Erosion Mechanism of 20G Steel Based on Gas-solid Two-phase Flow Nozzle Experiment

In recent years, natural gas leakage accidents occur frequently due to the thinning and perforation of the inner wall of natural gas pipelines, and the natural gas pipelines are faced with increasingly serious erosion and wear problems. To solve this problem, the work aims to clarify the erosion behavior and mechanism of gas pipeline materials to provide effective support for the design of anti-erosion materials and the extension of pipeline service life. Based on the ASTM-G76 test standard, the gas-solid two-phase flow nozzle erosion test research method was adopted and the air jet erosion test equipment was used to carry out erosion experiments on 20G steel, a commonly used material for natural gas pipelines, at different impact angles and impact speed. The micromorphologies of the samples were analyzed by means of specialized microinstruments. Ahlert erosion model was used to fit the experimental data, and the erosion rate equation of 20G steel was established. The sample size of 20G steel was processed into 20 mm×20 mm×5 mm (impact angle 15° and 30°) and 25 mm×25 mm× 5 mm (impact angle 45°-90°) with laser cutting instrument, and the surface of the pattern was polished with sandpaper to be eroded, cleaned, dehydrated and blown dry, and then placed in the dryer for use, and finally weighed with a balance. Before the experiment, the abrasive was weighed and dried in a 150° drying oven for 2 hours, and then the abrasive was poured into the sand storage tank in the equipment. With the help of air jet erosion device, the abrasive was sucked into the nozzle, and accelerated in the air flow, to realize impact pattern. During the experiment, the impact angle was adjusted by replacing the sample brackets with different angles (15°, 30°, 45°, 60°, 75° and 90°) to achieve the required conditions of the experiment. After the experiment, the debris on the surface of the pattern was cleaned, dehydrated and dried, and the weight of the pattern after erosion was weighed and the weight loss was calculated. The erosion mechanism was studied by scanning electron microscope (SEM). When the particle impact angle (15°-90°) increased, the erosion rate decreased. However, when the particle impact speed (15-72 m/s) increased, the erosion rate increased. When the impact angle increased, the erosion area decreased. At low impact angles (15° and 30°), the plowing of solid particles was the main erosion and material removal mechanism. At moderate impact angles (45° and 60°), the erosion mechanism presented a mixed form, with ploughing, compaction and cracking acting together on the material surface. At high impact angles (75° and 90°), compaction and cracking were the main erosion and material removal mechanisms. It is concluded that the erosion wear process of 20G under the action of gas-solid two-phase flow conforms to the typical erosion law of plastic materials, and the removal mechanism is not directly affected by particle impact speed, and the change of particle impact energy is the main factor affecting the erosion rate. The erosion rate equation which is suitable for comparison of erosion resistance of natural gas pipeline materials and CFD erosion model is established. The theory of erosion wear is improved, which provides effective theoretical support for solving practical erosion problems in future engineering. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.