Crack Analysis on Blade Tenon of Axial-flow Compressor for Blast Furnace
In view of the blade crack of axial flow compressor in blast furnace,the blade was detected by penetration flaw detection,chemical composition,metallographic structure,Vickers hardness,energy spectrum analysis and so on.The formation mechanism of granular carbides in metallographic structure was studied by heat treatment test for blades.The results show that,the microstructure of 20Cr13 martensitic stainless steel blades is tempered sorbite+non-melt carbide.A large amount of carbide does not melt into austenite at a quenching temperature of 950 ℃.The number,size and distribution of carbides in quenched and tempered microstructure are inherited from the characteristics of carbides before quenching.The inhomogeneous and dense distribution of unfused carbide particles and the distribution along grain boundary destroy the continuity of matrix microstructure,and creating conditions for crack initiation and propagation.Under the action of periodic bending stress,cracks appear in the root of tenon teeth.The crack propagates along dense carbide or grain boundary,forming the fatigue crack of certain depth and length.
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