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  • Vol. 54  期 3, 2024 2024年 54卷 第3期
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      YAN Qiangqiang,JIA Chuanbao,CHEN Chonglong,WANG Yinggang,HU Zhiwen,ZHENG Qingye

      DOI:10.7512/j.issn.1001-2303.2024.03.01
      摘要:A rotary arc narrow gap vertical welding equipment for 9% steel large-scale LNG storage tanks is proposed, aiming to solve the welding problems in the position of the vertical seam of LNG storage tanks. The new narrow gap TIG rotary arc welding process is adopted, in which the tungsten electrode is polished into a non-axisymmetric tip, and the tungsten electrode is rotated by motor control, so that the arc heats up both sides of the narrow-gap bevel periodically, which effectively solves the problem of fusion of the side walls. In order to cooperate with this process, a new type of narrow-gap TIG rotary arc welding torch is designed with wireless rotary conductivity, automatic wire feeding and dual path gas protection. At the same time, a set of automatic welding equipment suitable for the position of the vertical seam of LNG storage tanks is proposed, including a wall-mounted trolley and a welding trolley with vacuum adsorption. A full set of test equipment, including welding trolley, fully automatic wire feeder and welding power supply, was built in the laboratory to control the welding travel of the welding torch in the vertical seam position to prevent magnetization of 9%Ni steel, and at the same time to ensure the stability of the welding process. The welding test of 24 mm thick 9%Ni steel with a single layer and a single pass and the narrow gap bevel butt joint test verified that the new process can solve the problem of sidewall fusion in the narrow gap welding of thick plates. And due to the arc cycle rotation, the molten pool has a stirring effect, so that the weld surface shaping is also very smooth and beautiful. This study provides technical and equipment support for automatic and efficient welding of LNG tank vertical seam.  
      关键词:narrow gap;rotating arc;Side wall fusion;9%Ni steel;vertical welding;automated welding   
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      发布时间:2024-03-27
    • LI Yitong,YIN Ziqiang,SHEN Bo,WANG Shouren

      DOI:10.7512/j.issn.1001-2303.2024.03.02
      摘要:The study aims to investigate the effects of carbide orientation on the wear resistance of high-chromium alloy coatings prepared under different cooling conditions. Using high-chromium alloy flux-cored welding wires, two groups of wear-resistant coatings with different carbide orientations were prepared on Q235 substrates, namely water-cooled sample A and naturally cooled sample B. The results of sliding friction and impact abrasive wear experiments were analyzed by comparing the microstructure and microhardness, to reveal the mechanism of the effects of carbide orientation on the tribological properties of wear-resistant alloys. The results show that the front microhardness of group A with a large amount of vertically oriented (Fe, Cr)7C3 primary carbides is 16.92% higher than that of group B, which is mainly composed of eutectic mixtures and clusters of (Fe, Cr)7C3 primary carbides. In the sliding friction experiment, group A exhibits less adhesive wear distribution and a large number of microcracks, with the friction coefficient gradually decreasing to 0.007%; while group B shows a large number of metal particle adhesions, with the friction coefficient showing an upward trend, and the wear rate of 0.015% is higher than that of group A. In the impact abrasive wear experiment, the surface topography of group A is mainly characterized by shallow furrows and brittle fractures, while that of group B is mainly characterized by a large number of long and shallow furrows and spalling pits caused by micro-cutting; by comparing the weight loss curves, the wear rate of group A is 0.75%, while that of group B is 0.42%, indicating that group B with a large amount of lateral carbide distribution exhibits better impact wear resistance.  
      关键词:overlay;M7C3;carbide Orientation;impact wear   
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      发布时间:2024-03-27
    • ZHENG Junbao,YAN Yingjie,CAO Rui

      DOI:10.7512/j.issn.1001-2303.2024.03.03
      摘要:The evolution of precipitated phase of Fe-Ni based austenite alloy after aging at 740 ℃ with aging time was investigated. The effect of aging treatment on corrosion resistance of the alloy was studied by electrochemical corrosion test and Mott-Schottky analysis. The results show that aging treatment at 740 ℃ can promote the precipitation of γ′ phase [Ni3(Al, Ti)] in the alloy. The density and size of γ′ precipitated phase increase with aging time. At the same time, aging treatment can increase the number of spot defects on the alloy surface, reduce the density of the alloy passivation film, and lead to the decrease of the pitting resistance of the alloy. Constant potential anodic polarization treatment can effectively reduce the number of point defects on the alloy surface and enhance the alloy’s resistance to pitting corrosion. The self-corrosion current density of the alloy before aging is -6.697 7 A/cm2, while after aging for 4 hours and 8 hours, it is -5.716 4 A/cm2 and -6.081 2 A/cm2, respectively, both higher than before aging. After electrochemical surface modification, the self-corrosion current density of the alloy before aging is -7.490 125 A/cm2, and after aging for 4 hours and 8 hours, it is -6.127 403 A/cm2 and -6.486 164 A/cm2, respectively, still lower than before aging.  
      关键词:Fe-Ni based austenitic alloy;aging treatment;γ′ precipitated phase;pitting resistance;surface modified technique   
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      发布时间:2024-03-27
    • YAN Zhihang,WANG Wenxian,BIAN Gongbo,ZHANG Han,ZHANG Tingting

      DOI:10.7512/j.issn.1001-2303.2024.03.04
      摘要:In this article, the COMSOL Multiphysics simulation software is used to simulate the generation of arcs in a circuit when excited by a high-frequency pulsed current. Under the excitation of high-frequency pulse current, the conditions of arc generation near the surface tip of two metal plates with a certain angle and rough surface are discussed, and the formation mechanism of the arc is analyzed combined with electromagnetics. The results show that in the electric pulse-assisted rolling process, in addition to Joule heating, there is also the phenomenon of arc heating, which can generate an arc and cause two aluminum plates to combine to form a welded joint when loaded with a current of 300 A and a frequency of 10 kHz. As the current increases, the arc temperature and potential difference increase accordingly. At a current of 800 A, the arc temperature is 4 210 K and the potential difference is 54.5 V. The conditions for arc formation have been met, but the resulting arc is not stable.When loaded at 800 A, an arc of over 4 000 K can be generated and a welded joint formed within the first pulse cycle, and the heat source equation for arc generation is fitted.  
      关键词:electric pulse assisted rolling;arc thermal analysis;ultrasonic arc;high-frequency pulse current;rough surface   
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      发布时间:2024-03-27
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