| Stainless steel welded pipe has been playing an important role in the domestic steel pipe industry.Thanks to the rapid development of welding technology and hot rolled coil industry in recent ten years,the output of welded pipe continues to increase,and has been widely used in petrochemical,aerospace,automobile oil pipeline and other fields.Its small and medium diameter thin-walled 304 austenitic stainless steel straight welded pipe is gradually applied in nuclear power,aviation and other high-tech fields It has been applied.Welded pipe is mostly welded by different processes after the steel strip is cold-formed by the mold.Affected by different factors such as forming mold and welding process,welded pipe often has defects such as cracks,pores,partial welding,incomplete penetration and incomplete fusion.In addition,the production process of welded pipe is too long,and the straight weld is prone to torsion during welding,so there has been a lack of effective on-line detection means.Based on this,the research and development of stainless steel welded pipe ultrasonic on-line detection system,from the ultrasonic creeping wave,ultrasonic longitudinal wave and ultrasonic transverse wave three wave detection methods,on-line ultrasonic nondestructive testing process of weld is analyzed,and a set of ultrasonic on-line detection system suitable for stainless steel welded pipe production line is designed,which realizes the real-time detection of stainless steel welded pipe weld quality.In this paper,the on-line ultrasonic testing system for welded pipe is water immersion ultrasonic testing,which mainly includes the design of mechanical structure and signal processing system of ultrasonic testing system.The mechanical structure design is mainly for the structural design between the water tank,the probe bracket and the water circulation system.The purpose is to carry out full coverage scanning of the thin-walled stainless steel welded pipe and realize the water immersion ultrasonic on-line detection without blind area.The signal processing system is mainly composed of pci-5114 high-speed A / D acquisition card,industrial computer,display and other parts.The whole detection process is carried out in the water tank,with water as the coupling agent,the welded pipe moves forward at a constant speed in the water tank,and the line focusing flaw detection probe and distance measuring probe are evenly distributed around the welded pipe according to a certain rule,so as to realize the full coverage detection of the welded pipe.In the design process,a variety of welded pipe samples with artificial defects(holes,external surface cracks,internal incomplete penetration defects,abnormal grain structure)were made to simulate natural defects,and then the defects of welded pipe weld were analyzed.Matlab software is used to compile the signal processing program,realize the spectrum analysis and continuous wavelet transform of ultrasonic echo signal,extract the characteristic value and characteristic energy of different defects,analyze the echo characteristics of different sample pipe defects,and realize the judgment of welded pipe weld grain size. |
PDF Full Text Request