In order to improve the quality of stainless steel tube, "three-step method" is adopted

The "three-step method" of steelmaking and continuous casting for the production of stainless steel tube blanks has created conditions for improving the quality of stainless steel tube blanks and reducing costs. Some major stainless steel mills in the world have studied and adopted the “three-step method” of smelting stainless steel on the basis of the “two-step method”. At present, most of the professional stainless steel plants in Japan have adopted the “three-step method” production process. Germany Mannesmann Demark Metallurgical Technology has developed a set of process equipment specifically for the "three-step process". It includes an ultra-high power electric furnace, a MRP-L converter and a VOD unit. The process uses a stainless steel tube melting furnace, MRP-L converter oxygen lance fast decarburization, VOD vacuum furnace ultimately deep decarbonization. The basic starting point of this process is to combine and develop the advantages of the two processes, AOD and VOD, and overcome the shortcomings of large argon consumption and refractory material consumption and long processing time of AOD, achieving low consumption, shortening time, and reducing costs. purpose. Of course, electric furnace-AOD "two-step" smelting of stainless steel is also feasible. At present, more than 60% of the world's stainless steel is produced using the "two-step" process. Stainless steel blanks in foreign countries have basically continuous casting casters mainly in vertical and arc type, and horizontal casters are also used. Compared with a conventional steel ingot, the stainless steel continuous casting billet increases the metal yield by 10% to 15%, and the billet has better quality, saves energy, and reduces production costs. In the process of continuous casting, some stainless steel alloys are easily oxidized and easily lead to oxide inclusions. In addition, the viscosity of the molten steel is large, which can easily cause nozzle clogging. Because the solidification form of stainless steel is more complex, the thermal conductivity of molten steel is poor, and the slab is prone to cracks. Therefore, the cooling and drawing speed requirements are more stringent. Each tundish heating, non-oxidation protection casting, electromagnetic stirring, and liquid level automatic control are adopted. With a series of new technologies, the quality of the cast billet has been greatly improved, and some hard-to-cast steel grades such as titanium-containing stainless steel, single-phase austenitic stainless steel and martensitic stainless steel have been successfully cast, expanding the stainless steel continuous casting steel. Species.