When seamless steel tubes are cold drawn, hot rolled tube defects such as cracks or the presence of high-precision drawing fuel tank is made after the fracture occurred in the course, almost no plastic deformation occurred, generally are brittle fracture. Brittle fracture is caused by a variety of reasons. Such as: the grain boundary precipitates, regardless of which is stronger than the strength of the matrix or weak, are all causes cracks; segregation at the grain boundary inclusions is broken reasons; Furthermore, even in far less than the yield limit of the cross under variable loads, can also cause fatigue fracture occurred.


In general, the mechanical properties of hydraulic (pneumatic) components used in the design, materials are assumed to be homogeneous, continuous, isotropic, according to this method of analysis is considered safe design, sometimes accidents will happen rupture. The study found that low stress brittle fracture process occurs in a high strength metallic materials, the material organization is far from homogeneous, isotropic. Organizations have cracks, there will be inclusions, porosity and other defects that can be seen as material microcracks. In addition, the brittle fracture and also member of the relevant temperature. When people through research found that when the temperature drops below a certain temperature, the material will be converted into a brittle state, the impact absorbed energy decreased, a phenomenon known as cold brittleness, so the design but also according to the working temperature member select with a suitable cold-brittle transition temperature of the material.