Calcium Cored Wire is a new treatment in steelmaking developed in recent years, it can purify the molten steel, change the shape of inclusions and improve the castability of the metallurgy. It can significantly increase the yield of alloy, reduce the metal consumption and shorten smelting time.
It consists of steel strip rolled and stuffed with alloy powders, it is vertically inserted into the molten steel through the wire feeder. It has strong adaptability, less one-time investment and small occupied area.
Compared with conventional calcium treatment, calcium cored wire offers advantages in terms of deoxidation and desulfurization. It also improves the quality of steel casting and reduces steelmaking cost.
During calcium treatment, the cored wire is inserted into the molten steel in an appropriate position, where it melts to form a physicochemical reaction with the steel melt and aims to change the shape of inclusions. In the process, it avoids the reaction of added elements with air and slag, increases the element yield, and shortens the smelting time.
The metallurgical results obtained by using the PapCal and HDx equipment with a calcium cored wire, showed that the aimed calcium is reliably delivered very deeply into the ladle. The optimum conditions for this are achieved when the wire overcomes the ferrostatic pressure in the steel bath and the liquid inclusions of the cored wire have reached the liquid steel. This is made possible by a precise calculation of the aimed calcium content based on the steel chemical composition.
The metallurgical cored wire consists of an outer layer, a middle protective layer and an inner solid calcium metal core. It has high strength, good corrosion resistance and no pollution to steel. The core is made of a special alloy powder with low moisture absorption and no slag formation.
It can increase the yield of calcium in molten steel, change the inclusion form and improve cast ability, which is more convenient to use than adding calcium sulfide lumps at the bottom of the ladle. In addition, it has the advantage of reducing the energy consumption, slag formation and smelting cost.
Reasonable adjustment of the feeding speed has a great influence on the calcium absorption rate. If the feeding speed is too fast, it will cause the core wire to be consumed before it can absorb the molten steel. If it is too slow, it will cause the molten steel to violently tumble and the dissolved calcium bubbles may not be completely consumed before they float up to the surface of the molten steel.
The inclusions of molten steel metallurgy cannot be completely removed. The best way to mitigate their negative effects is to denaturate them. This can be done through various methods, such as slag blowing and cored wire injection. But the effect is only effective if the additives are added properly.
During the injection process, the cored wire is vertically inserted into molten iron or molten steel through the wire feeder. It melts at an ideal depth and a physicochemical reaction occurs. This process reduces the amount of slag that needs to be added and increases element yields.
In addition, the inclusions in the slag are denaturated by the calcium oxide and calcium aluminate complexes of the cored wire. This prevents them from returning to the liquid steel and improves casting quality. It also reduces hydrogenation and meets the requirements of high-purity steel. The morphology of the inclusions can be determined by a Zeiss-Ultra 55 field emission scanning electron microscope and their composition by an energy dispersive spectrometer (EDS). The inclusions can also be detected by carbon-sulfur detectors, nitrogen-oxygen determinators, and calcium iodide metering systems.
Core wire is a new treatment in steelmaking. It can purify the shape of steel inclusions, partly change the nature and shape of inclusions, improve the quality of molten steel, and enhance the castability of molten steel. It can also increase the yield of alloy, reduce the steel consumption, and cut down the cost of smelting.
The notch toughness of micro-alloyed structural C steels is usually superior to that of conventional structural C steels. This is a result of the finer ferrite grain size that results from controlled hot rolling and of precipitation strengthening by the addition of V, Nb, or Ti. The normalizing of these steels is problematic since their FP grains coarsen at the typical austenitizing temperatures used for normalizing, and therefore much of the precipitation strength increment is lost. Grain refining by cold rolling can help, but does not completely resolve this problem. In addition, the high carbon content of these steels can impair weldability.
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