How to reduce the brittle fracture of anchor bolts?

Anchor bolt is a kind of widely used and more important component, which is often used in concrete anchoring. Compared with anchor bolts above grade 5.8, anchor bolts above grade 5.8 will appear brittle fracture (including chemical anchor bolts and mechanical anchor bolts ) during use, and have considerable strength and better plasticity; however, many projects have a strong impact on grade 8.8 or above. Anchor bolts put forward requirements. Usually, anchor bolts of grade 5.8 or higher have higher strength, better tensile and shear bearing capacity, and higher hardness, lower plasticity, and easier fracture during construction, which increases the difficulty of construction.

01 Material issues.

For example, if the carbon and phosphorus content in steel exceeds the standard, it may lead to reduced plasticity, brittle fracture in construction, and excessive sulfur content may lead to increased hot brittleness and decreased corrosion resistance; raw materials are the fundamental factor affecting the comprehensive performance of anchor bolts. There may be more problems and potential risks in use. However, the problems of raw materials are often not directly identifiable, and the process stability of different raw material manufacturers often determines the stability of bolt products. Therefore, the supply of high-quality raw materials is very important.

02 Process issues.

The first is the heat treatment process; some alloy steels can achieve higher strength through heat treatment. Inappropriate heat treatment will reduce the toughness of the material and the impact resistance. The physical and chemical properties of different materials are different, and the sensitivity to the heat treatment process is also different; , Stable materials is a problem that material manufacturers have repeatedly considered. In short, good and stable raw materials are the prerequisite to ensure product quality. The controllability and stability of the entire production process can reduce the number and number of problems; self-inspection of products and project matching tests can be very good Improve the quality of shipments.

The second is to use the galvanizing process; the greater the strength of the material, the greater the sensitivity to "hydrogen embrittlement"; in the plating process, the pickling, electroplating, degreasing and other links may infiltrate hydrogen, and excessive amounts will produce " The effect of hydrogen embrittlement, so the process of “hydrogen embrittlement” is very important. In addition, improper heat treatment will also cause the surface layer of the bolt to be hard, reducing its plasticity and brittle fracture.

03Construction issues.

What is the main reason for this situation? The main reason is improper construction method. When constructing concrete embedded parts, steel bars are often encountered, especially large-sized anchor bolts. The construction workers on the construction site often choose to drill diagonal holes to avoid the steel bars. After the anchor bolts are installed, the anchor bolts are broken into the right position; when the breaking angle is not particularly large, the anchor bolts of grade 4.8 and 5.8 will not appear obvious. Cracking or breaking. The anchor bolts above 8.8 are more sensitive to the bending angle. The larger the bending angle, the more likely it is to crack or break directly, or to break directly with a hammer. Therefore, it is especially important to promote the correct installation method. Usually, the anchor bolt should be installed perpendicular to the concrete, and avoid the place where there are steel bars.