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Refinement of the Bearing Steel Processing Technology (1)

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Dnebe Special Steel Works, a company with a long history in producing bearing steel, has developed various advanced processes such as electric arc furnace smelting, electroslag remelting, and vacuum arc remelting. These techniques are used to produce different types of bearing steels, including GCr15, GCr15SiMn, GCr20SiMn, GCr4, GCr15V, 55SiMo5VA, 95Cr18, Э И347, and more. The product specifications include hot-rolled bars with diameters ranging from φ8 to 220mm, and precision forged cold-drawn bars from φ2 to 40mm. Additionally, hot-rolled wire rods from φ8 to 13mm and cold-rolled wire rods from φ2 to 12.5mm are also produced, along with special finish bars. As customer demands evolve and new technologies emerge, the production process for bearing steel has continuously been improved. Initially, customers did not require electroslag or vacuum arc remelting, but as standards like ГОСТ801-78 became more stringent, there was a growing need for lower oxygen content and fewer non-metallic inclusions. In the early stages, the process involved tempering molten steel in a 60-ton alkaline electric arc furnace, followed by pouring into high-alkalinity slag ladles and casting into ingots weighing between 2.8 to 3.6 tons. The steel contained oxides and non-metallic impurities, with oxygen levels ranging from (25–40) ppm. During the 1970s and 1980s, efforts were made to enhance steel purity and reduce oxygen content. This led to the use of CaO-Al₂O₃ liquid slag for refining and vacuum slag treatment. Although this method helped reduce oxide and sulfur content, it still resulted in relatively high noise pollution and was not widely adopted. Another approach involved using solid slag materials like lime and fluorspar for steel refining. While this improved product yield—especially for sections below 40mm—it still left oxygen levels too high (up to 30 ppm), failing to meet the requirements of ГОСТ801-78 (≤20 ppm). In the 1980s, external treatment methods were introduced, reducing gas content and improving steel purity. By 1991, the factory began using a ladle furnace, and in 1996, they adopted the Danieli ladle furnace. These improvements significantly enhanced steel purity, reduced oxide and sulfide content, and lowered oxygen levels to around 18 ppm. In 1999, the application of Mannesmann’s sulfur removal technology, along with STM and DIN specifications, helped identify non-metallic inclusions and oxygen content. The process was further refined through testing different tapping plans, using solid slag for deoxidation, and optimizing ladle slag and furnace operations. The "fine" argon blowing process was emphasized, and during casting, argon-protected steel flow was maintained to ensure accurate oxygen sampling and control.

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