| The development of rail transit provides convenience for people to travel,and the increase of train speed requires more and more high braking system.As a safety part of train braking system,brake disc must have the technical characteristics of moderate friction factor,long service life and no damage to the brake disc.At present,the 25 T train at 160km/h has been replaced by the Fuxing CR 200 J with a top speed of 200km/h.The cast iron brake disc has been upgraded to a steel brake disc.It is of great practical significance to develop resin-based friction material matching the steel brake disc.This paper aims to prepare high-wear-resistant resin-based friction materials suitable for steel brake discs by optimizing the content of components,study the influence of heat treatment process on the properties of resin-based friction materials,predict their long-term service performance,explore the relationship between the third shape and friction properties during the braking process of materials,and clarify the friction and wear mechanism of materials.The research content and methods of this paper include the following four points:(1)Through orthogonal test,the effects of the contents of cashew shell oil modified phenolic resin,nitrile rubber and magnesium oxide on the mechanical properties and friction and wear properties of resin-based friction materials were studied.The evaluation criteria of multi-index weighted scoring method was established to quantify the average friction coefficient,thermal decay resistance,volume wear rate and dual mass wear of the samples,and the quantitative results of each sample were weighted and summarized.The resin-based friction material formula with the highest comprehensive score is selected.Scanning electron microscope was used to observe the third shape of the tribological wear test process at different speed and explain the tribological wear mechanism of materials.(2)The effects of lubricants(flake graphite,petroleum coke)and abrades(NFJ high-temperature binder,cashew shell oil friction powder)on the mechanical properties and friction and wear properties of resin-based friction materials were studied by orthogonal test.Multi-index weighted scoring method was used to optimize the formula of resin-based friction materials.Scanning electron microscopy and X-ray energy spectrometer were used.Explore the relationship between the third body formed with or without lubricants and abrasives and the friction and wear properties.(3)The effects of steel fiber-reduced iron powder,copper fiber-electrolytic copper powder and hybrid steel fiber-reduced iron powder and copper fiber-electrolytic copper powder on the mechanical properties and tribological and wear properties of resin-based friction materials were studied by means of fiber-particle reinforcement,and the internal mechanism of hybrid fiber-particle coupling reinforced materials was explored.(4)By changing the heat treatment process of resin-based friction materials,the corresponding relationship between the insulation temperatures of 180°C,220°C and260°C and the mechanical properties and friction and wear properties of resin-based friction materials was explored to predict the friction and wear properties of materials under long-term service conditions.The results are as follows:(1)The optimum mass fraction:10%cashew shell oil modified phenolic resin,2%nitrile rubber and 4%magnesium oxide.The relationship between the mechanical properties,friction and wear properties of the resin-based friction materials and the components was investigated.It was found that magnesium oxide could improve the hot pressing process and increase the yield of the materials.(2)Further optimized mass fraction:6%flake graphite,3%petroleum coke,3%NFJ high-temperature binder and 6%cashew shell oil friction powder,revealing that the third body formed by the friction property regulator can reduce the wear of resin-based friction materials and dual disks.(3)Hybrid fiber-particle coupling reinforced resin-based friction materials with excellent comprehensive properties were prepared.The hybrid fiber-particle coupling reinforced components were 15%steel fiber-5%reduced iron powder and 15%copper fiber-5%electrolytic copper powder.It was found that hybrid fiber-particle coupling enhanced the Rockwell hardness,compression properties and friction and wear properties of resin-based friction materials.(4)The optimal formula was determined,and the thermal insulation temperature of the heat treatment process was studied.The tribological properties of the resin-based friction material with heat treatment at 180°C were predicted in three stages:good-unqualified-excellent.(5)After optimized formulation and process,the properties of the materials are as follows:density 2.69 g/cm~3,Rockwell hardness 106.1 HRR,impact strength 0.378 J/cm~2,compression modulus 1371.5 MPa,compression strength 138.4 MPa;The average friction coefficient at each braking speed is 0.373,0.339 and 0.298,and the volume wear rate and dual mass wear are 0.18 cm~3/MJ and 0.63 g,respectively.Its performance is in line with industry standards. |
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