Research On Nodular Cast Iron Of High Silicon Solution Strengthening

Ductile iron is widely used in the components of mechanical industry because of its excellent mechanical properties and low cost. The components of mechanical industry has been frequently used on the components which meet the high qualified of complex loading, high strength, toughness, abrasive resistance, such as camshaft,cylinder head of cars field, inlet or discharge casing of gas turbine field. Due to the porperties of ductlie iron, it’s required to reach high quality level for this kinds of components. Besides of normal mechanical property, it is also required to have high or low temperature resistance, good corrosion resistance, high impact resistance and excellent dimensional stability. Along with the further research for ductile cast iron,many of steel material and gray iron has been replaced by ductile cast iron, ductile iron has been developed into one of the important industry material.With the development of science and technology, cast iron production technology in the continuous innovation, current common grade of ductile iron are QT400-18 、QT500-7、QT600-3、QT700-2 etc. It contains 30%~60% pearlite in the matrix for grade of QT500-7 and QT600-3, though the castings which used this kind of grade can be reached the higher tensile strength, the elongation and yield strength is low relatively,moreover, the processability of this kind of grade is inferior compared with grade QT400-18, because the alloy contains a certain amount of pearlite, which will lead to wear of machine tool more during machining process. In order to get the ductlie cast iron with high tensile strength, higher yield strength, elongation and good processability, silicon is addied by Ba Si inoculant to inoculate, and using alloy nodularizer of Fe Si Mg and the pour-over nodularization method is chosen. In other word through into some kind of solute elements to form a solid solution to make the metal reinforcement, the solute atoms which is into the solid solution causes the lattice distortion, the lattice distortion increases the resistance of dislocation movement and thus inhibits the dislocation slip, which will increase the strength and hardness of alloy by solid solution strengthening. Strength and hardness of the material are improved and the toughness and plasticity are increased when the concentration of solute atoms is appropriately. Experimental research shows that through the principle of using silicon solid solution strenghthening, keeping a certain silicon content in the molten iron has been developed the technology method of ductile iron which can be produced higher grade material, such as grade QT500-14 and QT600-10, this kind of grades has been solved the property of weak yeild strength elongation and processability problem.