Heavy rail smelting pure steel making technology
In the production of national standard heavy rails, the smelting link is the key to laying the foundation for quality. Heavy rails need to withstand huge pressure and impact, and the purity of molten steel is extremely high.
Nowadays, converter or electric furnace smelting combined with off-furnace refining process is widely used. Hot metal pretreatment is the first step, and the content of harmful elements in hot metal is reduced by desulfurization, dephosphorization and other operations. For example, in a large steel plant, the sulfur content of hot metal is reduced from 0.03% to below 0.005% by blowing magnesium powder and other methods, providing high-quality raw materials for subsequent smelting.
Entering the converter or electric furnace smelting, key components such as carbon content are accurately controlled. Taking the production of U71Mn heavy rail steel as an example, the carbon content must be strictly controlled at 0.65%-0.76%. Subsequent off-furnace refining uses LF (ladle refining furnace), RH (vacuum circulation degassing device) and other equipment. LF refining produces white slag to absorb inclusions in molten steel, while RH degasses, decarburizes and fine-tunes the composition in a vacuum environment. After this series of operations, the gas content in the steel is greatly reduced, and the size and number of inclusions are reduced, providing pure molten steel for rolling high-quality heavy rails, ensuring the internal quality of heavy rails, and improving their strength and toughness.