What are the factors affecting the absorption of inclusions in molten steel by casting powder?

The submerged nozzle injection in the mold causes the molten steel to move convection, and the inclusions floating on the steel slag interface of the mold may be involved in the solidification shell due to the fluctuation of the liquid level of the mold, resulting in bad subcutaneous inclusions or slag inclusion on the surface and affecting the surface quality. Therefore, it is hoped that the inclusions floating to the steel slag interface will soon be absorbed and dissolved by the slag layer.

In order to make the inclusions floating on the steel slag interface quickly transferred to the liquid slag, this process is determined by: (1) the contact area of the steel slag interface; (2) viscosity of liquid slag; (3) the ability to dissolve inclusions.

That is to say, the better the fluidity of slag, the larger the contact area of steel slag, the easier the inclusion into slag.As long as the inclusions enter the slag, the slag can quickly absorb and dissolve, and the ability of the inclusions dissolution mainly depends on the chemical composition of the slag, that is, the content of Ca0 and Si02 (Ca0%/Si0O2% is called basicity) and the original content of A1203 in the slag.

The production test indicates that the solubility of A1203 inclusions increases with the increase of basicity, and decreases when the basicity is greater than 1.1. When the content of original Al203 in slag is greater than 10%, the dissolved A1203 in slag decreases rapidly. Therefore, the ratio of Ca0% to SiO2% in slag should be 0.9 ~ 1.0, and the original A1203 content should be as low as possible, generally less than 10%.

What is the solubility of the slag layer on the molten steel surface of the mould to the inclusion of A1203? It is pointed out that when Ca0%/Si02%=0.9 ~ 1.0, the content of A1203 in the slag is more than 20%, and the compound with high melting point precipitates, so that the melting point of the slag increases, the viscosity increases, and the floating inclusions can no longer be absorbed.

However, in the pouring process, the mould casting powder is constantly consumed and absorbs the floating inclusions, so that the slag is enriched by A1203.In order to maintain good A1203 absorption capacity of slag without changing slag properties, the following measures can be taken:

(1) When preparing slag powder, choose appropriate raw materials and reduce the content of A1203 in the original slag as much as possible;

(2) Appropriate increase of slag powder consumption, dilute the content of A12O3 in slag;

(3 In the process of stilting, A1203 is enriched with slag in the slag, and slag exchange with crystallizer can be used.