Thixocast Fe-based alloy material and process for heating the same

Abstract

A thixocast Fe-based alloy material is provided, from which a cast product having mechanical properties uniform over the whole thereof can be produced. The Fe-based alloy material comprises 1.8% by weight≦C≦2.5% by weight, 1.0% by weight≦Si≦3.0% by weight, 0.1% by weight≦Mn≦1.5% by weight, 0.5% by weight≦Ni≦3.0% by weight, and as the balance, iron (Fe) including inevitable impurities. The eutectic crystal amount Ec is in a range of 10% by weight<Ec<50% by weight.

What is claimed is  
     
         1 . A thixocast Fe-based alloy material comprising 
 1.8% by weight≦C≦2.5% by weight,    1.0% by weight≦Si≦3.0% by weight,    0.1% by weight≦Mn≦1.5% by weight,    0.5% by weight≦Ni≦3.0% by weight, and    as the balance, iron (Fe) including inevitable impurities,    wherein a eutectic crystal amount Ec is in a range of 10% by weight<Ec<50% by weight.    
     
     
         2 . A thixocast Fe-based alloy material comprising 
 1.8% by weight≦C≦2.5% by weight    1.0% by weight≦Si≦3.0% by weight    0.8% by weight≦Mn≦1.5% by weight, and    as the balance, iron (Fe) including inevitable impurities,    wherein a eutectic crystal amount Ec is in a range 10% by weight<Ec<50% by weight.    
     
     
         3 . A thixocast Fe-based alloy material, comprising carbon (C) of a content in a range of 1.8% by weight≦C≦2.5% by weight, silicon (Si) of a content in a range of 1.0% by weight≦Si≦3.0% by weight, manganese (Mn) of a content in a range of 0.6% by weight≦Mn≦1.5% by weight, at least one of nickel (Ni) of a content in a range of 0.2% by weight≦Ni≦3.0% by weight and titanium (Ti) of a content in a range of 0.05% by weight≦Ti≦0.6% by weight, the total sum of the Mn content, the Ni content and the Ti content being equal to or larger than 0.8% by weight (Mn+Ni+Ti≧0.8% by weight), and the balance being iron (Fe) including inevitable impurities, wherein a eutectic crystal amount is in a range of 10% by weight<Ec<50% by weight.  
     
     
         4 . A thixocast Fe-based alloy material according to  claim 1 ,  2  or  3 , wherein a solid phase rate R in a semi-molten state is set at R>50%.  
     
     
         5 . A process for heating a thixocast Fe-based alloy material having a chilled structure into a semi-molten state in which solid and liquid phases coexist, 
 the process comprising setting an average rate H R  of heating to a point A 1  in an Fe—C based equilibrium diagram to be in a range of 0.5° C./sec≦H R ≦6.0° C./sec, and setting a maximum temperature gradient T G  of the inside of the Fe-based alloy material per unit distance to be at T G ≦7° C./mm.    
     
     
         6 . A process for heating a thixocast Fe-based alloy material according to  claim 5 , further setting a sonic velocity Sv of said Fe-based alloy material determined by an ultrasonic velocity measurement to be at Sv≧5,600 m/sec.