Research On Fatigue Properties Of Local 304 Steel And Its Welding Structure

At present, welding is one of the most important methods in joining in the project. Since its characteristic in linking up, there are concentration of stresses and kinds of defects and remains of stresses in the welding joints. Under alternative loading effect, the fatigue crack possibly initiates within the seam of welding structure, and easily results in fatigue failure.The quality of welding structure in nuclear energy has important impact on the operation of the whole set of equipment. This article regards power pressure pipelines which are wildly used in nuclear power and the key equipment as the object of study. This article regards 304 steel which is wildly used in pressure pipelines and pressure Vessels as test object.The aim of this article is to study fatigue properties of the material and the welding structure. In the basis of fatigue theory and searching literature, the load level is decided. Then article establishs the plan of the experimentation. First, experiment of static tensile testing is carried on to test the basic mechanical properties, for example, tensile strength, yield strength and the tensile strength of the welding structure. Then fatigue experiment is carried on to study the fatigue properties of glazed samples which are sorts of size. The purpose is this test to study the main factors which affect the fatigue properties of the structure, such as the effect of size. Then, some samples which are welding structure with one welding line and three welding lines are tested to study fatigue properties under fatigue pressure.The fatigue fractures of the destroyed samples are analyzed to observe the fatigue origin of the crack and the final rupture area. And the properties of different parts of the sorts of samples will also be studied. As to study more fatigue mechanism, metallurgical experiment is carried on. This arcticle studies metallurgical about the base metal of the material and the welding structure. After fatigue test, this article observes their metallurgical and analyses the diversification. The rusults reveal that the grains of HAZ become small and the properties are improved.As the concentration of stresses exists in the arc of the samples, there will be some random truncation datas in the test datas. Based our experience, the distribution of fatigue life obeys Weibull distribution. This article combines addition of rank and method Correlation coefficient to estimate three parameters of Weibull distribution. Finally, this article adopts Matlab to protract the curve of Weibull distribution and forecast the life span of the welding structure.