Steel purification with Calcium Cored Wire is an injection metallurgical method to add pure metal calcium into the molten steel in the process of deoxidation, desulphurization and inclusion modification. It can greatly improve the calcium treatment efficacy of molten steel and reduce energy consumption.
This paper aims to achieve the following goals: 1. Avoiding the mixing unevenness of the iron powder and calcium powder.
The metal calcium in powdered form has a very large surface area and it easily oxidizes when exposed to the liquid steel. The oxidation of the metal calcium can lead to the splashing of the steel slag and reduce the alloy infusion efficiency. In addition, the core wire in powdered form is not easy to keep in place due to its loose nature and slag adhesion.
In order to overcome these disadvantages, a method of ladle feeding using the alloy cored wire was developed. Compared with spraying the alloy directly into the ladle, packing the alloy powder into cold rolled low carbon steel strip to make a cored wire of any length and using it for feeding into the molten steel is more efficient because the alloy can be fully dissolved in the proper position to produce a chemical reaction.
The high-density pure solid calcium core wire has a uniform wire diameter, good toughness and is not easy to break during the feeding process. It is suitable for the treatment of various steels and can effectively reduce costs.
Because of its high affinity with oxygen and low density and melting point, pure metal calcium is oxidized easily when it is directly added into the molten steel. This is one of the biggest problems in traditional methods such as adding calcium alloy directly into the ladle and spraying calcium into molten steel.
The advantage of core wire is that it can avoid the oxidation of metal calcium by injecting it into the liquid steel at a certain velocity. It also can effectively modify and control the nature of the oxide inclusions in the liquid steel, for example transforming spinels into aluminates and spherroidizing sulfides. This not only helps eliminate nozzle clogging in cast aluminum killed steel, but also improves the tranverse toughness and strength of steel.
In the metallurgical industry, the calcium treatment by cored wire is the most common method of steel purification. It can efficiently deoxidize and desulphurize the steel, change the composition of inclusions, prevent nozzle clogging in cast aluminum killed smelting, and improve mechanical properties of steel.
Incorporating metal calcium into molten steel with pure core wire can avoid the pollution of molten steel caused by mixing iron powder and slag. It can also reduce the quantity of slag used in the process, and can significantly reduce the production of fumes during welding, thus greatly improving the working conditions for technicians.
The pure core wire consists of an outer sheath made of cold-rolled low carbon strip, which is tightly wrapped around a core of metal calcium powder. The sheath is bonded to the core of the calcium alloy through sintering, making it possible to prevent powder leakage during the operation.
The core wire is fed into the molten steel by using a conventional wire feeder, and the injection depth can be easily adjusted. The use of the core wire can deeply reduce the content of harmful elements such as oxygen and sulfur in the molten steel, change the composition of inclusions, and help to avoid nozzle clogging of cast aluminum killed steel.
The use of calcium cored wire significantly reduces hidden costs. It eliminates activities like grinding and sandblasting prior to welding, as well as the cost of applying antispatter coating. In addition, it prevents arc slag build-up and reduces slag removal costs.
The core is made of metal calcium powder which is pulverized into a certain size and wrapped with strip steel, then through fine shaping and intermediate frequency annealing it gets shaped into cored wire. This is then wound into coils, according to the customer’s requirment.
The alloy cored wire is injected into the molten steel smoothly with a wire feeder to perform physical and chemical reactions at an ideal depth, thus purifying inclusions and improving quality and castability. It can also improve steel performance and alloy yield, shorten smelting time, and control the composition. This greatly reduces the cost of iron and steelmaking and improves economic benefits. It also avoids nozzle clogging of aluminum killed steel and reduces the amount of slag discharged.
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