They contain such chemically active components as Ca and Ba in various proportions, have different degrees of efficiency, which makes it possible to vary their use depending on the degree of initial contamination of the melt and possible limitations on silicon in it. Calcium contained in these modifiers has low solubility in iron, reacts actively with oxygen, sulfur, hydrogen and other elements, purifies the boundaries of grains of carbonitrides, sulfides that make steels brittle. Calcium promotes modification of the products of aluminum deoxidization leading to the formation of readily removable globular NMI.As a result, the pliability and impact strength of steels increases. Calcium vapors are highly resilient, which significantly decreases its recovery in steel in the absence of barium.
Barium (Ba) does not easily dissolve in iron but, unlike calcium, it has a low pressure of vapors in the zone where its modifier dissolves (5.2 kPa at 1,600°C).As the melting point of barium is relatively low (710°C), it reacts earlier and more efficiently with oxygen and sulfur, and its high surface tension (wettability) promotes rapid and complete removal of reaction products.
The presence in one modifier (alloy) of calcium and barium which are fully reciprocally soluble, when liquid, lowers the elasticity of their vapors in steel. Due to a slower rate of evaporation of the elements the period of reaction of calcium with the melt increases. As a result, its purification of oxygen and sulfur progresses more efficiently and the degree of calcium recovery increases due to the modification of a larger amount of NMI.