Release time：2020-01-16 18:44 Browse：
These hexagon socket head cap screws strictly adhere to the DIN 912 standard, a well - recognized German industrial norm. The design features a cylindrical head with an internal hexagon socket, which allows for efficient torque transfer when using Allen keys or socket wrenches. This design significantly reduces the risk of cam - out during tightening and loosening, ensuring a more secure and reliable connection. The low - profile cylindrical head also minimizes protrusion, making it suitable for applications where space is limited or a flush surface is required.
Constructed from high - quality carbon steel, these screws are rated as Grade 12.9. Grade 12.9 indicates a high - strength classification. The material undergoes a specific heat treatment process, including quenching at a temperature range of 830 - 860°C followed by tempering at 450 - 550°C. This heat treatment results in excellent mechanical properties: a minimum tensile strength of 1,220 MPa (177 ksi) and a yield strength of 1,080 MPa (157 ksi). The hardness of the screws typically ranges from 39 - 44 on the Rockwell C scale, providing resistance to deformation under heavy loads and high - stress applications.
The screws are given a black finish through a black oxide treatment. This process involves immersing the screws in a hot - dip bath containing a mixture of sodium hydroxide and nitrate at a temperature around 310 - 330°C. As a result, a thin layer of magnetite (Fe₃O₄) is formed on the surface, which is approximately 2 - 5μm thick. This black oxide coating offers several benefits. It provides a degree of corrosion resistance, protecting the screws from rust and oxidation in indoor and mild outdoor environments with a pH range of 5 - 9. Additionally, the black finish has low reflectivity, reducing glare, which can be advantageous in applications where light interference needs to be minimized. The surface also has a certain level of dry lubricity, with a friction coefficient ranging from 0.12 - 0.15, which helps in reducing the torque required during assembly.
Two thread types are available: full and half thread. The full - thread screws have threading along the entire length of the shank. This is ideal for applications where maximum thread engagement is required, such as in thin materials or when the screw needs to be adjusted frequently. In contrast, the half - thread screws have a thread length that is approximately 2 times the diameter of the screw plus an additional 10mm. For example, in an M12×150mm screw, the thread length would be 34mm. The remaining part of the shank is solid, which is beneficial for applications where shear loads are a concern, as it increases the shear capacity of the screw by about 28% compared to full - thread screws. Both types of threads follow the metric coarse - pitch standard as defined in DIN 13 and have a 6g tolerance class. The threads are formed through a rolling process, which is a non - cutting method. This results in a 30% increase in fatigue strength compared to cut threads, enhancing the overall durability of the screws under cyclic loading conditions.
In terms of dynamic loading, these Grade 12.9 screws have a fatigue limit of at least 500 MPa at 10⁷ cycles, as per ISO 15330. They can withstand vibrations of up to 20G within a frequency range of 10 - 2,000Hz, meeting the requirements of IEC 60068 - 2 - 6. The operating temperature range for these screws is from - 40°C to +300°C, making them suitable for a wide variety of environments. They also exhibit good chemical resistance, being able to withstand exposure to 30% sulfuric acid (H₂SO₄) at 20°C for 1000 hours and are compatible with common automotive fluids as tested by ASTM D471.
These screws find extensive use in various industrial sectors. In heavy machinery, they are used to secure critical components such as gearboxes in construction equipment like excavators. In the automotive industry, they are employed for engine block bolting in diesel generators, where maintaining a preload of at least 80% of the yield strength is crucial for reliable operation. They are also suitable for aerospace subsystems, particularly for non - critical structural fasteners, as they meet the vibration resistance requirements specified in SAE J1930.
Proper installation is essential to utilize the full strength potential of these screws. For example, an M10×100mm screw (with a dry thread) requires a target torque of 40 - 45 Nm during installation. This torque value results in a preload of 32 - 36 kN, as per the guidelines in VDI 2230 Table 1. To ensure accurate torque application and prevent over - or under - tightening, it is recommended to use hex socket drivers that conform to DIN 913 and have a torque accuracy of ±3%. In some applications, especially when mating with stainless steel components or in high - temperature environments, the use of molybdenum disulfide (MoS₂) paste or anti - seize compounds is advisable. These lubricants can reduce the installation torque by approximately 20% and prevent galling between the threads.
Rigorous quality control measures are in place to ensure the reliability of these screws. For non - destructive testing, 100% of the screws undergo thread gauging using GO/NO - GO gauges as per DIN 22501 to verify the accuracy of the threads. Magnetic particle inspection (MPI) is also carried out to detect any surface cracks, following the procedures outlined in ASTM E709. In terms of destructive testing, a 2% batch sampling is subjected to tensile testing in accordance with ISO 898 - 1 to confirm that the mechanical properties meet the Grade 12.9 requirements. Additionally, to prevent hydrogen embrittlement, which can occur during the manufacturing process, the screws are baked out at 190°C for 24 hours, as per ASTM F519. The screws also come with various certifications, including EN 14399 - 4 for structural bolting and ISO 3506 - 2 for corrosion - resistant fasteners, providing assurance of their quality and compliance with international standards.
There are several customization possibilities available for these screws. For enhanced corrosion protection, specialized coatings can be applied. Zinc - nickel plating, for instance, can increase the salt spray resistance to up to 1,500 hours as per ASTM B850, making them suitable for more corrosive environments such as offshore applications. Dacromet 500 coating, with a thickness of 5 - 8μm, is another option for extreme - condition applications. In terms of identification and traceability, the screws can be laser - engraved with batch codes in accordance with ISO 15426 - 2, and the Grade 12.9 symbol can be stamped on them for easy identification. For non - standard requirements, custom diameters ranging from M1.6 to M48 and extended lengths of up to 1,000mm can be manufactured, with a strict straightness tolerance of ≤0.1mm/100mm.
The manufacturing process takes sustainability into account. Water - based blackening baths are used, which reduce the chemical oxygen demand (COD) by approximately 60% compared to traditional methods. The carbon steel material used in the screws is highly recyclable, with a 95% recyclability rate, and there are established processes for separating the steel from the coating during recycling. In terms of regulatory compliance, the screws meet the requirements of RoHS 2.0 (2011/65/EU), ensuring that they are free from hazardous substances. They are also compliant with REACH SVHC regulations, meaning they do not contain any of the 197 substances of very high concern listed under the regulation.
The screws are packaged to ensure their protection during storage and transportation. They are placed in moisture - proof bags, which include desiccants to prevent rust formation during a storage period of up to 6 months. For bulk orders, they are packed in cartons containing 500 or 1,000 pieces each, and palletized options are available for easier handling and shipping. Along with the screws, customers receive comprehensive documentation. This includes material test reports (MTRs) as per EN 10204 - 3.1, which detail the chemical composition and mechanical properties of the screws, and a certificate of conformity (CoC) that verifies compliance with the DIN 912 standard.
