Release time：2020-01-16 18:44 Browse：
We do not recommend a hardness of 12.9 for long and elongated long screws, because the longer the length of the long screws, the greater the risk of brittleness, and the same is true for small diameter long screws, for most application environments, 4.8-8.8 hardness is sufficient.
When discussing the reasons why lengthening screws are not recommended to do 12.9, we first need to understand the basic characteristics of 12.9 high-strength screws and their application scenarios, and then further analyze why under certain conditions, such as lengthening screws, the use of this level may bring unnecessary risks and challenges.
1. Basic characteristics of 12.9 high strength screws
Grade 12.9 high-strength screws, as an upgrade of the traditional 10.9 screws, are significantly characterized by higher strength, tensile, pull-out and anti-slip forces. The surface of this screw has been specially heat treated, which not only improves the wear resistance, but also significantly enhances the corrosion resistance, thus extending the service life. In addition, 12.9 high strength screws also have the advantages of light weight, high strength, small space occupation, making it widely used in aviation, automotive, petrochemical, mining, metallurgy, mechanical equipment and other fields.
However, it is these superior performance that also brings specific usage limitations and challenges.
2. Risk of delayed rupture
When high pretension stress is applied to high strength bolts, delayed cracking may occur, which leads to delayed brittle fracture. This phenomenon is particularly significant when the strength of the steel exceeds a certain threshold, especially when the strength reaches or exceeds 1200MPa, the risk of delayed fracture increases dramatically. For lengthening screws, due to their increased length, more complex force distribution, and possible processing errors or improper installation, it is easier to accumulate stress in long-term use, thereby increasing the risk of delayed fracture.
3. Technical requirements for installation and maintenance
The installation and maintenance of Class 12.9 high strength screws is extremely technically demanding and needs to be operated by skilled personnel. For lengthening screws, due to the increase in length, the precision control during installation is more difficult, and a slight deviation may affect the mechanical performance of the screws, and even lead to early failure. In addition, regular inspection and maintenance is also an important part of ensuring the safe use of 12.9 high strength screws, and the inspection and maintenance of lengthening screws may be more cumbersome and complex due to the diversity of the use environment.
4. Cost and cost-effective consideration
Grade 12.9 high strength screws due to the use of special materials and complex production process, its price is significantly higher than ordinary screws. For lengthening screws, due to the increase in material consumption and processing difficulty, the cost will further rise. Therefore, in terms of cost performance, unless it is in the case of high requirements for strength and reliability, the use of 12.9 extension screws may not be cost-effective.
5. Alternatives and practical applications
In practical applications, for occasions that require lengthening screws, we can consider other more suitable solutions. For example, reduce the need for screw length by optimizing the structural design, or choose to use a screw model that is slightly less strong but less costly and easier to install. In addition, for some special environments or application scenarios, screws made of composite materials or special alloys can also be considered to meet specific use requirements.
conclusion
In summary, the reasons why the extension screw is not recommended to do 12.9 mainly include the risk of delayed fracture, the technical requirements of installation and maintenance, and the consideration of cost and cost-effective. In practical applications, we should reasonably select suitable screw models and specifications according to specific needs and environmental conditions to ensure the safe and reliable operation of the equipment and maximize economic benefits.
#8.8 outer hexagon extension screw #8.8 flange extension screw # Extension screw # Extension extra long screw # screw
