Main points of intermediate frequency melting furnace steelmaking
First, the task of steelmaking
The main raw materials for smelting are scrap steel and a part of pig iron. There are many rusts in the purchased scrap, and there are mud and other dirt in the steel. The content of sulfur and phosphorus in the steel is also high. The task of steelmaking is to smelt the raw materials of the above conditions into high-quality molten steel with low gas content, high inclusion content, qualified composition and temperature. Specifically, the basic tasks of steelmaking are:
( 1 ) melting solid charge (cast iron, scrap, etc.);
( 2 ) making the elements such as silicon, manganese and carbon in the molten steel reach the specification components;
( 3 ) removing harmful elements such as sulfur and phosphorus and reducing their content below the specified limit;
( 4 ) removing gas and non-metallic inclusions in the molten steel to make the molten steel pure;
( 5 ) adding alloying elements (melting alloy steel) to meet the requirements;
( 6 ) The molten steel is superheated to a certain temperature to ensure the need for pouring;
( 7 ) In order to increase production and reduce costs, it is necessary to rapidly steel-making;
( 8 ) Cast into a good casting.
Second, the method of steelmaking
There are many methods for steel making, mainly induction furnace steelmaking, open hearth steelmaking, and electric arc furnace steelmaking.
Electric arc furnaces and induction furnaces commonly used in steel casting workshops. They have looser requirements on raw materials, higher quality of molten steel, and the steelmaking cycle is suitable for the characteristics of cast steel production. It is convenient to open and stop the furnace, and it is easy to coordinate with the progress of the molding and boxing processes. Organize production. In addition, the equipment for electric steelmaking is relatively simple, with less investment, and the infrastructure construction speed and capital recovery are fast.
In recent years, induction furnace steelmaking has gradually developed. Induction furnace steelmaking process is relatively simple, and the quality of molten steel can also be guaranteed. Many factories use induction furnace steelmaking to cast small castings, especially in investment casting, and widely use induction furnaces to melt molten steel.
In heavy machinery plants, open hearth steelmaking is still used today. The capacity of open hearth furnaces is generally larger than that of electric furnaces. The steelmaking of open hearth furnaces can produce a large amount of molten steel at one time, which is suitable for pouring large and complex heavy castings. However, the period of the open hearth steelmaking is long, and the time for refining a furnace steel generally takes more than six hours. The open hearth structure is large and complex, the output is low, and the quality of the molten steel is not as good as that of the electric furnace, so its development is greatly limited. In some countries, new open hearths are no longer built.
In recent decades, pure steel top-blown converters have been widely used in the steelmaking industry for steelmaking. This steelmaking method is fast, high in productivity, and the quality of molten steel is also guaranteed. This type of furnace is more suitable for steel ingot production.
With the development of production and science and technology, new steelmaking methods for DC arc furnaces, vacuum induction furnaces and refining equipment have emerged, and the quality of molten steel has been greatly improved, and the quality of castings has been greatly improved.
