合金元素对高强管线钢埋弧焊缝组织性能的影响

通过对X80管线钢进行埋弧焊接试验,分析了合金元素Mn、Ni对高强度管线钢埋弧焊缝的显微组织和力学性能的影响.试验结果表明,当Mn元素含量过高时,焊缝金属的冷裂纹敏感指数提高,细化原奥氏体晶粒尺寸,对针状铁素体形核不利湘比较而言,Ni元素对焊缝的冷裂纹敏感指数影响较小,且使焊缝金属易于产生交滑移,更易保证焊缝针状铁素体含量,从而提高焊缝金属的韧性;另外,随着Mn、Ni元素含量的增加,焊缝金属中先共析铁素体受到抑制.     

B元素对药芯焊丝焊缝金属针状铁素体形成的影响

利用金相组织观察、冲击试验和热膨胀试验,研究了B元素含量变化对高强钢药芯焊丝焊缝金属中针状铁素体形成的影响,得到了不同试验温度下焊缝金属冲击吸收功. 结合透射电镜分析和分级淬火试验从热力学和动力学的角度对B元素影响机理进行了分析. 结果表明,焊缝金属组织晶界中含有自由状态的B元素具有抑制晶界铁素体形核利于针状铁素体生成的作用;N元素含量增加会降低晶界B元素含量,并提高奥氏体向铁素体转变的温度,减少针状铁素体含量;针状铁素体是在以Ti元素和Mn元素的氧化物为核心,以Cu元素和Mn元素的硫化物为外层,以BN为过渡层的复杂结构上形核并长大的;针状铁素体含量的增加有利于提高焊缝金属冲击吸收功,–60 ℃冲击吸收功最大为70 J.     

埋弧焊烧结焊剂中MnO应用的试验分析

通过对烧结焊剂中常用组分MnO的物理化学性质的分析,试制了三种烧结焊剂,并进行了接头组织及力学性能的对比试验.结果表明,烧结焊剂中加入适量的MnO,对提高焊剂的碱度、增加焊剂还原性、净化焊缝、改善脱渣、成形等工艺性能具有很大的作用.与此同时,适量MnO的加入,还可以合理控制焊缝金属中Mn的含量,稳定奥氏体,降低γ→α转变温度,为焊接接头组织中针状铁素体的形成创造良好的环境,并进一步提高了焊缝金属的力学性能.     

低合金高强度钢焊缝针状铁素体联锁组织与性能

采用金属包埋切片微米-纳米表征法和电子背散射衍射技术分别研究了焊缝金属中针状铁素体形核夹杂和联锁组织特征。结果表明,由于Mn元素扩散到夹杂物内部使得周围形成贫Mn区,诱发针状铁素体在复合夹杂物上形核。同时针状铁素体还可以在已经形成的铁素体表面激发形核;铁素体生长过程中同原奥氏体保持固定取向关系;铁素体相互之间发生硬碰撞和交错现象;这些因素共同形成针状铁素体联锁组织。这种细小有效晶粒尺寸的针状铁素体联锁组织具有良好的强韧性匹配。     

低合金钢焊缝的针状铁素体微观组织

针对X70管线钢多道焊焊缝金属,利用Gleeble1500热模拟机进行了热模拟试验,对焊缝金属中初生针状铁素体组织及其与非金属夹杂物之间的关系以及经历二次热循环后感生形核的针状铁素体组织进行了SEM及TEM分析.结果表明,针状铁素体边界存在着一层富碳的薄膜,其长大既存在切变转变的特征,同时也伴随着C原子的扩散过程.共感生成的二次针状铁索体是在初生针状铁索体基体的高密度位错处形核并以一定的速度迅速长大到有限的尺寸.初生针状铁素体和共感形核针状铁素体都是在奥氏体晶内形核、长大,都具有细化奥氏体晶粒、提高多道焊焊缝金属和焊接热影响区韧性的作用.     

低碳贝氏体钢用烧结焊剂的研制及性能研究

基于低碳贝氏体钢的微观组织和性能研究分析,研制出以CaF_2-MgO-Al_2O_3-CaO为渣系的低碳贝氏体钢用高速埋弧焊烧结焊剂,匹配Mn-Ni-Mo-B合金系焊丝施焊,得到了一组性能优异的焊剂。结果显示:CaF_2加入量控制在23%以下,并增加TiO_2和SiFe含量来代替部分SiO_2时,得到的焊缝工艺性能优异,力学性能也能够满足使用要求。焊缝金属组织主要由针状铁素体、粒状贝氏体、以及少量的先共析铁素体和块状铁素体构成,较硬的粒状贝氏体弥散分布在较软的铁素体基体上,这种混合组织增加了裂纹扩展的路径,极大地增强了焊缝金属的韧性。而提高Al_2O_3和TiO_2的含量,同时将MnO的含量控制在6%左右,可以得到较多的针状铁素体,细化组织,使焊缝冲击韧性达到198 J。     

低合金高强度钢焊缝金属中针状铁素体的微观组织

利用光学显微镜,扫描电子显微镜及EBSD(electron backscattering diffraction)分析技术对800MPa级低碳微合金高强度钢的焊缝金属进行了分析.结果表明,焊缝金属组织主要为针状铁素体和贝氏体.针状铁素体以夹杂物为核心形核,该夹杂物主要是以Al2O3为核心形成的钛氧化物.针状铁素体以夹杂物为核心多维形核呈放射状生长,仅某些方向的针状铁素体晶核迅速长大,生长方向存在取向择优.EBSD分析同样表明针状铁素体晶粒存在取向择优.观察到由同一夹杂物生长,沿同一直线方向背向生长的针状铁素体取向相同,沿不同方向生长的针状铁素体取向不同,说明其沿原奥氏体惯习面生长,并非与夹杂物共格.     

X100管线钢埋弧焊匹配焊剂及其接头性能分析

采用均匀设计法对X100管线钢埋弧焊用烧结焊剂进行设计,选用其中5种高碱度氟碱性焊剂,配合焊丝进行埋弧自动焊接试验,着重分析了两种焊剂焊接接头的拉伸性能、金相组织、硬度、冲击吸收功及冲击断口形貌等.结果表明,焊剂中适量添加MnO对焊剂工艺、接头韧性有较大影响,它可以提高焊缝熔深,增加渣的流动性,抑制咬边,同时抑制高温铁素体的生成而对焊缝中针状铁素体的形成有利.所研制的5种焊剂中,2号焊剂焊接接头综合性能最佳,满足X100管线钢API—5L标准要求.     

D32钢FCB埋弧焊焊接接头组织分析

采用FCB焊对20 mm厚的D32高强度船体结构钢板使用不同的焊剂进行焊接,得到不同的焊接接头。总结了FCB焊焊接接头的结晶生长方式,并对比分析了使用不同焊剂的两种焊接接头的微观组织形貌和化学组成。结果表明:使用NSH-55EM焊剂所得焊接接头的组织主要是针状铁素体和珠光体;使用55E-6/B-5焊剂所得焊接接头的组织主要由先共析铁素体、侧板条铁素体及少量针状铁素体、珠光体组成;所得焊缝金属的Mn/Si值55E-6/B-5焊剂比NSH-55EM焊剂的低,合金元素Ti、B和Ni过渡焊缝中较少,使焊缝组织不同,从而引起性能差别较大。     

高强度低合金钢埋弧焊缝成分和显微组织分布特征

进行了X80管线钢埋弧焊接试验,分析了其焊缝的成分、显微组织不均匀性特征.焊缝区的Mn、Ni合金元素的成分不均匀程度较小,Ce、Ti、Al等针状铁素体形核元素在焊缝中心区偏析.熔合区至焊缝中心,焊缝组织变化为:柱状晶形态的先共析铁素体及其分布的粒状贝氏体-大块状的粒状贝氏体→小块状的粒状贝氏体和少量的针状铁素体→针状铁素体.试验分析表明,熔合区附近的焊缝金属难以获得针状铁素体,但可以通过调整合金元素,避免高温铁素体生成,而以粒状贝氏体来提高焊缝区的整体强韧性.     

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.