Calcium treatment process is one of the most important steps in secondary metallurgy before casting. Calcium treatment with cored wire can deeply reduce the content of harmful elements and change the composition of inclusions. It also can avoid clogging of casting nozzles and improve the castability of some steel grades.
Traditionally, calcium or calcium alloy is injected into the molten steel via spraying method or a wire feeder. But this way, the deoxidizer can not reach the deeper position of the molten steel. Also, the calcium metal can be contaminated by the melted iron.
In this case, the cored wire is fed in a deep position of the molten steel to avoid contaminating the melted iron and ensure the calcium is fully absorbed into the molten steel. This can reduce the consumption of calcium powder by about 15%. The injection speed of the cored wire should be carefully selected to maximize the absorption of the calcium and to avoid causing blockage of the continuous casting steel. Moreover, the solid core pure calcium wire is hard and difficult to break, so it has more advantages compared to the calcium iron or calcium silicon wire. Especially, this high-density core pure calcium wire has the advantage of not slipping and running during feeding.
For the steelmaking process, calcium has an effect on deoxidation and desulfurization. It can modify the nature of oxide inclusions into liquid ones that do not clog casting nozzles and reduce alumina (AL2O3) slag pollution of molten steel.
However, simple calcium addition methods, such as spraying or dumping it loosely into the molten steel, cause the element to evaporate quickly, which causes the reaction to fail. In order to solve this problem, the alloy cored wire method has been developed.
The cored wire consists of calcium-containing powder packed into cold rolled low carbon steel strips. The cored wire is fed into molten steel with the help of a wire feeder to melt in the depth of the molten steel ladle and add calcium. The feeding position of the solid core calcium wire has an important influence on the calcium absorption rate, and it is better to feed it into the molten steel near the center of the descending flow, where the melting point of molten steel is lower.
The calcium treatment process with Calcium Cored Wire can avoid an adverse effect on the quality of steel due to the introduction of harmful elements into the molten steel. Compared to the standard method of adding calcium alloy directly into the ladle or spraying it into the molten steel, this method provides a more stable and cost-effective calcium treatment effect.
Furthermore, it can reduce the consumption of calcium in tons of steel by avoiding the waste caused by the injection of iron powder and other additives. It can also save energy by avoiding the evaporation of calcium in the injection process.
In addition, it can improve the metallurgical performance of the steel by changing the nature of oxide and sulfide inclusions in molten steel. For example, it can eliminate clogging of caster nozzles caused by alumina (AL2O3) inclusions in Aluminum killed steel. It can also prevent slag formation in the molten steel and help to achieve a higher level of purity.
The feeding process with Calcium Cored Wire is much smoother than that of spraying or adding calcium iron directly into liquid steel. This is due to the core wire’s hard line which makes it difficult for the core material to break or run during feeding, so that the feeding operation is much more reliable and steady.
The pure calcium cored wire is made of a high purity solid extruded calcium rod wrapped around a cold rolled steel strip. It is a perfect substitute for conventional calcium feed wire in the steel melting shop because it can avoid the problems like low yield, frequent wire breaking during wire feeding and SEN clogging experienced with conventional calcium feed wire.
Cored wire can also help to solve the problem of slag pick-up which is prohibited for some low silicon content steel grades and reduce the steel-making costs. In addition, it can purify the molten steel, modify inclusions and improve the castability of continuous casting steel.
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