Alloy cast iron and manufacturing method of vane using the same

Abstract

An alloy cast iron, a method of manufacturing a vane for a rotary compressor, and a vane for a rotary compressor using the alloy cast iron are disclosed. The alloy cast iron according to one exemplary embodiment includes, by weight, 3.2 to 3.8% carbon, 2.0 to 2.6% silicon, 0.5 to 1.0% Manganese, 0.2 to 0.6% chrome, 0.1 to 0.6% molybdenum, 0.04 to 0.15% titanium, less than 0.3% phosphorus, less than 0.1% sulphur, and the rest percentage of iron and foreign materials, wherein the alloy cast iron includes a martensitic matrix structure, flake graphite, and 15 to 30% carbide in volume ratio.

What is claimed is: 
     
         1 . An alloy cast iron comprising, by weight:
 3.2 to 3.8% carbon (C);   2.0 to 2.6% silicon (Si);   0.5 to 1.0% manganese (Mn);   0.2 to 0.6% chrome (Cr);   0.1 to 0.6% molybdenum (Mo);   0.04 to 0.15% titanium(Ti);   less than 0.3% phosphorus (P);   less than 0.1% sulphur (S); and   a remainder of iron (Fe) and foreign materials,   wherein the alloy cast iron comprises a martensitic matrix structure, flake graphite, and 15 to 30% carbide in volume ratio.   
     
     
         2 . The alloy cast iron of  claim 1 , further comprising an inoculant added in a molten state. 
     
     
         3 . The alloy cast iron of  claim 2 , wherein the inoculant is added by 0.4 to 1.0% of the mass of the molten mass. 
     
     
         4 . The alloy cast iron of  claim 1 , wherein the alloy cast iron is formed by cooling the molten metal in a cast to transform into the martensitic matrix structure through quenching and tempering. 
     
     
         5 . The alloy cast iron of  claim 4 , wherein the quenching is carried out by keeping the alloy cast iron at a temperature of 860 to 950° C. for 0.5 to 1.5 hours and cooling the alloy cast iron to room temperature. 
     
     
         6 . The alloy cast iron of  claim 4 , wherein the tempering is carried out by keeping the quenched alloy cast iron at a temperature of 180 to 220° C. for 0.5 to 1.5 hours, and cooling the alloy cast iron to room temperature. 
     
     
         7 . The alloy cast iron of  claim 4 , further comprising a sulfurized layer having a thickness of 0.005 to 0.0015 mm, the sulfurized layer being formed by carrying out ion-sulfurizing for the alloy cast iron transformed into the martensitic matrix structure. 
     
     
         8 . The alloy cast iron of  claim 1 , further comprising 0.01 to 0.5% by weight of niobium (Nb). 
     
     
         9 . The alloy cast iron of  claim 8 , further comprising 0.1 to 0.5% by weight of vanadium (V). 
     
     
         10 . The alloy cast iron of  claim 1 , further comprising 0.06 to 0.01% by weight of boron (B). 
     
     
         11 . The alloy cast iron of  claim 1 , further comprising 0.2 to 0.4% by weight of copper (Cu). 
     
     
         12 . A method for manufacturing a vane for a compressor comprising:
 a smelting step of preparing a molten metal comprising, by weight, 3.2 to 3.8% carbon (C), 2.0 to 2.6% silicon (Si), 0.5 to 1.0% manganese (Mn), 0.2 to 0.6% chrome (Cr), 0.1 to 0.6% molybdenum (Mo), 0.04 to 0.15% titanium (Ti), less than 0.3% phosphorus (P), less than 0.1% sulphur (S), and a remainder of iron (Fe) and foreign materials;   a casting step of obtaining a semi-product comprising flake graphite and 15 to 30% by volume of carbide by injecting the molten metal in a cast and cooling the molten metal;   a grinding step of grinding the cooled semi-product into a predetermined shape; and   a heat treatment step of carrying out a heat treatment for the ground semi-product to transform into a martensitic matrix structure.   
     
     
         13 . The method of  claim 12 , further comprising an inoculation step of injecting an inoculant into the molten metal. 
     
     
         14 . The method of  claim 12 , wherein the heat treatment step comprises:
 a quenching process of keeping the ground semi-product at a temperature of 860 to 950° C. for 0.5 to 1.5 hours and cooling the semi-product to room temperature; and   a tempering process of keeping the quenched semi-product at a temperature of 180 to 220° C. for 0.5 to 1.5 hours and cooling the semi-product to room temperature.   
     
     
         15 . The method of  claim 12 , further comprising a fine grinding step of finely grinding the completely heat-treated semi-product. 
     
     
         16 . The method of  claim 12 , further comprising an ion-sulfurizing step of forming a sulfurized layer on a surface of the completely heat-treated semi-product, the sulfurized layer being 0.005 to 0.0015 mm thick. 
     
     
         17 . The method of  claim 12 , wherein the alloy cast iron further comprises 0.01 to 0.5% by weight of niobium (Nb). 
     
     
         18 . The method of  claim 17 , wherein the alloy cast iron further comprises 0.1 to 0.5% by weight of vanadium (V). 
     
     
         19 . The method of  claim 12 , wherein the alloy cast iron further comprises 0.06 to 0.01% by weight of boron (B). 
     
     
         20 . The method of  claim 12 , wherein the alloy cast iron further comprises 0.2 to 0.4% by weight of copper (Cu).