The use of cored wire must be based on sound principles in order to achieve optimum deoxidising efficiency and improve steel quality. In order to achieve optimum results when using flux cored wire, it is necessary to determine the correct methodology for its application.
1. It is recommended that the feed rate be reasonably controlled.
Feed rate has a significant effect on the rate of calcium absorption. Feeding too fast or too slow will decrease the rate of absorption. Once the core wire is fed to a certain depth, it will begin to melt. It must be ensured that the depth is sufficient to significantly affect the melting and dispersion of the calcium bubbles. The hydrostatic pressure exerted by the steel will favour the complete consumption of the material before it reaches the height of the steel. An appropriate feed rate favours calcium extraction. If the rate is too high, the steel is subjected to localised formation of large quantities of calcium vapour. The liquid is subjected to intense agitation, which results in the rapid volatilisation of a significant amount of calcium vapour into the surrounding atmosphere. Conversely, the calcium vapour is not dissolved early enough and therefore rises in large quantities, which in turn reduces the yield. Conversely, if the rate is insufficient, the depth of feed will be insufficient for complete dissolution. The cored wire will rise to the level of the molten steel and will be wasted before the molten steel has time to solidify.
2- It is very important to select the proper thread position.
The position of the cored wire also has a significant effect on calcium extraction. The optimum position of the cored wire feed point is in the centre of the downward flow of molten steel, as far away as possible from the bright ring of the argon blast. This location allows the calcium to change to a gaseous or liquid state, allowing it to be fully absorbed by the molten steel. The downward flow causes the pressure to drop, prolonging the residence time of the calcium in the molten steel.