Additive for treating molten iron to produce cast iron with zero contraction and with lonsdaleite-type spheroidal graphite

Abstract

Additive for the thermochemical treatment of molten iron in order to separate, distribute, agglomerate, precipitate, spheroidize and/or crystallize combined, solvated and/or colloidal carbon present in molten iron in the liquid state into graphite in its hexagonal diamond or Lonsdaleite form, in order to produce ductile, nodular, spheroidal, vermicular, coral, spheroidized or grey iron with superior mechanical properties, iron with high metal yield and zero contraction during casting; the additive comprises two or more elements in the metallic state selected from the S-block of periods 2 to 7 of the periodic table of elements; and two or more elements in the metallic state selected from F-block of periods 6 to 7 of the periodic table of elements. The additive makes it possible to produce cast iron parts with Type I and II spheroidal graphite in hexagonal diamond or Lonsdaleite form as per the ASTM-A247 standard.

1 . A method for producing cast iron items with spheroidal graphite in hexagonal diamond or Lonsdaleite form, the method comprises the steps of:
 preparing a molten iron with carbon from a determined metallic load;   reacting the molten iron with a spheroidizing agent, wherein the spheroidizing agent comprises:
 two or more elements in metallic state selected from S-block of periods 2 to 7 of the periodic table of elements, wherein each of said S-block elements is present in an amount of 2 to 15% by weight of the total spheroidizing agent; and 
 two or more elements in metallic state selected from F-block of periods 6 to 7 of the periodic table of elements, wherein each of said F-block elements is present in an amount of 1 to 15% by weight of the total spheroidizing agent; 
 wherein each of said elements is in metallic state with a purity of at least 85%, and wherein said elements are physically incorporated without forming ionic or covalent bonds in alloys or compounds that includes its mother phase or solvent; 
   allowing the formation and precipitation of spheroidal graphites in the molten iron in liquid phase by a thermochemical reaction; and   pouring the molten iron into a mold.   
     
     
         2 . The method according to  claim 1 , wherein the two or more elements in metallic state selected from S-block of periods 2 to 7 are selected from the group IA of the periodic table of elements. 
     
     
         3 . The method according to  claim 2 , wherein the two or more elements in metallic state selected from S-block of the group IA from the periodic table of the elements are selected from the group consisting of lithium, sodium, potassium, and rubidium. 
     
     
         4 . The method according to  claim 1 , wherein the two or more elements in metallic state selected from F-block of periods 6 to 7 are selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, actinium, thorium, and protactinium. 
     
     
         5 . The method according to  claim 1 , wherein the two or more elements in metallic state selected from S-block of periods 2 to 7 are selected from the group IIA of the periodic table of elements. 
     
     
         6 . The method according to  claim 5 , wherein the two or more elements in metallic state selected from S-block of the group IIA from the periodic table of elements are selected from the group consisting of beryllium, magnesium, calcium, and barium. 
     
     
         7 . The method according to  claim 1 , wherein further includes elements selected from P-block of group IV A of the periodic table of elements. 
     
     
         8 . The method according to  claim 7 , wherein the elements selected from P-block of group IV A are selected from the group consisting of carbon and silicon, in an amount of 7 to 70% by weight of the total additive. 
     
     
         9 . The method according to  claim 1 , wherein further includes elements selected from P-block of group VI A of the periodic table of elements. 
     
     
         10 . The method according to  claim 9 , wherein the elements selected from P-block of group VI A are selected from the group consisting of oxygen and sulfur, in an amount of 7 to 70% by weight of the total additive. 
     
     
         11 . The method according to  claim 1 , wherein the cast iron is selected from ductile, nodular, spheroidal, vermicular, coral, spheroidized or grey iron of high mechanical properties. 
     
     
         12 . The method according to  claim 1 , wherein the method has a metallic yield from 55 to 95%, preferably from 75% to 95%. 
     
     
         13 . A cast iron item prepared according to the method of  claim 1 , the item of cast iron comprises:
 lanthanide contraction elements and scandide contraction elements in stoichiometric proportion according to the percentage of additive as a spheroidizing agent and the additive as an activator agent used during the preparation of the cast iron item;   at least 80% of the presence of spheroidal graphite in hexagonal diamond or Lonsdaleite form in accordance with the ASTM-A247 standard Type I and II spheroid classification;   a minimum graphite spheroid density of 300 spheroids/mm 2 ; and   a spheroidal graphite size smaller than number 4.