About Hot-dip Galvanized Bolt Standard

Due to the wide range of uses of hot-dip galvanized bolts, the amount of hot-dip galvanized bolts in the country is very large, so domestic large and small fastener practitioners, whether they are production or trade, have poured into this industry. However, there is still a big difference between a national standard hot-dip galvanized bolt and an ordinary hot-dip galvanized bolt. We only know whether the hot-dip galvanized bolt is good or bad, but what requirements must the national standard hot-dip galvanized bolt meet before it can be regarded as a national standard hot-dip galvanized bolt? What about the bolts?

    The first is the production standard. There are three standards for bolts. The first is GB/T5782, which belongs to the half-thread external hexagonal type. The second is GB/T5783, which belongs to the standard of full-thread. The other is the German standard. It is produced by DIN933 or DIN931, and its corresponding size is slightly different from the national standard.

    But what is really important is its mechanical properties. The mechanical properties of hot-dip galvanized bolts refer to the properties that bolts need to possess under working conditions. It includes the strength, plasticity, hardness, toughness and fatigue resistance of hot-dip galvanized bolts. aspect.

    The first is deformation. You may ask, how can hot-dip galvanized bolts be deformed? In fact, when an external force acts on a national standard hot-dip galvanized bolt, we cannot see the micro-deformation state of the thread with the naked eye. When the external force is removed, the national standard hot-dip galvanized bolt will return to the original performance of plastic deformation, so we The fact that the hot-dip galvanized bolt is invisible to the naked eye does not mean that it has no deformation.

    Another important data of hot-dip galvanized bolts that meet the national standard is the strength of the bolt. It means that after the screw is installed, when the nut and the screw are locked together, the screw will not be affected and will not damage the strength index of the screw. Hot-dip galvanized The strength of zinc bolts actually refers to the mechanical properties of the bolts. Different materials have different mechanical properties. If necessary, the user can ask the supplier to provide a test report on the mechanical properties of the hot-dip galvanized bolts. This also involves another important indicator: tensile strength.

    The tensile strength of hot-dip galvanized bolts is a destructive test, which is to use force until the national standard hot-dip galvanized bolts used for testing are pulled off. Record the data at the time of final fracture, the maximum value of which is the tensile strength of the hot-dip galvanized bolt. To put it simply, it is how much force it can withstand and continue, but if you want to know the result, you can only get the final data by pulling it off first. And this process will also record another yield strength data, which is the stress at which the hot-dip galvanized bolt deforms when it is first stressed, that is, from which force it begins to deform.

    How long can hot-dip galvanized bolts last? This requires how long the lasting strength of the hot-dip galvanized bolts is. Under the condition of constantly changing temperature, apply force to the hot-dip galvanized bolts continuously, and then keep it constant under a certain force. The normal test time basically reaches 100,000 hours, so this data is difficult to collect because it takes too long. So in this process, we can mainly observe its plasticity and elongation. The plasticity of hot-dip galvanized bolts is actually to prevent the sudden quality problems of the screws, and the elongation rate is the range of changes when the screws are broken. These are required by national standards and can be compared.

    The hardness index of hot-dip galvanized bolts is also a very important parameter. The degree of bolts before hot-dip galvanizing and after hot-dip galvanizing must meet the requirements of the national standard. The hardness is different. For hot-dip galvanizing Zinc bolts have a direct impact on the fatigue strength. How long it can be used also matters.

    The last is the anti-corrosion performance index of hot-dip galvanized bolts. It is impossible for hot-dip galvanized bolts to be used outdoors and in contact with the atmosphere without rusting at all, but there are requirements in the national standard for how long hot-dip galvanized bolts will not rust. The length of rusting time plays a role in the stress corrosion cracking of national standard hot-dip galvanized bolts. If it is in a particularly harsh environment, we have to lower the requirements. If it is in a conventional environment, we need national standard hot-dip galvanized bolts It must be guaranteed to be rust-free for at least five years.