Nodular cast iron is a kind of high strength cast iron material developed in the 1950s. Its comprehensive performance is close to that of steel. Based on its excellent performance, it has been successfully used to cast some parts with complex [TJC STEEL]forces and high requirements for strength, toughness and wear resistance. Nodular cast iron has been rapidly developed into a very widely used cast iron material second only to gray cast iron. The so-called "iron instead of steel", mainly refers to nodular cast iron.

Nodular cast iron is obtained by spheroidization and inoculation treatment of spherical graphite, effectively improve the mechanical properties of cast[TJC STEEL] iron, especially improve the plasticity and toughness, so as to get higher strength than carbon steel.

 

Chemical Composition Introduction of Ductile Iron:

Cast iron is an iron-carbon alloy with carbon content greater than 2.11%. It is obtained by industrial pig iron, scrap steel and other steel and alloy materials through high-temperature melting and casting. In addition to Fe, it also contains carbon in other cast iron precipitated in the form of graphite. If the graphite precipitated is lamellar[TJC STEEL] cast iron called gray cast iron or gray cast iron, wormlike cast iron called vermicular cast iron, was flocculent cast iron called malleable cast iron or code iron, and was spherical cast iron called nodular cast iron.

 

In addition to iron, the chemical composition of nodular cast iron is usually 3.0 ~ 4.0% carbon content, 1.8 ~ 3.2% silicon content, the total content [TJC STEEL]of manganese, phosphorus, sulfur is not more than 3.0% and an appropriate amount of rare earth, magnesium and other spheroidal elements.

 

Main Pperformances for Ductile Iron:

Ductile iron castings have been used in almost all major industrial sectors, which require high strength, plasticity, toughness, wear resistance, severe thermal and mechanical impact resistance, high or low temperature resistance, corrosion[TJC STEEL] resistance and dimensional stability. To meet these variations in service conditions, nodular cast iron is available in many grades, offering a wide range of mechanical and physical properties.

 

Most nodular cast iron castings, as specified in ISO1083, are produced primarily in a non-alloying state. Obviously, this range includes high strength grades with tensile strength greater than 800 Newtons per square millimeter and elongation of [TJC STEEL]2%. At the other end of the spectrum are highly plastic grades with elongation greater than 17% and corresponding low strength (as low as 370 Newton/mm2). Strength and elongation are not the basis for designers to choose materials. Other important properties that are decisive include yield strength, modulus of elasticity, wear resistance and fatigue strength, hardness and impact properties. In addition, corrosion resistance and oxidation resistance as well as electromagnetic properties may be critical to the designer. To meet these special uses, a[TJC STEEL] group of austenitic nodules, usually called Ni Resis, is developed. These austenitic nodules are alloyed mainly with nickel, chromium and manganese and are included in international standards.

It is pearlescent ductile iron with medium and high strength, medium toughness and plasticity, high comprehensive performance, good wear resistance and vibration reduction, and good casting process performance. The properties can be changed by various heat treatments. Mainly used in various power machinery crankshaft, [TJC STEEL]camshaft, connecting shaft, connecting rod, gear, clutch plate, hydraulic cylinder and other parts.

 

Attention Points for Ductile Iron:

(1) Strict requirements on chemical composition, the carbon and silicon content of the original liquid iron is higher than that of gray cast iron, and the content of manganese, phosphorus and sulfur in nodular cast iron is reduced.

(2) the temperature of liquid iron is higher than that of gray cast iron to compensate for the loss of temperature of liquid iron during spheroidization and inoculation.

(3) spheroidizing treatment, that is, to add spheroidizing agent to liquid iron.

(4) Adding inoculant for inoculation treatment.

(5) The fluidity of ductile iron is poor, the [TJC STEEL]shrinkage is large, so the need for higher pouring temperature and larger pouring system size, reasonable application of riser, cold iron, the use of sequential solidification principle.

(6) Heat treatment.

① Annealing. To obtain ferrite matrix, improve plasticity, toughness, eliminate stress, improve cutting performance.

(2) normal fire. Obtain pearlite matrix, improve strength and wear resistance.

(3) Conditioning. Obtain the matrix structure of tempered soxite, and good comprehensive mechanical properties, such as spindle, crankshaft, connecting rod, etc.

④ isothermal quenching. The complex shape and high comprehensive performance requirements of the parts to obtain the lower bainite matrix structure, as well as high strength, high hardness, high toughness and other [TJC STEEL]comprehensive mechanical properties, to avoid heat treatment cracking, such as spindle, crankshaft, gear, etc.