20 January 2019, Volume 43 Issue 1

    

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  Research Situation and Application Prospect of Sanicro 25 Heat-Resistant Steel

  ZHANG Xin, CAI Wenhe, DU Shuangming, ZHANG Kun

  Materials For Mechanical Engineering. 2019, 43(1): 1-7. https://doi.org/10.11973/jxgccl201901001

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  The microstructure, mechanical properties at high and low temperatures, corrosion resistance, processability and weldability of Sanicro 25 heat-resistant steel were reviewed. The application status of Sanicro 25 heat-resistant steel was summarized. The application prospect of Sanicro 25 heat-resistant steel was expected.
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  Properties of Polycrystalline Cubic Boron Nitride Prepared by Spark Plasma Sintering

  LI Jian, MA Yao, LIANG Lixing, WANG Hailong, ZHANG Rui

  Materials For Mechanical Engineering. 2019, 43(1): 8-12. https://doi.org/10.11973/jxgccl201901002

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  Cubic boron nitride (cBN) was coated by SiO₂ using the sol-gel method, and then polycrystalline cubic boron nitride (PcBN) was prepared by spark plasma sintering (SPS) under the pressure of 100 MPa at 1 700℃ for 10 min using Al powder, B₄C powder and carbon powder as sintering additives. The sintering ability, phase composition, micro-morphology, mechanical properties of PcBN and the cutting performance of fabricated cutter were studied. The results show that the combined effect of sintering additive, in-situ reaction and activation of cBN particles promoted the densification of PcBN, obtaining a relative density of 97%. The main crystalline phase of PcBN was cBN, and also included SiO₂, Al₃BC₃ and SiC phases. The hardness of PcBN was (38±3.5) GPa, and bending strength was (425±23) MPa. At the same cutting speed, the breakdown area of the front surface and the wear band length of the rear surface of cutter made of the obtained PcBN were smaller than those of PcBN (BN11) cutter fabricated by a Japanes renowned company. When the cutting speed increased from 200 m·min^-1 to 400 m·min^-1, the wear degree of cutter made from PcBN was slighter than that of BN11 cutter, indicating the cutting performance of cutter made from PcBN prepared by SPS was better than that of BN11 cutter.
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  Electrochemical Hydrogen Diffusion Behavior of B2 Phase FeAl Alloy

  LUO Zhaoyi, WANG Xisheng, ZHANG Guikai, HUANG Guangqi, YANG Feilong, XIANG Xin, HU Meijuan, TANG Tao

  Materials For Mechanical Engineering. 2019, 43(1): 13-18. https://doi.org/10.11973/jxgccl201901003

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  The B2 phase FeAl alloy was prepared by powder metallurgy method with iron powder and aluminum powder as raw materials. The electrochemical hydrogen diffusion behavior of B2 phase FeAl alloy was studied by electrochemical method. The results show that the pores in the prepared B2 phase FeAl alloy were few and small, and the segregation region with black and white stripe-like substructure similar to pearlite appeared in the microstructure. The aluminum content in the segregation region was higher than that in the unsegregated region. The stabilized hydrogen diffusion current density was slightly smaller than the limited hydrogen diffusion current density at different hydrogen current densities. The diffusion flux, effective diffusion coefficient and solubility of hydrogen in B2 phase FeAl alloy increased with the increase of cathode hydrogen charging current density. Under the action of cathode hydrogen charging current, the hydrogen desorption rate constant of alloy surface on the hydrogen charging end side was much larger than the adsorption reaction rate constant. Only a very small amount of hydrogen could be adsorbed to the surface and penetrated into the alloy, indicating that the occurrence of hydrogen embrittlement in the B2 phase FeAl alloy was relatively slow in the water vapor environment at room temperature.
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  Effect of CO₂ Partial Pressure on Corrosion Behavior of N80 Steel in Auxiliary Steam Drive Oil Environment

  DONG Baojun, ZENG Dezhi, SHI Shanzhi, YU Huiyong, CHEN Yuxin, LU Wenting

  Materials For Mechanical Engineering. 2019, 43(1): 19-22,26. https://doi.org/10.11973/jxgccl201901004

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  The high temperature and high pressure autoclave was used to simulate the working conditions of CO₂ auxiliary steam drive oil gas injection well. The coupon corrosion test was conducted on N80 steel at 160℃ and CO₂ partial pressures of 1-4 MPa, and the effect of CO₂ partial pressure on corrosion behavior of N80 steel was studied. The results show that with CO₂ partial pressure increasing, the corrosion rate increased first and then decreased; when the CO₂ partial pressure was 2 MPa, the corrosion rate reached the maximum value of 0.073 7 mm·a^-1. The main composition of corrosion products of N80 steel was FeCO₃ and a small amount of Fe₂O₃. With the increase of CO₂ partial pressure, the size of FeCO₃ crystals decreased, and FeCO₃ crystals mixed together when CO₂ partial pressure was 3-4 MPa. Under the test condition, the corrosion rate of N80 steel was 0.034 7-0.073 7 mm·a^-1 which was lower than the corrosion rate control line of oil field (0.076 mm·a^-1) and met the property requirement of CO₂ auxiliary steam drive oil well casing.
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  Modification of 6061 Aluminum Alloy Plate for Automotive by Friction Stir Processing

  HUANG Fang, ZHANG Xuehui, YE Jianmei

  Materials For Mechanical Engineering. 2019, 43(1): 23-26. https://doi.org/10.11973/jxgccl201901005

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  The modification of 6061 aluminum alloy plate for automobile were carried out by friction stir processing, and the tensile properties and corrosion resistance at different rotation speeds (300-1 100 r·min^-1) and travel speeds (120-300 mm·min^-1) were studied. The results show that when the travel speed was 300 mm·min^-1, with increasing the rotation speed, the tensile strength and yield strength of 6061 aluminum alloy first increased and then decreased, and the elongation changed with inflection; the self-corrosion potential first moved positively and then negatively; when the rotation speed was 600 r·min^-1, the tensile strength and yield strength were the highest, and the self-corrosion potential was the most positive. When the rotation speed was 600 r·min^-1, with increasing the travel speed, the tensile strength and yield strength of 6061 aluminum alloy increased, the elongation first decreased and then increased; the self-corrosion potential first moved positively and then negatively; when the travel speed was 300 mm·min^-1, the tensile strength and yield strength were the highest, and the self-corrosion potential was the most positive. When the rotation speed and travel speed were 600 r·min^-1 and 300 mm·min^-1, respectively, the tensile properties and corrosion resistance of 6061 aluminum alloy were the best.
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  Texture Evolution and Its Relationship with Plastic Strain Ratio and Work Hardening Index of IF Steel Containing Nb and Ti after Annealed at Different Temperatures

  DONG Dengchao, LIU Zhiqiao, ZHANG Ke, CEN Feng

  Materials For Mechanical Engineering. 2019, 43(1): 27-30. https://doi.org/10.11973/jxgccl201901006

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  The polar density and content of texture, plastic strain ratio and work hardening index of different thickness layers of IF steel plate containing Nb and Ti after continuous annealing at 790, 850, 910℃, which experienced cold rolling with reduction of 72%, were analyzed by X-ray diffractometer and tensile tester. The texture evolution and its relationship with plastic strain ratio and work hardening index after annealed at different temperatures were studied. The results show that with the increase of annealing temperature, the intensity of {001}〈110〉 texture in IF steel after annealing decreased, while that of {111}〈112〉 and {111}〈110〉 textures increased; the increase rate of the intensity of {111}〈110〉 texture was larger than that of {111}〈112〉 texture. The texture distributed uniformly in different thickness layers of IF steel annealed at different temperatures. With the increase of annealing temperature, the content of {111} plane texture increased, while that of {100} plane texture decreased; the volume ratio of {111} and {100} plane texture increased; the plastic strain ratio increased nonlinearly, and the work hardening index changed little. When the annealing temperature was 850℃, the anisotropy coefficient of plastic strain ratio was the smallest, and the texture distribution was the most uniform.
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  Typical Characteristics and Control Measures of Invisible Zinc Dross Defect in Hot Dip Galvanized Sheet

  CHEN Gang, DAN Binbin, YAN Kaiyong, RONG Zhijun, YAN Fei, SUN Fangyi

  Materials For Mechanical Engineering. 2019, 43(1): 31-35. https://doi.org/10.11973/jxgccl201901007

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  The micromorphology and micro-area chemical composition of five invisible zinc dross defects in hot dip galvanized sheet were studied by scanning electron microscope and energy spectrometer, and corresponding control measures were proposed. The results show that the invisible zinc dross defects in the hot dip galvanized sheet includedrich Al-Zn type, rich Fe-Al type, rich Fe-Zn type, residual Fe type and ZnO type. Rich Al-Zn zinc dross defect was loose shaped with color of grey and white; rich Fe-Al zinc dross defect was needle shaped or platy shaped with the color of off-white and distributed dispersively; rich Fe-Zn zinc dross defect was mixed with zinc coating or embedded in the zinc coating in the form of granules; residual Fe zinc dross defect was linear or flaky with color of black or dark grey, and the distribution was centralized; ZnO zinc dross defect was formed by ZnO embedded in zinc coating with continuous platy shape and distributed dispersively. After taking measures of high-aluminium control technology, equipment optimization and adjustment, dew point controlling and termly cleaning zinc ash, the overall average repair rate of the hot dip galvanized sheet was reduced from 40% to 6.88%, and the surface quality was improved obviously.
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  Composition Design and Property of High Quality Microalloyed Steel for Combing Equipment

  LU Zhong, YONG Qilong, ZHUO Chengzhi, LI Zhaodong, QIAN Dongyan, ZHANG Yongqing

  Materials For Mechanical Engineering. 2019, 43(1): 36-39. https://doi.org/10.11973/jxgccl201901008

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  The composition of a new type GRST-5 steel for carding wire was designed according to the performance requirements of carding wires of combing equipment, toughening principle and microalloying principle of high carbon steel, and the steel was prepared. The cold working performance, hardness, microstructure and wear resistance were studied, and compared with those of traditional 80WV steel carding wires. The results show that the designed GRST-5 steel contained 0.030wt%-0.040wt% niobium and 0.08wt%-0.12wt% vanadium. The cold working performance of GRST-5 steel was better than that of 80WV steel; the intermediate process decreased, and the production cost decreased obviously. The average hardness of carding wire tooth tips made of GRST-5 steel was 820.25 HV, increasing by 30 HV compared with that made of 80WV steel. The microstructure of GRST-5 steel carding wires consisted of cryptocrystalline martensite, and the size of austenite was 3-5 μm. GRST-5 steel carding wires had the same wear resistance as 80WV steel carding wires had, indicating that GRST-5 steel could be a substitute material of 80WV steel in the manufacture of carding wires.
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  Development of Metal Type Flux-Cored Wire for Arc Fusion 3D Printing Marine Propeller Bracket

  SONG Shouliang, YU Shengfu, SHI Yusheng, DAI Yili

  Materials For Mechanical Engineering. 2019, 43(1): 40-44,49. https://doi.org/10.11973/jxgccl201901009

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  The metal type flux-cored wire for arc fusion 3D printing marine propeller bracket was developed by the alloying system design. The processing performance of the wire and the microstructure and mechanical properties of the deposited metal under the deposition current of 155-250 A and deposition voltage of 23-29 V were investigated. The flux cored wire was used to print the propeller bracket simulator, and the dimensional accuracy of the simulator was analyzed. The results show that the forming properties of the flux-cored wire was good, and the arc was stable. The spatter rate was less than 2.5%. The microstructure of the deposited metal was composed of pearlite, granular ferrite and lath bainite. The maximum width of bainite lath was about 0.80 μm, and there was high density dislocation and carbide in lath bainite. The yield strength of the deposited metal along the depositing direction was 550 MPa, and the tensile strength was 651 MPa; the impact absorbing energy at -20℃ was 58 J. The yield strength of the deposited metal in the vertical depositing direction was 538 MPa, and the tensile strength was 642 MPa; the impact absorbing energy at -20℃ was 60 J. Compared with ZG510 steel, the deposited metal had better strength-toughness properties. No cracks, pores and other defects were found in the propeller bracket simulator and the size deviation was within 1 mm.
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  Low Cycle Fatigue Damage Mechanism of GH4169 Nickel-based Superalloy at Elevated Temperature

  WANG Lei, LIU Yanming, CHEN Gang, LIU Jun

  Materials For Mechanical Engineering. 2019, 43(1): 45-49. https://doi.org/10.11973/jxgccl201901010

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  Low cycle fatigue tests at elevated temperature of 650℃ were conducted on GH4169 nickel-based superalloy after solid solution and double aging treatments. The cyclic response characteristics at different stress amplitudes (550, 600, 650 MPa) were studied. The morphology of fatigue fracture and secondary cracks was observed. The damage mechanism at different stress amplitudes was analyzed. The results show that the tested alloy showed cyclic softening characteristics at different stress amplitudes, and the degree of softening increased with the increase of stress amplitude. The crack propagation showed the transgranular propagation mode at the stress amplitude of 550 MPa, and the secondary cracks were mainly generated at inclusions and slip bands. When the stress amplitude reached 650 MPa, the crack propagation mode became transgranular-intergranular mixed propagation, and the secondary cracks were mainly generated at grain boundaries and slip bands. The deformation mechanism of the tested alloy changed from planar slip at a low stress amplitude to cross slip at a high amplitude.
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  Microhardness and Tensile Properties of Friction Stir Welded Joint of 2024 Aluminum Alloy at Different Welding Speeds

  HUO Renjie, JIN Yuhua, WANG Guangshan, LI Hailong

  Materials For Mechanical Engineering. 2019, 43(1): 50-53. https://doi.org/10.11973/jxgccl201901011

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  2024 aluminum alloy plate with thickness of 5 mm was welded by friction stir welding at different welding speeds (20-100 mm·min^-1). The microhardness and tensile properties of the welded joints were studied. The results show that the microhardness of the joint in the direction of perpendicular to the weld showed a W-shaped asymmetric distribution. The microhardness of the weld nugget zone was higher than that of the heat affected zone and the heat affected zone, but still lower than that of the base metal; the microhardness of the transition position between the heat affected zone and the thermo-mechanically affected zone was the lowest. With the increase of welding speed, the average microhardness of the weld nugget zone increased; the tensile strength and elongation of the welded joint increased first and then slightly decreased. When the welding speed was 80 mm· min^-1, the tensile strength and elongation both reached the maximum values of 347.2 MPa and 7.8%, respectively. The shear fracture of the joint occurred at the transition position between the heat affected zone and the thermo-mechanically affected zone, and the fractured position corresponded well with the position with the lowest hardness. The fracture mode of the joint was ductile fracture.
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  Microstructure and Impact Toughness of Heat Affected Zone of FB780 Steel Welded Joint with Different Welding Processes

  ZHU Hao, ZHANG Mei, YE Qingliang

  Materials For Mechanical Engineering. 2019, 43(1): 54-57,63. https://doi.org/10.11973/jxgccl201901012

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  The thermal cycle process of the heat affected zone (HAZ) of FB780 steel welded joint under single pass welding condition was simulated by the Gleeble-3500 thermomechanical simulator. The microstructures of HAZ at different welding peak temperatures and for different t_8/5 times (cooling time from 800℃ to 500℃) were studied, and the micro-hardness and impact toughness of HAZ under different welding conditions were tested. The results show that when the t_8/5 was the same, the microstructure of HAZ coarsened with the increase of peak temperature. When the peak temperature was constant, with the increase of t_8/5, the ferrite lath widened and gradually intergrated; the M/A component coarsened; the coarse ferrite grains were mixed with the fine quasi-polygonal ferrite grains; the metallographic homogeneity deteriorated. At the same peak temperature, the hardness and impact energy of HAZ decreased with the increase of t_8/5. At the peak temperature of 1 175℃ and t_8/5 of 6 s, the impact fracture morphology of HAZ at low temperature (-20℃) showed dimple pattern, and the dimple was relatively large; the toughness of HAZ at low temperature matched with that of the base metal; the hardness was relatively high; all indicated that the process was the best single pass welding process.
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  High-Temperature Wear Resistance of Ni-based Alloy Coating Prepared by Different Processes

  LIU Dong, ZHANG Lei, LIU Zhe, LI Bingzhong

  Materials For Mechanical Engineering. 2019, 43(1): 58-63. https://doi.org/10.11973/jxgccl201901013

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  The Ni-based alloy coatings were prepared on the substrate of 45 steel by flame remelting, plasma surfacing and intermediate frequency induction remelting with commercial Ni60 alloy powder as coating material, respectively. The phase composition, microstructure,microhardness and high-temperature wear resistance of the coatings were studied. The results show that Ni-based alloy coatings with low porosity were obtained. The main hard phases of coatings prepared by flame remelting and intermediate frequency induction remelting were carbides which distributed uniformly. The grains of coatings prepared by intermediate frequency induction remelting were relatively small, and the microhardness was relatively high. The grains of the coating prepared by plasma surfacing were big; the hard phases mainly consisted of borides and distributed unevenly; the coating had the lowest microhardness. The coating prepared by intermediate frequency induction remelting had excellent high-temperature wear resistance, and the wear mechanism was adhesive wear and abrasive wear; the high-temperature wear resistance of the coating prepared by flame remelting was not good, and the main wear mechanism was adhesive wear. The coating prepared by plasma surfacing had the worst high-temperature wear resistance, and the wear mechanism was adhesive wear and fatigue wear.
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  Microstructure and Mechanical Properties of T91 Steel Welded Joint with Transient Liquid-Phase Bonding Two-step and Three-step Heating Process

  CHEN Sijie, DING Guangzhu, LI Bao, ZHAO Pifeng

  Materials For Mechanical Engineering. 2019, 43(1): 64-68. https://doi.org/10.11973/jxgccl201901014

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  T91 steel tube was bonded by transient liquid-phase bonding under two and three-step heating process, respectively. The microstructure, element distribution and mechanical properties of the joints were investigated by scanning electron microscopy, energy dispersive spectrometer, electronic universal testing machine, Charpy test device and bending testing machine. The results show that T91 steel joint had good formation quality under two heating processes. The joint under two-step heating process had the approximate line weld and brazing characteristics, and the Ni enrichment in weld resulted in the formation of black brittle phase. The weld of joint under three-step heating process was curved; Ni element distributed evenly; the microstructure and composition of the joint were the same with those of the base metal; the tensile strength was 660 MPa, the impact energy was 25.7 J and the joint did not cracked during bending 180°; the mechanical properties were improved compared with that under two-step heating process. The fracture mode of the joint under two-step heating process was ductile-brittle mixed fracture, and the fracture mode under three-step heating process was typical ductile fracture.
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  High Temperature Tensile Deformation Behavior of New Titanium Alloy Sheet TA32

  GONG Zonghui, XIE Lansheng, CHEN Minghe, YE Jianhua

  Materials For Mechanical Engineering. 2019, 43(1): 69-74. https://doi.org/10.11973/jxgccl201901015

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  High temperature tensile tests at deformation temperatures of 650-850℃ and strain rates of 0.001-0.100 s^-1 were conducted on TA32 titanium alloy sheet. The influence of deformation temperature and strain rate on high temperature tensile deformation behavior of the alloy was investigated. The high temperature rheological constitutive model of TA32 titanium alloy was established on the basis of modified Hooke law and Grosman equation, and verified by tests. The results show that the flow stress of TA32 titanium alloy was significantly affected by the deformation temperature and strain rate. The flow stress decreased with the increase of deformation temperature and the decrease of strain rate. The tensile strength of the alloy reached 680 MPa at the deformation temperature of 650℃ and strain rates of 0.100 s^-1, which was about 80% of the tensile strength at room temperature; the alloy still had the relatively high strength. When the deformation temperature increased from 750℃ to 850℃, the elongation increased and the strength decreased obviously, indicating the alloy had relatively good plasticity. The true stress-true strain curves calculated by the established high temperature rheological constitutive equation were in agreement with the tested results, and the correlation coefficient and average relative error were 0.979 4 and 11.1%, respectively, indicating that the constitutive model could describe the high temperature tensile deformation behavior of TA32 titanium alloy.
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  Dynamic Mechanical Behavior and Constitutive Relationship of Superalloy GH4169

  LIU Xiao, YAN Huansong, KONG Zukai, ZHAO Zhenhua, LIU Lulu, CHEN Wei

  Materials For Mechanical Engineering. 2019, 43(1): 75-81. https://doi.org/10.11973/jxgccl201901016

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  The quasi-static tensile tests were conducted on smooth sample and notched sample of superalloy GH4169 under strain rates of 0.000 1-0.010 0 s^-1 at room temperature by the material testing machine. The dynamic tensile and compression tests were conducted under strain rates of 1×10²-4×10³ s^-1 at 20-400℃ by split Hopkinson tension and pressure bar setup. The quasi-static and dynamic true stress-true strain curves and failure strains were obtained. Based on the experimental data, the parameters of Johnson-Cook material model and failure model were confirmed by the stepwise fitting method. The dynamic compression behavior was simulated by Johnson-Cook model, and verified by the experiment. The results show that the yield strength of superalloy GH4169 increased with the increase of strain rate, and decreased with the increase of test temperature; the alloy had a strain rate strengthening effect and a temperature softening effect. The simulation results were in good agreement with the experimental results, and the maximum relative error of the true stress-strain curve was 5.91%, indicating that the Johnson-Cook constitutive model could describe the dynamic mechanical behavior of superalloy GH4169 well.
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  Welding Residual Stress Distribution of Heat Transfer Tube Inner Wall of Tube-to-Tubesheet Joint in Nuclear Steam Generator

  LI Ming, LIN Jian, LEI Yongping, LIU Xiaojia, LU Li

  Materials For Mechanical Engineering. 2019, 43(1): 82-86. https://doi.org/10.11973/jxgccl201901017

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  The welding residual stress on heat transfer tube inner wall of tube-to-tubesheet joint in nuclear steam generator was measured by cutting method with a self-built test platform for measuring the residual stress on the inner wall of the tube. The welding residual stress distribution on the heat transfer tube inner wall was studied by combining with finite element simulation. The results show that both tested axial and circumferential residual stresses near the weld of heat transfer tube inner wall of tube-to-tubesheet joint were tensile stresses. With the increase of distance from the weld center line, the residual tensile stress decreased and then changed to compressive stress. At the distance of 12 mm from the weld center line, the residual compressive stress was the largest, and at the distance of 21 mm from the weld center line, the residual stress decreased to the initial stress before welding. The simulation results of welding residual stress distribution on heat transfer tube inner wall were basically in agreement with the experimental results, indicating that the finite element model could accurately simulate the welding residual stress distribution on heat transfer tube inner wall of tube-to-tubesheet joint in nuclear steam generator.