重载铁路道岔60AT-PG4尖轨的感应加热

对重载铁路道岔60AT-PG4尖轨进行了感应加热及喷雾冷却工艺试验研究,检测了尖轨的化学成分及不同断面的显微组织和硬度。结果表明,PG4尖轨不同轨头断面硬化层深度在12～40 mm范围,断面洛氏硬度在39～41.5 HRC之间,轨头两侧硬化层深度在9～11 mm范围,断面洛氏硬度在37.5～42 HRC之间,硬化层组织均为索氏体,尖轨轨头踏面硬度平均值为388 HB,均符合TB/T1779—93《道岔钢轨件淬火技术条件》及GFKB014—2009《热处理钢轨技术条件》规定的技术要求。     

R350硬头轨离线热处理工艺试验

用60D40特种断面钢轨制造道岔尖轨,我国过去的制造技术路线是:先机加工轨头变截面,后对轨头感应热处理.实践表明,尖轨轨头工作边平直度很难达到客运专线道岔制造验收暂行技术条件,且生产效率较低.为使其制造路线改造为轨头先热处理后机加工,对60D40钢轨进行了R350硬头轨离线热处理工艺的近百次试验.试验结果表明,表面硬度、断面硬度分布、拉伸性能和显微组织各项质量指标均达到了BS EN 13674-2:2006中R350HT硬头轨欧洲标准的技术要求.本试验为我国道岔制造技术的提升并与国外标准接轨打下了基础.     

AT尖轨全长热处理研究

AT尖轻全长热处理采用中频感应加热、压缩空气吹冷淬火,对60AT铌稀土微合金道岔尖轨进行轨头全长尔速淬火工艺及性能的研究。通过热模拟试验研究,确定热处理加热温度和冷却温度。尖轨前端采用非工作面预留,解决了尖轨5～10mm断面的加热温度偏低的问题,从而使整个道岔尖轨获得均匀的淬火硬度和质量,避免了道岔尖轨调直折断和异常组织现象的发生,改善了与基本轨的密贴,提高了道岔尖轨的使用性能和安全性能。     

高速铁路道岔轨件的感应淬火与变形控制

对高速铁路道岔20 m以上的尖轨、基本轨进行了感应加热试验,并对热处理后的尖轨和基本轨的变形量和力学性能进行了测试。结果表明,轨头硬化层深度大于10 mm,断面硬度为34~38 HRC,金相组织为索氏体+少量铁素体。对淬火过程中轨件适当的预变形后,20~24 m的轨件变形挠度控制在150 mm范围内,满足了高速道岔组装过程中的技术要求。     

高速及重载道岔在线热处理钢轨压型跟端的感应热处理

为使高速及重载道岔AT钢尖轨跟端锻造热处理后组织与性能满足最新标准和线路使用要求,采用自主研发钢轨全断面感应加热+喷风冷却生产线,对高速及重载道岔60AT2-U71MnG及60AT1-U75V在线热处理钢轨压型跟端进行了热处理工艺试验,观察了硬化层的显微组织,检测了钢轨化学成分、硬化层深度、表面硬度、断面硬度、抗拉强度、伸长率及疲劳性能。结果表明,60AT2-60 kg/m(U71MnG材质)及60AT1-60 kg/m(U75V材质)在线热处理钢轨压型跟端经热处理后,钢轨轨头中心踏面硬化层深度不小于30 mm,显微组织为索氏体,表面硬度不小于320 HBW,抗拉强度不小于1200 MPa,伸长率不小于11%,表面硬度变化范围小于30 HBW,热影响软化区小于40 mm,弯曲疲劳强度达到200万次不断,各项技术指标均满足相关要求,可满足线路使用需求。     

护轨用槽型钢感应热处理工艺试验

对制造高速客专道岔护轨用槽型钢采用中频感应加热、完全喷风连续冷却、控制欠速淬火工艺,设计了三面同时加热的感应器和可控冷却速度的喷风装置;采用预弯反变形工艺措施减少热处理弯曲变形。结果表明,该槽型钢加热层深度大于25 mm,硬化层深度大于24 mm,表层下6 mm深处的硬度为37~43 HRC,24 mm深处硬度大于34 HRC,而且热处理畸变得到了有效控制,符合TB/T 3110—2005《33 kg/m护轨用槽型钢》技术条件要求。建议33kg/m护轨用槽型钢的材料性能标准等效采用国际标准UICBSEN13674:2006。     

道岔尖轨自5mm断面淬火试验

1　前言矮型特种断面钢轨 (简称ＡＴ轨 )用于制造道岔尖轨 ,与普通钢轨制造的尖轨相比 ,改善了尖轨的结构强度与稳定性。尖轨结构的设计改进使其承受垂直载荷更趋合理 ,但是尖轨轨头宽度≤ 1 0ｍｍ的各个小截面 ,在列车轴重增加 ,运行速度提高的条件下 ,其磨损愈来愈大。事实上 ,尖轨小断面磨耗严重 ,磨损速度加快 ,已成为制约道岔尖轨使用寿命的决定性因素。新的铁道部专业标准ＴＢ/Ｔ 1 779— 1 993《道岔钢轨件淬火技术条件》 ,对尖轨小断面淬火规定了技术要求和质量指标 ,但是尖轨小断面淬火的工艺与技术难题却一直未解决。因此 ,尖轨小…     

稀土微合金淬火钢轨接触焊焊后热处理工艺及设备

对稀土粹火钢轨接触焊焊后采用中频感应加热,轨头压缩空气社会火,其他部位正火的热处理工艺。研制了适合于该钢种的加热感应器和高速吹风冷却等装置。通过热模拟试验选择了合理的焊后热处理工艺参数,恢复了轨头强度和硬度,并大幅度地提高了焊接接头的韧塑性和综合性能,满足了无缝线路铺设使用要求。     

60AT1-U75V钢轨压型跟端感应热处理

对60AT1-U75V在线热处理钢轨压型跟端进行了中频感应预热+中频感应加热+喷风冷却+喷雾冷却工艺试验研究,分析了热处理后钢轨的硬化层金相组织、踏面硬度、横断面硬度、硬化层深度、抗拉强度及伸长率。结果表明,60AT1-U75V在线热处理钢轨压型跟端经热处理试验后,钢轨轨头中心踏面硬化层深度在16.5~20.5 mm范围,硬化层金相组织为索氏体,且12 mm硬化层深度内钢轨的断面硬度在36~41.0 HRC之间,表面硬度为375~405 HB,抗拉强度Rm大于1242 MPa,伸长率A大于10.8%,可满足TB/T 2635-2004《热处理钢轨技术条件》标准要求。     

BS80A护轨开口段淬火试验

本文介绍了一种BS80A护轨开口段表面感应淬火工艺试验过程及其工装使用情况。结果表明:900A钢BS80A护轨的开口段轨头,经过900～950℃欠速淬火和470～530℃回火处理,轨头表面获得深度δ8 mm的硬化层,硬化层金相组织为细珠光体+少量铁素体;截面硬度梯度为35.6～33.6 HRC;表面硬度、金相组织、硬化层帽型均达到了技术标准要求。确定的工艺参数和工装成功应用于铁路道岔BS80A护轨热处理生产中,可以在一定范围内推广应用。     

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.     

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。     

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.