盾构刀盘拆卸结构再制造设计及数值模拟

针对某盾构机拆卸刀盘的修复问题,进行了刀盘再制造工艺分析,通过有限元方法模拟讨论了牛腿支架及钢环加固对Q345B刀盘结构焊后变形和应力的影响,对比分析了空冷、预热加缓冷,厚板焊接坡口角度(焊缝宽度)对刀盘焊后变形与应力的影响规律。研究表明,采用牛腿支架装夹固定并通过钢环辅助固定后,可有效控制盾构机刀盘再制造修复时的焊接变形;刀盘拼焊时的预热加缓冷,对控制刀盘焊后的应力与变形具有显著的技术效果;对厚板焊接,设计合适的坡口角度(焊缝宽度),不仅可显著降低刀盘焊后的应力与变形,而且对减小热输入、提高焊接质量和生产效率具有技术经济价值。     

正火态DH36海工钢焊接冷裂纹敏感性研究

为了研究正火态DH36海工钢材料的焊接冷裂纹敏感性,本研究采用厚40 mm的DH36进行了不同预热温度对其冷裂纹敏感性影响的研究,并对该材料焊接接头不同位置的显微组织、 M-A岛分布及硬度等进行了研究。结果表明,该厚40 mm的DH36材料焊接后,其粗晶区有出现冷裂纹的倾向,采用60℃的焊前预热能降低材料斜Y型坡口试验断口冷裂纹率,材料可以实现一般结构件的焊接制作。焊前预热改变了焊接接头粗晶区的组织、降低了组织硬度,并延长了接头扩散氢的逸出时间,导致材料冷裂纹敏感性的降低。     

TBM密封耐磨环焊接工艺研究

为满足TBM主驱动司太立耐磨环焊接生产需求，从下料、焊前加工、焊接、焊后检测与处理等工序对司太立合金板进行研究。研究表明，采用激光切割下料、焊前加工坡口、TIG焊、焊后射线探伤与机械抛光处理、焊接过程中使用专用焊接工装装夹固定，并采取焊前预热(预热温度为250～350℃)、焊后后热(后热温度为200℃)缓冷措施，在合适的焊接参数下进行焊接，可获得成形美观、焊接质量良好的耐磨环件，其圆度及光洁度满足设计及安装要求；整体焊接工艺完善，切实可行，可满足批量化焊接生产需求。     

预热温度对Q420钢板焊接冷裂纹敏感性的影响

采用斜Y型坡口焊接裂纹试验,主要针对不同预热温度下的Q420钢板,采用GFR-81K2焊材进行了FCAW工艺下的焊接冷裂纹敏感性试验研究。研究结果表明:Q420钢在各种预热温度和110℃热处理条件下,其冷裂纹敏感性较低;对于焊材GFR-81K2而言,在各种预热温度和110℃热处理条件下,其冷裂纹敏感性较低;而预热110℃焊后热处理后反而出现了一定程度的裂纹率,因此,对于Q420钢及焊材GFR-81K2在预热110℃下的冷裂纹倾向性,焊后热处理工艺不推荐。     

炼钢托圈的组对及焊接工艺

介绍了酒钢炼钢厂50 t转炉托圈的组对及焊接,采取新颖的组对方法,使同轴度误差在控制范围内;采取合适的焊缝布置及探伤方法,确保转炉托圈组对后达到了使用标准,延长了其使用寿命.重点介绍了为防止焊接残余变形而采用的预热方法及参数、坡口形状及尺寸、焊接顺序及焊接工艺参数、层间温度和焊后热处理工艺及方法.     

大厚壁铸钢件补焊工艺研究

针对大厚壁铸钢件缺陷,采用异质冷补焊方法进行修复,在焊接过程中采用焊前预热、增加施焊过渡层、控制热输入、填充过程超声波跟踪消应力、控制层间温度等措施,可以简化工艺、有效控制焊接变形,对大厚壁铸钢件的抢修补焊具有指导意义。     

胺液吸收塔筒节纵缝焊接工艺

胺液吸收塔主材质为16MnR,是一种低合金高强度钢,其低温焊接性较差.通过采取焊前预热、控制焊接线能量和层间温度、焊后保温缓冷等工艺措施,并采用相应的检测方法,保证了胺液吸收塔的低温焊接质量.     

铸铁气焊工艺与焊接区硬度控制

使用微合金化铸铁焊丝,研究了气焊工艺对铸铁焊接区硬度的影响。结果表明,焊前预热和焊后保温对焊接区硬度有显著影响。预热温度升高,基体中铁素体含量增多,焊接区硬度值降低。200℃预热获得的焊接区硬度要比室温不预热焊的降低约HB30;焊后用火焰对焊接区金属持续烘烤2~6 min进行保温缓冷,亦可有效降低焊接区硬度。焊前预热和焊后缓冷措施的复合使用可达到控制焊接区硬度的最佳效果。     

P91钢的焊接性及其焊接工艺

通过分析P91钢的焊接性,明确预防焊接冷裂纹是保证焊接质量的首要措施,焊前预热和焊后热处理直接决定焊接接头的硬度,硬度偏高则无法充分消除焊接接头内应力,硬度过低则会降低材料的高温持久强度.结合钢管规格与材质,拟定焊接工艺参数,进行焊接试验、热处理试验和力学性能检验,形成P91钢焊接工艺.采取焊前准备、控制坡口加工、实时...     

低合金高强钢激光-电弧复合热源焊接冷裂纹敏感性分析

通过扩散氢含量测定,并利用经验公式计算JFE980S低合金高强钢冷裂纹敏感性和焊前预热温度,同时采用斜Y形坡口试验、金相试验以及残余应力测定等方法,研究低合金高强钢抗冷裂性能,对比分析了激光-电弧复合焊和MAG焊工艺对接头抗冷裂性能的影响.结果表明,激光复合焊抗冷裂性优于MAG焊方法.因复合焊加入了激光,使得焊缝熔深增加,拘束减小,并且激光在前,对焊接试板有一定的预热作用,使冷裂纹形成倾向进一步降低,特别是在无法预热的情况下,激光复合焊更能够体现出优势.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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).     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.