Elemental tin, ytterbium, etc., which promote pearlite generation, are given full attention

Higher carbon equivalents and higher silicon content favor the ferrite matrix, but the amount of silicon should not be too high, which will significantly reduce the toughness. Manganese promotes the formation of pearlite, the formation of carbides and segregation tendencies, and reduces the toughness of the material. The easy segregation of the plate results in the production of phosphorus eutectic at the grain boundaries, which is a serious and serious hazard to the toughness of ferrite ductile iron. Sulfur depletion nodulizer affects the spheroidization and the formation of spheroidal retreats and the formation of inclusions. Therefore, for manganese and phosphorus Sulfur should be strictly limited.

The residual amounts of rare earths and magnesium are controlled within the lower limit range with guaranteed spheroidization. The choice of chemical composition in production should be controlled within a certain range in accordance with the actual conditions, and sufficient attention should be paid to the elements of microsphere spheroidization and the elemental tin and antimony that promote the formation of pearlite. Stable and high-quality raw materials and fuels are the basic requirements for batch stable production of cast ductile iron tubes. The new iron should meet the requirements of high-carbon and low-mass silicon, low manganese, phosphorus, and sulfur, and ensure that the composition is basically stable. Coke should guarantee calorific value, strength and low sulfur.

The type and amount of spheroidizing agent have a prominent relationship with the stability of the quality of as cast ductile iron tubes and production, especially the white mouth tendency. China's ductile iron production usually uses rare earth magnesium spheroidizing agent, which is rushed into the spheroidizing process. The addition of rare earths can purify hot metal: rare people have strong desulfurization, deoxidation, and degassing capabilities. Stable rare earth oxides and sulfides are easily removed in the cast iron melting temperature range; rare earths are associated with low melting point elements such as arsenic, lead, zinc, and tin. Compounds with higher melting points are formed and are not melted in molten iron; rare earths are resistant to the effects of anti-graphitizing elements such as titanium and arsenic, neutralizing their harmful effects of graphitization, thereby relaxing their critical content in the original molten iron. It is the favorable aspect of adding rare earth.