Color marking of steel
Steel color marking is an important method used in industrial production to quickly identify steel type, grade, and specifications. By applying a specific color to the steel surface, it enables classification and differentiation, facilitating its storage, transportation, processing, and use. Color marking is intuitive, efficient, and cost-effective, making it widely used in steel production, machinery manufacturing, construction, and other fields. Understanding the rules and meaning of steel color marking is crucial for ensuring the proper use of steel and product quality.
The basic rules for steel color marking are based on the type and grade of steel. While different countries and regions have different standards, they generally follow similar principles. In my country, steel color marking is primarily based on the national standard GB/T 221-2008, “Method for Designating Steel Products,” and related industry standards, which specify specific coloring requirements for different types of steel. For example, carbon structural steel is typically painted with different colors on the ends or sides: Q235 steel is painted red, and Q345 steel is painted blue. Alloy structural steels are painted with different colored rings on the ends: 40Cr steel is painted green, and 20CrMnTi steel is painted yellow. Stainless steel color marking is more complex, requiring not only differentiation between grades but also delivery status. For example, solution-treated austenitic stainless steel is painted blue, while annealed ferritic stainless steel is painted red. The location and size of the color markings are also clearly defined. Generally, the color must be bright, clearly visible, and durable, ensuring quick identification during the steel’s circulation.
The color selection for steel markings is scientific and standardized, with different colors representing distinct meanings to avoid confusion and misidentification. Common colors include red, blue, yellow, green, white, and black, each with its own specific application. Red is often used to indicate higher-strength carbon structural steel grades, such as Q275 steel. Red provides a strong visual warning and is easily distinguishable from other colors. Blue is often used to indicate low-alloy, high-strength structural steel, such as Q355 steel. Blue conveys a sense of stability and reliability, consistent with the performance characteristics of this type of steel. Yellow is often used to indicate alloy structural steel, such as 35CrMo steel, for its striking characteristics and ease of identification. Green is often used to indicate stainless and heat-resistant steels, such as 0Cr18Ni9 steel. Green symbolizes corrosion resistance and environmental friendliness, aligning with the properties of stainless steel. In addition, combinations of two colors are sometimes used to convey more complex information, such as adding stripes or spots of another color to one color to distinguish different specifications or delivery states of the same grade.
The application process for steel color marking significantly impacts its quality and durability, necessitating the use of appropriate coating materials and application methods. The coating should exhibit excellent adhesion, corrosion resistance, and abrasion resistance, ensuring the color maintains its vividness and integrity during storage and transportation. Commonly used coatings include alkyd and epoxy. Alkyd is inexpensive and dries quickly, making it suitable for steel marking in general environments. Epoxy offers strong adhesion and corrosion resistance, making it suitable for marking steel in humid and corrosive environments. Application can be by hand or by spraying. Manual application is suitable for marking small batches and special-shaped steel, offering flexibility but lower efficiency. Spraying is suitable for marking large batches and standardized steel, offering high efficiency and uniform coating. Before painting, the steel surface must be cleaned to remove oil, rust, and scale to ensure a good bond between the coating and the steel surface. After painting, the coating should be completely dry before stacking or transporting to prevent rubbing or contamination of the marking.
Color-coded steel marking plays a vital role in practical applications, improving steel management efficiency while also reducing quality incidents caused by misidentification. In steel production, color-coded steel marking allows for quick differentiation between different steel grades, preventing mix-ups and misdelivery. In raw material warehouses at machinery manufacturers, color-coded steel markings allow for quick identification of required steel, improving material retrieval efficiency. On construction sites, color-coded steel markings allow construction workers to confirm steel specifications and properties, ensuring project quality. For example, bridge construction requires significant quantities of low-alloy, high-strength structural steel. Blue color-coded steel markings allow for quick identification of Q355 steel, preventing the misuse of less-than-strength steel and ensuring bridge safety. However, color-coded steel markings also have limitations. For example, the color can fade or peel over time, making it difficult to identify. Therefore, in practice, other identification methods, such as steel quality certificates and signage, are often needed to ensure accurate steel identification.
With the development of information technology, steel identification methods are constantly innovating. For example, the use of electronic identification such as barcodes and QR codes, combined with color-coded markings, has enabled digital management of steel information. Electronic identification can store more information, such as production batch number, chemical composition, mechanical properties, etc., and can be quickly read using scanning equipment, improving information accuracy and management efficiency. However, as a traditional identification method, color-coded marking still occupies an important position in industrial production due to its intuitive, convenient, and low-cost characteristics. In the future, color-coded marking of steel will be further integrated with electronic identification to form a more complete steel identification system, providing better support for the full life cycle management of steel.
