Method for removing slag during remelting of ni-based superalloy

Abstract

The invention discloses a method for removing the slag during the remelting of Ni-based superalloy, including: the master Ni-based superalloy is placed in a crucible located in a vacuum induction melting furnace; under the condition of maintaining a predetermined vacuum degree, the furnace cavity is heated to melt the master Ni-based superalloy, during the melting process, the metallic element Ca is thrown into the alloy melt, when the temperature in the furnace cavity rises to a predetermined degree, the master Ni-based superalloy is completely melted, at this time, the slag is formed on the surface of the alloy melt. When the master Ni-based superalloy is completely melted and enters the smelting stage, the metallic elements Ca, Ba, and Sr are put into the alloy melt in turn and the electromagnetic stirring is performed to rapidly remove the slag on the surface of the alloy melt.

What is claimed is: 
     
         1 . A method for removing slag during a remelting of Ni-based superalloy, wherein the removal method comprises the following steps in order:
 Step  1 : placing the master Ni-based superalloy in a crucible located in a vacuum induction melting furnace, closing the vacuum induction melting furnace, and pumping a furnace chamber to a predetermined degree of vacuum;   Step  2 : heating the furnace chamber under a predetermined degree of vacuum to melt the master Ni-based superalloy;   during a melting process, adding a metallic element Ca to the alloy melt by a feeder and performing an electromagnetic stirring;   wherein, when a temperature in the furnace chamber rises to a predetermined degree, the master Ni-based superalloy is completely melted, and a layer of slag is formed on a surface of the alloy melt;   Step  3 : when the master Ni-based superalloy is completely melted and enters a smelting stage, putting the metallic elements Ca, Ba, and Sr into the alloy melt in turn by the feeder in the smelting stage, and performing a process of electromagnetic stirring;   wherein, in the process of electromagnetic stirring, the slag on the surface of the alloy melt rapidly accumulates to the circumferential position of the contact between the surface of the alloy melt and a crucible wall, and the slag on the surface of the alloy melt is rapidly removed;   Step  4 : using a Ni-based superalloy to cast a product after removing the slag;   wherein in Step  1 , a vacuum degree in the furnace chamber does not exceed 20 Pa;   wherein in Step  2 , the vacuum degree in the furnace chamber should not exceed 20 Pa, and the temperature should be raised from room temperature to 850° C. at a heating rate of 80-100° C./min, wherein heat preservation is performed for 30-60 s, wherein after the heat preservation, argon is introduced into the furnace chamber, and the argon flow rate is 0.1-0.15 MPa/min, and then the metallic element Ca is added to the alloy melt within 10 s, the temperature continues to rise from 850° C. to 1430-1550° C. at a heating rate of 100-150° C./min, and wherein heat preservation is again performed for  30 - 60  s, and the master Ni-based superalloy is completely melted at this time;   wherein in Step  3 , in the smelting stage, argon is kept in the furnace chamber, and the argon flow rate is 0.15-0.25 MPa/min, the metallic elements Ca, Ba, and Sr are successively put into the alloy melt, and a time interval of the three metal elements is not more than 10 s; after the three metal elements are put into the alloy melt, the electromagnetic stirring is performed for 1-2 min, and then the furnace chamber is vacuum pumped until the vacuum degree does not exceed 20 Pa;   wherein in Step  2  and Step  3 , a total mass of metallic elements Ca, Ba, and Sr added to the alloy melt is 1-4 wt % of the mass of the master Ni-based superalloy, the mass of metallic elements Ca, Ba, and Sr added to the alloy melt accounts for 20-30 wt %, 10-20 wt % and 50-70 wt % of the total mass of metallic elements Ca, Ba, and Sr, respectively;   wherein in Step  2 , the mass of the metallic element Ca added to the alloy melt is 30-50% of the total mass of the metallic element Ca; in Step  3 , the mass of the metallic element Ca added to the alloy melt is 50-70% of the total mass of the metallic element Ca.   
     
     
         2 . The method for removing the slag during the remelting of Ni-based superalloy according to  claim 1 , wherein an oxygen content in the master Ni-based superalloy does not exceed 10 ppm and a sulfur content does not exceed 5 ppm; a material of the crucible is oxide refractory, and the oxide is any one of magnesium oxide, alumina, silicon oxide, mixture of magnesium oxide and alumina, mixture of alumina and silicon oxide, zirconia and barium zirconate. 
     
     
         3 . The method for removing the slag during the remelting of Ni-based superalloy according to  claim 2 , wherein in Step  2  and Step  3 , the metallic elements Ca, Ba, and Sr placed in the alloy melt are blocky or filamentous.