Study On Automatic Repair Wear Rail By Laser Cladding Fe-base Alloy Powder

The rail abrasion is getting more and more serious due to the high speed and heavy load of the train. Traditional rail welding repair technologies have many problems, such as slow repair speed, poor repair quality, poor impact toughness of bands between the welding layer and matrix, and so on. In this paper, the laser cladding, which has the advantages of high energy density, low heat input and high processing precision, was used to repair the surface of worn rail.For the point cloud data of rails, a 3D scanner was used to scan the rails. After processing, the point cloud data was reconstructed into the rail solid model. And the repair path was obtained in offline software. A set of data conversion software based on C# language was developed to realize the automatic conversion and recognition of a variety of data formats. According to the characteristics of laser cladding repair process, the corresponding control modules are added to realize the automation of the data conversion of the worn rail’s surface.In order to obtain the laser cladding process of Fe-base alloy powder on U71 Mn steel rail, orthogonal and single factor laser cladding experiments of single channel were carried out in turn, and four kinds of powders were tested by laser cladding on the top and side of the rail. The results show that the suitable process parameters of laser cladding Fe-base powder are laser power 1.2 k W, powder feeding rate 6 g/min,protective gas 5 L/min, scanning speed 4 mm/s, and the defocus +1 mm. The Fe-base containing vanadium powder and Fe-base containing titanium powder have better surface forming quality than those of Fe-base self-fluxing powders.The microstructure, hardness testing, tempering heat treatment and friction and wear test of U71 Mn rail laser cladding repair layer were studied. The results show that the microstructure of laser cladding layers are low carbon martensite, tempered martensite and ferrite. After tempering at 600 ℃, the microstructure of the cladding layers is mainly tempered sorbite. And the hardness of the cladding layers is 330~360HV. The cladding layers of Fe-base containing vanadium powder has the best wear resistance. The repaired rail have been carried out on the engineering line, and the wear of the rail is equal to that of the base metal.