The Influence Of Welding Process On The Quality Of Welding Joints For The Rectangle Pipe

Different welding procedures were adopted,purpose of investigation on the relationsh-ip between welding parameters and the microstructure and properties of welded joints. T-he analytic methods include ultrasonic testing,metallographic examination,hardness testing,microhardness test,impact test,Scanning Electron Microscope (SEM),bending test and postweld heat treatment. The products are rectangular tubes,and the sizes are 250mm×250mm×11.8mm,250mm×250mm×9.8mm,200mm×300mm×9.8mm and 200mm×300mm×11.8mm. The material is Q235.Through ultrasonic testing and microstructure observation,indicates that all the welding performance samples are qualified. All samples of the welded joint microstructure include decarburization layer,over-heated area,completely recrystallization of the district and incomplete recrystallization zone. The decarburization layer and the over-heated area are widmanstatten structure.Impact test is commonly used to measure metal toughness. The test uses GB2106-80"Metallographic xabi impact test method". The impact test indicate that the impact tough-ness of weld ispoor by the high frequency welding method. And certain heat treatment.must be taken to improveit.Bending test is taken by GB/T2653-1983, it is used for evaluation of flexural capacity of welds. Experiment shows that the samples have good performance of bending. Studied the influence of Ea, the heat-affected zone width, the V angle and the speed on bending performance of the welded joint. In order to get the proper welding process parameters.Postweld heat treatment is to improve the metallurgical structure and to improve the performance. Experiments show that the weld microstructure was refined by normalizing treatment. This will improve the performance greatly.