Cold Rolled Non-oriented Electrical Steel Annealing Process Research And Applications

The final magnetic and mechanical properties of the cold rolled non-oriented electrical steel are determined by their microstructure and texture, but the microstructure and texture are influenced by their chemical composition and production processes. The cold rolled non-oriented electrical steel samples of the experiments were taken from the Pangang group company LTD, they were industrial productions, without annealing and typical components. Samples annealed at salt bath with different anneal temperature and time, in the laboratory. Organizations, textures and hardness of cold rolled plates were analyzed by metallurgical microscope, iron loss tester, X-ray diffraction and hardness tester etc. Based on the results of laboratory, and the characteristics of Panzhihua Iron and Steel annealing unit No.1, preliminary annealing processes were drafted. This paper aims to provide basis for the formulation of anneal process of Panzhihua Iron and Steel No.1annealing production line, and cold rolled non-oriented electrical steel with high magnetic induction and low iron loss.The relationships among microstructures, textures and properties of cold rolled non-oriented electrical steel with0.6%Si、0.3%Al, were studied in this paper. The results show that:annealing processes have greater influences on the organization states and the texture volume fractions of cold rolled non-oriented electrical steel, they determine the ultimate performances. In order to obtain better performances, methods should be adopted. Such as improve annealing process, reduce the content of{111} plate texture, or cause it to weaken, increase the content of{100} and {110} plate textures, and make the grain size get up to a critical grain size, coarsen inclusions.The microstructures and textures of the samples before annealed were analysed. The microstructure is fibrous tissue, and preferred orientations are more obvious, most of them concentrate in near the [110] crystal axis. At this time, the magnetic properties of non-oriented electrical steel were poor, and difficult to meet customer requirements. Therefore the samples must be annealed to improve the performances.Samples were annealed in salt bath furnace at different temperatures and30seconds annealing time. The results found that:The samples completed recrystallization at750℃, fibrous tissues are disappeared completely, the organizations are the fine ferrite grains. The organizations near the surface grow up first, then near the center. Grain size grows up quickly with the annealing temperature increasing. The average grain size of samples is27u m, at850℃, the uniformity of the organizations are well. When the temperature is higher, grains size are grow up abnormally, and the uniformity is poor. The contents of textures changed greater at the end of the recrystallization than the cold rolled samples. Especially, the contents of textures near [110] crystal axis decreased more significantly. When the temperature is over750℃, variation curves of textures contents are a wave-shaped. Because the texture has bigger influence on magnetic induction, so the texture changes in the objective response to the change of the magnetic induction. The magnetic induction of samples before annealing is minimum, it gets the peak at750℃.When the temperature increases higher, with the increase of temperature, the magnetic induction has small changes, core loss decreases gradually.The samples annealed at different time and850℃. The grain size increases with the extension of the annealing time, the uniformity of the organizations become worse and worse, the contents of the textures change smaller, iron loss reduced, and the magnetic induction is also reduced, but the reduction scope is small.The relationships between annealing process and performance were studied in the laboratory, and accorded to the characteristics of Pangang NO.1line, drafted the annealing processes suitable for NO.1line.23000tons of cold-rolled non-oriented electrical steels were industrial produced, all of the mechanical properties were in line with the requirements of customers, magnetic induction qualified rate was96.6%, arrived at a predictable results.