The calcium silicon cored wire is a kind of metallurgical refining wire. It is simple in structure, convenient in operation, small in investment and safe.
It is widely used for molten steel deoxidation, desulfurization, alloy fine-tuning and control of the shape of inclusions. It is composed of gatherer, format roll, hold-down head, welding rolls and tube reducing roller.
Wrought magnesium (Mg) alloys are limited in application due to their low mechanical strength. While some studies have shown that their mechanical properties can be improved by cold working, alloy addition, aging and precipitation hardening, they are not competitive with medium-strength casting alloys.
Adding zirconium (Zr) in Mg alloys can improve their strength and corrosion resistance by reducing the harmful effect of Fe and Si elements on the corrosion performance. However, it requires expensive rare earth (RE) elements and is difficult to achieve the required metallurgical properties.
Cored wire feeding can effectively overcome these disadvantages by supplying the solid metal Mg alloy cores. The feeding equipment is simple in structure, convenient in operation, does not produce smoke, and the temperature drop of molten steel is small.
The application of magnesium-based alloys in biodegradable orthopaedic implants is inhibited by their high degradation rates in physiological environments and resulting loss in mechanical integrity. In this paper, an attempt is made to improve the degradation behaviour and the mechanical integrity of AZ91 magnesium-calcium alloy by applying calcium phosphate coatings.
The oxidation resistance of AZ91 magnesium-calcium alloy was improved by the addition of calcium, as evidenced by the results of electrochemical measurements (potentiodynamic polarisation and electrochemical impedance spectroscopy) and slow strain rate tests in modified-simulated body fluid. The result showed that the general and pitting corrosion resistances of AZ91Ca were enhanced significantly.
The in vitro cytotoxicity of common binary alloying elements has been compiled in Table 2 below, based on their effects on various cell lines as reported in the literature.
The use of the cored wire makes it possible to control the oxidation rate of the calcium magnesium alloy in molten steel and prevents the formation of a hard slag layer. This reduces the sulfate content of the molten steel, prevents harmful elements from entering the magnesium powder and improves the yield of the metal magnesium.
The corrosion resistance of the AZ91D magnesium alloy has been improved by coating it with a calcium phosphate conversion coating, and the performance of this alloy has been compared to that of a pure magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed that the AZ91Ca-coated alloy is significantly more resistant to general and pitting corrosion in modified simulated body fluid.
The cored wires used in metallurgy can be filled with pure calcium, with a mixture of calcium and iron powders or with aluminium powders. This provides a range of advantages such as a reduction in the sulfide content of the molten steel (so called sulphide containing cast iron), improved casting quality, and reduced slag content.
One of the most important steps in making cored wire is proportioning the different alloy powders to form a mix which is suitable for forming the core. In most cases this mixing takes place using mixers of ploughshare type, a feature which at times induces segregation phenomena of the different powders depending on their densities.
Cored wire uses a steel strip as wrapper, and is stuffed with alloy powders by specialized equipment. This process avoids reaction with air and slag, increases absorption of alloy additives, changes the form of impurities and improves the quality of molten steel.
The tin addition significantly reduces the corrosion rate of lead-calcium-tin alloy grids by increasing the thickness of the passive layer. This improvement is due to tin enrichment at the grid grain and subgrain boundaries, as well as tin concentration within the a-PbO lattice [16]. This leads to an increase in conductivity. It also decreases the rate of grid weight loss and growth during corrosion.
The calcium core enables the formation of a high-quality casting with excellent porosity, good wettability and low casting shrinkage. This helps to reduce the time needed for cooling and improves the surface finish of the final product.
Medical magnesium alloys are extensively researched as bone repair materials, but their rapid degradation rate has so far prevented clinical trials. The use of a calcium-based magnesium alloy could help to overcome this obstacle.
Studies have shown that Sr promotes the differentiation of bone marrow mesenchymal stem cells into osteoblasts, and therefore has an important role in improving the mechanical properties of magnesium alloys [147]. Researchers have developed several methods for coating medical magnesium alloys with Sr by chemical conversion, micro-arc oxidation, electrochemical deposition, sol-gel method, etc.
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