Impact of barium and strontium on calcium recovery level in ladle treatment of steel by complex modifiers with alkaline-earth metals

Abstract

Increasingly rigid requirements in terms of the steel products quality are forcing the technical experts of metallurgical production to look for new solutions to stabilize the steel quality. Much attention is paid to ladle treatment technologies and selection well-minded composition of modifiers, which makes it possible to reduce steel contamination by non-metallic inclusions. To solve this problem, complex modifiers containing both calcium and other alkaline-earth metals (barium and strontium) are used. The paper presents the results of the pilot scale tests of steel ladle treatment by complex modifiers with alkaline-earth metals (Si, Ca, Ba) in steel production with increased requirements to non-metallic inclusions in conditions of electric furnace steelmaking shop of JSC “Ural Steel”. During experimental work it was possible to reduce the maximum contamination score profile rolled steel from pipe steel grades for brittle silicates (GOST 1778) from 4.0 to 1.5 – 2.5, for non-deforming silicates from 4.0 to 3.0 – 3.5. The substitution of SK40 grade silicocalcium for experimental modifiers led to an improvement in the strength properties of rolled products, both in tensile tests and in impact bending tests at low temperatures. The indicated impact was observed in all variants of consumption the experimental master alloys. It is noted that with an increasing in the consumption of master alloys, the positive effect on the steel mechanical properties enhanced. It was established that the replacement of silicocalcium with experimental variants of master alloys made it possible to increase the calcium recovery by an average of 1.6 times when using Si – Ca – Ba, and by an average of 2.4 times when using Si – Ca – Ba – Sr. The use of complex modifiers made it possible to obtain the target value of residual calcium in the sample at significantly lower calcium consumption.