| China’s coastline is long,the coastal environment of railway construction is increasing year by year,coastal environment is very easy to produce corrosion phenomenon,which puts forward higher requirements for the corrosion resistance of railway tracks,fastener system in the railway track plays a role in the role of connecting up and down,it will be tightly connected with the track foundation into one,while the fastener system has a huge number,on average each meter will be installed in the track inside and outside the fastener system,fastener system in the installation,detection,replacement process is also very complex,which,The elastic strip is the most important part that produces fatigue fracture,and it is also the most frequent part of replacement and maintenance,and the elastic strip is corroded during operation and its corrosion phenomenon due to wear,and the corroded elastic strip is very prone to corrosion fatigue fracture.Therefore,this paper mainly takes 60Si2Mn spring steel as the research object,and analyzes the changes of mechanical properties of 60Si2Mn spring steel before and after heat treatment,and the changes of fatigue crack growth rate with the extension of corrosion time,the changes of corrosion products and the microscopic changes of corrosion layer under different corrosion time days by mechanical property test,fatigue crack growth test,microscopic analysis,corrosion product composition analysis and EDS energy spectrum analysis.The main work content and research conclusions of this paper are as follows:（1）The heat treatment process of 60Si2Mn spring steel was carried out,and the mechanical properties of the material before and after the heat treatment were measured by mechanical tensile test,and it was found that the raw materials in this batch could meet the requirements of the specification before and after the heat treatment,and the heat treatment could significantly improve the yield strength and tensile strength of the material.Using the secant method recommended by the national standard and the seven-point incrementing term method,and the three data processing methods recommended by foreign scholars to the Smith method to process the experimental data,it is found that the seven-point incrementing term method can better reflect the data results,have higher accuracy and better fitting effect.The fatigue crack growth curve of the heat treated material is more gentle,indicating that the fatigue resistance of the material after heat treatment is higher.The micromorphology of the crack was analyzed by scanning electron microscope,and it was found that the specimen before heat treatment had relatively many secondary cracks in the crack source area,crack propagation zone and transient fracture zone,and the secondary crack may be the reason why the material is more prone to fracture.（2）60Si2Mn spring steel made into standard（CT）specimen,using neutral salt spray test to accelerate corrosion of the sample,the sample is divided into salt spray0 days,25 days,40 days,60 days,90 days a total of 5 batches,after the completion of each batch take out the test according to the specifications for washing and drying treatment,and then on the MTS809 servo fatigue testing machine for fatigue crack growth test.Analyzing the fatigue cycle weeks of each batch test,it was found that the fatigue cycle weeks of each sample all oscillated around 330,000 cycles,and this test did not affect the fatigue cycle of the sample.The weight loss rate calculation was used to analyze the change of the corrosion layer of the sample,and it was found that with the extension of the corrosion time,the corrosion rate of the sample showed a downward trend,and the corrosion of the sample satisfied the law of the power function,and the power function equation was obtained as R=4.035t0.9099,which indicated that the corrosion products of the material in the neutral salt spray environment had an inhibitory effect on the corrosion of the sample.The test data under each batch were processed by group data processing and seven-point incrementing term method,and it was found that the fatigue crack growth curve did not change significantly,and the neutral salt spray corrosion test had little effect on the fatigue crack growth law of the material.Finally,in order to verify the reliability of the test data,the Paris formula is used to reverse the fatigue cycle cycle,and the results show that the test data are within its range,and the test is reliable.（3）In order to better observe the law and change of the specimen in the corrosion process,the test interval is reduced to 4 time periods of 5 days,15 days,25 days and40 days,and taken out for analysis after each time period is reached.First of all,the overall macroscopic angle was observed,and it was found that the early stage of the sample was mainly pitting corrosion,and there were many areas that were not corroded in the early stage,and with the extension of the corrosion time,the corrosion embroidery layer on the surface of the sample continued to accumulate,forming a thick corrosion layer.Using scanning electron microscopy（SEM）,it was found that the embroidery layer in the early stage mainly included needle-like products,cluster-like products,uncorroded areas and cracks,and with the extension of the corrosion test,the corrosive embroidery layer was more dense,mainly cluster-like products.XRD embroidery layer composition phase analysis of corrosion products,it is found that Fe3O4,γ-Fe OOH,α-Fe OOH three substances are mainly used in the corrosion products of the sample,and the corrosion mechanism of the sample is analyzed and found that the corrosion of the sample is a typical electrochemical corrosion process,the outside of the rust layer is constantly carrying out the transformation ofγ-Fe OOH toα-Fe OOH,making the structure of the outside of the rust layer more dense,the internal test of the rust layer is mainly based on Fe3O4 insoluble in water,and the two substances better protect the internal test of the rust layer. |
