Graphite fine grain strengthening inoculation treatment for cast iron

To refine the structure of gray cast iron, improve the mechanical properties of cast iron and make it uniform. Usually, a small number of substances that strongly promote graphitization (i.e. inoculants) are added to the molten iron before pouring. This treatment process is called inoculation treatment. Inoculated gray cast iron is called inoculated cast iron.

The commonly used inoculants include iron breaking, silicon calcium, rare earth Taijin, etc., of which the most commonly used is the ferroalloy containing 75%si. The addition amount of inoculant is about 0.2% ~ 0.5%, which depends on the thickness of the casting. The function of inoculant is to promote the nonspontaneous nucleation in the stone. Therefore, the full phase structure of inoculated cast iron is that fine graphite is uniformly distributed on the fine pearlite matrix. Its tensile strength can reach 300-400 MPa, its hardness can reach hb170-270, α K can reach 3 ~ 8 J / cm2, and the elongation is about 0.5%, which is higher than that of ordinary gray cast iron.

Graphite spheroidizing strengthening of cast iron -- spheroidizing treatment

1. production of nodular cast iron

Cast iron with spheroidal graphite is called nodular cast iron, or nodular cast iron for short. Nodular cast iron is produced by modularizing and inoculating molten iron with ash composition.

2. Microstructure and properties of ductile iron

The graphite in nodular cast iron is spherical, which has little damage to the matrix. The utilization rate of matrix strength can reach 70% - 90%. In addition. Ductile iron can give full play to the performance potential of the matrix through heat treatment, so it has good mechanical properties. The maximum tensile strength can reach 150x107n/m2, and the elongation can reach 25%. In addition, it has a high yield ratio, α K can reach 8-15j / cm2.

3. brand, chemical composition, and application of nodular cast iron

Nodular cast iron has the above excellent mechanical properties. Sometimes it can be used to replace carbon steel. It is applied to parts with large loads and complex, such as pearlite-based nodular cast iron, which is often used to manufacture crankshafts, connecting rods, cams, etc. in automobiles and tractors. It can also be used as a working cylinder, cylinder liner, and piston of a large hydraulic press. The ductile iron based on ferrite is mostly used to manufacture pressure valves, automobile rear axle housing, etc.

Properties of cast iron

The tensile strength, plasticity, and toughness of cast iron are lower than those of carbon steel. Although the mechanical properties of cast iron are inferior to those of steel, the presence of graphite endows cast iron with many properties that are inferior to those of steel. Such as good wear resistance, high vibration attenuation, low notch sensitivity, and excellent machining performance. In addition, the carbon content of cast iron is high, and its composition is close to eutectic composition. Therefore, the melting point of cast iron is low, about 1200 ℃, and the fluidity of molten iron is good. Due to the volume expansion of graphite during crystallization, the transmission shrinkage is small, and its casting performance is better than that of steel. Therefore, cast iron is usually made by the casting method, so it is called cast iron.

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