For example , most ductile iron castings specified by the International Organization for Standardization ISO1083 are mainly produced in non-alloyed form. Obviously, this range including tensile strength greater than 800 Newtons / mm, elongation of 2% of a high strength grades. The other extreme is the high plastic grade, which has an elongation greater than 17% , and the corresponding strength is low (the minimum is 370 Newtons / mm2). Strength and elongation are not the basis for designers to choose materials, and other decisive important properties include yield strength, elastic modulus , wear resistance and fatigue strength, hardness and impact properties. In addition, corrosion resistance and oxidation resistance and electromagnetic properties may be critical to the designer. In order to meet these special applications, a group of austenitic ductile irons have been developed , usually called Ni - Resis ductile irons. These austenitic ductile irons are mainly alloyed with nickel, chromium and manganese and are listed in international standards.