1. Introduction
For fastener export business, Mill Test Certificate (MTC / Material Test Certificate) is an essential technical document recognized by overseas engineers, supervisors and third-party inspectors. Many shipments pass visual inspection and dimension check, but get rejected directly because of inconsistent MTC information.
The most frequent issue is mismatch between heat number on certificate and the marking on bolts or packing label. Once the overseas supervisor raises objection, the whole batch may be detained or returned, causing huge logistics and time loss. This article sorts out standardized MTC audit points for bolt export.
2. What is MTC (Mill Test Certificate) for fasteners
MTC is the test report issued by steel mill or fastener factory, which records raw material heat information, chemical composition, mechanical test data, product standard and batch information. It proves that the goods comply with the ordered material grade and strength class.
2.1 The difference between MTC and ordinary COA
MTC supports project submission and third-party inspection, with formal signature and factory stamp. COA is a simple analysis sheet, which is usually only used for general non-civilian non-pressure parts. For high-strength bolts, stud bolts and pressure vessel fasteners, most European, American and Australian projects require a formal MTC.
3. Core check items of bolt MTC
Inspection Item | Acceptance Requirement |
Heat Number | Must be fully consistent with heat mark on bolts, packaging tag and packing list; one heat number corresponds to one independent test record |
Material Grade & Strength | Match purchase order: e.g. B7, 10.9, A2-70, A4-80; cannot use substitute material without written approval |
Applicable Standard | GB / ASTM / DIN / ISO standard must be same as customer order; mixed standard description is not allowed |
Chemical Composition | C, Mn, P, S, Si and alloy elements within the standard specified range |
Mechanical Property | Tensile strength, yield strength, elongation, hardness meet requirements of the grade |
Issuer Information | Factory name, signature, official stamp, test date must be complete; hand-altered MTC is invalid generally |
Product Description | Product type: hex bolt, stud bolt, nut, thread rod; size, thread type should match order |
Heat number on certificate does not match the marking on bolt / package. This is the top rejection reason in overseas project audit.
MTC shows one material, but actual goods use another cheaper grade for replacement.
Test data is copied from other batches; test date is later than production date.
Missing signature or official stamp; only a simple excel sheet without certification.
Mixed multiple heat numbers in one MTC without separate test records.
The standard version is outdated and not accepted by the project specification.
5. Standard MTC review workflow before shipment
Step 1: Confirm customer requirements in advance. Check whether the customer requires EN 10204 3.1 / 3.2 certificate. Step 2: Compare order sheet, packing mark and MTC heat number one by one. Step 3: Cross check material grade, strength class and referenced standard. Step 4: Verify chemical and mechanical test data against corresponding standard limit. Step 5: Check signature and stamp validity; avoid modified or erased content. Step 6: Save MTC file together with packing list and commercial invoice for customer submission.
6. FAQ
Q1: What is the difference between 3.1 and 3.2 MTC? A: EN10204 3.1 certificate is certified by manufacturer’s own inspection department. 3.2 needs independent third-party witness and signature, widely used for pressure vessel and critical equipment fasteners.
Q2: Can we use one MTC for multiple heat numbers? A: Not recommended for engineering projects. Overseas supervisors usually require independent MTC for each heat number.
Q3: If heat number printed on bolt is faint, will MTC be rejected? A: If the heat mark cannot be identified on fasteners, even a correct MTC may be challenged. Clear permanent marking is necessary.
