Method to obtain a high resistance gray iron alloy for combustion engines and general casts

A method to obtain a gray iron alloy, in an induction furnace, wherein the method comprising:

• a) deoxidizing of a liquid metal in a furnace by:
• increasing the furnace temperature inside a range of 1370° C.-1400° C., the silicon dioxide (SiO2) equilibrium temperature;
• turning off power to the furnace about for at least 5 minutes in order to promote flotation of coalesced oxides and other impurities;
• spreading an agglutinating agent on the surface of the liquid metal then
• removing said agglutinant material, now saturated with coalesced oxides from the liquid metal, leaving a cleaner liquid metal inside the furnace;
• b) by pre-nucleating:
• pouring from 15% to 30% of the liquid metal on a specific ladle;
• during operation, inoculating from 0.45% to 0.60% in % weight of a granulated inoculant of Fe—Si—Sr or Fe—Si—Ba—La alloys, right on a stream of the liquid metal;
• pouring back over inoculated liquid metal from the ladle to the furnace, in order to mix over inoculated metal from the ladle with the uninoculated metal remained into the furnace;
• wherein
• during this last operation, the furnace must be kept on “turn on” phase;
• and from thermal analysis,
• the product of pre-nucleating has two thermal parameters from the cooling curves with:
• a eutectic under cooling temperature, TSE, greater than or equal to 1115° C. and
• a range of eutectic recalescence, ΔT, with a maximum of 6° C., wherein TSE and ΔT are two thermal parameters from the cooling curves during solidification;
• during pouring an allowed temperature for HPI casts (Tp) is +/−10° C., in order to obtain a global cast modulus inside a range between 1.38 and 1.52;
• and
• the eutectoidic phase, the HPI microstructure presents graphite content on its matrix ≦2.3%, calculated by lever rule taking as reference the equilibrium diagram Fe—Fe3C.