The Application Of Pulsed TIG Cladding Technology In The Surface Strengthening Of Rod With Large Aspect Ratio

Hydraulic support is the key equipment to ensure the safety and high efficiency of production in coal mine.It is equipped with a large number of hydraulic cylinders with different functions and specifications.The surface of the piston rod of the hydraulic cylinder must be strengthened to ensure the working reliability and improve the service life.The traditional surface strengthening process is electroplating.Due to the environmental pollution caused by the electroplating process,it has been more and more replaced by new processes such as laser cladding.Laser cladding is a kind of hot-melt welding method,because of thermal deformation,it is generally applicable to thick wall cylinder and piston rod with small length diameter ratio.In order to explore a green and environmentally friendly technology suitable for surface strengthening of large aspect ratio bar(slender bar),improve the bonding strength,wear resistance and corrosion resistance of the surface strengthening layer of such bar,and avoid the occurrence of thermal deformation due to the excessive heat input during the surface strengthening process,pulsed TIG cladding technology was used to make 316 stainless steel cladding on 27SiMn.The effects of different process parameters on the properties of cladding layer were studied and the optimal combination of process parameters was predicted,then the temperature field of cladding process was simulated.Amplitude current,duty cycle and pulse frequency are the three main parameters of pulsed TIG cladding technology.Firstly,the samples were prepared according to the single factor variable.Through the measure ment,metallographic test,microhardness test and neutral salt spray test,the influence of the three process parameters on the boundary dimension,microstructure,hardness and corrosion resistance of the cladding layer was studied.Then,with the amplitude current,duty cycle and pulse frequency as the influencing factors and the width,thickness,hardness and corrosion resistance of the cladding layer as the inspection indexes,the orthogonal test with three factors and three levels was carried out.Through matrix analysis,the influence order and the optimal combination of process parameters were obtained.The numerical simulation of the temperature field in the process of cladding was carried out,the distribution characteristics and change rules of the temperature field in the process of cladding were analyzed,and the influence of the temperature field distribution on the solidification process of microstructure was studied.The results of analysis and test show that the hardness and corrosion resistance of the cladding layer are greatly improved compared with the matrix material;the influence of process parameters on the properties of the cladding layer is pulse frequency,amplitude current and duty cycle in order,the optimal combination of process parameters is:pulse frequency 15Hz,amplitude current 250A,duty cycle 37.5%;the simulation results show that the distribution of temperature field can directly affect the solidification process of micro structure.