The Research Of Real-time Monitoring And Evaluting Of Fiber Laser Weiding Quality For Complex Internal Flow Passage Component

Lightweight,high performance and thermal management efficiency are the eternal theme about design and manufacture of space engine main structure.It is an important structural form of the complex internal flow passage thin-walled sandwich structure with high thermal management efficiency and significantly reduced weight.Because of its complex structure and high manufacturing precision,it is a serious challenge for the manufacturing process and technology.Due to the superiority and flexibility of laser welding technology,it has been become the main manufacturing method for the complex inner flow passage component.The complex inner flow passage component have many characteristics,such as dense weld,variable weld track,high welding quality,high cost and non-destructive detection after welding and so on.It is necessary to perform real-time detection and evaluation of laser welding quality.The laser welding process is a far away from the equilibrium state of the physical metallurgy process.There are many factors that affecting welding quality.In this paper,laser welding process test of the austenitic stainless steel was experimented by fiber laser with coaxial protection technology.At the same time,the multi-band optical signals were synchronously collected by the laser welding monitoring system.By studying the effect of different laser process parameters and working conditions on the optical signals,combined with the weld macroscopic morphology,the mapping relationship between optical signals and welding quality were established.On this basis,the optical signals were calculated and analyzed.The evaluation method of welding abnormal state and welding defect were obtained.Finally,the experimental study of the application of real-time detection and evaluation technology of coaxial welding quality were carried out.This paper achieves the following research results:The multi-band optical signals can detect the stability and welding quality of the welding process in real time.At the same time,we found that the P signal(0~600 nm)and the T signal(1100~1800 nm)are mainly derived from the metal plume,and the plume have a greater impact on the P signal(1064 nm).The P signal and the T signal are very strong correlation.They are positively correlated with plume volume.By detecting the optical signals can reflect the change of penetration,which caused by the process parameters(laser power,welding speed and angle of incidence).The normalized value of the optical signals intensity are positively correlated with the welding power.It is negatively correlated with the welding speed.With the defocus amount changes from-6 mm to 6 mm,the curve generally exhibits a "V" shape distribution.Through the optical signal can detect welding defects(collapse,crater and without fusion lap weld),which caused by welding position and overlap gap.When the welding speed is less than 9 m/min,this method can detect the welding defect that caused by the overlap gap with the 1 mm and 2 mm thickness of plate.When the laser power and welding speed change,the RMS value of the optical signals(P signal and T signal)are quadratic with weld penetration.Using the mean algorithm to calculate the intensity of the P signal,the exact location of the welding defects can be obtained,and consistent with the test result.