铁粉粒度对粉末冶金材料制动摩擦性能的影响

采用粉末冶金工艺制备含4种粒度(20μm、30μm、50μm、70μm)铁粉增强的铜基摩擦材料,研究铁粉粒度对材料力学性能和制动摩擦性能的影响。采用TM-1型惯性试验台测试材料的制动摩擦性能,试验初速度为50~380 km/h。结果表明:铁粉粒度从20μm增加到70μm时,材料硬度从55.67 HRB降低到31.83HRB,剪切强度从12.56 MPa下降到10.27 MPa。这种硬度和强度的下降使大粒度样品表现出反常的摩擦特性:随着制动速度的提高,铁粉粒度为70μm的F70样品的摩擦因数不降低反而升高,当制动速度从120 km/h上升到380 km/h时,摩擦因数从0.338持续升高到0.356,并且从350 km/h后摩擦因数稳定不变。这种高而稳定的摩擦因数是保证列车在高速下紧急制动、平稳停驶所必需的。

Effect of iron powder particle size on brake friction performance of powder metallurgy materials

Cu-based powder metallurgy (PM) braking material containing iron powders with four kinds of particle size were fabricated,and the effect of iron powder particle size on the mechanical properties and brake friction per-formance was evaluated using universal testing machine and TM-1 inertial test stand. The initial brake speed is 50-380 km/h. Results show that the hardness of Cu-based friction materials decreases from 55.67 HRB to 31. 83 HRB and the shear strength decreases from 12.56 MPa to 10.27 MPa when particle size of iron powders increases from 20μm to 70μm. On the other hand,the samples with the largest iron particle size of 70μm present the relatively high friction coefficient. The friction coefficient increases from 0.338 to 0.356 as the brake speed increases from 120 km/h to 380 km/h,and keeps at 0.355 when the brake speed is above 350 km/h. The properly high and stable friction coefficient is required for high speed train to brake urgently at high speed.