20 January 2021, Volume 45 Issue 1
    

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  • Research Status and Development Trend of Wear-Resistant Copper Alloy
    LIU Yuning, WANG Yunpeng, ZHU Rufei, WANG Hu, BAI Yike, LOU Huafen
    Materials For Mechanical Engineering. 2021, 45(1): 1-7. https://doi.org/10.11973/jxgccl202101001
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    Development of high speed and high performance of mechanical equipments requires higher strength and better wear resistance of wear-resistant copper alloys. Although performance of traditional aluminum bronze series, manganese brass series and lead brass series alloys has been improved, their application scope is limited by various factors, such as material characteristics, processing technology and environmental protection, respectively. The application status and research progress of five typical wear-resistant copper alloys with high application values including Cu-Ni-Sn series, Cu-Al2O3 series, Cu-Nb series, Cu-C series (including copper/graphite, copper/graphene and copper/carbon nanotubes) and complex brass are described from preparation process, properties and application field. The problems in their development and application are analyzed, and their development prospect is also discussed.
  • Effect of Heat Treatment on Field Emission Properties of Ti-Doped Diamond-like Carbon Film
    LI Shuanping, LIU Zhubo, WANG Yongsheng, YU Shengwang, HE Zhiyong, ZHOU Bing
    Materials For Mechanical Engineering. 2021, 45(1): 8-13. https://doi.org/10.11973/jxgccl202101002
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    The Ti-doped diamond-like carbon (Ti-DLC) film was prepared by multi-target magnetron sputtering technique, and was heat-treated at different temperatures (300,350,400 ℃). The effects of heat treatment temperature on the microstructure, composition, band structure and field emission properties of the film were studied. The results show that compared with those before heat treatment, the proportion of sp2-C clusters in the Ti-DLC film after heat treatment at 300 ℃ increased; the optical band gap was the smallest, and the turn-on field with value of 5.43 V·μm-1 was the smallest, indicating the film had the best field emission performance. As the temperature was higher than 300 ℃, the content of diamond-like carbon in the films dropped, and a large amount of TiO2 formed; the optical band gap and the turn-on field increased, indicating the field emission performance of the films got worse. The field emission current of the film was not affected by the heat treatment temperature.
  • Effect of Quenching and Partitioning Process on Microstructure and Mechanical Properties of 60Si2Mn Spring Steel
    ZHOU Qingsong, HAO Qingguo, YANG Qi, ZHANG Ke, LIU Ping
    Materials For Mechanical Engineering. 2021, 45(1): 14-19,27. https://doi.org/10.11973/jxgccl202101003
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    60Si2Mn spring steel was treated by quenching and partitioning (Q&P) at different quenching temperatures (140,160,180 ℃). The microstructure and mechanical properties of the steel after Q&P treatment were investigated, and compared with those after traditional quenching and tempering (Q&T) treatment. The results show that the microstructure of 60Si2Mn spring steel after Q&P treatment consisted of retained austenite and martensite, and the volume fraction of retained austenite was more than 12%. The microstructure of the steel after Q&T treatment was tempered troostite/tempered sorbite. The strength and hardness of the steel after Q&P treatment decreased with increasing quenching temperature, and the percentage elongation after fracture, impact energy and product of strength and elongation increased, which were all larger than those after Q&T treatment. The comprehensive performance of the spring steel after Q&P treatment was better than that after Q&T treatment because of the transformation-induced plasticity effect caused by the restained austenite during deformation.
  • Preparation and Electrochemical Performance of Cobalt-DopedManganese Oxide Aqueous Zinc-ion Battery Cathode Material
    HU Rudan, SUN Jingwen, LIU Yifan, QIAN Xingyue, ZHANG Litong, ZHU Junwu
    Materials For Mechanical Engineering. 2021, 45(1): 20-27. https://doi.org/10.11973/jxgccl202101004
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    The cobalt-doped manganese oxide for aqueous zinc-ion battery cathode material was prepared by solvothermal, hydrolyzing and annealing with cobalt nitrate and manganese nitrate as raw materials. The microstructure and electrochemical performance of cobalt-doped manganese oxide was investigated. The results show that the prepared cobalt-doped manganese oxide h-CoMn3.2Ox had a hierarchical yolk-shell structure, and the porous shell surface was decorated with petal-like nanosheets with radial dimension of more than 100 nm. Both of the shell and nanosheets were composed of primary nanoparticles with average size of 5 nm. Cobalt-doping endowed manganese oxides with small size and delicate structure. h-CoMn3.2Ox had the manganosite MnO crystal structure. Compared with monometallic manganese oxide, h-CoMn3.2Ox exhibited relatively large specific surface areas and specific capacities, and had good cyclic stability. The energy-storage behavior of h-CoMn3.2Ox was attributed to sequent co-insertion of H+ and Zn2+.
  • Strength Degradation Behavior of P91 Steel for a Supercritical Unit
    WU Shuquan, HAN Tao, JIANG Shikai, ZHANG Zhibo, JIANG Feng
    Materials For Mechanical Engineering. 2021, 45(1): 28-33,40. https://doi.org/10.11973/jxgccl202101005
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    Reasons for the strength decrease of P91 steel for steam pipeline in a supercritical unit after service for 88 000 h were investigated from the aspects of martensite substructure, precipitate, solid solution element and dislocation density. The results show that after service the average diameter of M23C6 carbides in P91 steel increased from 78.0 nm to 190.6 nm, and Laves phase with average particle size of 393.2 nm was precipitated. The contribution value of precipitates to yield strength decreased by 38.7% because of the coarsening of M23C6 carbides, and the contribution value of Laves phase precipitation to yield strength was very small. The Ostwald ripening of M23C6 carbides and the precipitation of coarse Laves phase needed to consume C, Cr, Mo and Si elements in the matrix, which reduced the solid solution strengthening effect. The increase in strip block size and strip width of martensite had certain contribution to the reduction of yield strength. The dislocation density of serviced P91 steel was 6.4×1013 m-2, which was lower than that of unserved P91 steel (9.7×1013 m-2); the strengthening effect of dislocation on matrix decreased by 18.8%. Under the effect of all factors, the yield strength of P91 steel after service decreased by 27.0%.
  • Microstructure and Properties of 25Cr2Ni4MoV Steel Welded Joint underPre-welding and Post-welding Quenching and Tempering Treatment
    ZHANG Min, TONG Xiongwei, LI Jie, XU Shuai, JIA Fang
    Materials For Mechanical Engineering. 2021, 45(1): 34-40. https://doi.org/10.11973/jxgccl202101006
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    Microstructure, mechanical properties and corrosion resistance of 25Cr2Ni4MoV steel welded joint were compared and studied under conditions of pre-welding and post-welding quenching and tempering treatments. The quenching and tempering process was oil quenching at 920 ℃ for 1 h and tempering at 580 ℃ for 2 h. The welding process was manual electrode arc welding. The results show that by pre-welding quenching and tempering, the microstructure of the joint weld zone consisted of lath martensite, network δ-ferrite and M23C6 carbide. After the post-welding quenching and tempering, the δ-ferrite in the weld was dissolved, and the lath martensite, tempered sorbite and M23C6 carbide were formed. Under the post-welding quenching and tempering condition, the lath martensite in the weld was small and uniform, and the M23C6 carbide distributed in granular shapes on original austenite grain boundaries and martensite lath grain boundaries; the strength, impact toughness and corrosion resistance were better than those by the pre-welding quenching and tempering treatment.
  • Influence of Staircase Fatigue Test Data Closed or Not onStatistical Estimation of Material Fatigue Strength
    ZHENG Cheng, LU Qi, LI Hongtao
    Materials For Mechanical Engineering. 2021, 45(1): 41-45. https://doi.org/10.11973/jxgccl202101007
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    Two types of unclosed staircase chart were cited, and reasonable assumptions were made on the test results that may appear during the staircase fatigue test. The effect of test data closed or not on the fatigue strength was analyzed when the fatigue strength was statistically estimated by the staircase method. The results show that when the last-level stress in the staircase chart of unclosed test data was lower than the first effective stress, the statistically estimated fatigue strength after subsequent supplementary of hypothetical staircase chart was also lower than the statistically estimated fatigue strength from the original unclosed fatigue test staircase chart. When the last-level stress of the staircase chart of unclosed test data was higher than the first effective stress, the statistically estimated fatigue strength after subsequent supplementary of hypothetical staircase chart was also higher than the statistically estimated fatigue strength from the original unclosed fatigue test staircase chart. Even if test data was not closed, the fatigue strength statistically estimated from failure events and non-failure events may be equal.
  • Microstructure and Mechanical Properties of Laser Welded Joints ofLZ92 Magnesium Lithium Alloy
    JIANG Bingchun, FU Qin, HU Shaohua, TANG Lianyao, LIU Fangfang
    Materials For Mechanical Engineering. 2021, 45(1): 46-49. https://doi.org/10.11973/jxgccl202101008
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    LZ92 magnesium lithium alloy plate with thickness of 2 mm was welded by CO2 laser, and the microstructure, phase composition, micro-hardness and tensile properties of the welded joint were studied. The results show that LZ92 magnesium lithium alloy welded joint had good formability, and no obvious pores and cracks were found in the weld. The phase composition of the base metal and the weld was the same, consisting of α phase, β phase and intermediate phase Mg7Zn3. The base metal was composed of equiaxed β phase and dendritic and granular α phase; the heat-affected zone was composed of coarse β phase and a few fine granular α phase; a large amount of fine needle and granular α phases evenly distributed in the β phase in the weld and the grain boundaries of β phase disappeared. The hardness of the weld was the highest, followed by the base metal, and the hardness of the heat affected zone was the lowest. The tensile strength of welded joint was 158 MPa, which was 86.8% that of the base metal, and the elongation was 27%. The tensile fracture of the welded joint was located at the fusion line between the heat-affected zone and the weld; the fracture was composed of dimples and cleavage surfaces, indicating the fracture form was a mixed fracture.
  • Effect of Surface Pretreatment of 304 Stainless Steel on Properties of Deposited CrMoN Coating
    PENG Dingwen, HU Menglei, LIU Haojie, JIN Jie
    Materials For Mechanical Engineering. 2021, 45(1): 50-58,65. https://doi.org/10.11973/jxgccl202101009
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    The 304 stainless steel substrate was grinded to 1200# (1# process), 2000# (2# process) by sandpaper in sequence and grinded to 2000# and polished by diamond polishing paste with size of 0.5 μm (3# process), respectively, and then the CrMoN coating was deposited on the surface. The phase composition, surface and cross-section morphology, hardness, surface hydrophobicity, corrosion resistance and conductivity of the coating were studied. The results show that the roughness of the coating surface deposited on the substrate surface pretreated with 1# process was the largest, followed by that pretreated with 2# process, and the roughness that pretreated with 3# process was smallest. The phase of the coating consisted of CrN, Cr2N and Mo2N. With decreasing substrate surface roughness, the microhardness, free corrosion potential and water contact angle of the coating increased, and the corrosion current density and interface contact resistance after polarization decreased. The comprehensive properties of the CrMoN coating deposited on the substrate surface pretreated with 2# process were excellent, which were close to those pretreated with 3# process.
  • Influence of Post-Weld Annealing on Microstructure and Performance ofT-joint of SMA490BW/Q345E Dissimilar Steels in Bogie
    ZHANG Zhengjun, DING Yangxi, LIU Dejia, ZHU Liang
    Materials For Mechanical Engineering. 2021, 45(1): 59-65. https://doi.org/10.11973/jxgccl202101010
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    Butt welding was carried out on the T-joint of SMA490BW/Q345E dissimilar steels by CO2 shielded arc welding, and then the joint was annealed at 590 ℃ for 3 h. The microstructures, hardnesses and corrosion resistance before and after annealing were compared. The results show that before and after annealing, the weld interface was obvious in the joint, and the microstructures of the weld consisted of proeutectoid strip ferrite, pearlite and granular bainite. Before annealing, from surface to inner, the microstructure of the weld changed from coarse columnar grains to alternating columnar grains and equiaxed grains, and the hardness difference was large. After annealing, the microstructures of different layers had little difference, and the hardness distribution became uniform. The corrosion tendency of the annealed weld was reduced and the corrosion resistance was improved. During wet/dry cyclic exposure in NaCl solution, pitting corrosion occurred on the surface of non-annealed and annealed weld and the rust layer cracked in the latter stage of corrosion (100 h). The rust layer was denser after annealing.
  • Effect of Solution and Aging Treatment on Microstructure and Properties of Pressure Formed 6063 Aluminum Alloy
    LIU Quansheng, FAN Mengting, LUO Xinran
    Materials For Mechanical Engineering. 2021, 45(1): 66-72,79. https://doi.org/10.11973/jxgccl202101011
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    6063 aluminum alloy was prepared by pressure forming process, and then was treated by solution at 535 ℃ and aging. The effects of solution time (15-120 min), aging temperature (160-200 ℃) and aging time (1-24 h) on the microstructure, tensile properties and hardness of the aluminum alloy were studied. The results show that with increasing solution time, the grain size of 6063 aluminum alloy increased, and the primary Mg2Si phase gradually disappeard and redissolved in the matrix; but the solution time had no effect on the content and morphology of α-Al8Fe2Si phase and β-Al5FeSi phase. After solution treatment, with increasing aging temperature or aging time, the number of second phase Mg2Si increased, but a higher temperature or a longer aging time resulted in the coarse of the Mg2Si phase. With increasing solution time, aging time or aging temperature, the strength and hardness of the alloy increased first and then decreased, and the precentage elongation after fracture decreased first and then increased. The appropriate solution and aging treatment system for 6063 aluminum alloy was 535 ℃×60 min + 180 ℃×7 h; at this time the Mg2Si phase precipitated in the alloy was the smallest and dispersed, and the alloy had the highest strength and hardness and the appropriate precentage elongation after fracture.
  • Microstructure and Properties of Tb2TiO5-Dy2TiO5 Neutron Absorber Material
    LU Junqiang, CHEN Xiangyang, CHEN Fuliang, RAN Guang, WU Yizhen
    Materials For Mechanical Engineering. 2021, 45(1): 73-79. https://doi.org/10.11973/jxgccl202101012
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    Tb2TiO5-30wt%Dy2TiO5 neutron absorber material was prepared by high energy ball milling, cold isostatic pressing and high temperature sintering with Tb4O7 powder, Dy2O3 powder and TiO2 powder as raw materials. The microstructure of the powder mixture at different ball milling time (0-48 h), and the microstructure, thermophysical properties and corrosion resistance of sintered bulks at different sintering temperature (1 200-1 400 ℃) for different times (1-96 h) were studied. The results show that the grain size of powder mixtures decreased with increasing ball milling time, and the homogeneous nanocrystalline powder mixture was obtained by ball milling for 12 h. Tb2TiO5-Dy2TiO5 bulks with high density and orthorhombic structure was obtained after sintering nanocrystalline powder mixture at 1 300 ℃ for 96 h. The thermal conductivity and thermal expansion coefficient at 500 ℃ were 2.2 W·m-1·K-1 and 5.8×10-6 K-1, respectively. The corrosion rate of the bulks in deionized water at 360 ℃/18.6 MPa almost kept a constant and the mean corrosion rate was 0.18 mg·dm-2·h-1. The prepared bulks had high thermal conductivity, low thermal expansion coefficient and good corrosion resistance performance, which was an excellent candidate as neutron absorber materials for control rods.
  • Effect of Quenching Temperature on Corrosion Resistance of 40Cr13 Plastic Die Steel
    ZHANG Yan, WANG Zhenxu, XU Yu, SUN Chichi, XU Ruirui
    Materials For Mechanical Engineering. 2021, 45(1): 80-84. https://doi.org/10.11973/jxgccl202101013
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    40Cr13 plastic die steel was quenched at different temperatures (960,1 020,1 080,1 140 ℃), and the effect of quenching temperature on microstructure and hardness was studied. The steel was tempered at 200 ℃,and the corrosion resistance of the steel was studied by immersion test and electrochemical test. The results show that the microstructure of the test steel after quenching at different temperatures was composed of quenched martensite, carbides and a small amount of retained austenite. The microstructure became coarse with increasing quenching temperature, and the number of carbides decreased. When the quenching temperature was 1 140 ℃, network carbides precipitated on austenite grain boundaries in the microstructure. The hardness of the test steel increased first and then decreased with increasing quenching temperature. When the quenching temperature increased from 960 ℃to 1 080 ℃, the corrosion rate of the test steel after tempering in FeCl3 solution decreased; the diameter and depth of pitting holes on the surface of the test steel decreased, and the number increased. The free-corrosion potential of the test steel in NaCl solution increased, and the free-corrosion current density decreased; the corrosion rate decreased and the corrosion tendency decreased. The optimum the quenching temperature was 1 020 ℃; at this point, the quenched martensite was relatively small, and the hardness was the largest; the corrosion resistance was relatively good.
  • Strength Evaluation of Metal Materials by Spherical Indentation Test Method
    HUANG Liyang, GUAN Kaishu
    Materials For Mechanical Engineering. 2021, 45(1): 85-91. https://doi.org/10.11973/jxgccl202101014
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    The plastic parameters of materials were extracted from the loading part of load-depth curves obtained by coupling single indentation test and finite element simulation, and combining inverse method and simulated annealing particle swarm optimization. The strength of different metal materials was estimated on the basis of Ludwig hardening model and compared with the results obtained by uniaxial tensile test. The results show that the load-depth curves obtained by simulation almost coincided with those obtained by tests, and the relative error was less than 0.5%, indicating that plastic parameters could be extracted from indentation load-depth curves by simulated annealing particle swarm optimization. The true stress-true plastic strain curves extracted from indentation load-depth curves by inverse method based on Ludwig hardening model were not unique, but obvious convergence tendency of the strength estimated from the extracted true stress-true plastic strain could be observed. The strength of different metal materials obtained by the indentation tests was close to that obtained by tensile tests; the biggest relative errors of the yield strength and tensile strength were 5.9% and 4.3%, respectively, indicating that the strength of the metal materials could be evaluated accurately by indentation test method.
  • Comparison on High-Temperature Flow Behavior of HNi55-7-4-2 AlloyPredicted by Modified JC Model and BP-ANN Algorithm
    MA Bin, LI Ping, LIANG Qiang
    Materials For Mechanical Engineering. 2021, 45(1): 92-99. https://doi.org/10.11973/jxgccl202101015
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    Isothermal hot compression experiments of HNi55-7-4-2 alloy were conducted with a Gleeble-3500 thermal simulator at deformation temperatures of 873, 923, 973, 1 023, 1 073 K and strain rates of 0.01, 0.1, 1, 10 s-1, and the high-temperature flow behavior of the alloy was studied. The constitutive model of the alloy was established by the modified Johnson-Cook (M-JC) model and back-propagational artificial neural network (BP-ANN) algorithm with experimental data. The prediction accuracy of two models was comparatively analyzed. The results show that the flow stress of HNi55-7-4-2 alloy increased with increasing strain rate or decreasing deformation temperature. The average absolute relative errors between true stress predicted by the constitutive model on the basis of M-JC and BP-ANN algorithm model and test results were 14.63% and 0.35%, respectively and the correlation coefficient were 0.978 7, 0.999 9, respectively. The constitutive model by BP-ANN algorithm had higher prediction accuracy, and could decribe the high-temperature flow behavior of HNi55-7-4-2 alloy well.
  • Establishment of Bouc-Wen Model of MagnetorheologicalElastomers with Stiffness Softening Tests
    LU Jingjing, CHEN Xi, ZHOU Yadong, LI Jianchun, LI Yancheng
    Materials For Mechanical Engineering. 2021, 45(1): 100-104,108. https://doi.org/10.11973/jxgccl202101016
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    A self-designed stiffness softening shear test system was used to conduct shear test on isotropic magnetorheological elastomers (MRE), and the force-displacement hysteresis loop under different current, frequency, and displacement amplitude conditions was obtained. The dynamic mechanical characteristics of MRE was described by Bouc-Wen model, and the accuracy of the model was verified on the basis of test data. The influence law of test parameters on macroproperties of MRE was analyzed. The results show that the fitting results of Bouc-Wen model were in good agreement with the test data, and the root mean square error of shear force was less than 0.95, indicating that the model could well describe the stiffness softening and damping characteristics of MRE. When the forward current was applied, the stiffness of MRE decreased linearly with increasing current, and increased with frequency; the effect degree of current or frequency on the stiffness was weakened when the current was greater than 0.66 A or frequency was greater than 1 Hz. The damping of MRE decreased with increasing current, and decreased exponentially with increasing frequency; the damping tended to be stable when the current was greater than 0.66 A or frequency was 2.0 Hz.
  • Fracture Cause of Connecting Bolts in a Hydrogen Reciprocating Compressor
    LU Yan, TAN Jinzhu, LI Yang, WANG Chao, LUO Shenghua
    Materials For Mechanical Engineering. 2021, 45(1): 105-108. https://doi.org/10.11973/jxgccl202101017
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    The connecting bolts in a hydrogen reciprocating compressor were ruptured after woking normally for a period of time. The fracture cause of the bolts was investigated by fracture macro- and micro-morphology observation, chemical composition analysis, microstructure observation and mechanical property tests. The results show that the fracture mode of the bolts was low stress high cycle fatigue fracture. Under alternating stresses, some microcracks originated from the high stress concentration position at the root of the screw thread of the bolt. Improper heat treatment resulted in the mixed structure of tempered sorbite, upper bainite and ferrite, leading to the decrease of the strength and hardness of the bolts and the acceleration of fatigue crack propagation. Fianlly the fatigue fracture of connecting bolts occurred.
  • Fracture Cause of Chain Wheel Drive Shaft in an Oil Drilling Drawwork
    FAN Chunming, ZHANG Zengnian, WANG Degui, XU Hong, WANG Pinghuai
    Materials For Mechanical Engineering. 2021, 45(1): 109-112,118. https://doi.org/10.11973/jxgccl202101018
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    The fracture of chain wheel drive shaft in an oil drilling drawwork during operation ocurred. The reason for fracture of the chain wheel drive shaft was studied by fracture morphology observation, chemical composition analysis, mechanical property test and microstructure observation. The results show that the fracture of chain wheel drive shaft was early fatigue failure. The cracks initiated at the stress concentration of the rough transition fillet root at the step of φ210 mm and φ200 mm shafts of the chain wheel drive shaft, and expanded under alternating bending and torsion stresses, leading to the fatigue fracture of the chain wheel drive shaft finally. The existence of lamellar MnS inclusions in the structure and the banded segregation in the core promoted the growth of fatigue cracks.
  • Cracking Cause of Radiant Tube in a Continuous Annealing Furnace
    LI Yuanjun, WANG Lu, HUANG Jibo, ZHANG Ying, WANG Weize
    Materials For Mechanical Engineering. 2021, 45(1): 113-118. https://doi.org/10.11973/jxgccl202101019
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    The radiant tube in a continuous annealing furnace cracked during service. The cracking causes of the radiant tube were analyzed by fracture macromorphology and micromorphology observation, chemical composition analysis, mechanical property test and force analysis. The results show that the combined action of high temperature creep and high temperature oxidation corrosion led to the failure of radiation tube in the continuous annealing furnace. Under low stresses and high temperatures, holes formed by grain boundary sliding grew and connected to form cracks; the pores formed by the rupture of the oxide film accelerated the combination and growth of cracks, and the cracks propagated fast under the creep stresses, finally leading to the failure of the radiant pipe. After long-term service in a high temperature environment, the inner wall of the radiant tube was seriously thinned by oxidation corrosion; the strength of the radiant tube was obviously lower than the standard value, and the bearing capacity decreased, which resulted in the initiation of cracks in the stress concentration area of the high temperature concentration area and the final failure of the radiant tube.
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