Calcium treatment is one of the most important processes in secondary steel making before casting. Compared to other methods of calcium addition, cored wire can achieve a better deoxidation and desulfurization effect and save cost for the steelmakers.
The solid pure calcium cored wire consists of a metal sheath wrapped tightly around a powder sheath of calcium. The sheath of the cored wire has a smaller specific surface area and is not easily oxidized at the high temperature of molten steel.
The calcium treatment by injection of a cored wire is an essential part of the secondary steel refining technology. It allows deoxidation, desulfurization and inclusion modification in the molten metal. However, it is difficult to reach an optimal calcium recovery, as the injection speed of the cored wire influences the rate of calcium incorporation into the melt.
AFFIVAL developed a new type of calcium wire, based on a thermal insulation layer sandwiched between two steel strips. This new wire, branded as PapCal or HDx, represents the State-of-the-Art in calcium treatment. Its metallurgical performances allow to decrease significantly the consumption of calcium in a LF furnace and to secure the quality of the casting.
Moreover, these new calcium alloys allow to reduce the amount of harmful elements introduced in the melt during the casting process. This allows to avoid an adverse effect on the final product quality by preventing the formation of sulphur-rich oxide inclusions and by inhibiting the growth of pre-existing cracks.
Calcium is used in liquid steel treatment to reduce the aluminum killed steel clogging at the caster nozzle and to perform deoxydation, desulfurization and inclusion modification. The most effective way to carry out alloy additions is by cored wire injection.
In order to achieve the best results, it is necessary to optimize both the cored wire and the injection process. This can be achieved by minimizing the consumption of calcium, increasing the magnesium concentration and adjusting the feeding speed of the cored wire.
Injection efficiency and the deposition of weld metal depend on a number of factors, including transfer mode, shielding gas mixture and the arc characteristics of the cored wire. Due to their arc characteristics and low slag volume, metal-cored wires provide high deposition efficiencies of up to 92-98% with spray transfer and argon 85/CO2 15% mixture shielding gasses. This leads to significant savings in post-weld clean-up costs. This is particularly important in continuous operations.
The best way to ensure that welders can quickly get back to their jobs is to reduce the amount of time spent on pre- and post-weld activities. By switching to metal-cored wire, you can eliminate a significant portion of these steps, saving your operation money and time.
Using cored wire to inject calcium into liquid steel can help you improve the performance of your calcium treatment. By ensuring that the release of calcium takes place deep within the melt, you can achieve better deoxydation and desulfurization, as well as reduce the risk of caster nozzle clogging by inclusions such as alumina.
New calcium injection technologies such as PapCal or HDx represent the State-of-the-Art in the field of metallurgical chemistry, and a crucial step towards increasing efficiency and securing the iron casting process by decreasing consumption and minimizing standard deviation. This, in turn, contributes to reducing the cost of ownership for our customers.
Metal-cored wires offer good gap bridging and weld fusion that minimizes reject rates. They also reduce welding times, so you can increase productivity and improve your bottom line. These wires are specially formulated to provide "best-in-class" mechanical properties. Some have higher toughness than required by code.
The calcium treatment by cored wire is an essential process in secondary steelmaking for the deoxidation and desulphurization of the liquid steel. In addition, it is used for inclusion modification and castingability improvement. Its success depends on the optimization of the injection conditions. In this context, the injection speed of the cored wire is critical.
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