Calcium silicon manganese alloy is a common compound deoxidizer in steel making. It is used for melting of stainless steel and special alloys.
Cored wire is made from rolled and stuffed steel strip with different alloy powders. When the sheath of cored wire enters molten steel, it is vertically and stably inserted into the ideal position, which can avoid reaction with air and slag, and improve absorption of metallurgy additives.
Calcium cored wire is widely used in steelmaking. It can effectively treat oxygen in molten steel, reduce the generation of oxide and improve the morphology of inclusions. It can also deal with harmful elements, such as Sulfur and Phosphorus, in molten steel. The use of cored wire can greatly increase the alloy yield, reduce the consumption of metals and save the cost of refining.
Cored wire is a metal strip wrapped with pure calcium or alloy powder through a professional cored wire machine. It is then inserted into the molten steel to avoid nozzle clogging and relieve slag contamination. It can greatly reduce the consumption of calcium in tons of steel and improve the effectiveness and efficiency of molten steel treatment.
The feeding speed of the cored wire has a great influence on the absorption rate of calcium. Too fast will result in a decrease in absorption rate, while too slow can cause calcium to be burned into gas and float into the slag layer. Therefore, the optimum feeding speed must be determined by analyzing the actual steelmaking plant data.
The cored wire is inserted smoothly into the molten iron and steel with a special feeder. It melts at an ideal depth in the molten steel and a physicochemical reaction takes place. The addition process can purify the morphology of the steel inclusions, change their shape and improve castability, which can help to improve the quality of the finished products.
Incorporating calcium additives in the form of cored wire has been a highly effective and efficient means of achieving desulfurization in steelmaking. This process significantly reduces the amount of sulfur present in the molten metal, enabling steelmakers to achieve desired levels of purity for their final products and meet quality standards.
The encapsulated pure metal calcium wire in a steel sheath (also known as cored wire) is inserted into the steel melt with help of a wire injection system. This ensures a higher recovery of calcium in the finished steel than that achieved by simply adding Ca / CaSi lumps to the molten metal. It also saves time and costs, while providing greater consistency than conventional methods.
The calcium cored wire’s high reducing capacity enables it to deoxygenate the molten steel, removing any impurities by forming low-melting compounds with them, which are then discharged from the steel. It also enhances the quality of the steel by reducing the formation of undesirable sulfide inclusions, which can negatively impact the mechanical properties of the final product. Its versatility makes it suitable for a variety of steelmaking processes, including basic oxygen furnaces and electric arc furnaces. In addition to reducing sulfur content, it also contributes to cleaner air and an improved working environment. The process is particularly critical in the automotive industry, where high-quality steel components must be free of sulfide inclusions.
Inclusion modification is a key process for the removal of non-metallic inclusions in secondary steel refining. It is important to remove the harmful inclusions and convert them into low melting point plastic inclusions to improve the production and performance of steel. The calcium treatment method is an effective way of modifying inclusions in steel production. The injection of calcium alloy in the form of cored wire has good metallurgical performances and high efficiency for deoxidation, desulfurization and inclusion modification.
The injected calcium is mainly distributed into the liquid phase of the steel bath. The process of inclusion modification is influenced by the temperature and reactivity of the liquid steel. In order to obtain a better understanding of the impact of the calcium injection on the inclusion distribution, a computational model has been developed. This model uses a combination of CFD and thermodynamic calculation to simulate the dissolution of the cored wire into the liquid steel and its influence on the inclusion distribution.
The results show that the morphology of B-type brittle inclusions is greatly modified after calcium treatment. The inclusions in sample 1 exhibited a spherical shape, whereas those of the samples with different calcium content were mainly semi-liquid or liquid. In addition, the size distribution of inclusions in sample 3 was narrower than that of the other two samples. This indicates that the incorporation of calcium into the inclusions is beneficial for obtaining dispersed inclusions with fine size.
Inclusion modification during the wire injection process is not as simple as merely changing from solid inclusions to liquid ones. The morphology of the inclusions varies according to the underlying steel composition and temperature. This complicates the prediction of the behavior of inclusions in cored steel.
A combination of fluid-dynamic calculations and thermodynamic simulations has been used to model the formation, evolution, and interactions of the solid and liquid inclusions during the injection period. The results obtained with the model agree well with the observations made by metallographic examination. The morphology of the inclusions is irregular with a size ranging from several micro-meters to several hundred micro-meters. They are surrounded by a thin oxide layer and are dominated by calcium silicates, with an average MgO content of about 6.6 wt.%.
The inclusions formed by the dissolved Ca and oxygen are a mixture of aqueous and gaseous species. The aqueous species mainly comprise spherical and flat phases. The spherical inclusions are more volatile and have poor deformability, which can be the cause of relatively poor trip surface quality for the rolled steel strip.
The spherical inclusions have a lower melting point than the crystalline ones and can be easily separated from the steel melt by mechanical methods. Therefore, the cored wire has a better mixing effect than pure solid calcium wire.
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