The Mill Test Certificate (MTC), also called a Certificate of Compliance or Inspection Certificate, is a legal document that must be thoroughly verified upon receipt of the material. Key information to check includes:
1. Material Grade and Standard: Confirming it states Q355B and references the correct material standard (GB/T 1591-2018) and product standard (GB/T 706-2016).
2. Traceability Information: Heat Number (Melt Number) and Batch/Lot Number. These are the primary keys for traceability. The certificate number and date of issue are also important.
3. Chemical Composition: The table showing actual results for C, Si, Mn, P, S, and other specified elements. Verify they are within the limits for Q355B. Crucially, check the calculated Carbon Equivalent (CEV or Pcm) value.
4. Mechanical Properties: Actual test results for: Yield Strength (ReH), Tensile Strength (Rm), Elongation (A) – verify they meet the minimums for the relevant thickness. Charpy Impact Energy (KV2) – confirm the test temperature (+20°C) and that the average value is ≥34J. Bend Test Result – typically stated as "sound" or "no cracks".
5. Product Description: Description of the product (e.g., "Hot-rolled H-beam"), dimensions (height, flange width, web thick., flange thick.), length, and quantity.
6. Test Details: Identification of the test piece location (e.g., from web end), orientation (longitudinal), and the testing standards used (GB/T 228.1, GB/T 229, etc.).
7. Manufacturer Information: Full name and address of the producing steel mill.
8. Statement of Compliance: A clear declaration that the material complies with the specified standards, signed or stamped by the mill's authorized inspector. The verifier should cross-check the heat/batch numbers against the markings on the beams themselves (usually painted or tagged). Any discrepancies or values out of specification should be immediately flagged with the supplier. This certificate is essential for quality records and may be required by building authorities or the client's inspector.