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What is the online heat treatment quenching and tempering step?

1. Quenching stage. This process consists of a water cooling system placed in the rack. Reasonable and effective water-cooling equipment allows the rolling stock to be cooled violently here. On the surface of the rolled piece, the cooling value exceeds the martensite critical value, so that a martensite structure can be formed on the surface.

  2. The tempering phase. At this time, the rolled piece is exposed to the air after passing through the water cooling system, and the heat of the core is transmitted to the surface layer to temper the surface, so-called self-tempering.

   3. Cooling stage. This phase occurs later, mainly because the austenite of the core undergoes an isothermal phase transition to obtain the final metallographic state. Online heat treatment is an effective method to improve the quality, which can improve the internal structure of the rolled piece, thereby obtaining better mechanical strength. The on-line heat treatment of the rolled product can be carried out by quenching to form the martensite structure of the surface layer, and through the heat transfer of the core, self-tempering the surface martensite, so that the surface layer obtains the tempered martensite structure. The core is cooled by the surface layer, resulting in a large temperature drop, thereby refining the resulting pearlite structure, which not only increases the hardness of the surface layer, but also improves the core structure. In addition, in-line heat treatment enhances the mechanical properties of the steel sheet and reduces the carbon and alloying elements. On-line heat treatment combines control heating, controlled rolling and controlled cooling into a complete energy-saving production process, thus saving a lot of energy and reducing costs.
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