Calcium silicon iron treatment agent is a kind of steel additive used to modify the composition, size and structure of oxides, sulphides and silicates in liquid steel. This modification helps control inclusion morphology, particularly during hot working.
The conventional method of adding Ca is to spray it or dust it into the molten steel ladle. Cored wire, which uses a sheath of low-carbon steel strip as an inner core, can feed the Ca to the deeper position of molten steel for better effect.
At the steelmaking temperatures, calcium exists only in vapor form. Therefore, it cannot directly react with the oxygen (O) and sulfur(S) in molten steel to remove them. It can only react with them at the calcium vapour/liquid steel interface if it is inserted into molten steel through cored wire injection.
Cored wires are made of steel strip, stuffed with alloy powders and used in ferrous metallurgy for out-of-furnace treatment of molten steel and pig iron. They are inserted smoothly into the molten steel through a wire feeding system, thus avoiding reaction with air and slag, increasing absorptivity of metallurgy additives, and improving the quality of molten steel and cast steel.
The solid core calcium line has a smaller specific surface area than the cored wire, and it is not easily oxidized by the molten steel around it, so it can continue to function effectively in the molten steel for longer. It can be used as a deoxidizer, desulfurizer, and to change the composition of inclusions in molten steel to prevent nozzle clogging.
The inoculation of molten steel by spraying or sprinkling calcium carbide cannot fully eliminate the unreacted sulfur and oxygen from the molten steel. Besides, the insufficient inoculation causes many problems like nozzle blockage and abrasion. However, the calcium cored wire technique makes the contact between Ca and molten steel as intimate as possible. This can not only improve the quality of smelting steel but also greatly reduce pollution.
The solid-core calcium wire wrapped with an alloy strip is inserted smoothly into molten steel by using special equipment, so that it can be fed at an ideal position in the molten steel, and the melted iron powder and the cored calcium are completely mingled together to produce chemical reaction. This helps to avoid the reaction with air and slag, increase element yield, alleviate nozzle blocking and improve casting sequence. It also plays a role in modifying the size and morphology of inclusions, thereby improving the after rolling ductility of steel.
According to the invention, a cored wire for treating molten cast iron consists of a sheath of iron material and a filling of fine-grained magnesium master alloy. The magnesium master alloy is composed of 8 to 15% by weight of magnesium, 42 to 48% by weight of silicon, and the rest essentially of iron.
When calcium is sprayed directly into the molten steel, it can only reach the upper position of the molten steel and react easily, which will result in a lot of metal calcium dust. This will cause excessive reoxidation, which can generate high melting point calcium aluminates and nozzle blockage.
However, when a steel clad calcium wire is fed into the molten steel through a cored wire feeding system, it can achieve the same effect as spraying. This will avoid the mixing unevenness of calcium and iron powder, which will increase the treatment efficiency of the molten steel. This is an economical way of utilizing calcium to treat the molten steel.
Calcium cored wire consists of a high-density solid pure calcium wire as the core, and is wrapped with cold-rolled low-carbon steel strip to form the steel sheath. This design prevents the leakage of calcium powder during the feeding process, which makes it more convenient and effective to use.
It can be used to treat molten steel in the following ways: deoxidation, desulfurization, alloying, microalloying and inclusion denaturation of continuous casting steel. Compared with conventional calcium addition methods, calcium cored wire can effectively reduce the consumption of calcium per ton of steel and significantly reduce costs.
Moreover, the calcium sheath can collect oxides and harmful substances in molten steel to form slag, thereby improving the quality of molten steel. Therefore, it can greatly improve the production efficiency of converter steel workshops. The emergence of this new technology can also make the steel-making process safer and more environmentally friendly. Therefore, it is a valuable addition to the steel-making industry.
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