20 February 2022, Volume 46 Issue 2
    

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    Technical Review
  • Research Progress on Tribological Properties of Motion Pair Materials in Sea Environment
    XU Wanxing, ZHAN Shengpeng, JIA Dan, YANG Tian, TU Jiesong, LI Yinhua, DUAN Haitao
    Materials For Mechanical Engineering. 2022, 46(2): 1-9,62. https://doi.org/10.11973/jxgccl202202001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    With the further development of abundant marine resources, the friction and wear problems of marine mechanical equipment motion pairs have been paid more and more attention by researchers. The research status of main materials of motion pairs, including metal, ceramic and polymer in marine environment is summarized, the influencing factors of tribological properties of motion pair materials under marine conditions are analyzed, and the research progress of deep-sea tribology testing equipment is discussed, which can provide support for the selection and application of motion pairs of marine mechanical equipment.
    • Testing & Research
  • Magnetoconductance Characteristics of Magnetic-Sensitive Elastomer Doped with Soft Magnetic Particles with Different Particle Sizes
    JU Benxiang, ZHUANG Qiuhui
    Materials For Mechanical Engineering. 2022, 46(2): 10-14. https://doi.org/10.11973/jxgccl202202002
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    Taking vulcanized silicone rubber as matrix, the magnetic-sensitive elastomer(MSE) samples with various compositions of micron(particle size of 5-8 μm) and submicron(particle size of 200 nm) soft magnetic particles were prepared under conditions with magnetic field and without magnetic field, and the magneto-conductance characteristics of MSE samples were studied by conductance device and magnetic field-dependent conductance test system. The mechanism of magnetoconductance was explored. The results show that the magnetoconductance of MSE filled with micron particles under preparation condition with magnetic field increased significantly with increasing particle doping content. With increasing doping content of submicron particles, under the condition of magnetic field preparation, the adsorption effect occurred between micron and submicron particles in MSE doped with micron and submicron particles, the increase values of zero-field conductance and magnetoconductance decreased greatly, and the magnetoconductance property became weak. The different size particle-doped MSE under preparation condition without magnetic field could not form an effective conductive channel, and the magnetoconductance characteristics were significantly lower than those of the same content particle-doped MSE under preparation condition with magnetic field.
  • Molten Pool Size and Weld Quality of Pulsed Micro-plasma Arc Welding of Stainless Steel Ultra-Thin Sheets
    XU Lei, HE Jianping, PAN Xuehang
    Materials For Mechanical Engineering. 2022, 46(2): 15-19. https://doi.org/10.11973/jxgccl202202003
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    The profile change of molten pool during pulsed micro-plasma arc welding of ultra-thin sheets were collected by a backlight-based molten pool visual sensing inspection system. The influence of ratio of base current to peak current(0.29-0.71), duty cycle(30%-70%) and pulse frequency(25-100 Hz) on the weld molten pool size and weld quality of 304 stainless steel ultra-thin sheets under average current of 1.8 A was studied. The results show that under the experimental conditions, the weld pool width and area were less than 2.5 mm and 3.5 mm2, respectively. The largest width and area of molten pool gradually decreased with increasing ratio of base current to peak current, duty cycle and pulse frequency. Three different types of welds, including discontinuous welds, continuously non-uniform width welds, and continuously uniform width welds, were obtained under different process parameters. The weld formation quality was the best and the weld was continuously uniform width weld under the duty cycle of 50%, the ratio of base current to peak current of 0.50, and the pulse frequency of 25, 100, 500 Hz.
  • Microstructures Evolution and Strengthing-Toughening Mechanism of S460G1 Steel Heavy Plate During Quenching and Tempering
    SONG Xin, LI Wei, BING Chun, YU Tao, BI Jianwei
    Materials For Mechanical Engineering. 2022, 46(2): 20-30. https://doi.org/10.11973/jxgccl202202004
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    150 mm thick S460G1 steel heavy plate was obtained by hot rolling after strictly controlling rolling process, and then quenched at 870—960 ℃ and tempered at 550—660 ℃. The microstructure evolution and strengthing-toughening mechanism of the steel plate were researched. The results show that from the surface to the center of hot rolled steel plate, the microstructure was acicular ferrite→granular bainite→ferrite and pearlite. After quenching, the microstructure on the plate surface was lath martensite, one quarter thickness of the plate was mainly granular bainite and the center of the plate were ferrite and pearlite. After quenching at 900 ℃ and 930 ℃, the original austenite grains at the one quarter thickness of the plate were fine and uniform, and the grain size distribution was concentrated with ranging of 4.12—31.88 μm and 5.02—32.69 μm, respectively. After quenching at 930 ℃ and tempering at 600—630 ℃, the microstructure on the plate surface was tempered sorbite, and the microstructures of one quarter thickness and center of plate were similar to those at quenching state, but the trend of equiaxed lath ferrite and coarsened ferrite was strengthened; at this time the steel plate had excellent comprehensive mechanical properties with the yield ratio of not higher than 0.85. Martensite/austenite(M/A) island decomposing, a large amount of precipitate, dislocation eliminating and equiaxial ferrite deforming were the main reasons for the excellent strength and toughness of the hot rolled steel.
  • Effect of Shot Peening Process on Surface Properties and Microstructure of 1Cr11Ni2W2MoV Steel Nut
    FANG Jun, ZHAN Yuting, JIN Kai
    Materials For Mechanical Engineering. 2022, 46(2): 31-34,42. https://doi.org/10.11973/jxgccl202202005
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    Three different shot peening processes(dry shot peening, dry shot peening followed by wet shot peening and wet shot peening) were used to strengthen the surface of 1Cr11Ni2W2MoV steel nut. The effects of shot peening process on the residual stress, roughness and microstructure of nut surface were compared. The results show that the residual compressive stress on the nut surface after wet shot peening was the largest, and the maximum residual compressive stress located at the large arc section, reaching 550 MPa; the surface roughness Ra was the smallest with the range of 0.75-0.85 μm. After dry shot peening, the surface residual compressive stress of nut was the smallest, and the surface roughness Ra was the largest ranging from 2.5-3.2 μm. After shot peening, the outer grains of nut was broken and refined obviously, while the grains of the center did not change obviously. After wet shot peening and dry shot peening followed by wet shot peening, 0.15 and 0.25 mm depth residual stress layers were formed on nut surface, respectively. The suitable process for strengthening the surface of 1Cr11Ni2W2MoV steel nut was dry shot peening followed by wet shot peening.
  • Microstructure and Impact Toughness of Dissimilar Steel Electron Beam Welded Joints of Thick Ferritic Stainless Steel/16Mn Steel Plates
    WANG Chaoran, LI Dong
    Materials For Mechanical Engineering. 2022, 46(2): 35-42. https://doi.org/10.11973/jxgccl202202006
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    Electron beam welding was carried out between 40 mm thick ferritic stainless steel plate and 16Mn steel plate by electron beam biased to the side of 16Mn steel, and the microstructure and impact toughness of different areas of the welded joints were investigated. The results show that the microstructure of the weld was mainly lath martensite; with increasing distance from the upper surface of the weld, the impact toughness of the weld decreased, and the fracture was characterized by quasi-cleavage and uncleavage. The microstructure of the heat affected zone at 16Mn steel side was mainly composed of acicular ferrite and feathery upper bainite; the maximum impact absorption energy was 113 J, and the impact toughness was the best; the fracture type was ductile and brittle mixed fracture. The microstructure of the heat affected zone at ferritic stainless steel side was mainly composed of ferrite, martensite and granular carbides; the impact absorption energy ranged from 6 J to 10 J, and the impact toughness was the worst; the fracture type was brittle fracture, which was related to the coarse ferrite grains and brittle carbides.
  • Microstructure and Hardness of Electron Beam Selective Melting Formed TC4 Titanium Alloy
    TONG Shaohui, LI Dong, LIANG Mengqiang, DING Ting, LENG Xinghuan
    Materials For Mechanical Engineering. 2022, 46(2): 43-47. https://doi.org/10.11973/jxgccl202202007
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    The TC4 alloy samples with different dimension(?8 mm×25 mm, ?25 mm×8 mm) were fabricated by electron beam selective melting forming technique. The evolution of microstructure and hardness along the powder deposition direction was studied. The results show that the microstructure of the sample with dimension of ?8 mm×25 mm was composed of acicular α clusters at prior β columnar grain boundaries and net-basket-shaped widmanstatten structures formed by interlaced acicular α phase in grains. The axis of prior β columnar grains was parallel to the direction of powder deposition and grew through every deposition layer. The residual β phase dispersed among α phase matrix. The top microstructure of the sample with dimension of ?25 mm×8 mm consisted of acicular α' phases. The acicular α' phase in the middle microstructure was decomposed into α phase and β phase, and the width of α phase was relatively large. The strip α phase in the bottom microstucture grew through prior β grains to form clusters. The residual β phase dispersed in the continuous network among α phase matrix. The microhardness of the part with acicular α or α' phase of large length-width ratios was higher than that with strip and lamellar α or α' phase of small length-width ratios.
  • High Temperature Endurance Property and Steam Oxidation Resistance of G115 Steel
    MA Yunhai, WANG Yanfeng, ZHAO Shuangqun, WANG Miaomiao
    Materials For Mechanical Engineering. 2022, 46(2): 48-57. https://doi.org/10.11973/jxgccl202202008
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    The high temperature endurance test of G115 steel was carried out under different stresses at 625—700 ℃ to study its high temperature endurance performance, and the 1×105 h long-term endurance strength of the steel was extrapolated by the Larson-Miller(LM) parameter method. The oxidation test of G115 steel was carried out at 650 ℃/27 MPa steam parameter for 2 000 h, and the surface and cross-section morphology, phase composition and microarea composition of the oxide film were studied and compared with those of T92 steel. The results show that under the action of reinforcement of copper-rich phase, the long-term endurance strength of G115 steel at 650 ℃ was 82 MPa, which was significantly higher than 53 MPa of T92 steel. The steam oxidation resistance of G115 steel was better than that of T92 steel, and the thickness of oxide film on the surface of G115 steel was about 102 μm, which was smaller than about 110 μm of T92 steel. The oxide film structure of the two was similar. The outer oxide layer consisted of coarse columnar Fe3O4, and the inner oxide layer consisted of fine Fe-Cr spinel and a small amount of Fe3O4; the outer oxide layer had many holes, and the tendency of spalling was relatively large.
    • Material Properties & Application
  • Microstructures and Tensile Properties of 0Cr18Ni9 Steel Thin-Wall Tube Welded Joints by P-TIG Under Different Process Parameters
    LI Ning, LIU Shaolong, DING Xuesong, XU Yuhong, FAN Wenlei, SU Huanchao, WANG Boyu
    Materials For Mechanical Engineering. 2022, 46(2): 58-62. https://doi.org/10.11973/jxgccl202202009
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    Pulse tungsten inert gas arc welding(P-TIG) was applied to weld 0 Cr18Ni9 steel tubes with specification of ?14 mm×2 mm, and the microstructure and tensile properties of joints under different base current(20-30 A), peak current(40-60 A), pulse frequency(0.3,0.5 Hz) and pulse width ratio of 50% were studied. The results show that the microstructures of the weld of joints under different process parameters were all austenite+δ ferrite, but the shape and content of the δ ferrite were significantly different; the austenite grains in the heat-affected zone were significantly coarsened. Under the pulse base current of 20 A, the peak current of 40 A and the pulse frequency of 0.3 Hz, the ferrite in the weld of the joint was vermicular with relatively high content, and the austenite grain size in the heat affected zone was small; the tensile properties of the joint was the best with yield strength of 401.38 MPa, tensile strength of 701.51 MPa and yield ratio of 0.57, and the fracture was composed of equiaxed dimples with uniform shape and small size.
  • Effect of High-power Laser Quenching on Microstructure and Wear Resistance of 35CrMo Steel Surface Layer
    YANG Junlong, HUANG Min, HU Liuyi, LIU Yongchao, WAN Leilei, WANG Yu
    Materials For Mechanical Engineering. 2022, 46(2): 63-67. https://doi.org/10.11973/jxgccl202202010
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    Surface quenching treatment of 35CrMo steel was carried out by high power laser. The microstructure, hardness and wear resistance of surface layer under different laser power(1.6,2.4,3.2,4.0 kW) were studied. The results show that when the laser power was 1.6 and 2.4 kW, the undissolved ferrite existed on the surface layer of 35CrMo steel, and the surface layer hardness was lower than that of the substrate; the wear mass rate of the steel was almost the same as that of the substrate after grinding with GCr15 steel, indicating the steel had bad wear resistance. When the laser power was 3.2, 4.0 kW, the surface layer microstructure was all tempered martensite, and the average surface layer hardness reached 640 HV, which was about 20% higher than that after conventional water quenching. The wear mass rate under laser power of 3.2 kW was the lowest, no obvious wear trace could be found on the surface, and the wear resistance was significantly improved compared with the substrate. When the laser power was up to 4.0 kW, the higher self-tempering degree of martensite resulted in a slight decrease in hardness and wear resistance compared with the laser power of 3.2 kW.
  • Protective Performance of Waterborne Inorganic Zinc Shop Primers after Short-Term High Temperature Treatment
    LIU Juncheng, HUANG Lei, FANG Zhiqiang, YANG Yu, WANG Guoqing
    Materials For Mechanical Engineering. 2022, 46(2): 68-74,80. https://doi.org/10.11973/jxgccl202202011
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    D1510 H and D1610 two waterborne inorganic zinc shop primers with different compositions were sprayed on the low-carbon steel plate or PET film, and short-term(3 min) high temperature treatments at different temperatures(400, 600, 700, 800 ℃) were carried out. The protective performance of two shop primers was studied by thermogravimetric differential scanning calorimetry analysis, outdoor exposure test and neutral salt spray test. The results show that after short-term high temperature treatment, both of the two shop primers had residual metal zinc indicating they had a certain protective performance. D1510H shop primer had high inorganic content; the shop primer had dense surface structure after high temperature treatment at 800 ℃, and still had good outdoor protective performance; the shop primer was suitable for the protection of large steel structures with short processing cycle and subsequent partial surface treatment measures. D1610 shop primer had high content of organic matter and metal zinc, and had loose surface structure after high temperature treatment at 700,800 ℃, but could withstood high temperature treatment at 600 ℃; it was suitable for the protection of substrates with long processing cycles and subsequent comprehensive secondary rust removal.
  • Effect of Pre- and Post-Weld Heat Treatment on Microstructure and Properties of 2195 Al-Li Alloy Double-Sided Friction Stir Welded Joints
    ZHANG Jijun, CAO Juyong, XING Yanfeng, ZHANG Chengcong
    Materials For Mechanical Engineering. 2022, 46(2): 75-80. https://doi.org/10.11973/jxgccl202202012
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    6 mm thick 2195 aluminum-lithium alloy plates were connected by double-sided friction stir welding. The effects of pre- and post-weld heat treatment(410 ℃×1 h annealing + 510 ℃×1 h solution and 155 ℃×1 h artificial aging) on the microstructure and mechanical properties of joints were compared and studied. The results show that the grains in the weld nugget area of the joint with pre-weld heat treatment were small and equiaxed, and the average grain size was about 9.2 μm. The grains in the weld nugget area with post-weld heat treatment grew abnormally, and the average grain size reached 0.3 mm. The tensile strength of the joint with pre-weld heat treatment was about 4.7% higher than that with post-weld heat treatment, and the percentage elongation after fracture was improved obviously. The tensile fracture mode of the joint with pre-weld heat treatment was ductile fracture, and that with post-weld heat treatment was brittle fracture. The maximum bending angle of the joint with pre-weld heat treatment was larger than the joint with post-weld heat treatment, indicating the joint had good plastic deformation ability.
    • Physical Simulation & Numerical Simulation
  • Numerical Simulation of Microstructure Evolution and Mechanical Behavior of Medium-Mn Steel During Uniaxial Tension
    SUN Yuyang, ZHANG Mei, GU Yuqing, ZHANG Jie
    Materials For Mechanical Engineering. 2022, 46(2): 81-87. https://doi.org/10.11973/jxgccl202202013
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    Based on the microstructure obtained by test, the representative volume element(RVE) model of 7Mn steel was established. The microstructure evolution, stress and strain distribution during uniaxial tension of 7 Mn steel after warm rolling and annealing at different temperatures(600-630 ℃) was simulated by ABAQUS software and compared with the test results. The results show that when residual austenite was distributed along the tensile direction, it was tended to occur collaborative deformation to alleviate the strain concentration in ferrite and make the system in a high stress state. After annealing at 600 ℃, the residual austenite had high stability, and only part of austenite transformed into martensite at the end of uniform plastic deformation. The residual austenite almost transformed into martensite during tension after annealing at 630 ℃. The simulated residual austenite content was in good agreement with the test results and the relative error was less than 5%, verifing the accuracy of simulating microstructure evolution by RVE model. The simulated stress-strain curves after annealed at 615,630 ℃ were in good agreement with test results, and the relative error was less than 5%, verifing the accuracy of simulating uniaxial tensile behavior by RVE model. There was a large deviation between the simulation and the test results after annealed at 600 ℃ because of ignoring the refinement strengthening and solution strengthening in each phase constitutive model.
    • Material Testing and Equipment
  • Development and Reliability of Micro-Scale Indentation Testing Equipment
    WU Jie, SUN Kun, MA Zengsheng
    Materials For Mechanical Engineering. 2022, 46(2): 88-94. https://doi.org/10.11973/jxgccl202202014
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    Based on the Oliver-Pharr method and the fracture toughness test method, a micro-scale indentation testing equipment was successfully developed. Its mechanical reliability was verified by the finite element method, and the mechanical property parameters of the high-purity aluminum and zirconia ceramics were tested by the equipment to verify the test performance of the equipment. The results show that the developed micro-scale indentation testing equipment had stable structure, reasonable design, good closed-loop control stability and low noise level, and met the test requirements. The hardness, elastic modulus and fracture toughness of high-purity aluminum and zirconia ceramics measured by this equipment under different indentation loads were consistent with the results obtained by standard indentation equipment, and the relative error was smaller than 7%, which proved the accuracy of the test results of the equipment.
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