High strength flange external hexagon
Black carbon steel hexagonal flange DIN6921 Class 10.9 hex flange bolts are primarily fabricated from high – quality carbon steel with specific alloying elements added to achieve the 10.9 – class strength requirements.
Description
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Product Material
Black carbon steel hexagonal flange DIN6921 Class 10.9 hex flange bolts are primarily fabricated from high - quality carbon steel with specific alloying elements added to achieve the 10.9 - class strength requirements. The carbon content in the steel is carefully controlled, usually within a range that, combined with other elements like manganese, silicon, and trace amounts of alloying agents, enables the bolts to meet strict mechanical property standards.
To attain the 10.9 - class strength, the carbon steel undergoes a precise heat - treatment process. This includes annealing to relieve internal stress and refine the grain structure, quenching to increase hardness and strength rapidly, and tempering to adjust the hardness and toughness to an optimal balance. As a result, these bolts can achieve a minimum tensile strength of 1000 MPa and a yield strength of 900 MPa, endowing them with excellent load - bearing capacity and the ability to withstand significant mechanical stresses.
The “black” appearance is typically achieved through a surface treatment process. This can involve black oxide coating, where the steel surface undergoes a chemical reaction to form a thin, black, corrosion - resistant oxide layer. Alternatively, it may be achieved by using black - colored anti - corrosion paints or coatings, which not only provide a certain degree of corrosion protection but also give the bolts their distinctive black color.
Product Models
The product line of these hex flange bolts includes various models categorized according to the DIN6921 standard, size, length, and specific application requirements:
Standard Metric Models: In accordance with the DIN6921 standard, these bolts are available in a wide range of metric sizes. Bolt diameters typically range from M6 to M36, while lengths can vary from 10mm to 300mm or more, catering to different fastening needs in various projects. Standard models feature the characteristic hexagonal flange head design specified by the DIN6921 standard, which provides a larger bearing surface area for better load distribution during fastening, reducing the risk of surface damage and enhancing the stability of the connection.
High - Load - Capacity Special Models: For heavy - duty industrial applications, large - scale construction projects, and critical infrastructure installations, high - load - capacity special models are offered. These bolts usually have larger diameters and thicker flange heads compared to standard models. They are designed to handle substantial tensile and shear forces, making them ideal for securing heavy machinery, large - scale structural components in buildings and bridges, and other applications where high - strength and reliable fastening is crucial.
Custom - Length Models: To meet specific project requirements, custom - length models are available. These bolts can be manufactured with non - standard lengths within the tolerance range allowed by the DIN6921 standard. Custom - length bolts are particularly useful in unique assembly scenarios where standard - length bolts are not suitable, ensuring a precise fit and optimal performance in the application.
Manufacturing Process
The production of black carbon steel hexagonal flange DIN6921 Class 10.9 hex flange bolts involves multiple precise steps while strictly adhering to the DIN6921 standard and quality - control measures:
Material Preparation: High - quality carbon steel raw materials are carefully sourced. Rigorous inspections are carried out on the chemical composition, mechanical properties, and surface quality of the steel to ensure compliance with the requirements for the 10.9 - class strength and the DIN6921 standard. The steel bars or rods are then cut into appropriate lengths according to the specified bolt sizes.
Forming: The carbon steel is formed into the characteristic hexagonal flange head and bolt shank through cold - heading or hot - forging processes. Cold - heading is commonly used for smaller - sized bolts, which is efficient for high - volume production and can accurately form the shape while maintaining dimensional accuracy in line with the DIN6921 standard. For larger - diameter bolts, hot - forging is applied. In this process, the steel is heated to a malleable state and then shaped under high pressure to achieve the required strength and precise dimensions, including the specific shape and size of the hexagonal flange head as defined by the standard.
Threading: After forming, the bolts undergo threading operations. Thread rolling is the preferred method as it creates a stronger thread by cold - working the metal, improving the fatigue resistance of the bolts. Specialized threading dies are used to ensure that the thread pitch, profile, and dimensions precisely match the requirements of the DIN6921 standard, guaranteeing compatibility with corresponding nuts and threaded holes.
Heat Treatment: To achieve the 10.9 - class mechanical properties, the formed bolts are subjected to a series of heat - treatment processes. This includes annealing at a specific temperature to relieve internal stress and refine the grain structure of the steel. Then, quenching is performed by rapidly cooling the heated bolts in a quenching medium, which significantly increases their hardness and strength. Finally, tempering is carried out to reduce the brittleness caused by quenching and adjust the hardness and toughness of the bolts to the optimal level required for the 10.9 - class, ensuring they can withstand the specified loads and stresses.
Surface Treatment: To obtain the black appearance and enhance corrosion resistance, the bolts undergo surface treatment. In the case of black oxide coating, the bolts are immersed in a chemical solution containing oxidizing agents. This solution reacts with the iron in the steel surface to form a thin, black, adherent layer of iron oxide. If black - colored anti - corrosion paints or coatings are used, the bolts are first cleaned thoroughly to remove any contaminants, and then the paint or coating is applied evenly, either by spraying, dipping, or brushing, followed by a curing process to ensure proper adhesion and durability.
Quality Inspection: Every batch of bolts is subject to rigorous inspection in accordance with the DIN6921 standard. Dimensional checks are performed to ensure that the bolt's diameter, length, thread specifications, head size, and flange dimensions meet the standard's precise requirements. Mechanical tests, including tensile strength, hardness, and torque tests, are conducted to verify that the bolts can withstand the specified loads and meet the strength and performance criteria of the 10.9 - class. Visual inspections are carried out to check for surface defects, proper black surface treatment coverage, and any non - compliance with the standard's appearance requirements. Only bolts that pass all quality tests are approved for packaging and distribution.
Surface Treatment Process
The surface treatment of these bolts is crucial for both appearance and performance enhancement:
Black Oxide Coating Process: The black oxide coating process begins with a thorough cleaning of the bolt surface. This involves degreasing to remove any oil, grease, or organic contaminants, usually using solvents or alkaline solutions. Then, pickling is carried out to remove rust, scale, and other inorganic impurities from the surface, typically with an acid solution. After cleaning, the bolts are immersed in a hot black oxide solution, which usually contains sodium hydroxide, sodium nitrite, and other additives. The chemical reaction between the solution and the steel surface forms a thin layer of black iron oxide (magnetite, Fe₃O₄) on the bolt surface. The thickness of this layer is usually very thin, typically in the range of 0.5 - 1.5 microns. After coating, the bolts are rinsed thoroughly to remove any residual solution and then dried. To further enhance corrosion resistance, a post - treatment process may be applied, such as applying a thin layer of oil or wax to fill the pores in the oxide layer and provide additional protection.
Black - Colored Coating Process: When using black - colored anti - corrosion paints or coatings, the pre - treatment is similar to that of the black oxide coating. After the bolts are cleaned and dried, the paint or coating is applied. The application method depends on the type of coating material and the production scale. Spraying is a common method for large - scale production, as it can provide an even and thin coating layer quickly. Dipping is suitable for smaller - scale production or when a thicker coating is required. Brushing may be used for touch - up or in applications where precise coating is needed. After application, the bolts are cured according to the specific requirements of the coating material. This may involve air - drying at room temperature, baking in an oven at a specific temperature for a certain period, or using other curing methods, to ensure that the coating fully hardens and adheres well to the bolt surface, providing long - lasting protection and maintaining the black appearance.
Application Scope
Black carbon steel hexagonal flange DIN6921 Class 10.9 hex flange bolts are widely used in various industries and applications:
Building and Construction: In construction projects, especially in the construction of steel - structure buildings, bridges, and large - scale industrial plants, these bolts play a vital role. They are used for connecting steel beams, columns, and trusses. The 10.9 - class strength ensures that they can withstand the heavy loads and mechanical stresses generated during construction and in the long - term operation of the structures. The hexagonal flange head design distributes the load evenly, reducing the risk of damage to the connected components and enhancing the overall stability of the structure. The black surface treatment not only provides a certain degree of corrosion resistance but also gives the bolts an aesthetically pleasing appearance, which can be an advantage in architectural applications where the bolts may be visible.
Industrial Machinery Manufacturing: In the manufacturing of industrial machinery, these bolts are essential for assembling critical components. They are used to secure heavy - duty parts, such as engine blocks, gearboxes, and frames of large - scale machinery. The high strength of the 10.9 - class bolts allows them to withstand the vibrations, shocks, and heavy loads generated during the operation of the machinery. The black surface treatment helps protect the bolts from the harsh industrial environment, which may contain dust, moisture, and various chemicals, extending the service life of the bolts and ensuring the reliable operation of the machinery.
Automotive and Transportation Industries: In the automotive industry, these bolts are used in vehicle assembly, particularly for securing components that require high - strength fastening, such as engine components, chassis parts, and suspension systems. The 10.9 - class strength ensures the safety and reliability of the vehicle under various driving conditions. In the transportation sector, for trucks, trains, and ships, these bolts are used to fasten critical structural and mechanical components. The black color can also help in camouflage and protection against minor scratches and abrasions during transportation and operation.
Energy and Power Generation: In power plants, including thermal, nuclear, and renewable energy facilities, these bolts are used for fastening equipment, pipes, and structural components. They need to withstand high temperatures, pressures, and mechanical stresses in the power - generation environment. The 10.9 - class strength and the corrosion - resistant black surface treatment ensure the long - term reliable operation of the bolts, reducing the risk of component failures and maintenance costs in these critical energy - production facilities.
Product Advantages
High - Strength and Reliable Fastening: With a 10.9 - class strength rating, these bolts offer excellent tensile and yield strength. They can firmly connect structural components and withstand heavy loads, vibrations, and shear forces, ensuring the stability and safety of engineering structures and machinery in various applications. The full - thread design and the precise manufacturing process based on the DIN6921 standard further enhance the reliability of the fastening.
Optimal Load Distribution: The hexagonal flange head design provides a larger bearing surface area compared to regular hex head bolts. This design distributes the load more evenly during fastening, reducing the risk of surface damage to the connected materials, especially for softer materials or thin - walled components. It also enhances the overall stability of the connection, making it more resistant to loosening under dynamic loads and vibrations.
Good Corrosion Resistance: Although the black surface treatment methods vary, both black oxide coating and black - colored anti - corrosion paints or coatings provide a certain degree of corrosion resistance. The black oxide layer or the coating film acts as a barrier, preventing moisture, oxygen, and other corrosive substances from coming into direct contact with the carbon steel surface, thus extending the service life of the bolts, especially in environments with moderate humidity and corrosive elements.
Standardized Design and Compatibility: Complying with the DIN6921 standard, these bolts offer a standardized design, ensuring compatibility and interchangeability across different projects and industries. The standardized dimensions, thread specifications, and head design allow for easy replacement and the use of standard tools, simplifying the procurement, installation, and maintenance processes. This standardization also reduces the risk of errors in assembly and enhances overall project efficiency.
Aesthetic Appeal: The black appearance of these bolts can provide an aesthetically pleasing look, which can be an advantage in applications where the bolts are visible, such as in architectural and design - focused projects. The uniform black color can also help in identifying and organizing bolts during installation and maintenance, improving work efficiency.
Cost - Effective: These bolts offer a cost - effective solution for high - strength fastening needs. Their standardized production, wide availability in various sizes, and the relatively simple surface treatment processes contribute to overall cost savings in projects, while still providing reliable performance and durability.
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