| Steel Grade and Strength Level | Confirm whether the product is designed for automotive structural, crash-management, or forming applications. | Common AHSS strength classes include approximately 590 MPa, 780 MPa, 980 MPa, and 1,180 MPa minimum tensile-strength levels. The exact yield strength, tensile strength, and elongation must come from the applicable specification. | Mill test certificate, product standard, grade designation, heat number, and signed technical data sheet. | Do not approve material from the tensile-strength label alone. Match yield strength, elongation, bend performance, and forming requirements with the drawing or application specification. |
| Applicable Standard | Check whether the supplied standard is accepted in the destination market and by the end user. | Possible references include Chinese GB/T standards, ASTM A1008/A1008M for cold-rolled carbon steel sheet, EN 10346 for continuously hot-dip coated flat steel products, and ISO or customer-specific specifications. | Full standard number and edition, compliance statement, chemical composition limits, mechanical-property tables, and deviation list. | Specify one governing standard in the purchase contract. If equivalent standards are proposed, require a written equivalence review before production. |
| Chemical Composition | Verify carbon, manganese, silicon, aluminum, chromium, molybdenum, boron, phosphorus, sulfur, and microalloying additions where applicable. | Composition limits vary by grade. AHSS chemistry is normally controlled to balance strength, weldability, ductility, and processing behavior. | Heat-analysis results, product-analysis results where required, and laboratory test method references. | Set maximum limits for phosphorus and sulfur when weldability and fatigue performance are critical. Check carbon equivalent or equivalent weldability criteria when specified by the end user. |
| Mechanical Properties | Check yield strength, tensile strength, elongation, uniform elongation, total elongation, and work-hardening behavior. | Properties depend on thickness, rolling direction, test method, and grade. A reported elongation value is meaningful only with its gauge length and test standard. | Production-lot test results, transverse and longitudinal values where required, specimen orientation, gauge length, and test temperature. | Use the same test method and specimen direction for supplier qualification and incoming inspection. Avoid comparing elongation figures obtained under different methods. |
| Forming and Ductility | Assess hole expansion, bendability, edge cracking resistance, stretch-forming behavior, and springback risk. | Advanced high-strength grades may have high tensile strength but lower forming margins than mild steel. Hole expansion and bend performance are application-specific. | Forming-limit data, hole-expansion results where applicable, bend-test records, forming simulation data, and sample trial results. | Request trial coils or sheets for stamping validation before mass shipment. Confirm tool radius, cutting clearance, lubrication, and blank direction. |
| Thickness and Dimensional Tolerance | Verify nominal thickness, width, length, flatness, edge condition, camber, and thickness variation across and along the coil. | Dimensional tolerances must follow the agreed product standard and purchase specification. Tighter tolerances may require a special agreement. | Dimensional inspection report, calibration records, coil map, and measured values at defined sampling locations. | State nominal dimensions, tolerance class, measurement method, and acceptance rules in the contract. Confirm whether thickness includes coating mass. |
| Surface Condition | Inspect scratches, dents, roll marks, rust, scale, pits, stains, oil residues, and surface waviness. | Surface-quality requirements vary between exposed automotive panels, interior parts, structural components, and general engineering applications. | Surface-quality class, approved reference samples, inspection photographs, and pre-shipment inspection report. | Define acceptable and unacceptable defects with photographs or physical samples. Specify whether minor cosmetic defects are permitted on non-exposed surfaces. |
| Coating Type and Mass | For coated AHSS, confirm zinc, zinc-iron, zinc-aluminum, or other coating type, surface treatment, and coating designation. | A designation such as Z100 commonly represents a nominal total coating mass of 100 g/m² on both sides, subject to the applicable standard and its tolerance rules. | Coating certificate, coating-mass test results for each side where required, surface-treatment information, and coating adhesion results. | Specify coating type, nominal mass, minimum local mass if applicable, oiling or passivation requirements, and whether the material will be painted or welded after delivery. |
| Weldability | Review resistance spot welding, laser welding, arc welding, heat-affected-zone softening, and process-window requirements. | Weldability is affected by chemistry, coating, thickness, electrode condition, current, weld time, and force. Higher-strength grades may require narrower process control. | Welding-process recommendation, weld-lobe data where available, carbon-equivalent information if specified, and customer validation results. | Conduct welding trials using the actual thickness combination and coating condition. Confirm minimum nugget size and weld-quality criteria with the end user. |
| Microstructure and Metallurgy | Confirm whether the grade is dual-phase, complex-phase, martensitic, transformation-induced plasticity, or another AHSS family. | Microstructure directly influences strength, ductility, hole expansion, forming behavior, fatigue, and fracture mode. | Metallographic report, representative micrographs, phase description, heat-treatment route, and consistency data between heats. | Use the same grade family and microstructural target during qualification. Do not substitute a higher-strength grade without confirming forming and welding compatibility. |
| Quality-System Capability | Evaluate process control, traceability, laboratory capability, calibration, nonconformance handling, and corrective-action procedures. | Automotive supply chains commonly expect documented quality management and lot-level traceability. Certification alone does not prove product conformity. | Quality-management certificate, process-control plan, inspection plan, calibration list, audit records, and sample corrective-action report. | Perform a remote or on-site supplier audit before the first commercial order, especially for safety-critical or crash-relevant components. |
| Inspection and Testing | Decide which tests will be performed by the supplier, an independent inspector, and the importer. | Typical checks include chemical analysis, tensile testing, dimensions, surface inspection, coating mass, flatness, and packaging condition. | Approved inspection and test plan, sampling level, test standards, laboratory accreditation details, and release procedure. | Make pre-shipment inspection a contractual requirement. For critical material, retain samples and arrange independent verification of selected coils or sheets. |
| Traceability | Ensure every coil, slit coil, or sheet bundle can be linked to a heat, production date, test report, and packing record. | Heat number and coil number should remain identifiable after slitting or cutting whenever practical. | Coil list, bundle labels, heat numbers, barcodes or QR codes, mill certificate, and packing list cross-reference. | Reject mixed or unclear identification. Require advance approval for any relabeling, coil splitting, or consolidation of lots. |
| Packaging and Corrosion Protection | Check export packaging, edge protection, wrapping, skids, coil orientation, lifting points, and moisture protection. | Steel is vulnerable to mechanical damage and wet-storage corrosion during ocean transport, particularly under humid conditions. | Packing specification, loading photographs, container or vessel loading record, moisture-protection details, and weight verification. | Use packaging suitable for ocean freight and the destination climate. Agree on coil eye orientation, maximum package weight, and handling markings before production. |
| Shipping and Import Documents | Verify that commercial, technical, customs, and transport documents are consistent. | Common documents include commercial invoice, packing list, bill of lading, certificate of origin, mill test certificate, insurance document where applicable, and customs classification information. | Draft document set before shipment, harmonized-system classification confirmation, country-of-origin information, and required import permits. | Check destination-country duties, trade remedies, safeguard measures, and marking requirements before signing the purchase order. |
| Commercial Terms and Risk Allocation | Clarify specification hierarchy, inspection rights, claims procedure, delivery terms, payment milestones, and remedies for nonconforming material. | Incoterms define responsibilities for transport, insurance, customs clearance, and risk transfer; they do not define product quality. | Signed purchase specification, quality agreement, Incoterms rule and named place, inspection clause, warranty period, and dispute-resolution terms. | Link final payment to document approval and inspection results where commercially feasible. Define replacement, credit, sorting, and return procedures for nonconforming goods. |
| Trial Order and Supplier Approval | Use a controlled qualification process before placing a full-volume order. | A practical sequence is document review, sample testing, forming or welding trial, pilot shipment, incoming inspection, and production approval. | Supplier questionnaire, approved sample report, trial-order results, corrective-action log, and final approval record. | Start with a limited, traceable trial lot. Approve regular supply only after mechanical, dimensional, surface, processing, packaging, and documentation results meet the agreed requirements. |
