Effect of inoculation treatment and holding time on microstructure and mechanism of high nickel-chromium cast iron
High nickel-chromium centrifugal composite rolls have excellent strength and hardness as well as great re-sistance to thermal shock and thermal cracking,which is attribute to the good match of graphite and eutectic carbides in the structure of high nickel-chromium cast iron.However,the unsuitable inoculation would not effectively im-prove the structure and even form inclusions to deteriorate the material properties.Meanwhile,in the process of roll manufacturing,holding time of high-temperature iron liquid in the intermediate ladle is uncertain,due to the instabili-ty of iron smelting process and casting process.Eutectic carbide and graphite in the as-cast structure of high nickel-chromium cast iron was studied after holding for 3 h,5 h and 7 h,and followed by adding 0.4％,0.8％and 1.2％in-oculant before pouring.The influence of holding time and inoculant treatment on hardness was also compared.The results show that with the increase of holding time,the average size and volume fraction of graphite increases,but the number density decreases,and the content of eutectic carbides decreases obviously.After inoculation treatment with holding time of 3 h,the nucleation of graphite could be effectively promoted,but the average size and number density of graphite did not improve significantly even if the amount of inoculant was increased after increasing holding time.When the holding time is less than 5 h,the content of eutectic carbide can be reduced by inoculation treatment,but the content of eutectic carbide can be increased by inoculation treatment after increasing the holding time.The hard-ness of high nickel-chromium cast iron decreases gradually with the increasement of holding time.When the holding time is more than 5 h,the hardness of incubated samples can increase 16HRC.In the smelting process of high nickel-chromium cast iron,the holding time should be controlled within 3 h,too long holding time will lead to excessive growth of graphite and reduce the amount of graphite.At this time,the amount of graphite can be increased by adding 0.4％-1.2％inoculant,but after holding for more than 5 h,even adding inoculant can not effectively improve the amount of graphite.
high nickel-chromium cast ironinoculation treatmentholding timegraphiteeutectic carbide
NETL
NSTL
万方数据
