Development Of New Type High Strength And High Elasticity Coefficient Gray Cast Iron With Low Residual Stress And Study On The Microstructures And Propetties

A kind of new type cast iron material which don't include Ni,Mo element is developed through studing the relationship of structure and properties of commen high strength gray cast iron.Through metallurgical microscope,tensile test machine and so on,the microstructure of the new type cast iron was analyzed,and all the mechanical properties were measured,such as tensile strength,elasticity coefficient,wear resistance,density,impact energy,bending strength.The metallurgical properties of the new type cast iron were also assessed.The results show that the tensile strength of the new type gray cast iron is up to 343.3MPa,the elasticity coefficient is 113.7GPa,the bending strength is 659.9MPa,the impact energy is 3.9J,the density is 7.3206g/cm~3,and the residual stress is down to 67.2MPa.Compared with the commen high-strength cast iron, the tensile strength and the bending strength of the new type cast iron material improved 8.2%and 12.2%,respectively.And the brinell hardness and the wear-resistance increased 6.2%and 6.5%,respectively.In addition,the metallurgical properties of the new type cast iron such as carbon saturation degree, degree of normality and quality index are meet the design requirements.So,the new type gray east iron material is a new type high-strength cast iron material with high elastic modulus and low-stress.The influence of gray cast iron by heat treatment,such as annealing, multi-permeation,austempered was also studied.After the annealing process,the residual stress reduced by 23.3-44.3%.After the treatment of multi-penetrating technology,the surface micro-hardness is as high as 780HV,which is 3 times of the matrix,the wear resistance increased 69.8%and the corrosion resistance is 312 hours for corrosion-level 9.After the austempered process technology,the tensile strength of gray cast iron is as high as 451.3MPa,which increased 42.2% compared to the original materials;the wear resistance increased 47.99%;the brinell hardness increased 16.6%;the impact energy increased 20.8%.So,all of the process would be effectively improve the performance of gray cast iron.In the end of this paper,the reasons of why the new type cast iron has excellent performance were discussed and the nucleation and growth of the graphite was also analyzed by the knowledge of solid-state phase changes and thermodynamics.