Influence of Ultrasonic Treatment on the Structure of High-carbon Steel

Specific qualitative requirements force steel manufacturers to strive to obtain ingots of the highest quality available the measure of which are on one hand, the cleanliness and homogeneity of chemical composition of steel, and the largest equiaxed zone on the other hand. Nowadays, a decided majority of steels is manufactured with continuous casting with structure homogenisation through electromagnetic mixing of steel, both in the crystalliser and in the cooling zone. However, no such treatment is performed by traditional steel casting technology. There are numerous information available in the specialist sources concerning the changes taking place as result of ultrasonic treatment applied in crystallising metals and cast iron. The most apparent effect of such treatment observed is the size reduction of grains. One of the direct effects of the impact of ultrasonic field is the change of structure of metals during solidification. Ultrasounds eliminate columnar structures and exert positive influence on formation of equiaxed grains and homogeneity of metals. Structural changes in solidifying metals occur due to the processes taking place in the liquid-solid two-phase zone such as formation of crystal nucleuses and mixing. All these changes are caused by the impact of ultrasonic waves with a specific power and frequency. The propagation of waves also leads to such phenomena as cavitation, acoustic wind and radiation pressure 1-6 .