Process progress of oriented electrical steel
1. The industrial production of grain-oriented electrical steel has always used a high-temperature heating process for cast slabs to ensure stable high magnetism. However, the disadvantage is that there is a lot of oxide slag, the burning loss can reach 5%, and the yield rate is low; the furnace bottom needs to be cleaned frequently, which reduces the output. ;High fuel costs;short furnace life;high manufacturing costs;many product surface defects. Attempts to lower the heating temperature of cast slabs have been made for many years. At present, there are mainly the following methods: replacing Si with Mn, adding Cu and nitriding, etc. High manganese electrical steel replaces part of Si with Mn and adds a trace amount of Al as an inhibitor, which can reduce the slab heating temperature, lower the annealing temperature of the final product and omit the decarburization annealing process. In 1989, Yuki Yabu and others from Sumitomo Metal Corporation of Japan proposed a new carbon-free Si-Mn electrical steel that is easy to process. Around 1995, Yasunari Yoshitomi and others from Nippon Steel Corporation also studied this new type of Si-Mn electrical steel. Mn steel. In recent years, Japan has been studying this new type of steel. Another method to reduce the slab heating temperature is to add Cu to electrical steel. Cu has many effects on the properties of grain-oriented electrical steel, one of its important roles is to act as an auxiliary inhibitor and reduce the slab heating temperature. The third main method to reduce the slab heating temperature is nitriding treatment after decarburization annealing. Nippon Steel Corporation has been conducting research work in this area. Recently, Ste-fano Fortunati and others from Terni Company in Italy proposed a method to produce high magnetic induction oriented electrical steel using CSP (Compact Strip Production) process and nitriding method.
2. Use thin slab continuous casting and rolling and thin strip casting and rolling processes to produce grain-oriented electrical steel
With the development of the world economy, especially driven by the Chinese economy, the world's production and consumption of electrical steel has increased year by year. At the same time, in order to reduce the cost of electrical products and equipment, companies are paying more and more attention to the development and research of low-cost, high-performance new electrical steel products. Domestic and foreign research has begun to develop grain-oriented electrical steel production technology in a short-process, low-cost, and high-efficiency way of thin slab continuous casting and rolling. Thin slab continuous casting and rolling technology is a new short-process, low-cost steel metallurgical production technology. China has carried out development and research on thin slab continuous casting and rolling technology to produce non-oriented electrical steel. If the thin slab continuous casting and rolling process is used to produce general oriented electrical steel, it will not only reduce the technical difficulty of development and research, but also meet the needs of products of different qualities and grades.
Thin strip casting and rolling technology directly casts and rolls molten steel into hot-rolled coils of 2 to 3 mm, which will significantly shorten the process flow. In this process, the time-temperature relationship is the most critical factor, because the inhibitor must be precipitated from the crystallizer outlet to the winding machine in about 1 minute. By controlling the cooling rate and online deformation, uniformity can be obtained of inhibitors. In order to stabilize and improve the status of the inhibitor, normalization must also be carried out. In order to obtain better ductility and good cold working properties of the steel strip, the steel strip can be heat treated online. In terms of strip shape, thickness tolerance and surface defects, there is still room for in-depth development and research.
3. Continuous annealing of oriented electrical steel replaces bell annealing
Replacing the bell annealing furnace with a continuous annealing furnace to complete secondary recrystallization and purify inhibitors in steel has become an important method for producing high-end oriented electrical steel. This annealing process takes only minutes instead of days, significantly reducing annealing time. High-temperature continuous annealing not only has high output, but also can save energy by more than 20%. Continuous annealing units are developing towards high speed and multi-function.