Release time：2020-01-16 18:44 Browse：
When discussing the two questions of "Why not grade 8.8 cement anchors" and "heat treatment process of concrete anchors", we first need to understand the basic characteristics, application scenarios and the meaning of strength grades of cement anchors and concrete anchors, and then in-depth analysis of the principle of tempering technology and its role in improving the performance of anchors.
Why not do 8.8 cement anchors?
Cement anchor, as a kind of screw screw composed of steel bar and cement, its design intention and main application scenarios determine the choice of its strength level is not simply to pursue high values. First, we need to clarify the meaning of the intensity rating of 8.8. In the field of fasteners, grade 8.8 indicates that the standard value of the ultimate tensile strength of the material is not less than 800MPa, and the yield ratio (the ratio of yield strength to tensile strength) is not less than 0.8, that is, the yield strength is not less than 640MPa. This strength level is sufficient for many high-strength connection needs, but the specificity of cement anchors lies in their material composition and the environment in which they are used.
1. Material composition: cement anchors are mainly composed of steel bars and cement, and their strength depends not only on the material of steel bars, but also on the strength of cement slurry, the bonding force between steel bars and cement and other factors. Therefore, the simple pursuit of a high strength grade of steel bars cannot directly improve the carrying capacity of the entire anchor bolt.
2. Application scenario: Cement anchors are widely used in construction engineering, bridge engineering, tunnel engineering and other fields, which require not only high strength, but more importantly durability, stability and construction convenience. For example, in tunnel projects with complex geological conditions, cement anchors need to have good corrosion resistance and long-term stability, rather than simply high strength.
3. Economy: Increasing the strength level of the anchor bolt often means an increase in cost. In applications where very high strength is not required, selecting anchors with a high strength grade can cause unnecessary waste.
To sum up, the cement anchor is not made 8.8 grade not because its technology cannot be achieved, but based on the comprehensive consideration of material characteristics, application scenarios and economy.
Heat treatment technology of concrete anchor bolt
The heat treatment process of concrete anchors, including self-cutting anchors and self-tapping anchors, is very important to improve the mechanical properties of anchors. The heat treatment process mainly includes annealing, normalizing, quenching and tempering steps, among which tempering treatment (quenching + high temperature tempering) is the key to improve the overall performance of the anchor bolt.
1. Tempering principle: tempering treatment by quenching the anchor material to obtain high hardness and high strength martensite structure, then through high temperature tempering martensite into tempered sortensite or tempered troosite, so as to ensure high strength at the same time, improve the plasticity and toughness of the material. This process effectively improves the mechanical properties of the anchor bolt and makes it more adaptable to the complex and changeable engineering environment.
2. Function analysis:
Improve strength: quenching makes the anchor material obtain high hardness, improve its tensile strength and yield strength.
Improved toughness: High temperature tempering eliminates the internal stress and brittleness generated by quenching, improves the plasticity and toughness of the anchor bolt, and makes it not easy to break when subjected to impact or vibration.
Enhanced corrosion resistance: For stainless steel anchors, appropriate heat treatment can also enhance their corrosion resistance and prolong their service life.
Optimized installability: For self-cutting anchors and self-tapping anchors, a good heat treatment process can also ensure that the screw is not easily damaged when cutting through the concrete, reducing the installation difficulty and resistance.
conclusion
The reason why cement anchors are not rated 8.8 is based on the comprehensive consideration of their material characteristics, application scenarios and economy. The heat treatment of concrete anchors, especially the tempering treatment, is of great significance for improving the mechanical properties of anchors and adapting to complex engineering environment. In practical engineering, choosing the appropriate anchor type and specification, combined with scientific heat treatment process, is the key to ensure the safety and quality of engineering.
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