Study On Inner Defects Of Large Turbine Guide Vanes Fabricated With Electro-slag Casting

Electro-slag Casting was the process of metal refinement and solidification, whichcould make the castings have well quality. But with the rapid development applicationof the technology, casting defect was emerged especially in large castings, andsometimes resulted in reject. So resolve some technique problem of electro-slagcasting was the sticking point in production.In this pager, according to the dissection analysis of large turbine Guide vaneswhich fabricated by electro-slag casting, the property,form mechanism and preventivesmeasure of casting inner defects was studied.The inner defects was the associated defects of porosity,gas hole,encrustingmatter and crack, and its macroscopical figure was exiguous araneose crack aroused byhydrogen and transformation stress.In the process of electro-slag casting, when the volume and depth of metal liquidbath was too large, the vertical cooling rate of crystallizer and temperature gradientwould lower relatively, which made the solidification zone widen and reinforcementshrinkage channels obstructed. The solidification condition of liquid bath front edgewas deteriorated to arouse inner defects in the last solidification place.Modulating the chemical composition of slag to transfer its properties couldimprove the refinement and purification effect, and modulating the cooling intensityand the matching of fusion casting voltage and current could make metal liquid bathachieve anticipative figure and depth, which could ensure the solidification rate inorder to avoid inner defects.Exerting the advantage of electro-slag casting in large castings and improving itsquality had an important value in nation major project application.