Cored wire is a steel strip which is rolled and stuffed with alloy powders. Calcium iron cored wire is made of a mixture of metal calcium and 65%-72% iron powder as the inner layer, wrapped with cold-rolled low carbon steel as the sheath. The cored wire is inserted smoothly into molten steel and melts in the ideal position, avoids reaction with air and slag, increases absorptivity of metallurgy additives.
Compared to spraying alloy powder directly into the ladle, packing the alloy into cold-rolled low carbon strip and forming it into cored wire before insulating it makes it easier to control the amount of addition, which is more economical for steelworks. The high-density pure solid calcium core wire is not easily broken during the feeding process, and can be used for the treatment of different types of molten steels.
The solid calcium core wire can be inserted into the molten steel smoothly and quickly by using a wire feeder, which is more convenient than the spraying method and prevents calcium dust from spreading out of control. It also avoids the mixing unevenness of iron powder and calcium powder that often occurs in the pulvis calcium wire used in the past.
The alloy cored wire can be injected into the liquid metal at an ideal speed to perform physical and chemical reactions, thus achieving better deoxidation and desulphurization effects, changing the nature of inclusions by transforming spinels into aluminates and spherroidizing sulfides, eliminating nozzle clogging in cast aluminum killed steel, improving steel quality and castingability, shortening smelting time and reducing energy consumption. Moreover, it can improve the calcium treatment efficiency of the molten steel furnace and reduce the labor intensity of workers. It can also be used as an inoculant in converter steel workshops.
In copper smelting, sulfur decreases the surface tension of molten iron and increases the contact angle between liquid copper and iron solid. It also hinders graphitization from a kinetic point of view, and it is difficult to remove sulfur in molten copper. Hence, desulfurization is an important process in the metallurgy of copper smelting.
Using cored wire, alloy powders can be put into the molten steel smoothly and evenly and can make a good chemical reaction. This enables to avoid the reaction of added elements with air and slag, increase absorptivity of metallurgy additions, and achieve deoxidation, desulfurization and alloy fine-tuning of molten iron.
According to thermodynamic calculations, CaO can react with FeS and Cu2S, but it is hard for CaC2 to react with Cu2S. Therefore, a method that uses calcium sulfide (CaSO) as a reducing agent for desulfurization of copper is proposed.
The metal compositions of molten iron and slag were detected by inductively coupled plasma atomic emission spectrometry (Prodigy, Optima 4300 DV, Lehman, NY) and atomic absorption spectrophotometer (G4 ICARUS, Bruker Ltd, Karlsruhe, Germany). The microstructures of copper slag and the metal sample were analyzed by scanning electron microscopy (SEM, SU-8010, Hitachi, Tokyo). The micrograph of the Cu-Fe alloy before desulfurization showed a main matrix of pearlite, while after desulfurization, a large number of nano-copper spheres with a diameter of 200-800 nm appeared in the metal.
Inclusion modification is a key process in steel smelting. However, the traditional method of adding calcium metal powder or particles into molten steel can cause an explosive reaction and quickly degenerate into an oxide, which cannot enter the upper or deeper position of the molten iron to react. This method also causes nozzle clogging, thereby limiting its application. The invention of the alloy cored wire solves this problem by using a low-carbon sheath to encase powdered minerals, metals and ferroalloys. The sheath can be inserted into the smelting furnace by the injection system without damaging the smelting process, and the inclusions inside are tightly surrounded.
The calcium treatment can modify the morphology and distribution of inclusions in high carbon hard-wire steel. According to the thermodynamic calculated results based on Factsage 7.2 software, the B-type alumina inclusions can be transformed into liquid calcium aluminate inclusions in the high carbon steel with an appropriate amount of calcium addition. The morphology of the calcium aluminate inclusions is close to spherical and their aspect ratio decreases with the increasing amount of the calcium content in the inclusion.
When the magnesium was added into the smelting furnace, it could prevent the formation of oxides and modify the morphology of the B-type alumina inclusions into complex ones with small aspect ratio. This can reduce their deformation during the hot forging process, thus avoiding the harmful effects on the final product quality.
In order to obtain a better deoxidation and desulfurization result, it is necessary to ensure that the alloys introduced into the liquid steel reach the upper and deeper position of the molten steel. Since the alloy powder can easily vaporize at high temperatures, simply throwing it into the molten steel leads to combustion and does not enter the desired position in the molten steel. This is why cored wire has become a preferred method of alloy addition.
Cored wire consists of a pure calcium sheath wrapped around an iron core. The sheath is extruded into different diameters and can be made from a variety of alloy materials, depending on the required characteristics. It does not pollute the molten steel and requires minimal auxiliary equipment, making it an ideal solution for reducing refining costs.
The calcium iron alloy in cored wire has strong deoxidation and desulfurization properties and can change the shape of inclusions in molten steel, improving fluidity, machinability and impact toughness, as well as ductility. It can be fed into the molten steel using various wire feeding methods. It can be used as a warming agent in converter steel workshops, an inoculant for cast iron and an additive in the production of ductile iron. In addition, it can be used as a refining addition for continuous casting steel.
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