What factors affect the absorption of inclusions in molten steel by protective slag?
Release time:
2020-07-28
Immersed nozzle pouring causes convective movement of molten steel within the crystallizer. Due to fluctuations in the crystallizer's liquid level, inclusions floating to the interface between the molten steel and slag may be drawn into the solidified shell, leading to subsurface inclusions or slag entrapment in the slab, affecting surface quality. Therefore, inclusions floating to the slag interface will be rapidly absorbed and dissolved by the liquid slag layer.
To ensure that inclusions floating on the steel-slag interface are quickly transferred to the liquid slag, this process depends on:
（ 1 ）The interfacial contact area of the slag;
（ 2 ）The viscosity of the liquid slag;
（ 3 ）The ability of the protective slag to dissolve inclusions.
In other words, the larger the contact area of the slag, protective slag the better the fluidity, the easier it is for inclusions to enter the protective slag. Once the inclusions enter the slag, protective slag they can be rapidly absorbed and dissolved, protective slag The ability to dissolve inclusions mainly depends on the chemical composition of the slag, namely the content of calcium oxide and silicon dioxide (calcium oxide % / silicon dioxide % is called basicity) and the original content in the slag. Al2O3的含量。
Production tests show that as basicity increases, protective slag slag dissolution Al2O3 of inclusions increases. When basicity is greater than 1.1时，溶解Al2O3 the ability to dissolve Al2O3 decreases. When the original content in the slag exceeds 10 %, protective slag the dissolution of inclusions in the slag Al2O3 rapidly decreases. Therefore, when preparing protective slag, the ratio of CaO Cao % to SiO2 % should be 0.9-1.0 ，the original Al2O3 content should be as low as possible, usually less than 10 %.
protective slag How great is the dissolution capacity of the liquid slag layer on the steel surface for Al2O3 inclusions? It points out that when Cao % /SiO _ 2 % =0.9 ~ 1.0 ，in the slag Al2O3 decreases. When the original content in the slag exceeds 20 %，high-melting-point compounds will precipitate, increasing protective slag the melting point and viscosity, making it unable to absorb floating inclusions.
However, during casting, protective slag is constantly consumed, and floating inclusions are constantly absorbed, causing protective slag the slag to be Al2O3 enriched. In order to maintain a protective slag with good absorption capacity without changing the slag properties, the following steps can be taken. Al2O3能力的保护渣，可以采取以下步骤。
（ 1 ）When making slag powder, select appropriate raw materials to minimize the original slag Al2O3 content
（ 2 ）Properly increase the amount of slag powder to dilute the Al2O3 content in the slag;
（ 3 ）During casting, as protective slag in Al2O3 is enriched, the slag can be changed using a crystallizer.
For more information on protective slag questions, please contact Luoyang Turner High Temperature Instrument Co., Ltd.
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