High-strength nodular iron with good weldability and machinability

Abstract

A nodular iron alloy and automotive components, such as differential and drive axle components, are provided. The nodular iron alloy may include iron, about 3.1-3.3 wt % carbon, about 2.7-4.3 wt % silicon, about 0.15-0.40 wt % manganese, about 0-0.10 wt % magnesium, about 0-0.2 wt % nickel, about 0-0.4 wt % copper, about 0-0.30 wt % chromium, about 0-0.03 wt % phosphorus, and about 0-0.02 wt % sulfur. The nodular iron alloy may have an ultimate tensile strength of at least 620 MPa as-cast. This alloy possesses favorable weldability to weld with steel components without substantial preheating or post heat treatment for a strong and tough weldment, and it has good machinability to facility comprehensive machining operations.

What is claimed is: 
     
         1 . A nodular iron alloy comprising:
 iron;   about 3.1 to about 3.3 weight percent carbon;   about 2.7 to about 4.3 weight percent silicon; and   about 0.15 to about 0.40 weight percent manganese.   
     
     
         2 . The nodular iron alloy of  claim 1 , wherein the silicon is provided in an amount of about 3.5 to about 4.1 weight percent. 
     
     
         3 . The nodular iron alloy of  claim 2 , wherein the iron is provided in an amount of at least 86.55 weight percent. 
     
     
         4 . The nodular iron alloy of  claim 3 , further comprising magnesium in an amount not exceeding 0.10 weight percent. 
     
     
         5 . The nodular iron alloy of  claim 4 , further comprising nickel in an amount not exceeding 0.2 weight percent. 
     
     
         6 . The nodular iron alloy of  claim 5 , further comprising copper in an amount not exceeding 0.4 weight percent. 
     
     
         7 . The nodular iron alloy of  claim 6 , further comprising chromium in an amount not exceeding 0.30 weight percent. 
     
     
         8 . The nodular iron alloy of  claim 7 , further comprising sulfur in an amount not exceeding 0.02 weight percent. 
     
     
         9 . The nodular iron alloy of  claim 8 , further comprising phosphorus in an amount not exceeding 0.03 weight percent. 
     
     
         10 . The nodular iron alloy of  claim 3 , wherein the nodular iron alloy has an ultimate tensile strength greater than 620 MPa as-cast. 
     
     
         11 . The nodular iron alloy of  claim 10 , having an elongation of greater than 6%. 
     
     
         12 . The nodular iron alloy of  claim 3 , wherein the nodular iron alloy is substantially free of cobalt and molybdenum. 
     
     
         13 . The nodular iron alloy of  claim 11 , wherein the iron is present in an amount of 65-85% of a ferrite microstructure and in an amount of 15-35% of a pearlite microstructure, wherein the iron surrounds a plurality of graphite nodules. 
     
     
         14 . An automotive component created from a nodular alloy according to  claim 3 . 
     
     
         15 . The automotive component of  claim 14 , wherein the automotive component is one of a differential component and a drive axle component. 
     
     
         16 . A nodular iron alloy consisting essentially of:
 about 3.1 to about 3.3 weight percent carbon;   about 2.7 to about 4.3 weight percent silicon;   about 0.15 to about 0.40 weight percent manganese;   0 to about 0.10 weight percent magnesium;   0 to about 0.2 weight percent nickel;   0 to about 0.4 weight percent copper;   0 to about 0.30 weight percent chromium;   0 to about 0.03 weight percent phosphorus;   0 to about 0.02 weight percent sulfur; and   the balance iron.   
     
     
         17 . The nodular iron alloy of  claim 16 , wherein the silicon is provided in an amount of about 3.5 to about 4.1 weight percent. 
     
     
         18 . The nodular iron alloy of  claim 17 , wherein the nodular iron alloy has an ultimate tensile strength greater than 620 MPa as-cast. 
     
     
         19 . The nodular iron alloy of  claim 18 , the nodular iron alloy being substantially free of cobalt and molybdenum, wherein the iron is present in an amount of 65-85% of a ferrite microstructure and in an amount of 15-35% of a pearlite microstructure, and wherein the iron surrounds a plurality of graphite nodules. 
     
     
         20 . An automotive component created from a nodular iron alloy according to  claim 16 .