Petroleum machinery castings are subjected to complex environmental and load conditions such as high pressure, high temperature and corrosion during oil exploitation and processing. These factors may lead to fatigue cracks in castings and affect the safety and service life of equipment. Therefore, it is of great significance to analyze and improve the fatigue properties of petroleum machinery castings. This paper will discuss the analysis method and improvement strategy of fatigue properties of petroleum machinery castings.
Fatigue performance analysis of petroleum machinery castings
Fatigue crack initiation
Under the action of cyclic load, small cracks will occur in the stress concentration area of petroleum machinery castings. These cracks usually originate on the surface of the casting and gradually expand with the repeated action of stress.
Fatigue crack growth
When the crack is formed, the crack will expand along the direction perpendicular to the stress with the periodic change of the stress. The propagation rate of crack is usually related to stress, material properties and environmental factors.
Fatigue fracture
When the crack extends to a certain extent, the petroleum machinery castings will fracture in an instant, resulting in equipment failure. Fatigue fracture is one of the main failure forms of petroleum machinery castings.
In order to improve the fatigue performance of petroleum machinery castings, it is necessary to improve from the following aspects:
Material properties have an important effect on the fatigue properties of castings. The selection of materials with high strength, high toughness and fatigue resistance helps to improve the life of the casting. For example, high-strength alloy steel, wear-resistant cast iron and other materials have good fatigue resistance and can be used to manufacture castings in key parts.
Reasonable design structure is helpful to reduce the degree of stress concentration and improve the stress status of castings. For example, the use of rounded corners or transition zones in key parts of the casting to reduce stress concentration; The stiffness and anti-fatigue properties of castings can be improved by rationally arranging reinforcement bars.
The heat treatment process can change the structure and properties of the internal structure of the material, so as to improve the fatigue properties of the casting. For example, by quenching, tempering and other processes to improve the strength and toughness of the material; Surface strengthening treatments such as shot peening and rolling are used to improve surface hardness and fatigue resistance.
During manufacturing and use, factors that cause stress concentration, such as scratches and bumps, should be avoided as much as possible. In addition, vibration aging process can also be used to eliminate casting stress and reduce stress concentration during use.
For important petroleum machinery castings, real-time monitoring and diagnosis can be carried out during use to find and deal with potential fatigue cracks in time. For example, acoustic emission technology, X-ray flaw detection and other methods are used to detect the internal cracks of castings.
The fatigue properties of petroleum machinery castings have an important influence on their service life and safety. The fatigue properties of castings can be effectively improved by reasonable selection of castings materials, optimization of structure design, improvement of heat treatment process and reduction of stress concentration factors. At the same time, real-time monitoring and diagnosis of the use process of important castings helps to find and deal with potential fatigue cracks in time, and improves the safety and service life of the equipment.
