Heat Treatment Process And Wear Resistance Mechanism Of Bainitic And Martensitic Wear Resistance Cast Steel For Cone Crusher Liner

Cone crusher is a key equipment in the mining industry.Its working environment is complicated and the workload is huge.Therefore,wear-resistant liners are set to protect the structure of the cone crusher.As the most important work and consumable parts of the cone crusher,its performance and service life directly affects the work efficiency and production costs.At present,high manganese steel is widely used in crusher liners in china,which is characterized by low yield strength and initial hardness.If the work hardening effect cannot be fully exerted,the wear resistance of high manganese steel is difficult to meet the needs of cone crushers.In this paper,along the idea of improving the strength and hardness,and maintaining certain impact toughness,thereby improving the comprehensive wear resistance,a bainite and martensite wear resistant cast steel for cone crusher liner with bainite and martensite as the main microstructure was designed.The phase transformation of bainite and martensite wear resistant cast steel was studied.Ac1,Ac3 and Ms were 762 ℃,843℃ and 281℃,respectively.The material had good hardenability.The martensite transformation could occur in the cooling rate range of 40℃/s to 0.05℃/s,and a certain amount of bainite structure could be obtained in the cooling rate range of 5℃/s to 0.05℃/s.The optimal heat treatment process of bainite and martensite wear resistant cast steel was 900℃ holding for 2 h,air cooling or furnace cooling,300℃tempering for 2 h.The mechanical properties under current heat treatment process were:tensile strength 1478 MPa,yield strength 1233 MPa,hardness 52.1 HRC,impact energy 20.6 J.The effect of heat treatment process parameters on the mechanical properties and microstructure of the bainite and martensite wear resistant cast steel was analyzed.The results showed that the quenching holding temperature directly affects the original austenite grains,martensite packets and blocks.The size of the laths had a hysteresis.The quenching cooling rate effected the content of bainite and martensite in the microstructure.Mn,S,C and Si compounds at the grain boundaries in the martensite structure reduced the toughness.In the bainite structure,the high angle grain boundaries and the precipitates of Y2O3 were beneficial to toughness.The martensite structure had a higher density of dislocation entanglements and a finer lath microstructure,so the nano-hardness was higher than that of the bainite structure.Two-body pin-disc wear test and the three-body impact abrasive wear test were conducted to compare the wear resistance of the bainite and martensite wear resistant cast steel and Mn13Cr2.The results showed that the wear resistance of the bainite and martensite wear resistant cast steel in the pin-disk wear test and 1 J,2 J,4 J impact abrasive wear test are 197%,38%,99%,246%higher than Mn 13 Cr2,respectively.The three-body impact abrasive wear test after salt spray corrosion was carried out.The wear resistance after salt spray corrosion for 1 h,2 h,4 h,8 h and 24 h was reduced by 10%,42%,54%,57%and 58%,respectively.A dimensional wear analysis method was proposed to explain the wear resistance mechanism of the bainite and martensite wear resistant cast steel.One-dimensional wear analysis describes the work hardening mechanism and the phase transiformation along the normal direction of the worn surface.The work hardening mechanism of the bainite and martensite wear resistant cast steel was twins,high-density dislocations and retained austenite transformation.The work hardening mechanism of Mn13Cr2 was dislocation entanglement and stacking faults.Two-dimensional wear analysis pointed out that the two-body friction and wear forms of Mn13Cr2 and the bainite and martensite wear resistant cast steel were mainly adhesive wear and abrasive wear,respectively.Three-dimensional wear analysis explained that strain fatigue,cracks,furrows,embedded abrasive and extrusion accumulation were the main wear mechanisms of the bainite and martensite wear resistant cast steel in three-body impact abrasive wear.Embedded abrasive particles,furrows,strain fatigue,cutting,extrusion accumulation and spalling pits were the main wear mechanisms of Mn13Cr2.Four-dimensional wear analysis explained the wear behavior under the synergistic effect of salt spray corrosion and impact abrasive wear.The wear mechanism of low-degree corrosion samples was still mainly manifested as ploughing,strain fatigue and embedded abrasive particles.The subsurface deformation zone of the sample wear was narrow.After that,with the prolongation of salt spray corrosion time,the furrow became shorter and deeper,the abrasion loss increased,the deformation zone of the sample wear subsurface layer disappeared,and the wear resistance of the material deteriorated.A formula was established to estimate the weight loss of the bainite and martensite wear resistant cast steel under the synergistic effect of salt spray corrosion and impact abrasive wear.Trial-produced a set of bainite and martensite wear resistant cast steel liners.The heat treatment parameters for industrial production were set to 910±10℃ for 5 hours,forced air cooling,310±10℃ tempering for 8 hours,and air cooling.The microstructure and mechanical properties of the trial-produced liner basically met the index requirements.The overall mechanical properties and wear resistance of the liner were uniform,and the service life after trial service exceeded the average life of the currently used domestic liner by more than 50%.