Research On Microstructure And Properties Of Rolling Low Carbon Ductile Iron Grinding Ball

Rolling method is used to produce grinding ball with high efficiency and low cost,ausferrite has high strength,good toughness and excellent comprehensive properties.This paper combines the superiority of rolling method and the excellent properties of ausferrie,producing rolling low carbon ductile iron grinding ball which served in the large semi-autogenous mill,as-cast microstructure of low carbon ductile iron and the effect of heat treatment on microstructure and mechanical properties of grinding ball were investigated,corrosion and wear resistance of grinding ball were respectively experimented and analysed,and microstructure and properties of rolling low carbon ductile iron grinding ball were contrastive studied with ADI grinding ball?CADI grinding ball?Forged steel grinding ball I and Forged steel grinding ball II which four grinding balls served in the large semi-autogenous mill.The results showed that:(1)Various factors affect the as-cast microstructure of low carbon ductile iron,using the CA-5 alterative has the best treatment effect and the graphite is the smallest and round;the fading time is in the range of 3 min?12 min,as the fading time increases,the spheroidization rate of graphite decreases,the grains become finer,and the austenite dendrites gradually becomes coarser;the carbon content is in the range of 0.8 wt.%?1.4wt.%,with the increase of carbon content,the number of graphite spheres increases,the content of carbides increases,the austenite dendrites gradually become finer and the eutectic structure increases;the graphite decreases,the carbides disappear,the grains become finer,and the hardness decreases after low carbon ductile iron billet was forged.(2)The matrix microstructure and mechanical properties of rolling low carbon ductile iron grinding ball after austempering heat treatment show a certain gradient,with increasing depth from the surface,the matrix microstructure gradually changes from ausferrite to troostite,and the hardness and impact toughness gradually decreases,and the hardened layer depth between 30 mm?35 mm.(3)When the austempering temperature is in the range of 220??300?,the matrix microstructure of the rolling low carbon ductile iron grinding ball is mainly composed of austenite.with the increase of austempering temperature,the amount of acicular ferrite in the matrix microstructure of the grinding ball surface samples first increases and then decreases,and the acicular ferrite gradually becomes coarser;austenite content and its carbon content shows an increasing trend;hardness shows a decreasing trend,and impact toughness shows a trend of increasing first and then decreasing,and when the austempering temperature is 280 ?,the comprehensive mechanical properties of rolling low carbon ductile iron grinding ball is best.(4)When the austempering temperature is in the range of 220??300 ?,with the increase of austempering temperature,the corrosion resistance of rolling low carbon ductile iron balls first decreases and then increases;wear resistance gradually decreases;the impact corrosion wear resistance first increases and then decreases,and when the austempering temperature is 260?,the the impact corrosion wear resistance of rolling low carbon ductile iron grinding ball is best.(5)Compared with other 4 kinds of grinding balls,rolling low carbon ductile iron grinding ball has highest overall hardness,good toughness and excellent comprehensive properties,shows good impact corrosion wear resistance with less weight loss.