Nodular cast alloy

Abstract

A nodular cast alloy, a casting made therefrom, and a production process therefor, which has a perlitic-ferritic microstructure for cast iron products and has a high strength combined with good ductility and toughness even in the cast state, including, as nonferrous constituents, C, Si, Ni, Mn, Cu, Mg, Cr, Al, P, S and normal impurities, characterized in that the nodular cast alloy in the cast state without subsequent heat treatment achieves a high static strength of a 0.2% offset yield strength of ≥600 MPa and a tensile strength of ≥750 MPa combined with good ductility of an elongation at break A5 of from 2 to 10%.

What is claimed is: 
     
         1 . A nodular cast alloy that has a perlitic-ferritic microstructure for cast iron products, and has a high strength combined with good ductility and toughness even in the cast state, comprising, as nonferrous constituents, C, Si, Ni, Mn, Cu, Mg, Cr, Al, P, S and normal impurities, wherein the nodular cast alloy contains:
 from 2.8 to 3.7% by weight of C,   from 1.5 to 4% by weight of Si,   from 1 to 6.2% by weight of Ni,   from 0.02 to 0.05% by weight of P,   from 0.025 to 0.06% by weight of Mg,   from 0.01 to 0.03% by weight of Cr,   from 0.003 to 0.3% by weight of Al,   from 0.0005 to 0.012% by weight of S,   from 0.03 to 1.5% by weight of Cu,   from 0.1 to 2% by weight of Mn, and   a balance of Fe and unavoidable impurities,   wherein the nodular cast alloy in the cast state without subsequent heat treatment achieves a high static strength of a 0.2% offset yield strength of ≥600 MPa and a tensile strength of ≥750 MPa combined with good ductility of an elongation at break A5 of from 2 to 10%.   
     
     
         2 . The nodular cast alloy according to  claim 1 , wherein the alloy contains from 2 to 3.5% by weight of Si, where the sum of the contents of Ni and Si in the alloy is ≤9% by weight and at the same time the ratio (Ni+0.5*Mn)/(1.5*Si) is ≤1.5 and a purely perlitic-ferritic microstructure comprising >50% of perlite, balance ferrite, is obtained on cooling from the casting temperature to room temperature. 
     
     
         3 . The nodular cast alloy according to  claim 2 , wherein the alloy contains from 2.2 to 3.3% by weight of Si. 
     
     
         4 . The nodular cast alloy according to  claim 1 , wherein the alloy contains from 2.5 to 5.2% by weight of Ni, where the sum of the contents of Ni and Si in the alloy is ≤9% by weight and at the same time the ratio (Ni+0.5*Mn)/(1.5*Si) is ≤1.5 and a purely perlitic-ferritic microstructure comprising >50% of perlite, balance ferrite, is obtained on cooling from the casting temperature to room temperature. 
     
     
         5 . The nodular cast alloy according to  claim 4 , wherein the alloy contains from 4.0 to 5.2% by weight of Ni. 
     
     
         6 . The nodular cast alloy according to  claim 1 , wherein the alloy contains from 0.2 to 0.5% by weight of Mn, where the sum of the contents of Ni and Si in the alloy is ≤9% by weight and at the same time the ratio (Ni+0.5*Mn)/(1.5*Si) is ≤1.5 and a purely perlitic-ferritic microstructure comprising >50% of perlite, balance ferrite, is obtained on cooling from the casting temperature to room temperature. 
     
     
         7 . The nodular cast alloy according to  claim 6 , wherein the alloy contains from 0.15 to 0.4% by weight of Mn. 
     
     
         8 . The nodular cast alloy according to  claim 1 , wherein the alloy contains from 0.03 to 0.5% by weight of Cu, where the sum of the contents of Ni and Si in the alloy is ≤9% by weight and at the same time the ratio (Ni+0.5*Mn)/(1.5*Si) is ≤1.5 and a purely perlitic-ferritic microstructure comprising >50% of perlite, balance ferrite, is obtained on cooling from the casting temperature to room temperature. 
     
     
         9 . The nodular cast alloy according to  claim 8 , wherein the alloy contains from 0.03 to 0.1% by weight of Cu. 
     
     
         10 . The nodular cast alloy according to  claim 1 , wherein the alloy contains from 0.003 to 0.25% by weight of Al, where the sum of the contents of Ni and Si in the alloy is ≤9% by weight and at the same time the ratio (Ni+0.5*Mn)/(1.5*Si) is ≤1.5 and a purely perlitic-ferritic microstructure comprising >50% of perlite, balance ferrite, is obtained on cooling from the casting temperature to room temperature. 
     
     
         11 . The nodular cast alloy according to  claim 10 , wherein the alloy contains from 0.003 to 0.02% by weight of Al. 
     
     
         12 . The nodular cast alloy according to  claim 1 , wherein more than 90% of the graphite present has a spherical shape immediately after casting and cooling. 
     
     
         13 . The nodular cast alloy according to  claim 1 , wherein a perlitic-ferritic matrix microstructure of the cast part immediately after casting and cooling is from 55 to 90% perlitic and the remaining ferrite preferably has a globular shape. 
     
     
         14 . The nodular cast alloy according to  claim 1 , wherein the microstructure of the cast part immediately after casting and cooling has from 200 to 1200 spheroids per mm 2 . 
     
     
         15 . The nodular cast alloy according to  claim 1 , wherein the graphite particles have a size distribution of at least 5% of the size 8, from 40% to 70% of the size 7 and not more than 35% of the size 6 in accordance with DIN EN ISO 945. 
     
     
         16 . The nodular cast alloy according to  claim 1 , wherein the cast part has a Brinell hardness of from 260 to 320 HBW. 
     
     
         17 . A chassis component of a motor vehicle comprising the nodular cast alloy according to  claim 1 , wherein the chassis component is selected from the group consisting of a wheel carrier, a pivoting bearing, an axle guide, a crankshaft, and a rear axle housing. 
     
     
         18 . A method for producing a cast part, comprising:
 providing the nodular cast alloy according to  claim 1 ,   casting the part with the nodular cast alloy; and   cooling the cast part,   wherein no heat treatment is carried out on the cast part after the casting and the cooling of the cast part.