热轧层流辊道内冷辊回水结构的优化改进

针对某热轧厂1 580 mm生产线精轧出口层流辊道内冷辊频繁发生操作侧轴承失效问题,对其原因进行了分析,同时核算了内冷辊受热轴向膨胀后操作侧轴承侧向间隙。结果表明：操作侧轴承侧向间隙满足使用要求,轴承失效和辊筒受热膨胀无关;操作侧轴承失效的直接原因是轴套制造精度低导致骨架油封失效、内冷辊高速旋转“吸水”效应,使冷却回水进入轴承座内部,进一步造成润滑不良进而造成轴承失效。为此,对内冷辊回水结构进行了优化改进：在操作侧轴承座端盖和水套之间增加法兰,延长轴套及安装轴套的轴头,在轴头和轴套之间增加O型密封圈。改进后两年的使用周期内没有发生过轴承失效故障。     

数控机床主轴轴承失效分析

某数控机床主轴轴承运行613 h后出现振动异常,发现失效轴承个别钢球表面存在明显损伤痕迹,通过宏微观观察,化学成分分析,能谱分析等方法对钢球表面的损伤痕迹进行研究。结果表明,由于金属异物颗粒进入轴承,异物与钢球发生粘着磨损,随着粘着磨损作用加剧,在钢球表面产生“白层”,“白层”内部萌生接触疲劳裂纹,疲劳裂纹扩展使钢球表面剥落,形成剥落坑,引起轴承失效。失效轴承的各部件硬度差值超出标准,加速了轴承的失效。因此建议对轴承添加防尘盖或密封圈,提高润滑油脂的洁净度,避免外界异物污染轴承引起失效,并在实际生产中加强轴承材料的质量控制。     

谐波减速器用柔性轴承疲劳寿命实验与失效分析

柔性轴承是谐波齿轮减速器的重要组成部分。为了研究柔性轴承的失效特性,研制了一种可进行柔性轴承疲劳寿命实验的专用试验机。该试验机的加载装置能够与柔性轴承的内圈一起旋转,并可在外圈主轴两端同步施加载荷。通过对四套柔性轴承进行疲劳寿命试验,观察到了几种柔性轴承的失效现象。实验后测量了沟道的宽度,深度和表面粗糙度。实验结果表明:柔性轴承的内圈仅在主轴末端出现磨损和疲劳剥落现象,而外圈可能出现疲劳断裂和剥落现象。此外,还发现柔性轴承套圈沟道的磨损是不均匀的。     

SKF滚动轴承的失效分析

送风机电机滚动轴承在运行过程中发生温度骤升而失效.对失效轴承解体表明,A电机轴承内圈表面出现麻坑及剥落;B电机轴承外圈出现断裂.轴承中的润滑脂已硬化失效.采用化学分析、硬度测定、红外光谱、拉曼光谱、X射线衍射、热失重分析、扫描电镜及金相分析等方法对失效轴承及润滑脂进行分析.结果表明,润滑脂的硬化导致了金属摩擦副之间的直接对磨,加重了轴承滚道表面的磨损.A轴承的失效主要是由电蚀所引起;B轴承外圈因表面硬度偏低,易产生磨损,在轴承滚动过程中的交变应力作用下发生断裂.     

谐波减速器用柔性轴承疲劳寿命实验与失效分析（英文）

柔性轴承是谐波齿轮减速器的重要组成部分。为了研究柔性轴承的失效特性,研制了一种可进行柔性轴承疲劳寿命实验的专用试验机。该试验机的加载装置能够与柔性轴承的内圈一起旋转,并可在外圈主轴两端同步施加载荷。通过对四套柔性轴承进行疲劳寿命试验,观察到了几种柔性轴承的失效现象。实验后测量了沟道的宽度,深度和表面粗糙度。实验结果表明:柔性轴承的内圈仅在主轴末端出现磨损和疲劳剥落现象,而外圈可能出现疲劳断裂和剥落现象。此外,还发现柔性轴承套圈沟道的磨损是不均匀的。     

轧机油膜轴承的失效故障树分析

以轧机油膜轴承为研究对象,分析了引起其发生失效的各个因素,建立了轧机油膜轴承失效故障树。通过对故障树的定量分析,得出了轧机油膜轴承故障树的各阶最小割集,从而确定了锥套损坏、衬套损坏和润滑油变质为轧机油膜轴承失效的主要形式,并提出了预防轧机油膜轴承失效和提高轧机油膜轴承可靠性的相关措施。     

奥克斯纳立泵滑动轴承副的失效分析

对奥克斯纳立泵滑动轴承副进行了失效分析。结果表明:该轴承副的失效是由于选材不当造成。轴承副的内外轴套WC硬质合金层的粘结剂Co被温热的稀硫酸溶解造成WC粒子脱落,并加速了轴套的磨损。在WC层被磨掉后,内轴套基体材料UB_6因温热磷酸和Cl~-腐蚀和机械磨损引起失效破坏。     

汽车轮毂轴承的断裂失效分析

通过外观检查、成分测试、硬度测试、金相组织和扫描电镜观察等方法,对某品牌汽车3个轮毂轴承失效件进行分析,找出了造成轮毂轴承最终断裂失效的原因。结果表明,3种轮毂轴承的内圈和外圈的组织都符合JB/T 1255-2001标准的要求;1#轮轴轴承失效的原因是由于化学成分不合格和轴承内圈滚道的表面硬度较低;2#轮毂轴承的化学成分、硬度和组织都满足要求,失效原因在于密封性较差,而使得外圈滚道中外界硬度相对较高的颗粒落入滚道,造成磨损加剧;3#轮毂轴承外圈碳含量较低,使得外圈滚道表面硬度偏低,且由于润滑条件不好引起了粘着磨损,加剧了轴承的磨损,并最终造成失效。     

特大型四列圆锥滚子轴承失效分析

针对国内某钢厂穿孔机用特大型四列圆锥滚子轴承出现异响、轴承失效的问题,对失效轴承进行了外观、金相组织、外形尺寸和硬度检查,判定轴承材料、表面硬度符合标准。分析认为裂纹为大挡边与滚子端面剧烈摩擦发热所致。尺寸变形因安装拆卸时对轴承的加热冷却措施不当所致。安装时中外圈的倾斜导致了轴承各列游隙不均,导致B列受力较大最终失效。指出多列轴承安装时需注意对各列游隙的控制。     

G20Cr2Ni4A轴承滚动体开裂失效分析

G20Cr2Ni4钢轴承滚子是安装在大型轴承上作为滚动体使用的,该滚子经表面渗碳后再经淬火回火处理。送检的滚子在试车约2 h后断裂,造成轴承失效。采用金相显微镜、洛氏硬度计、扫描电镜、X荧光光谱仪等,对该轴承滚子的开裂原因进行了分析。结果表明:金相组织、硬度、渗碳层厚度和化学成分等均合格。氢脆引起的内应力与外应力叠加是造成滚动体由内向外疲劳开裂失效的主要原因。     

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.