在现实生活中，锅炉压力管道和压力容器面临复杂的内外环境，这些裂缝是混合的。一般情况下，是根据裂缝产生和发展的原因来分类的，而裂缝的形成与锅炉的使用、结构、材料、部件等有关，不同的部件、不同的材料、不同的用途，锅炉压力容器压力管道裂缝的形成是不同的。
　　In real life, boiler pressure pipes and pressure vessels are faced with complex internal and external environment, and these cracks are mixed. In general, it is classified according to the causes of crack generation and development, and the formation of crack is related to the use, structure, materials, components, etc. different parts, different materials, different purposes, the formation of crack in pressure pipe of boiler and pressure vessel is different.
　　应力腐蚀裂纹的产生是应力与腐蚀性介质(高浓度碱性水)相互作用的结果。这种裂缝主要发生在锅炉蒸汽管和容器管基础上。当这些成分与碱液接触时，碱液的腐蚀性引起了金属微观世界的化学变化，即金属晶体与晶界之间的电位差造成两者之间的弱电流，导致金属产生裂纹。通过对裂纹的微观观察，发现裂纹有两个主裂纹和两个二次裂纹，主裂纹的发展趋势是通过晶内，二次裂纹的发展趋势是沿晶界辐射。易产生这种裂纹的材料是奥氏体不锈钢，它是在水蒸气作用下通过应力形成的。
　　The generation of SCC is the result of the interaction between stress and corrosive medium (high concentration alkaline water). This kind of crack mainly occurs on the basis of boiler steam pipe and vessel pipe. When these components are in contact with alkali liquor, the corrosiveness of alkali liquor causes the chemical changes in the micro world of metal, that is, the potential difference between the metal crystal and the grain boundary causes the weak current between the two, which leads to metal cracks. Through the microscopic observation of the cracks, it is found that there are two main cracks and two secondary cracks in the cracks. The development trend of the main cracks is through the crystal, and the development trend of the secondary cracks is along the grain boundary radiation. The material easy to produce this kind of crack is austenitic stainless steel, which is formed by stress under the action of water vapor.

　　疲劳裂纹是锅炉压力容器压力管道检测中经常遇到的问题之一。它通常发生在应力集中的设备中。这种裂缝开始时相对较小，在中后期会继续扩展和扩展。疲劳裂纹有三种类型:机械疲劳裂纹、热疲劳裂纹和腐蚀疲劳裂纹。
　　Fatigue crack is one of the common problems in the inspection of boiler pressure vessel pressure pipeline. It usually occurs in equipment with stress concentration. This kind of fracture is relatively small at the beginning, and will continue to expand and expand in the middle and later period. There are three types of fatigue crack: mechanical fatigue crack, thermal fatigue crack and corrosion fatigue crack.
　　机械疲劳裂纹的常见部位有叶轮、叶片、辅助旋转设备等部件，而这些裂纹大多是从设备的表面开始，呈一条直线，开始相对较短，逐渐向内扩展，直至连续变成一条长裂纹，稳定增长。这种裂纹的来源一般是材料缺陷区、刀痕、接头、尖角、孔的位置。
　　The common parts of mechanical fatigue cracks are impeller, blade, auxiliary rotating equipment and other components, and most of these cracks start from the surface of the equipment, in a straight line, relatively short at the beginning, and gradually expand inward, until they become a long crack continuously and grow steadily. The source of this kind of crack is generally the defect area of the material, the knife mark, the joint, the sharp angle and the position of the hole.