Method for treating spheroidal graphite iron and pouring device thereof

Abstract

A method for treating spheroidal graphite iron includes the step: pouring molten spheroidal graphite iron into a pouring electrical furnace ( 1 ); covering the molten spheroidal graphite iron ( 5 ) with alkali slag ( 6 ) which is melted at high temperature and rich in alkali earth metal ion, rare earth metal ion, or mixture of them; connecting the molten spheroidal graphite iron ( 5 ) with the negative pole of the direct current source by one pole ( 7 ); connecting the alkali slag ( 6 ) with the positive pole of the direct current source by another pole ( 4 ), treating the molten spheroidal graphite iron ( 5 ) with the alkali slag ( 6 ) which is used as electrolyte. The method can prevent the spheroidized fading velocity of the spheroidal graphite iron. The pouring electrical furnace can be used for treating the molten spheroidal graphite iron.

1 - 13 . (canceled) 
     
     
         14 . A processing method for avoiding degradated spheroidization and pouring temperature drop of liquid spheroidal graphite cast iron during pouring process, characterized in that, comprising: liquid spheroidal graphite cast iron to be poured is filled into a special pouring electric furnace device provided with a set of DC electro-slag system: high temperature molten alkali slag abundant in active metal ions such as Mg 2+  and Ca2 +  is paved above the liquid spheroidal graphite cast iron, an upper part of the furnace body is provided with a graphite electrode inserted into a layer of molten alkali slag, an electrode connected to a DC power supply system is provided in the liquid spheroidal graphite cast iron, the liquid spheroidal graphite cast iron is sealed by the high temperature molten alkali slag floating on the top thereof, so that the liquid spheroidal graphite cast iron in the furnace is completely isolated from oxygen in the atmosphere; meanwhile, through the principle of “DC electrolytic cell”, the liquid spheroidal graphite cast iron serves as a cathode, the graphite electrode inserted into the layer of molten alkali slag serves as an anode, and the molten alkali slag serves as a liquid electrolyte; a direct current of low voltage large current is conducted after the furnace is filled with the liquid spheroidal graphite cast iron, the strength of the direct current is determined as follows according to the capacity of the electric furnace: a current equivalent of 20˜50 Faraday for each tone of liquid spheroidal graphite cast iron per hour, some electric energy is converted into chemical energy after the direct current is conducted to urge charged ions to directionally move under the attraction of oppositely charged electrode, electrolytic reaction will occur in the high temperature alkali slag with a temperature controlled as 1500° C.˜1700° C., when enough amount of the direct current is conducted, an electrode potential at a slag-metal interface will achieve an electro-chemical balance meeting the requirement of spheroidization technology, between the content of free-state [Mg] in the liquid spheroidal graphite cast iron and the content of ionic state (Mg 2+ ) in the slag, which also restrains [Mg] atoms in the liquid spheroidal graphite cast iron from turning into Mg 2+  cation due to electron loss and entering the slag, so as to keep the content of residual Mg in the liquid spheroidal graphite cast iron. 
     
     
         15 . A pouring electric furnace device for the processing method according to  claim 14 , comprising: a furnace body, a pouring tap hole and a feeding iron-inlet provided on the furnace body, and means in sets for quantifying poured liquid spheroidal graphite cast iron, the structure of the furnace body may be bottom pouring type, air pressure type or tilting type, characterized in that, an upper part of the furnace body is provided with a graphite electrode, high temperature molten alkali slag abundant in active metal ions such as Mg 2+  and Ca2 +  is paved above the liquid spheroidal graphite cast iron in the furnace, a bottom electrode is provided in the liquid spheroidal graphite cast iron, a lower end of the graphite electrode provided on the upper part of the furnace body is inserted into the alkali slag; a DC power supply system is provided so that an upper part of the graphite electrode is connected to a positive pole of the power supply to serve as an anode, a water cooling bottom electrode or side electrode in the liquid spheroidal graphite cast iron is connected to a negative pole of the power supply to serve as a cathode. 
     
     
         16 . The pouring electric furnace device according to  claim 15 , characterized in that, an induction heating device, a gas or fuel nozzle heating device, an oxygen-gas flame nozzle heating device, a plasma heating device, or all of them may be additionally provided into the furnace body to heat the liquid spheroidal graphite iron. 
     
     
         17 . The pouring electric furnace device according to  claim 15 , characterized in that, the refractory material of lining of the DC electro-slag pouring device is preferably tamped and built with magnesia alkali refractory material, calcined dolomite alkali refractory material, magnesia and magnesia carbon brick alkali refractory material, or calcined dolomite and magnesia carbon brick alkali refractory material; it is emphasized that refractory material abundant in SiO 2  and Al 2 O 3  shall not be used for tamping. 
     
     
         18 . The pouring electric furnace device according to  claim 15 , characterized in that, the composition of the alkali slag covering the top of the liquid spheroidal graphite cast iron in the DC electro-slag pouring device is multivariate slag abundant in active metal ions such as (Mg 2+ ) and (Ca 2+ ), and the melting point of the slag is controlled in an appropriate range of 1250° C.˜1500° C.