As hardware raw materials, the presence of inclusions in the molten steel during the production process will seriously affect the performance of the steel and restrict the use of the steel. Therefore, effective measures must be taken to remove the inclusions in the steel and improve the performance of the steel. The removal methods of inclusions in molten steel mainly include molten steel argon blowing technology, crystallizer electromagnetic technology, and tundish filtration technology.
1. Argon blowing technology
Argon blowing stirring is a relatively mature technology in modern steelmaking applications. The principle is to use a special device to uniformly blow inert gas into the molten steel to form tiny bubbles. When the bubbles float, the interfacial tension is used to adsorb the inclusion particles on the surface and float to the liquid surface to remove. In the argon blowing technology, another technology has been developed, that is, the tundish air curtain retaining wall. It is a row of ventilation devices buried in the bottom of the bag. By blowing micro bubbles into the molten steel, a gas curtain retaining wall is formed. The inclusions collide with the bubbles when passing, and are adsorbed on the surface of the bubbles to float, suitable for the removal of 50-200μm inclusions.
2. Electromagnetic technology of crystallizer
The electromagnetic technology of crystallizer includes electromagnetic stirring and electromagnetic braking, and their working principles are similar. Electromagnetic stirring is to set a linear motion sensor behind the slab in the crystallizer to generate a moving magnetic field to drive the molten steel near the meniscus in the crystallizer to rotate and flow in the horizontal direction to achieve the purpose of stirring. Suitable for removing inclusions less than 20μm.
Electromagnetic braking is to add a pair of constant electromagnetic fields to the two wide faces of the crystallizer, so that the direction of the magnetic field passes through the two wide faces of the crystallizer perpendicularly. After the molten steel flows out of the side hole of the nozzle, it passes through the magnetic field at high speed and vertically. Because the molten steel conducts electricity, an induced current will be generated. Under the action of the electromagnetic field, the molten steel will receive an electromagnetic force in the opposite direction of its own flow. The purpose of braking. The technology was first jointly developed by Sweden and Japan, and the metallurgical effect is good.
3. Tundish filtering technology
The tundish filtration technology is to add a filter device on the basis of retaining walls and dams, mainly to remove inclusions through mechanical blocking and surface adsorption. The filter is made of refractory material with a microporous structure, which spans on the two wide surfaces of the tundish, completely separating the tundish, and molten steel can only pass through the micropores. This not only prolongs the residence time of the inclusions in the molten steel, but also ensures the residence time of the micro-inclusions in the molten steel, and also ensures that the micro-inclusions have enough time to be adsorbed on the filter to achieve the purpose of removing the inclusions . Suitable for all inclusion particles larger than 20μm.
In application, the existing technology is difficult to complete the task of completely removing the inclusions, so a variety of technologies should be combined to find a more reasonable and feasible inclusion removal method and technical parameters to achieve "zero inclusions".
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