Numerical Simulation And Experimental Study On Remanufacturing Process Of Spool Parts

Flat gate valve is a key component in oil transportation line,whose main function is to control the on-off and flow direction of hydraulic oil circuit.Its main material is 40Cr steel,which has strong tensile strength,yield strength,high fatigue strength and good toughness.It is often used as high-quality structural steel,but its corrosion resistance and friction and wear resistance are poor.As the crude oil pipeline itself contains H₂S,SO₂,CO₂and other chemicals which are easy to corrode the valve core,Spool parts are vulnerable to chemical erosion,damaging their surfaces.If the valve core parts are kept in its high-temperature and high-pressure acidic medium environment for a long time,it is easy to cause the surface failure of the valve core parts.The repair technology of laser cladding has a broad application prospect in the rapid repair of metal parts because of its advantages of good process repeatability and net forming repair of defect parts.IN718 alloy coating has become one of the most widely used high-temperature alloy coatings at present because of its good high-temperature microstructure stability,anti-oxidation corrosion performance and excellent fatigue and creep resistance.It can be used to repair and modify the failure and damage characteristics of valve core parts,so that its surface has better performance than the original one,thus coping with its complex and harsh working environment.However,due to the characteristics of"sudden rise"and"sudden drop"in the process of laser cladding,local high heat and so on,the residual stress of damaged valve core parts after remanufacturing and repairing may be too large or even deformed,so it is necessary to study the distribution and change of temperature and stress in the process of laser cladding.However,due to the rapid changes of temperature and stress in the cladding process,it is difficult to completely capture the dynamic changes in the cladding process by experimental methods.In recent years,with the development of computer simulation technology,it is easier to calculate the transient changes in the multi-physical coupling field by using high-performance computer hardware,and then improve the related experimental process,which is also an important direction of intelligent development in the future laser cladding field.Based on the above analysis,the specific contents of this paper are as follows:(1)In order to explore the optimal process parameters of laser cladding of valve core,the influence of laser power,scanning speed and spot radius on cladding layer temperature was studied by finite element temperature field.The results showed that the cladding layer temperature increased with the increase of laser power,and gradually decreased with the increase of scanning speed and spot radius.The optimal process parameters of single-pass laser cladding were determined according to the temperature distribution of cladding layer.In order to determine the optimal lapping ratio of multi-channel laser cladding,the change of the maximum residual stress at different lapping ratios was studied,and then the lapping ratio at the minimum residual stress was determined.(2)According to the heat accumulation effect found in the optimization process of laser cladding process parameters,the thermal cycle curves of single laser cladding and multi-laser cladding in the remanufacturing process of valve core parts are studied,and the heat accumulation in the cladding process is explored,and the processing technology is reasonably planned to ensure that the temperature rise of cladding layer will not be too high,which will affect the performance of remanufactured products.Finally,the temperature at the end of cladding layer is detected by infrared thermal imager and compared with the predicted value of temperature field,which verifies the accuracy of temperature field simulation.(3)The distribution law of residual stress on the cladding surface of valve spool parts was explored,and a laser cladding residual stress measurement method based on blind hole method was established.The accuracy of stress field simulation was verified by comparing the measured results with the simulated ones,which has certain guiding significance for the laser cladding remanufacturing process of similar parts.