铝合金推进剂箱体焊接技术及展望

介绍几种先进铝合金箱体焊接技术工艺特点,包括变极性TIG焊、变极性等离子焊、电子束焊、搅拌摩擦焊及摩擦塞焊。总结每种焊接技术的特点及应用范围,分析未来铝合金推进剂箱体焊接技术的发展趋势。     

大型齿轮座下箱体焊接工艺

国内某产品使用的大型齿轮座下箱体胚料,广泛采用铸造成型工艺生产,由于结构原因,其铸造工艺复杂、缺陷多、产品率低、生产成本较高。结构“铸改焊”后,工艺相对简单、焊接质量易于保证、产品合格率及材料利用率高,可大幅降低制造成本,因此焊接齿轮下箱体应用前景广泛。但大型齿轮下箱体焊接中,因材料板厚大,焊缝密集,焊接应力大,极易产生裂纹,同时焊接变形大,焊后加工尺寸难以保证。本文针对某大型齿轮座下箱体的焊接,在结构工艺分析的基础上,制定了合理的焊接工艺并得以实施。结果表明:采用CO;气体保护焊与富氩气体保护焊相结合的焊接方法,选择正确的放量尺寸、焊接顺序、焊接参数、坡口形式和相应的焊前、焊中及焊后热处理等工艺,完全能够满足结构的设计要求。     

超高层钢结构厚板电渣焊焊接工艺研究

随着建筑钢结构行业的快速发展,超高层建筑钢结构越来越多,箱体是超高层建筑最典型的构件形式。箱体内隔板电渣焊在建筑钢结构中的应用越来越广泛,厚板电渣焊的难度较大。文中通过80 mm厚隔板的电渣焊焊接工艺评定试验,采用焊前预热、焊接工艺参数调整及焊后保温等措施保证了厚板电渣焊的焊接质量,为后续项目厚板电渣焊提供了经验,具有一定的借鉴意义。     

大型斗轮轴的CO2焊

DQL (1200)/(1200)·30型斗轮堆取斗机的斗轮轴,是斗轮中的重要结构件。斗轮轴材质为45钢,由法兰和轴焊接而成,结构见图1。法兰与轴套装后在主轴的端面及外表面形成两道环缝。过去采用手工电弧焊,预热、清渣等交错进行,工作量大,焊后易出现裂纹、夹渣、未焊透等缺陷。为提高焊接质量和工作效率,采用高效、低成本、焊后变形小的CO_2焊焊接斗轮轴。     

热交换器箱体焊缝开裂原因分析

热媒油交换器箱体在焊缝连接处发生开裂、造成漏油,引发了火灾和爆炸。失效分析结果表明,引起热媒油交换器箱体焊缝开理解的主要原因是连接热交换器和箱体侧面钢板的角焊缝坡口设计不合理,靠民焊缝根部严重未焊透;另外,焊接质量不高对此也有一定的影响。     

大型箱体结构件的焊接变形控制研究

对大型箱体结构件焊接变形的种类和原因进行分析,以一个组焊结构件实例进行一系列防止焊接变形的控制研究,并在实际生产中得到验证,总结出控制此类结构件焊接变形的措施,为提高生产效率,减少返工具有指导意义。     

A型电力机车变压器箱体组焊工艺分析

本文主要分析TA型机车变压器箱体的结构特点和使用性能，通过对焊接方法、焊接材料及组焊工艺等方面进行研究和实践，总结出合理的焊接规范，并对制造过程中出现的工艺难点，采取了相应的工艺措施，确保产品的制造质量。     

T型接头单面焊三面成型

我厂生产的水泥车水箱,箱体结构见图1。箱体四周的两块壁板与中间的一块隔板形成了两道对接焊缝与四道角焊缝。壁板与隔板的材质为A_3,厚3毫米。以往用手工电弧焊焊接,生产效率低,焊接变形大。我们学习兄弟单位的经验,经过反复试验,用埋弧焊进行单面焊三面成型的焊接,并把水箱结构改成图2形式。将原来手工焊需要八     

32MPa注水泵上箱体焊接质量控制

32MPa 注水泵是兰州石油机械厂研究所开发的油田注水新型设备。将水加压到32MPa,然后注入地下,以提高原油产量。其中注水泵箱体是焊接结构,分上箱体和下箱体,上箱体结构复杂,下箱体则比较简单,箱体分别由20mm、30mm、50mm、60mm 不同厚度的钢板组焊而成,材料全部是 A3钢。上箱体外形尺寸是1980mm×1620mm×1430mm,结构见图1。     

薄壁箱体结构的MIG钎焊技术应用

介绍了MIG钎焊焊接薄壁箱体结构的技术应用研究情况,针对MIG钎焊技术特点、与传统的CO_2气体保护焊参数对比分析。主要介绍了2种不同的焊接方法,通过对2种典型零件焊接、技术参数选取、实施过程和方法的应用、焊接变形情况分析及评价,最终得出结论:MIG钎焊在薄壁件焊接上具有一定优势。     

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.     

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.