Improving the quality of rail steel by treatment outside the furnace

Metal temperature in the ladle after blowing was 1515-1525~ in 80% of the cases, while 10% of the heats were delivered for teeming at 1505-1514~ Their teeming proceeded normally, and no additional losses with the crusts were seen. It should be noted that 10% of the heats were delivered for teeming at a temperature greater than 1525~ An analysis (Fig. 2) showed that ending the blow at a steel temperature higher than 1520~ sharply increases the probability of welding of ingots to the mold. Blowing with argon promotes more complete averaging of the chemical composition of the metal: the maximum deviations from the ladle analysis decrease from 0.06 to 0.04% with respect to manganese content and from 0.05 to 0.02% with respect to silicon content. When the metal is treated in the ladle with a slag-forming mixture, its content of nonmetallic inclusions is further lowered: the degree of desulfurization increases and may reach 47%. In a series of commercial heats subjected to such treatment (12,000 tons), the mean sulfur content of the finished steel was 0.026%, versus the 0.036% for heats processed as usual. In other words, an additional 28% sulfur reduction was achieved by treatment of the metal with slag.