| Railway freight car brake shoe is formed by composite friction materials and steel-back.Since the multi-components are complex and the high recovery cost of waste Railway freight car brake shoes friction material,no research has been done on the recycling of waste friction material at home and aboard.As solid wastes,waste brakes shoes not only do harm for environmental pollution,but also cause a waste of resource.The recycling and reuse of waste Railway freight car brake shoe friction material were studied in this paper.The steel backs and composite friction materials were separated by physical method and chemical pyrolysis method and the waste friction material blocks were made into recycled material powders.What's more,the analysis of the particle and components of recycled powder were also analyzed in this paper.To make full reuse of waste friction materials,the recycled powder was added as a main raw material,new components,such as,rubber modified phenolic resin and steel fiber and composite mineral fiber,inorganic filler,were used to produce car brake linings by molding pressing technique.The tribological properties,shear strength,thermal expansion rate,impact strength and compress strain of brake linings were tested.The SEM was used to observe the friction interface,wear debris to analyze the friction and wear mechanisms.Physical separation method is easy and the technique and equipment are simple,but the separation efficiency is low and it separates the shoe incompletely.While chemical pyrolysis method is complex and requires high cost,but the separation efficiency is high,which is suitable for recycling large amounts of waste brake shoes.Component analysis indicated that there were still components of inorganic mineral bauxite,barite,feldspar powder,sepiolite,iron steel fiber and sulfur and the recycled powder can be reused.The stability of friction coefficient of brake linings made by chemical pyrolysis powder is higher than the lining made physical powder so that chemical pyrolysis separation is the suitable method to separate waste brake shoes.The appropriate formulation of component to recycle the waste friction materials is the recycled powder 7080 wt%,rubber modified phenolic resin 7.510 wt%,graphite 611 wt%,steel fiber 47 wt%,composite mineral fiber 01 wt%,iron powder 04 wt% and inorganic filler 02 wt%.The linings were hot-pressed at 165±5 ? and 70 MPa,holding for 6 min and then the linings were post-cured at 0120 ? for 12 hours.The average friction coefficient was stable between 0.410.43 at 100350 ?,the sum of wear loss was between 2.853.14×10-7 cm3/?N·m?,the heat fading rate was between 2.34%,the thermal recovery rate was 9698% and the offset of friction coefficient was 0.03 meaning recycling of waste friction materials does not decrease the friction and wear performance.The shear strength is 3.524.02 MPa at 20 ? and 12.27 MPa at 300 ?.The thermal expansion ratio is 0.120.16% and the impact strength is 0.360.60 J/cm2.The compress strain is 0.440.50% at 20? and 0.580.62% at 400 ?.The new made car brake lining can meet the operating requirements of car brake lining by GB5763-2008.The main wear mechanisms of the new made car brake lining were particle abrasion and adherence abrasion,the particle abrasion occurred at100200 ? and the adherence abrasion taken place at the temperature between 200350 ?.The cost of the new made car brake lining which made by recycled powder as main raw material is 9.2110.24 Yuan every set.The cost of the car brake lining which made by all new raw materials is 14 Yuan every set.The cost of the new made car brake lining which made by recycled powder as main raw material is lower than the cost of the car brake lining which made by all new raw materials. |
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