| In view of the heavy oil thermal recovery process requirements, and according to high temperature and high pressure(290 ℃ and 21 MPa) design requirements of the Y joint, high temperature Y joint which can intelligently transform production status and test condition was designed based on the hydraulic transmission principle.The actual operation condition of Y joint put forward higher requirements on the sealing performance and corrosion performance. As the research background is based on the research and development of Y joint.Through prototype experiments and finite element analysis of the overall structure of the Y joint, it was optimized and improved continuously, until the functional and sealing performance can meet design requirements under high temperature and high pressure, in order to realize the intelligent transformation in normal operation.The Y joint whose main material is 42 Cr Mo steel was chosen as the research object, through the high temperature corrosion test and electrochemical corrosion experiment, laser shock processing on its corrosion resistance was studied, and the main research contents and the results obtained are as follows.1. Function、sealing performance test and internal flow field simulation test of Y joint Through the function and sealing performance verification of the prototype in normal and high temperature, the prototype structure was constantly optimized and improved.ANSYS software was applied to simulate the internal flow field of device check valve under four different openings, then the internal flow field velocity distribution and turbulent kinetic energy distribution were analyzed. A test rig was set up for testing export flow、import flow and export pressure differential of the device under four openings.Research shows that: By removing 0.3 mm allowance to optimize the size of the metal type O sealing ring with groove installation. The metal o-rings wall thickness and coating is improved, and between the adjacent two bolt holes, two M17 threaded holes are added and installation process is standarded. The local deformation of subject materials due to uneven tress caused by the circumferential bolt clamping, which ensures sealing performance the between the left and right half body of the joint. Considering the high temperature expansion performance of materials and installation clearance, and the sealing performance of seal tongue in operating condition can be insured by applying packing ring combination sealing way.When the check valve opening is limited in 50 mm, internal flow of the device is relatively s Tab., and the turbulent kinetic energy loss is small, high production efficiency can be obtained. The biggest dissipation parts of turbulent kinetic energy is in one-way valve fluid turbulence area, so during the design, transition end-face taper angle in one-way valve inlet should be increased,and surface machining accuracy of ball valve should be improved, which can help to build a foundation of the device to reduce the energy loss in the structure optimization.2.Experimental study and numerical simulation of laser shock processing on 42 Cr Mo steel.Laser shock processing technology was applied for surface treatment of 42 Cr Mo steel,and the material hardness and residual stress measurement was used to explore the effect of laser shock processing.Through the ANSYS/LS-DYNA software, laser shockprocessing finite element model of 42 Cr Mo steel was established to simulate impact wave process and its residual stress field, and the final experiment and simulation results were analyzed.Research has shown that laser shock processing on 42 CrMo steel has a significant effect on improvement of hardness and the residual compressive stress. The influence hardness layer can achieve 0.6~0.7 mm, and the influence residual compressive stress layer can reach 0.65 mm or so. The simulation result shows that blast effect inside the material can form s Tab. residual stress field. Von Mises stress value and the residual stress value shows the tendency of increase with the increase of impact energy, and 8J and 6J double impact energy effect is basically the same. The residual compressive stress in the depth direction can affect the 0.48 mm. Constitutive model in the simulation process had gone through a simplified processing, and a single point of impact was used, but actually, the measured values are more lap, and at the early stages before processing, the material has produced a certain size of residual stress before the measurement. As a result, a gap between numerical simulation and the experimental values conforms to the theory of common sense, and both show consistency on that the laser shock processing can improve the internal residual compressive stress of 42 CrMo steel material.3. High temperature corrosion test and electrochemical corrosion experiment OF 42 Cr Mo steel before and after the laser shock processingHigh temperature corrosion and electrochemical corrosion were applied to explore effect of laser shock processing on 42 Cr Mo steel corrosion resistance. By observing the material surface corrosion microscopic morphology and acquiring energy spectrum diagram, the high temperature corrosion resistant effect can be measured. Electrochemical corrosion effect can be analyzed by electrochemical polarization curve measurement and observation of material micro corrosion morphology after electrochemical experiments.Research shows that: after treated by laser shock processing, 42 Cr Mo steel high temperature corrosion resistance was improved.Only a minor crack extension exists in material surface, crack depth in the surface is relatively shallow, and surface oxidation film shedding almost disappears.After reinforcing by laser shock on material surface,corrosion resistance of 42 CrMo steel material, as a whole, is improved obviously. Polarization curve of corrosion potential, on the whole, move forward, and compared with the original sample, the corrosion current fell a little too, which means that corrosion tend to be smaller.Impedance spectroscopy analysis results also show that, after laser shock,impedance arc radius increase, which implies that corrosion resistance is improved. It can also be seen from material micro-structure figure that the decrease in the number of material corrosion pit class after laser shock, pit depth becomes shallow, degree of whole material corrosion becomes lighter.Polarization curve measurement and material surface micro-structure observation after electrochemical corrosion show the consistency that it can improve the corrosion resistance of 42 Cr Mo steel material after the laser shock processing. |
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