X80管线钢的焊接性研究

X80管线钢是西气东输二线工程的主导钢材,其焊接质量直接决定管线的安运行全.采用热模拟技术研究了X80管线钢焊接热影响区工艺条件、组织和力学性能之间的关系.结果表明X80管线钢焊接粗晶区的组织类型为贝氏体和铁素体,不存在典型的M组织,淬硬性倾向较小.粗晶区的软化现象不太显著.焊接线能量对粗晶区的冲击韧性影响最为显著.当采用8kJ/cm的线能量和60℃的预热温度时,粗晶区的晶粒较细,组织由板条贝氏体和一定量的粒状贝氏体组成,由于粒状贝氏体对板条贝氏体的分割作用,使板条贝氏体的长度较小,方向性差,表现的韧性最优越.因此在X80管线钢的焊接中为使粗晶区获得较高的韧性,应采用较小的线能量和合适的预热温度.     

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粗晶区是焊接接头的薄弱环节.通过对X80管线钢进行热模拟、金相显微镜和透射电镜分析后表明,粗晶区的组织主要为板条束贝氏体和粒状贝氏体;X80管线钢焊接热影响区粗晶区冲击韧性较差,存在严重脆化,粗晶区脆化是由于晶粒的粗化以及M-A组元数量增多造成的;随着t8/5的增加,粗晶区的冲击韧性和硬度随之降低;峰值温度越高,X80级管线钢的组织越粗大、韧性越低;中间临界区是焊接热影响区中另外一个韧性较薄弱的区域.     

冷却时间对X80钢焊接热影响区粗晶区组织及性能的影响

利用Gleeble热模拟试验机模拟研究了X80钢焊接热影响区粗晶区组织在不同冷却速度下的变化规律,研究了冷却时间、组织和性能之间的关系。结果表明,X80钢焊接热影响区粗晶区组织主要由板条贝氏体和粒状贝氏体组成。随冷却时间t8/5时间增加,板条贝氏体含量逐渐减少,由细长状转变成粗大片状、并趋于平行;粒状贝氏体含量逐渐增加,其间的马氏体M/奥氏体A组元数量增加,间距缩短,面积增大。随冷却时间t8/5时间增加,焊接热影响区粗晶区冲击韧性先增加后减小;当t8/5=7 s时,X80钢焊接热影响区粗晶区组织为少量的粒状贝氏体,且弥散分布于大量板条贝氏体之间,细化板条贝氏体,增加有效晶界,起到细化和强化作用,冲击断口分布着大量的细小韧窝,为明显的韧性断裂。     

X80管线钢焊接粗晶区的组织和性能

采用热模拟技术研究了X80管线钢粗晶区组织和低温韧性的变化规律，讨论了冷却时间、组织和性能之间的关系。结果表明，焊接粗晶区主要由板条束状贝氏体和粒状贝氏体组成。当t8/5在6～8s时，粒状贝氏体含量较多，其分割作用使板条贝氏体的方向性减弱，使板条更为细小；M—A组元呈块状，尺寸较小且均匀分布在基体上，冲击韧度最优越；当t8/5增大或减小时，板条束状贝氏体的含量均增加，板条粗大，M—A组元在冷却速度较快时呈长条状，冷却速度较慢时呈块状且相对含量增加，尺寸增大，均使冲击韧度显著下降。     

焊后热处理对X80和30CrMo钢热影响区粗晶区韧性的影响

通过冲击、金相试验和扫描电镜分析,研究了焊后热处理(PWHT)对X80钢和30CrMo钢热影响区粗晶区韧性的影响。结果表明,X80钢侧焊态和PWHT后粗晶区组织均主要为板条贝氏体和粒状贝氏体;30CrMo钢侧焊态粗晶区组织主要为贝氏体和低碳马氏体,PWHT后粗晶区组织为贝氏体和回火索氏体。M/A组元的形成是造成X80侧钢焊态粗晶区韧性较低的主要原因,而30CrMo钢侧焊态粗晶区韧性较差是组织粗化及上贝氏体的形成造成的。PWHT后,热影响区粗晶区的韧性明显改善,这主要是由于粗晶区组织细化,脆硬组织数量变少,应力集中程度降低。     

热输入对X80管线钢焊接粗晶区组织与性能的影响

采用热模拟技术模拟研究不同热输入对X80管线钢焊接粗晶区组织与性能的影响。结果表明,焊接热影响粗晶区组织主要由板条状和粒状贝氏体组成,随着热输入的增加,焊接热影响粗晶区的板条贝氏体数量逐渐减少,粒状贝氏体数量逐渐增加,彼此交错分布。当热输入E=20 kJ/cm时,焊接热影响粗晶区晶粒虽有所长大,但板条贝氏体和粒状贝氏体交叉混合分布,表现出较好的冲击性能。通过分析得出,采用焊前预热和小热输入的焊接工艺既可以减少高温停留时间tH,防止晶粒粗化,又可以相应的提高800℃到500℃的停留时间t8/5,给组织相变提供适当的时间,以达到改善X80管线钢手工焊工艺。     

X80管线钢焊接性分析

利用Gleeble热-力学模拟试验机,通过热膨胀法测得不同焊接热循环条件下X80管线钢的相变温度和时间。分析不同焊接冷却速度下X80管线钢焊接粗晶区组织、显微硬度和冲击韧性的变化规律。在此基础上,绘制得到X80管线钢的SH-CCT曲线。当焊后冷却度在10~50℃/s之间时,X80焊接粗晶区的显微硬度和冲击韧性皆高于母材。     

X70管线钢在役焊接局部脆化区的组织及精细结构

采用焊接热模拟试验研究了X70管线钢在役焊接粗晶区和临界粗晶区的显微组织及其精细结构,并和常规焊接进行了对比.结果表明,X70管线钢在役焊接粗晶区和临界粗晶区的组织在类别上与常规焊接相差不大,主要都是粒状贝氏体和贝氏体铁素体,不同的只是数量的多少和尺寸的大小.透射电镜下,在役焊接和常规焊接的粗晶区与临界粗晶区的主要形貌都是铁素体板条和分布在板条之间或板条基体上的岛状物,铁素体板条的亚结构都是高密度位错.在役焊接粗晶区和临界粗晶区的铁素体板条宽度都比常规焊接的要小,位错密度都比常规焊接的要高.     

焊接热循环对X80管线钢粗晶区韧性和组织的影响

利用焊接热模拟技术、光学金相、透射电子显微镜和示波冲击韧度试验、断裂韧度试验研究了焊接热循环对X80管线钢粗晶区韧性和组织的影响。试验结果表明,在六种热循环参数下,X80管线钢模拟粗晶区具有不同的显微组织,当焊接热循环参数较小时,以下贝氏体和板条马氏体为主,随着热循环参数的增大,以粒状贝氏体为主,且其中的M—A岛的形态由细短条状转变成大长条状或大块状,分布由晶界转向晶内,同时数量增多,韧性恶化。     

07MnNiCrMoVDR钢焊接粗晶热影响区的韧化机理

选用垂直于07MnNiCrMoVDR钢板轧制方向的模拟试样,在Gleeble-3500热模拟试验机上对该钢焊接粗晶热影响区的组织转变和韧性进行了研究.结果表明,粗晶区的组织类型主要是贝氏体和低碳板条马氏体的混合组织,粗晶区的低温韧性最差,随着冷却速度的减小,贝氏体由下贝氏体向上贝氏体和粒状贝氏体转变.在高温回火热处理后,粗晶区有再热脆化的倾向,易产生再热脆化,存在再热裂纹的可能性较大.再热脆化的主要原因是晶界析出粗大的碳化物,冷却速度越大,再热脆化现象越严重.     

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.