In the production process of petroleum machinery castings, due to various reasons, there may be some defects, such as pores, sand holes, cracks and so on. These defects will not only affect the performance and service life of petroleum machinery, but also pose a potential threat to the safety of petrochemical production. This paper will discuss the common defects of petroleum machinery castings and their prevention methods.
Common defects in petroleum machinery castings
Porosity: Porosity refers to the circular or oval holes present inside or on the surface of the casting, usually due to the failure of gas to discharge in time during smelting or the involvement of air during pouring. The porosity will reduce the density and strength of the casting.
Sand hole: Sand hole refers to the presence of holes inside or on the surface of the casting, usually due to the lack of strength of the sand mold or caused by washing sand during pouring. Sand holes will reduce the wear resistance and service life of castings.
Cracks: Cracks are cracks on the surface or inside of the casting, usually due to excessive cooling or mismatched alloy composition. Cracks will reduce the strength and toughness of the casting.
Inclusions: Inclusions are non-metallic inclusions present in castings, usually due to impurities mixed during smelting or slag inclusion during pouring. Inclusion will reduce the density and wear resistance of castings.
Segregation: Segregation refers to the phenomenon of uneven chemical composition within the casting, usually due to uneven temperature during melting or uneven flow during pouring. Segregation will reduce the mechanical properties and service life of castings.
Methods for preventing defects in petroleum machinery castings
Optimize the melting process: select the right raw materials and melting equipment, control the melting temperature and time, to ensure that the melting is full and uniform. At the same time, adding an appropriate amount of inoculant and spheroidizing agent can promote the grain refinement and increase the density of liquid metal.
Improve the pouring system: reasonably design the flow rate and direction of the pouring system to avoid air or sand. The ceramic filter and other devices are used to filter out impurities and slag inclusion during smelting.
Enhanced cooling process: control the cooling speed to avoid cracking caused by excessive cooling. Adopt appropriate insulation measures to reduce the temperature difference between inside and outside the casting and reduce the risk of stress concentration.
Improve the quality of the mold: the selection of high-strength, high-precision mold materials to improve the manufacturing accuracy and surface finish of the mold. The hardness and wear resistance of the die were improved by heat treatment.
Strict control of chemical composition: Select the appropriate alloy composition to avoid component segregation. Pre-furnace assay and chemical analysis are used to ensure that the alloy composition meets the requirements.
Strengthen production management: establish a sound production management system and strictly control all aspects of the production process. Strengthen staff training and education, improve the technical level and responsibility of staff.
Testing and inspection: The use of non-destructive testing technology such as ultrasonic detection, X-ray detection and other means to carry out a comprehensive test and inspection of the casting. Take remedial measures in time to ensure that the product quality meets the requirements.
The defects of petroleum machinery castings have an important influence on the safety and stability of petrochemical production. In order to prevent these defects, it is necessary to take comprehensive measures from many aspects such as raw materials, melting process, pouring system, cooling process, mold quality, chemical composition control and production management. Strengthening the detection and inspection work in the production process, discovering and dealing with defects in time, is helpful to improve the quality and reliability of petroleum machinery castings, and ensure the smooth progress of petrochemical production.
