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ระดับ 8.8
These structural bolts primarily utilize stainless steel as the base material, which endows them with excellent corrosion resistance and durability.
Description
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Product Material
These structural bolts primarily utilize stainless steel as the base material, which endows them with excellent corrosion resistance and durability. Stainless steel grades commonly employed include 304 and 316. Grade 304 stainless steel offers good general - purpose corrosion protection, making it suitable for indoor and many outdoor applications with moderate environmental exposure. Grade 316 stainless steel, containing a higher proportion of molybdenum, provides enhanced resistance to harsh chemicals, saltwater, and extreme conditions, making it the preferred choice for marine, chemical, and coastal construction projects.
The “HDG” in the product name refers to Hot - Dip Galvanizing (HDG), an additional protective treatment. After the stainless - steel bolts are formed, they are immersed in a molten zinc bath at around 450 - 460°C. The zinc reacts with the surface of the stainless steel to form a series of zinc - iron alloy layers, followed by a pure zinc outer layer. This thick and durable galvanized coating further enhances the corrosion resistance of the bolts, providing an extra layer of protection against the elements and extending their service life in various harsh environments.
Product Models
The product line of ASTM A325/A325M HDG stainless - steel full/half - thread heavy hexagon structural bolts encompasses various models categorized according to the ASTM standards, along with size, thread type, and load - bearing capacity:
Standard Metric and Imperial Models: In line with ASTM A325 (imperial) and ASTM A325M (metric) standards, these bolts are available in a wide range of sizes. For the imperial system, diameters typically range from 1/2" to 1 - 1/2", while in the metric system, they range from M12 to M36. The length of the bolts can vary from 2" (or 50mm) to 12" (or 300mm) or more, depending on specific application requirements. Standard models feature either full - thread or half - thread designs. Full - thread bolts have threads along the entire shank length, providing consistent fastening performance, while half - thread bolts have threads on only part of the shank, which is beneficial for applications where a non - threaded portion is required to reduce friction or for specific load - distribution needs.
High - Load - Capacity Models: Engineered for heavy - duty structural applications, high - load - capacity bolts are designed with larger diameters and thicker hex heads to handle substantial tensile and shear forces. These bolts are often used in critical structural connections of large - scale buildings, bridges, and industrial facilities. They strictly adhere to the stringent dimensional and performance requirements of ASTM A325/A325M standards, ensuring reliable performance under heavy loads and extreme conditions.
Special - Application Models: For unique construction scenarios, special - application models are available. These may include bolts with specific thread pitches, custom lengths, or modified head shapes. For example, in some complex structural designs, bolts with extended non - threaded shanks or specialized thread profiles are required to meet the precise assembly and load - bearing requirements. These special - application models still comply with the core ASTM A325/A325M standards while offering tailored solutions for specific projects.
Manufacturing Process
The production of ASTM A325/A325M HDG stainless - steel full/half - thread heavy hexagon structural bolts involves multiple precise steps while strictly complying with ASTM standards and quality - control measures:
Material Preparation: High - quality stainless - steel raw materials, such as steel bars or rods, are carefully sourced. Rigorous inspections are carried out to verify the chemical composition, mechanical properties, and surface quality of the materials, ensuring they meet the requirements of ASTM A325/A325M standards and the specified stainless - steel grades. The stainless - steel materials are then cut into appropriate lengths according to the specific size requirements of the bolts.
Forming: Metal bolts are typically formed through cold - heading or hot - forging processes. Cold - heading is commonly used for smaller - sized bolts. In this process, the stainless - steel is shaped into the characteristic heavy hex head and the bolt shank using dies in multiple stages. This method is efficient for high - volume production and can create accurate thread forms and bolt shapes while maintaining compliance with the ASTM standards' dimensional tolerances. Hot - forging is applied to larger or high - strength bolts, where the stainless - steel is heated to a malleable state and then shaped under high pressure to achieve the required strength and dimensional accuracy as per the ASTM standards.
Threading: After forming, the bolts undergo threading operations. For full - thread bolts, threads are created along the entire length of the shank, while for half - thread bolts, threads are only formed on the designated portion. 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 ASTM A325/A325M standards, guaranteeing compatibility with corresponding nuts and threaded holes.
Heat Treatment (if required): In some cases, depending on the specific stainless - steel grade and application requirements, the bolts may undergo heat - treatment processes. Heat treatment can optimize the mechanical properties of the stainless steel, such as enhancing its strength, hardness, and toughness, to meet the stringent performance requirements of structural applications specified in the ASTM standards.
Hot - Dip Galvanizing: The formed bolts are first thoroughly cleaned to remove any contaminants, oil, or scale. Then, they are fluxed to ensure proper wetting by the molten zinc. After that, the bolts are immersed in a molten zinc bath at approximately 450 - 460°C for a specific period. During this process, the zinc diffuses into the surface of the stainless steel, forming a series of zinc - iron alloy layers and a thick outer layer of pure zinc. Once removed from the bath, the bolts are allowed to cool, and any excess zinc is removed. This hot - dip galvanizing process provides a robust and long - lasting protective coating.
Quality Inspection: Every batch of bolts is subject to rigorous inspection in accordance with ASTM A325/A325M standards. Dimensional checks are performed to ensure that the bolt's diameter, length, thread specifications, head size, and thickness meet the standard's precise requirements. Mechanical tests, including tensile strength, proof load, and hardness tests, are conducted to verify that the bolts can withstand the specified loads and meet the strength and performance criteria. Visual inspections are carried out to check for surface defects, proper hot - dip galvanizing coverage, and any non - compliance with the standard's appearance requirements. Additionally, corrosion - resistance tests may be performed to ensure the effectiveness of the HDG coating. Only bolts that pass all quality tests are approved for packaging and distribution.
Surface Treatment Process
The hot - dip galvanizing (HDG) surface treatment is a crucial feature that significantly enhances the performance of these structural bolts:
Pre - treatment: Before hot - dip galvanizing, the bolts undergo a thorough pre - treatment process. This starts with degreasing, where the bolts are cleaned using solvents or alkaline solutions to remove any oil, grease, or organic contaminants on the surface. Then, pickling is carried out by immersing the bolts in an acid solution (usually hydrochloric or sulfuric acid) to remove rust, scale, and other inorganic deposits. After pickling, the bolts are rinsed thoroughly to remove any residual acid. Finally, a fluxing process is performed, where the bolts are dipped in a flux solution. The flux helps to remove any remaining oxides, improves the wetting of the bolt surface by the molten zinc, and prevents re - oxidation during the galvanizing process.
Hot - Dip Galvanizing Process: The pre - treated bolts are then immersed in a molten zinc bath at around 450 - 460°C. The high temperature of the zinc bath causes a metallurgical reaction between the zinc and the stainless - steel surface. Initially, zinc atoms diffuse into the stainless - steel substrate, forming a series of zinc - iron alloy layers with different compositions. These alloy layers provide excellent adhesion between the zinc coating and the base metal. Subsequently, a thick outer layer of pure zinc is deposited on top of the alloy layers. The thickness of the galvanized coating can typically range from 80 - 120 microns, depending on the size and type of the bolts, as well as the specific requirements of the ASTM standards and the application.
Post - treatment: After hot - dip galvanizing, the bolts may undergo post - treatment processes. One common post - treatment is passivation, where the bolts are treated with a chemical solution (such as chromate - based or non - chromate - based solutions) to form a thin, protective oxide layer on the surface of the zinc coating. This passivation treatment further enhances the corrosion resistance of the galvanized coating, improves its appearance, and provides some protection against white rust formation. Additionally, the bolts may be inspected for any surface irregularities, and in some cases, they may be subjected to mechanical processes such as brushing or shot - blasting to remove any excess zinc or to smooth the surface.
Application Scope
ASTM A325/A325M HDG stainless - steel full/half - thread heavy hexagon structural bolts are widely used in various critical construction and industrial applications:
Building Construction: In large - scale building projects, these bolts are used for connecting steel beams, columns, and trusses, forming the structural framework of buildings. Their high strength and excellent corrosion resistance, enhanced by the HDG treatment, ensure the long - term stability and integrity of the building structure, whether it is a commercial skyscraper, an industrial warehouse, or a residential high - rise. The full/half - thread design allows for flexible and secure fastening in different structural connections, meeting the diverse requirements of building design and construction.
Bridge Construction: Bridges are exposed to various harsh environmental conditions, including moisture, traffic - induced vibrations, and corrosive substances. These structural bolts are essential for connecting bridge components, such as girders, piers, and decking. The ASTM - compliant design and the robust HDG coating enable the bolts to withstand heavy loads, vibrations, and corrosion, ensuring the safety and durability of the bridge infrastructure over its service life.
Industrial Facilities: In industrial plants, refineries, and manufacturing facilities, these bolts are used for assembling heavy machinery, equipment frames, and structural supports. The high - load - capacity models can withstand the heavy operational loads and vibrations generated by industrial equipment. The corrosion - resistant properties of the stainless steel, combined with the HDG coating, protect the bolts from industrial pollutants, chemicals, and moisture, reducing maintenance requirements and minimizing the risk of structural failures in industrial settings.
Offshore and Marine Structures: For offshore platforms, ships, and marine installations, where exposure to saltwater and harsh marine environments is constant, these bolts are highly valued. The superior corrosion resistance of 316 stainless steel, along with the additional protection provided by the HDG coating, makes them capable of withstanding the corrosive effects of seawater, humidity, and marine atmospheres. They are used for fastening various marine components, ensuring the reliability and safety of offshore and marine structures.
Infrastructure Projects: In infrastructure projects such as power plants, transmission towers, and large - scale water treatment facilities, these structural bolts play a vital role in ensuring the stability and functionality of the structures. Their compliance with ASTM A325/A325M standards guarantees consistent quality and performance, while the HDG treatment provides long - term protection against environmental factors, contributing to the overall durability and service life of the infrastructure.
Product Advantages
High Strength and Load - Bearing Capacity: Complying with ASTM A325/A325M standards, these bolts offer high strength and excellent load - bearing capacity. They are designed to withstand significant tensile, shear, and fatigue loads, making them suitable for critical structural connections in various construction and industrial applications. The robust construction, combined with the appropriate choice of stainless - steel grade and heat treatment (if applicable), ensures reliable performance under heavy loads and extreme conditions.
Superior Corrosion Resistance: The combination of stainless - steel base material and hot - dip galvanizing provides superior corrosion resistance. Stainless steel already offers good inherent corrosion protection, and the HDG coating adds an extra layer of defense against the elements. This makes the bolts highly suitable for use in harsh environments, including coastal areas, marine applications, and industrial settings with high humidity or exposure to chemicals, significantly extending their service life and reducing maintenance costs.
Standardized and Reliable Design: Adhering to the ASTM A325/A325M standards, these bolts offer a standardized design, ensuring compatibility and interchangeability across different projects and regions. The strict quality - control measures during manufacturing, as required by the standards, guarantee consistent quality and performance. This standardization simplifies the procurement, installation, and maintenance processes, reduces the risk of errors, and provides peace of mind for engineers, contractors, and project owners.
Versatile Thread Design: The availability of both full - thread and half - thread options provides versatility in different applications. Full - thread bolts are ideal for applications where a uniform clamping force is required along the entire length of the bolt, while half - thread bolts can be used to optimize load distribution, reduce friction, or meet specific design requirements. This flexibility allows for customized fastening solutions to meet the diverse needs of various construction and industrial projects.
Long - Lasting Protection: The hot - dip galvanizing process creates a thick and durable zinc coating that adheres well to the stainless - steel surface. This coating provides long - lasting protection against corrosion, abrasion, and other forms of environmental degradation. The post - treatment processes, such as passivation, further enhance the durability of the coating, ensuring that the bolts maintain their performance and appearance over an extended period, even in the most challenging environments.
Enhanced Safety: In structural applications, the reliability and performance of these bolts are crucial for ensuring the safety of buildings, bridges, and other infrastructure. Their high strength, corrosion resistance, and compliance with strict ASTM standards contribute to the overall structural integrity, reducing the risk of structural failures and ensuring the safety of people and property.
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