Cold rolled coil surface quality inspection standards: comparison between ISO3574 and GB/T708

In the steel manufacturing and processing industries, cold-rolled steel coil is widely used in the automotive, home appliance, electronics, and construction industries due to its excellent surface quality, high dimensional precision, and superior mechanical properties. Its surface quality directly determines the quality and value of the final product. Therefore, familiarity and understanding of relevant international and national standards are crucial. This article will provide an in-depth comparison and analysis of two authoritative standards: International Standard ISO 3574 and Chinese National Standard GB/T 708, to help you make more informed decisions in production, procurement, and quality control.

I. Standard Overview and Positioning
GB/T 708-2006 "Cold-rolled Steel Sheet and Strip - Dimensions, Shape, Weight, and Permissible Deviations"

Positioning: This is a Chinese product standard. It not only specifies surface quality requirements for cold-rolled steel sheet and strip, but also, more importantly, defines technical parameters such as dimensions, shape, theoretical weight, and their permissible deviations. Surface quality is only one aspect of its coverage.

Application Scenario: Primarily applicable to domestic trade, production, and acceptance, it serves as the most basic and commonly used technical basis for cold-rolled steel coil products in China.

ISO 3574:1999 "Cold-rolled carbon steel sheet for commercial and stamping purposes"

Positioning: This is an internationally recognized product standard. It comprehensively specifies the classification, chemical composition, mechanical properties, dimensional tolerances, and surface quality requirements for cold-rolled carbon steel sheet for commercial and stamping purposes.

Application: Suitable for international trade and recognized by numerous countries and companies. This standard is often used as the acceptance criteria for export products or high-end manufacturing.

III. How to Select and Apply: Advice for Practitioners
Domestic Market and Procurement:

GB/T 708 is preferred. It is the cornerstone of domestic contracts and is familiar to and implemented by all domestic manufacturers. When signing contracts, be sure to specify the surface quality grade (e.g., requiring FC grade surface) and use this as the acceptance criteria.

International Trade and Export:

ISO 3574 or other international standards specified by the buyer (such as EN, ASTM, or JIS) must be used. ISO 3574 is a universal international standard that effectively avoids trade disputes caused by discrepancies in standards. Inquiries and contracts should clearly specify the brand name and corresponding surface quality expectations.

High-end manufacturing (such as automotive exterior panels and high-end appliance panels):

Even in China, many high-end manufacturers will reference or draw upon the more stringent defect determination criteria in ISO 3574, based on GB/T 708, or even establish even stricter internal control standards. Understanding the detailed requirements of the ISO standard is crucial.

Quality Inspection and Acceptance:

Regardless of which standard is adopted, a standardized visual inspection process should be established, including standardized illumination, viewing distance, and angle. For controversial defects, ISO 3574 provides more detailed textual basis for determination.

IV. Conclusion
In summary, both GB/T 708 and ISO 3574 are essential standards for the cold-rolled coil industry.

GB/T 708 is a foundational product standard for the Chinese market, emphasizing integrated design (size, shape, and surface), with concise and practical regulations.

ISO 3574 is a comprehensive product standard for the global market. Its surface quality requirements are more detailed and scientific, closely linked to material mechanical properties, and enjoy greater international acceptance.

For businesses, "adhering to national standards internally and relying on international standards externally" is a fundamental principle. A thorough understanding of the differences and key focuses of the two standards can help companies take the initiative in quality control, cost management, and market development, ensuring that products meet the expectations of diverse customer groups and enhancing market competitiveness.