Ductile Iron Has High Performance And Low Cost, But How To Solve The Shrinkage And Porosity Phenomenon?(2)

Preventive measures

(1) Control the composition of molten iron: maintain a high carbon equivalent (>3.9%); minimize the phosphorus content (<0.08%); reduce the amount of residual magnesium (<0.07%); use rare earth magnesium alloys for treatment, The residual amount of rare earth oxides is controlled within 0.02%～0.04%. The external carbon source should be supplemented with a fully graphitized recarburizer.

(2) The process design should ensure that the casting can continuously replenish the high-temperature molten metal from the riser during solidification. The size and quantity of the riser should be appropriate, and strive to achieve sequential solidification.

(3) If necessary, use cold iron and subsidies to change the temperature distribution of castings to facilitate sequential solidification.

(4) The pouring temperature should be 1300～1350℃, and the pouring time of a ladle of molten iron should not exceed 25min to avoid spheroidization and recession.

(5) Improve the compactness of the sand mold, generally not less than 90; the sand hits the sand uniformly, and the moisture content should not be too high to ensure that the mold has sufficient rigidity.