The invention provides a calcium metal core encased in an aluminum strip or sheath. When inserted smoothly into the molten iron or molten steel, it reaches an ideal position to react.
Particulate metallic calcium metal is hydroscopic and reactive, which causes combustion or splashing. It can also cause the aluminum jacket to melt at an insufficient depth.
Cored wire is a kind of deoxidizer and desulfurizer that has the advantage of reducing the cost of iron making and steel casting, increasing alloy yield and improving the quality of casting. It is widely used in the smelting industry and foundry industry. It is mainly used as deoxidizer and desulfurizer in converters and ladle furnaces. It can also help to change the shape of non-metallic inclusions and improve the quality of cast iron and cast steel products.
This type of cored wire has a sheath of low-carbon steel and a powder filling of metal calcium, silicon, aluminum, manganese, carbon, chromium, sulfur and accompanying elements. The sheath and the core are connected by an intermediate layer of refractory. The high density pure calcium core wire has a smaller specific surface area than conventional powder and is less susceptible to oxidation during operation, which reduces the risk of contamination of the molten steel with other oxide inclusions.
The solid calcium core wire can be fed smoothly into molten steel by a wire feeder. It melts into molten steel at an ideal depth and is absorbed by the liquid steel. This method is more efficient than spraying calcium powder into molten steel and avoids reaction with air and slag, which increases the element yield and improves the quality of cast iron and cast steel.
In the prior art a granular calcium powder is encased in an aluminum strip to introduce it into the molten ferrous metal bath. The use of the core reduces the vapor pressure of the introduced calcium which results in a quieter, more reproducible reaction. However, problems still exist such as surface oxidation of the metallic calcium, splashing during the introduction and unreproducible results. The present invention solves these problems by providing a cored wire comprising a composite core with an aluminum strip encased in a steel sheath. The core has a composition of calcium, silicon, aluminum and manganese with a percentage of each material in the range of 10% to 90%, balance being aluminum. The use of the cored wire allows a more reproducible calcium recovery, enables treatment to take place in all ladle types and minimizes splashing.
In addition the cored wire can be used to introduce a master alloy into the molten metal and to control the size of inclusions. This is achieved by synchronizing the processes of the formation, release into the metal and melting of the iron-calcium-silicon master alloy within the sheath. This also helps to round off non-metallic inclusions in the liquid steel and thus improves casting capabilities. The result is a substantial increase in the utilization of the calcium contained in the composite core.
The addition of aluminum, silicon and manganese increases tensile strength, but decreases elongation. Zinc has no significant effect on room-temperature properties. Grain refinement by titanium and boron has limited effect, but silver additions increase elongation. Titanium and boron also improve corrosion resistance. Lead and cadmium significantly decrease alloy properties, and antimony has a deleterious effect on castability. Magnesium, sodium and zirconium have a positive influence on castability.
By means of professional cored wire equipment, calcium silicon alloy powder can be inserted into molten iron or steel at the ideal depth through a cored wire machine and thereby produce a chemical reaction. This avoids reaction with air and slag, and improves the absorptivity of metallurgy additives. This makes it an effective composite deoxidizer, desulfurizer and to change the form of the steel impurities such as sulfur and phosphorus.
The calcium content of the filling composition is adapted to the chemistry of the iron-calcium-silicon master alloy, which is formed in the sheath of the cored wire. Irregular compacting of the powder filling in the sheath results in a disproportional quantity of the material introduced into the steel bath or metal liquid, which has negative effects and limits wire application. The high calcium content in the cored wire prevents premature metal calming of the sheath in the local interaction area, and it is possible to achieve a considerable improvement in calcium loading efficiency.
Due to low calcium solubility at steelmaking temperatures, Ca can only be added as a solid into liquid metal by cored wire. This is important because it improves fluidity, cleanliness and surface quality in cast irons and ductile cast steels and also creates violent agitation, which reduces gas content and prevents oxidation of the slag.
Cored wire for calcium treatment is made by breaking metal calcium into a suitable particle size, and then wrapping it in cold-rolled low carbon strip to form a composite material of any length. The steel strip has a hard line that does not slip or run when feeding the cored wire, which significantly improves the feeding process and reduces work intensity.
The high-density core pure calcium wire has a smaller specific surface area than traditional powder cored wire, making it less prone to oxygen scavenging and contamination of molten steel. It is also easier to maintain because it can be fed at a lower velocity than conventional powder cored wire.
The high purity and density of the pure calcium core provides a higher calcium absorption rate than the calcium alloy core wire. The steel sheath protects the core, which allows the wire to reach deeper into molten steel and stay there longer to ensure complete denaturation of inclusions. It also helps to achieve a high calcium recovery rate.
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