How to deal with the Decarburization Phenomenon in High Strength Bolt Heat Treatment?

As a Rail Spike Manufacturer, share with you.
There is a process in the High Strength Bolt manufacturing process to improve the comprehensive mechanical properties of the fastener, which is the heat treatment process. This process has a very important impact on the quality of high-strength bolts, especially the inherent quality of high-strength bolts.
Processing and producing a high-strength bolt has a very complicated process, and high-strength bolts that pass multiple processes and are strict in each process can be regarded as basically qualified. In order to fully meet the pre-designed standards, more rigorous inspections, reasonable storage, transportation, and correct installation are required before finally realizing the true role of a high-strength bolt.

High Strength Bolt
In the process of heating the billet, the phenomenon that the carbon content of the surface metal is reduced or even does not contain carbon due to oxidation is called decarburization, which is a type of steel defect and is generally called surface decarburization. The surface layer of metal decarburization is called a decarburization layer. High carbon steel (such as bearing steel), tool steel, spring steel, etc. will reduce surface hardness due to decarburization, affecting wear resistance, machinability and fatigue resistance. Steels with high carbon content are usually inspected for decarburization layers.
With the development of the times, the continuous heat treatment production line with protective function has occupied a dominant position since the 1990s. In addition to the excellent sealing performance of the furnace, the temperature and process parameters are controlled by computer, and the equipment's fault alarm and display functions are also readily available. During the whole process of quenching and tempering, some oxidizing gas will be brought from the outside of the furnace. The reaction with the rust on the surface of the high-strength bolt through a series of chemical changes will cause the decarburization of the high-strength bolt material itself. According to the research of technicians, the decarburization degree of medium carbon alloy steel is more serious than that of carbon steel, and the fastest decarburization temperature is between 700 and 800 degrees Celsius. The main reason is that the objects attached to the surface of the steel wire decompose compounds very quickly under certain conditions. If the gas control of the continuous mesh belt furnace is not good, the decarburization of the screws will be too bad. When the high-strength bolt uses the cold heading forming process, the annealed decarburized layer of the original material still exists, and it is extruded to the top of the high-strength bolt thread.At this time, the surface of the high-strength bolt that needs to be quenched cannot be obtained. Pre-designed hardness requirements, at this time the mechanical properties of high-strength bolts will be greatly reduced.
Our company also has Railway Bolts on sale, welcome to consult.

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