Research On Magnetic Memory Technology To Evaluate Quality Of Heat Treatment

Following the development of industrialization in our society, there are many components and equipments enduring mutative and periodic stress in manufacture,such as industrial boiler and pressure vessel .These equipments appear fatigue cracks and destroyed. These phenomena not only hinder the development of economic in our country, but it also endangers the safety of person and equipment. This may bring magnitude losing in industrial manufacture.Many equipments destroyed by fatigue stress abruptly; no obvious distortion beforehand.It is difficult to find this phenomenon by common check technology.Metal Magnetic Memory technique(MMM technique) make use of the existing of geomagnetism, utilize transudatory magnetic field produced by stress concentrative area in part of ferromagnetism components, in order to find hidden cracks in equipments and configuration and forecast the area of cracks appear. It needs no pretreatment, convenience and shortcut. Now, this technique is being researched abundantly in our country and in foreign. But the estimate of Metal Magnetic Memory character about cracks and stress concentrative only develop on graph pass"zero"and dHp/dX appears extremum, while result is not quite credible. Also, the Metal Magnetic Memory semaphore character about fatigue cracks from producing to equipment destroyed is insufficient, because of this, it is difficult to form the fatigue damnify discriminating standard.Thereby, this text use two kinds of material components (integer and seal) .as experiment components.Through surveying Metal Magnetic Memory graph of metal stick and seal structure under bended fatigue load, we want to search the rule of Metal Magnetic Memory semaphore character on bug which is foreknow. As all kings of heat treatment frequently used in industrial production, we compare the Metal Magnetic Memory semaphore character in different phase of heat treatment.Following work has been finished in this text: At first, we introduce knowledge about background of research, such as Metal Magnetic Memory,fatigue and heat treatment. Then, analyses the relationship between stress area of crack point and transudatory magnetic field, and affect of reducing component's concentrated stress after improving metals'crystal structure. The first relationship discusses mechanism of Metal Magnetic Memory which used as detect cracks, the other subscribe heat treatment affection.Secondly, this text researches Metal Magnetic Memory character from producing to microcosmic expand, including change of magnetic field intensity Hp(y) and graph.Next, we have surveyed Metal Magnetic Memory character of crack which macroscopically expands to destroy. The text also summarizes variety of Hp(y) and graph. At the same time, we found method to judge the extent of fatigue crack and concentrated stress through Metal Magnetic Memory character.Afterward, this text summarizes the rule of Metal Magnetic Memory graph of real structure in different phase, and illuminates how to checkout the quality of heat treatment through Metal Magnetic MemoryFinally, colligating all facts in research, the text sum up Metal Magnetic Memory character in different contents and phases.