approval number.
Heat Number Match: Heat No. on MTC matches stamp on every plate.
Chemical Composition: C, Si, Mn, P, S all within specification limits.
Mechanical Properties: Yield, tensile, elongation actual values meet or exceed minimum.
Impact Properties (if required): Average ≥ 27J, no single value < 20J.
Dimensions & Quantity: Thickness, width, length, and number of plates match physical inspection.
Surveyor Stamp: Legible class society surveyor signature or electronic stamp.
Mill QA Stamp: Official mill quality stamp and signatory.
Traceability Statement: Explicit statement of compliance with the relevant class society rules.
Document Status: Original or certified electronic copy; no unverified alterations.
All items pass → Release for unloading and archive MTC.
Any "Critical" item fails → Stop unloading; immediately notify procurement and supplier.
How We Help You Avoid MTC Risks
As a specialized marine steel supplier, we understand that document-to-product consistency is your top priority. We therefore commit to:
Pre-shipment Review: Before dispatch, we send high-resolution scanned MTCs for your advance review-allowing your QC to verify heat numbers, specifications, and data before steel arrives.
Stamp Confirmation: We provide photos of plate stamps alongside the MTC for traceability.
Surveyor Coordination: If required, we can arrange pre-shipment inspection by CCS/ABS/LR/DNV surveyors at the mill or warehouse, providing endorsed MTCs ready for yard acceptance.
Full Documentation Package: MTC originals, packing list, certificate of origin, and other documents travel with the shipment, ensuring immediate inspection upon arrival.
why choose us?
We promise to provide genuine and verifiable factory certification certificates from the China Classification Society (CCS A steel) and product inspection certificates along with the goods. This is a crucial requirement for the shipyard's warehouse acceptance process.
Common specifications (CCS A 6-40mm) are in ample supply and can be cut to any length as per customer requirements. This feature helps shipyards reduce waste from leftover materials and lower procurement costs.
Based on the size of the order and the history of cooperation, we can offer competitive payment terms to help the shipyard optimize its cash flow.
one-stop solution
professional team
high quality
Choose YUXIN steel group, and what you purchase is not merely the steel plates, but also a complete warranty system and a sense of responsibility.
Our address
Tianjin, China
Phone Number
(86)-15937221771(WeChat)
(86)-15837212056(WhatsApp)
info@chinasteelcompany.com
FAQ
01.How are the names of the ship plates determined? For example, what does CCS A mean?
A: Indicates that the strength level is of general strength. The general strength steel plates are divided into four grades: A, B, D, and E. The main difference lies in the test temperature for impact toughness (grade A at 0°C, grade B at 20°C, grade D at -20°C, and grade E at -40°C).
02.When purchasing the ship plates, what documents can you provide?
Traceability: The furnace number and batch number on the certificate must be consistent with the physical markings on the steel plate.
Data: It must include actual measured data such as chemical composition, mechanical properties (yield, tensile strength, impact value), etc.
03.What is the minimum order quantity?
04.Can you provide cutting and processing services?
China one-stop steel processing procurement
Through years of understanding and precipitation of steel, Yuxin Group has now become a mature steel processing and manufacturer, providing various products for many construction companies and steel structure companies around the world. Thanks to Yuxin Group's professionalism and integrity, it has become a world-renowned enterprise.
