ZS165-250型减速机齿轮轴断齿原因分析

通过宏观断口、化学成分分析、硬度测试、金相分析等试验分析,对ZS165-250减速机齿轮轴断齿原因进行了分析。结果表明,该齿轮轴齿部断裂为接触疲劳断裂,导致接触疲劳断裂的原因是该齿轮轴齿面硬度过低以及金相组织不良,并提出了避免类似质量事故的预防措施。     

某转向齿扇摇臂轴断齿失效分析

通过对化学成分、金相组织及渗碳层显微硬度的检测,结合断口形貌观察,分析了某转向齿扇摇臂轴齿轮断齿的原因。结果表明:扇形锥齿轮齿根槽角处的刀痕和折叠等加工缺陷,导致齿根部位产生应力集中,是断齿的主要原因;而齿轮渗碳层的高碳势稍有过热组织促进了轮齿的疲劳断裂。     

风电齿轮箱齿轮剥落分析

通过断口分析、材料理化检测分析,风电齿轮箱齿轮的断齿是齿轮原材料质量或制造工艺缺陷所致。齿轮在渗碳热处理过程中存在内氧化缺陷,降低材料的疲劳寿命和耐磨性,使用中在应力集中的轮齿根部沿晶界萌生疲劳裂纹,裂纹经扩展最终导致断齿失效。     

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 通过化学成分、常温力学性能、断口分析、高低倍金相和显微维氏硬度测试、渗碳层深度检测以及人工断口分析等实验分析了安装在农用三轮车上的齿轮轴断裂原因。结果表明,热处理不当导致材料力学性能偏低偏脆是齿轮轴发生快速脆性断裂的主要原因。     

装载机后桥减速器齿轮轴崩齿失效分析

对装载机后桥减速器齿轮轴伞齿段崩齿进行了断口分析及金相显微分析.结果表明,齿表面渗碳层深度不足,并有脱碳现象,渗碳层组织粗大,使用中存在偏载现象等问题,是造成齿轮轴伞齿段发生崩齿失效的主要原因.     

风电增速机内齿圈断裂原因分析

某材质为17Cr2Ni2Mo的风电增速机内齿圈在风场使用不到两个月即发生断裂。本文通过低倍、高倍、断口等理化试验,对该内齿圈断裂原因进行了分析。分析结果表明,该内齿圈断裂性质为疲劳断裂,其产生原因是齿根部位有效硬化层深度过低以及存在粗大回火马氏体组织。     

台架试验中齿轮断齿的原因分析

采用显微组织分析,结合断口形貌分析、齿形齿向分析对齿轮断齿原因进行失效分析.结果表明,齿根圆角表层非马氏体组织深度不符合技术要求,但非本次断齿的主要原因.齿轮断齿根本原因为齿根次表面存在大尺寸氧化物夹杂,在试验持续受力过程中以该夹杂为疲劳源发生鱼眼状疲劳断裂.     

齿轮轴伞齿段崩齿失效分析

对失效件进行宏观分析、断口微观分析、齿面显微分析等,结果表明:齿表面渗碳层深度不足,并有脱碳现象,渗碳层组织粗大,使用中存在偏载现象等问题,是造成齿轮轴伞齿段发生崩齿失效的主要原因.     

风电齿轮箱小齿轮齿面剥落原因分析

某风场1.5 MW风电机组齿轮箱中速轴小齿轮失效.该齿轮箱设计寿命20 a,实际使用了5 a.齿轮的材质是20CrNiMo,齿面经过渗碳淬火.采用宏观观察,微观观察和断口分析并结合其它理化测试,分析了小齿轮失效的原因.现场宏观观察发现,大部分轮齿相对完好,只有两支轮齿失效,其中一支齿面剥落,另一支齿面硬化层开裂.经分析,齿面剥落和齿面开裂的原因相同.导致齿轮失效的原因是:齿面粗糙度较大,较深的加工刀痕在异常冲击载荷的作用下造成齿面开裂,随后在循环工作载荷的作用下,萌生了疲劳裂纹并不断扩展,最终导致齿面硬化层脱落.建议提高齿轮表面加工质量,降低表面粗糙度,同时改进齿轮箱制动技术,避免异常载荷冲击造成齿面过载.     

风电齿轮箱小齿轮断齿原因分析

风电场1.5 MW风电机组齿轮箱在运行中出现故障,经检查发现中速轴小齿轮出现断齿现象。采用宏观观察、微观观察、并结合相关理化性能测试,综合分析得出齿轮的失效原因。结果表明,风电齿轮箱中速轴小齿轮断裂性质为疲劳断裂,在断口上观察到清晰的疲劳弧线,裂纹源萌生于齿面接触疲劳产生的蚀坑中,而导致齿面严重接触疲劳的原因是偏载。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.