Flange with six external bolts
DIN6921 hex head flange bolts with yellow zinc plating, full teeth, and no serrations, conforming to ISO4162 and GB5787 standards, are mainly crafted from high – strength alloy steel in grades 8.8, 10.9, and 12.9.
Description
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Product Material
DIN6921 hex head flange bolts with yellow zinc plating, full teeth, and no serrations, conforming to ISO4162 and GB5787 standards, are mainly crafted from high - strength alloy steel in grades 8.8, 10.9, and 12.9.
For Grade 8.8 bolts, the alloy steel typically contains elements such as carbon, manganese, and silicon. After undergoing a series of heat - treatment processes, they can achieve a minimum tensile strength of 800 MPa and a yield strength of 640 MPa, making them suitable for general - to medium - heavy - duty applications where reliable fastening under significant loads is required.
Grade 10.9 bolts are made from alloy steel with more precise control over chemical composition and a more stringent heat - treatment process. They can reach a minimum tensile strength of 1000 MPa and a yield strength of 900 MPa, enabling them to withstand high loads, vibrations, and mechanical stresses, and are often used in critical structural connections in industrial machinery and construction projects.
The highest - grade 12.9 bolts are manufactured from high - quality alloy steel with strict impurity control and optimized heat treatment. They offer a minimum tensile strength of 1200 MPa and a yield strength of 1080 MPa, making them ideal for extremely heavy - duty applications, such as in aerospace components, high - performance automotive engines, and large - scale bridge construction.
The yellow zinc plating is a key surface - treatment feature. Zinc plating involves electroplating a layer of zinc onto the surface of the alloy steel bolts. The addition of specific chemical agents during the plating process imparts a yellow hue to the zinc coating. This zinc layer acts as a sacrificial barrier, corroding preferentially to protect the underlying steel, thereby enhancing the bolt's corrosion resistance.
Product Models
The product line of these hex head flange bolts includes various models categorized according to the DIN6921, ISO4162, and GB5787 standards, as well as size, length, and strength grade:
Standard Metric Models: In line with the relevant standards, 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, depending on specific application needs. Standard models feature a full - teeth design, where the threads extend along the entire length of the bolt shank, ensuring consistent fastening performance throughout. These bolts also have a hexagonal flange head without serrations, providing a larger bearing surface for better load distribution during fastening.
Strength - Graded Models: The bolts come in strength grades 8.8, 10.9, and 12.9. 8.8 - grade bolts are medium - strength models, commonly used in general industrial equipment installation, furniture manufacturing, and light - to medium - heavy construction projects. 10.9 - grade bolts are high - strength models, essential for applications in heavy - duty machinery, large - scale building structures, and transportation equipment where higher load - bearing capacity is required. 12.9 - grade bolts are ultra - high - strength models, specifically designed for critical and high - stress applications in industries such as aerospace, high - end automotive, and large - scale infrastructure construction.
Special - Length and Custom Models: For applications with specific length requirements or unique design needs, special - length and custom models are available. These bolts can have non - standard lengths within the tolerance range specified by the relevant standards. Custom models may also include modifications to the head size, flange thickness, or other dimensions to meet the exact requirements of specialized projects, while still adhering to the core standards for quality and performance.
Manufacturing Process
The production of these bolts involves multiple precise steps while strictly complying with DIN6921, ISO4162, and GB5787 standards and quality - control measures:
Material Preparation: High - quality alloy steel raw materials are carefully sourced to meet the requirements of the specified strength grades and standards. Rigorous inspections are carried out on the chemical composition, mechanical properties, and surface quality of the steel. The steel bars or rods are then cut into appropriate lengths according to the specific size requirements of the bolts.
Forming: The alloy 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. For larger - diameter or high - strength bolts (such as 10.9 and 12.9 grades), 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 per the standards.
Threading: After forming, the bolts undergo threading operations. Since these are full - teeth bolts, threads are created along the entire length of the shank. 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 relevant standards, guaranteeing compatibility with corresponding nuts and threaded holes.
Heat Treatment (for high - strength grades): Bolts of strength grades 8.8, 10.9, and 12.9 undergo heat - treatment processes. This typically includes annealing to soften the steel and eliminate internal stress, quenching to increase hardness and strength, and tempering to adjust the hardness and toughness to the optimal level. The heat - treatment parameters are precisely controlled to ensure that the bolts meet the strict strength and performance requirements of their respective grades as defined by the standards.
Yellow Zinc Plating: The bolts are first thoroughly cleaned to remove any contaminants, oil, or rust. Then, they are immersed in an electroplating bath containing zinc salts and specific chemical additives. An electric current is applied, causing zinc ions to deposit on the bolt surface. The addition of chemical agents during plating imparts a yellow color to the zinc coating. After plating, the bolts may undergo post - treatment processes, such as passivation, to further enhance the corrosion resistance and durability of the zinc coating, ensuring compliance with the relevant corrosion - resistance requirements of the standards.
Quality Inspection: Every batch of bolts is subject to rigorous inspection in accordance with DIN6921, ISO4162, and GB5787 standards. 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 their respective grades. Visual inspections are carried out to check for surface defects, proper yellow zinc plating 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 yellow zinc - plating surface treatment is a key feature that provides both protection and identification for these bolts:
Zinc Plating Process: The zinc - plating process begins with a thorough cleaning of the bolt surface through degreasing and pickling to remove any dirt, oil, or oxide layers. This ensures good adhesion of the zinc coating. The bolts are then immersed in an electroplating bath containing zinc - rich electrolyte solutions. When an electric current is passed through the bath, zinc ions are attracted to the bolt surface and deposit as a metallic layer. The thickness of the zinc coating can typically range from 5 - 15 microns, depending on the application requirements and the standards' specifications, providing a primary layer of corrosion protection.
Yellow Coating Formation: The distinctive yellow color of the zinc coating is achieved by adding specific chemical agents to the electroplating bath. These agents react with the zinc during the plating process to form a thin, colored film on the surface of the zinc layer. This yellow coating not only serves as an aesthetic identifier but also provides additional corrosion resistance by enhancing the passivation properties of the zinc surface.
Post - Treatment: After zinc plating, the bolts may undergo post - treatment processes, such as passivation. Passivation involves immersing the bolts in a chemical solution, usually containing chromates or other passivating agents. This process forms a thin, protective oxide layer on the zinc surface, further enhancing its corrosion resistance and durability. The passivation treatment also helps to stabilize the yellow color of the coating and improve its resistance to fading and abrasion, ensuring that the bolts maintain their appearance and protective properties during use.
Application Scope
DIN6921 hex head flange bolts with yellow zinc plating, full teeth, and no serrations, conforming to ISO4162 and GB5787 standards, are widely used in various industries and applications:
Building and Construction: In construction projects, these bolts are used for various structural connections, including fastening steel beams, columns, and trusses. The different strength grades allow for selection based on the load requirements of the structure. For example, 8.8 - grade bolts are suitable for general building components, while 10.9 and 12.9 - grade bolts are used in critical load - bearing connections of high - rise buildings, bridges, and large - scale industrial plants. The hexagonal flange head design distributes the load more evenly, reducing the risk of surface damage and enhancing the stability of the connections. The yellow zinc plating provides corrosion resistance, protecting the bolts from the elements in both indoor and outdoor construction environments.
Industrial Machinery Manufacturing: In the manufacturing of industrial machinery, these bolts are essential for assembling components, securing equipment frames, and attaching various parts. High - strength grades like 10.9 and 12.9 are used to withstand the heavy loads and vibrations generated during machinery operation. The full - teeth design ensures consistent and reliable fastening throughout the length of the bolt, while the yellow zinc - plated surface resists corrosion from industrial pollutants and moisture, extending the service life of the bolts and the machinery they assemble.
Automotive and Transportation Industries: In the automotive industry, these bolts are used in vehicle assembly, such as attaching engine components, chassis parts, and body panels. The different strength grades can meet the diverse load - bearing requirements of various automotive applications. The yellow zinc plating helps the bolts withstand the harsh operating conditions, including exposure to road salts, moisture, and varying weather conditions. In the transportation sector, for trucks, trains, and ships, these bolts are used for securing various components, ensuring the safety and reliability of the vehicles during operation.
Electrical and Electronics Equipment: In the electrical and electronics industries, smaller - sized bolts are used for securing electrical enclosures, panels, and components. The full - teeth design allows for precise tightening, and the corrosion - resistant yellow zinc plating protects the bolts from the potentially corrosive effects of humidity and electrical environments, ensuring the long - term reliability of the electrical and electronic systems.
General Equipment Installation and Maintenance: For general equipment installation and maintenance tasks in various industries, these bolts offer a reliable and cost - effective fastening solution. Their availability in a wide range of sizes and strength grades, as per the relevant standards, makes them suitable for different types of equipment and applications. The easy - to - identify yellow zinc - plated coating also helps in quickly distinguishing them from other bolts during installation and replacement processes.
Product Advantages
High - Strength and Reliable Fastening: With strength grades 8.8, 10.9, and 12.9, these bolts offer excellent tensile and yield strength, capable of firmly connecting structural components and withstanding heavy loads, vibrations, and shear forces. The full - teeth design ensures consistent and reliable fastening along the entire length of the bolt shank, providing enhanced stability and load - bearing capacity in various applications.
Superior Corrosion Resistance: The yellow zinc - plating provides effective corrosion resistance, protecting the alloy steel bolts from rust and degradation. The zinc layer acts as a sacrificial barrier, and the post - treatment processes further enhance its protective properties. This makes the bolts suitable for use in a variety of environments, including those with moisture, humidity, and mild corrosive substances, extending the service life of the bolts and the components they fasten.
Standardized Design and Compatibility: Complying with DIN6921, ISO4162, and GB5787 standards, 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, and reducing the risk of errors in assembly.
Optimal Load Distribution: The hexagonal flange head without serrations 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, especially on softer materials, and enhancing the overall stability of the connection. It is particularly beneficial in applications where a secure and stable fastening with minimal surface deformation is required.
Easy Identification: The distinctive yellow color of the zinc coating makes these bolts easily identifiable, facilitating quick selection and installation during assembly and maintenance tasks. This visual identification helps prevent mix - ups with other types of bolts, improving work efficiency and reducing the risk of incorrect installations.
Cost - Effective: Offering a balance of performance and cost, these bolts provide a cost - effective fastening solution for a wide range of applications. Their standardized production, availability in various sizes and strengths, and good corrosion resistance contribute to overall cost savings in projects by reducing the need for frequent replacements and maintenance.
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