Silicon steel is an important soft magnetic alloy.The silicon steel used in the generator field is mainly full-process electrical steel with a thickness of 0.50mm,and some thermal power units use silicon steel or oriented silicon steel with a thickness of 0.35mm,which is mainly used for stator punching in generators.Due to the complex structure of the generator and the multi-directional mixed distribution of the magnetic circuit,the generator industry has higher quality requirements for silicon steel,as follows:
1.Full process silicon steel sheet.
Due to the huge size of the current generator set(such as the diameter of the Three Gorges stator exceeding 20m),the stacking process requires special requirements(such as stacking on the construction site,etc.),making it impossible for the stator to be annealed,and the full process silicon steel is used.
2.High requirements for plate size.
Such as 300,600,1000MW turbogenerator stator core laminated lengths are 5100,6731,8150mm respectively.The size of the stator with such a length and the lamination thickness of more than 10,000 sheets have extremely strict requirements on the vertical and horizontal differences between the silicon steel sheets.
3.High electromagnetic performance requirements.
Due to the high-efficiency design requirements of the generator,the loss of the silicon steel sheet should be as low as possible.The lower the loss,the higher the efficiency of the unit.The efficiency of 300 and 600MW turbo generators should exceed 98%,the efficiency of hydro generators should also exceed 98%,and the efficiency of some small generators should also reach 96%.Therefore,high magnetic induction,high magnetic permeability and magnetic aging effect are required.Small,mechanical properties require good fatigue resistance and low stress sensitivity.
4.Good insulation performance.
When the major domestic producers of high-grade silicon steel supply silicon steel products in the field of generators,some of them use special insulating coatings according to the performance requirements of generators.The silicon steel products supplied by TISCO to generator companies at home and abroad are usually coated with C5 or C6;the silicon steel products supplied by Baosteel to the generator industry mostly use H coating(thick coating)and self-adhesive coating;Silicon steel products mostly use T4 coating or T5 coating.
The interlayer resistance of silicon steel insulation coating for large generators can reach more than 10000Ω.mm2/sheet.When using silicon steel,generator manufacturers often carry out secondary painting treatment,generally using C6 water-soluble paint or organic paint For the second coating,in order to ensure the bonding performance of the two coatings,silicon steel manufacturers are required to use C6 coating.
In short,due to the special performance requirements of generators,there are very high requirements for high-grade non-oriented silicon steel in terms of same-plate difference,electromagnetic performance and coating performance.
