Experimental Study On Hardness Matching Of High Speed Wheel And Rail Materials

The rail wear in China high-speed railway is very small in tangent lines,while the work hardening of which is also slight.Concave wear and polygon wear of high-speed wheels are emerging in these years.In order to solve these problems,this paper has carried out laboratory research and field tests concerning wheel-rail hardness matching to give reasonable matches and hardness ratio of wheel-rail material.The anti-wear and anti-fatigue performance of two wheel materials ER8 and ER8 C is studied.The initial law of work hardening and abrasion of high speed wheel and rail material was obtained.High-speed wheel-rail hardness ratios of different countries are various.The high-speed wheel-rail hardness ratio(wheel / rail)in Europe and China is close to 1: 1,while Japan is above 1.2:1.Some countries have improved the wheel hardness to solve the problem of abnormal wheel wear.Friction and wear tests of 9 specimens pairs made of wheel and rail materials were completed by Amsler tester based on Hertz contact theory.Vertical load was 490 N and slippage was 10% during the tests.When the wheel-to-rail hardness ratio is in the range of 1.05: 1 ~ 1.15: 1,the system wear is relatively low,while the wear of wheel /rail sample is more balanced and the wheel sample deformation is smaller.The wear of specimen is approximately linear with the test cycle.For the first time,the phenomenon of polygon wear was measured in laboratory.With the increase of the hardness value,the polygon wear of wheel specimen is obviously reduced.Besides,when the hardness of the rail is low,the polygon wear of the wheel specimen is smaller.The friction and wear tests of ER8 and ER8 C high speed wheel materials over U71 MnG rail were completed by MJP-30 A tester.The U71 MnG rail specimen show less wear with ER8 C specimen.ER8 C wheel specimen's anti-wear,anti-fatigue performance is significantly better than ER8 material.There were no significant differences in surface damage of U71 MnG rail specimens in different test groups.Field tests were carried out to study the work hardening and wear of high speed wheel and rail material.Results show that: 1)The tread hardness values of ER8 and ER8 C fluctuate are in the range of 300-320 HB and 310-335 B after 200,000 kilometers.2)The work hardening of wheel tread is not uniform.3)Hardness of rails on tangent lines grows slowly,the relative hardening rate of rails on Wuhan-Guangzhou high-speed railway is in the range of 3.1% to 8.5% with 44 million tons gross weight.4)ER8 and ER8 C wheel tread wear rate is about 0.04 ~ 0.05mm/million km.5)The vertical wear rate of rails on Beijing-Shanghai high-speed railway is about 0.0017mm/Mt.Improving the wheel hardness(to improve wheel/rail hardness ratio)is a feasible method to solve the wheel-rail material application problems.It is recommended to be taken into account in the future selection of high speed wheel / rail materials.