These Precautions Must be Known for Ductile Iron Casting

Ductile iron is spheroidized and inoculated to obtain spheroidal graphite, which effectively enhances the mechanical function of cast iron, especially strengthens plasticity and resistance, so as to obtain higher strength than carbon steel. Ductile iron has rapidly developed into a very widely used cast iron material second only to gray cast iron.

1. The chemical composition is strictly required, and the carbon and silicon content of the raw iron liquid is higher than that of gray cast iron, which reduces the content of manganese, phosphorus and sulfur in ductile iron.

2. The furnace temperature of molten iron is higher than that of gray cast iron, so as to compensate for the loss of molten iron temperature during spheroidization and inoculation treatment.

3. Spheroidization treatment, that is, adding nodularizing agent to the molten iron.

4. Add inoculant for inoculation treatment.

5. Ductile iron has poor fluidity and large shrinkage, so it requires a higher pouring temperature and a larger size of the gating system.

6. Carry out heat treatment.

(1) Annealing. The ferrite matrix is obtained, which enhances plasticity, resistance, relieves stress and improves cutting function.

(2) Normalizing. A pearlite matrix is obtained to enhance strength and abrasion resistance.

(3) Quenching and tempering. Obtain the matrix structure of tempered sostenite, as well as good comprehensive mechanical functions, such as spindles, crankshafts, connecting rods, etc.

(4) Isothermal quenching. The parts with complex shape and high comprehensive performance requirements can obtain the matrix structure of the lower bainite, as well as the comprehensive mechanical functions such as high strength, high hardness and high resistance, and prevent cracking during heat treatment, such as spindles, crankshafts, gears, etc.

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