After more than two years of practical production, it is evident that the transformation and auxiliary design of our factory's 3,1 electric arc furnace have proven to be both reasonable and reliable. These improvements fully meet the current production requirements of our facility, ensuring smooth and efficient operations.
The implementation of the 81 tapping process for the existing electric arc furnace has demonstrated significant advantages, including lower investment costs and quicker results. As an intermediate step in the refining process, this method has been well-matched with the original refining furnace, thereby advancing the overall technological level of our plant’s production process.
However, after over a year of operation, the 8 Ding electric arc furnace has encountered some challenges. One major issue is the limited availability of scrap steel, which leads to inconsistent types and compositions. This variability causes unstable yield rates, complicates smelting operations, extends melting times, and makes slag control more difficult, ultimately affecting the performance of the refining furnace.
Additionally, the refractory grade used in our factory’s furnaces is relatively low, leading to rapid erosion of the furnace lining. The nozzle diameter tends to increase over time, requiring frequent replacements of the lining, which hinders the progress and optimization of key performance indicators for the electric arc furnace.
Another challenge comes from the fact that our factory operates three large and one small electric arc furnaces, along with a small billet continuous casting machine. In addition to its refining function, one of the furnaces also needs to align with the rhythm of the continuous casting process. This dual role has somewhat negatively impacted the furnace’s overall performance.
Acknowledgements:
Recent research conducted by the National Institute of Metals in Japan has focused on developing new welding materials for high-tensile-strength steels. This initiative is aimed at addressing the need for preheating during the welding process. The newly developed material, which includes nickel and chromium, initiates its martensite transformation at lower temperatures. Thanks to the combined effects of these elements, the material achieves the largest martensitic transformation zone under normal temperature conditions.
Cracks often occur in the welding or connection zones of high-tensile-strength steels at low temperatures. This happens because, as the temperature drops, the welding area—where hydrogen accumulates during the process—begins to contract, generating residual stress. However, with the use of the new materials, this residual stress shifts from tensile or expansion to compressive, significantly reducing the risk of cracking.
If these new welding materials are commercialized, they could enable electric arc welding techniques to be used for structural steel in ship bridge container construction and industrial machinery manufacturing. This development supports the ongoing research into ultra-high-tensile-strength steels with tensile strengths up to 800 MPa. For example, high-tensile-strength steel with a strength of 784 MPa has already been successfully applied in the construction of the Akashi Strait suspension bridge in Japan, where ultra-low hydrogen welding rods were employed.
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