封头开裂失效分析

通过理化检测对封头开裂进行失效分析。结果表明,封头开裂起源于气割面,气割面存在严重的氧化脱碳现象,脱碳层上存在密集的微裂纹和非金属氧化渣,表明气割产生的氧化脱碳层在内应力和外应力的作用下引起了封头的贯穿性开裂。     

实践中再谈不锈钢封头的冷成形开裂

卢忠敏曾在2011年第一期《锻造与冲压》发表了《为什么不锈钢封头会开裂》一文。此文虽然为行业内解决冷成形奥氏体不锈钢封头成形中的开裂及成形后的延迟开裂提供了一定的借鉴,     

304不锈钢封头应力腐蚀开裂失效分析

通过化学成分、金相组织、马氏体含量、扫描电镜观察和能谱分析等手段,对某304奥氏体不锈铜容器封头开裂原因进行了分析.结果表明:封头开裂属于形变马氏休和氯离子共同作用引起的应力腐蚀开裂.提出了相应的改进措施.     

空调四通换向阀失效分析

空调四通换向阀是空调温控的主要器件之一，在水压试验过程中，发现一定比例的空调四通换向阀产品漏水失效，给企业的正常生产带来干扰和重大的经济损失。对失效产品进行检查、分析发现空调四通换向阀中的不锈钢封头有开裂，封头采用进口铁素体不锈钢棒材。本文通过金相、SEM、EDAX等先进显微分析技术，发现铁素体不锈钢棒材内部有大量的沿轴向分布的硫化锰夹杂物。空调四通换向阀失效是封头的开裂引起的，而封头的开裂与封头材料内部有大量轴向分布的硫化锰夹杂物有关。     

燃油-液压油散热器泄漏失效分析

燃油-液压油散热器在使用过程中发生了泄漏。通过宏微观形貌观察、金相检查和焊缝熔深测试,确定了燃油-液压油散热器的泄漏性质及原因。结果表明：出口封头与壳体焊缝处的周向裂纹为疲劳裂纹,未焊合焊接缺陷的存在是导致其疲劳开裂的原因;壳体拼接焊缝处的轴向裂纹也为疲劳裂纹,焊接气孔缺陷的存在和焊缝熔深不足是导致其疲劳开裂的原因。燃油-液压油散热器泄漏是由于出口封头与壳体焊缝发生疲劳开裂造成的,壳体拼接焊缝发生疲劳开裂会造成壳体表面出现鼓胀,进一步增加了出口封头与壳体焊缝处的张应力,对最终的散热器泄漏起到促进作用。     

爆炸焊不锈钢复合钢板封头裂纹成因及解决方法

对16台大型爆炸焊不锈钢复合钢板制压力容器进行检验,发现14台容器封头内部存在大量裂纹,通过宏观检查、硬度测试、金相检测、磁记忆检测、介质组分分析等方法,确定封头内壁裂纹属应力腐蚀裂纹。磁记忆检测出裂纹发生的部位均为高应力区,与介质中含有的敏感性F~-、Cl~-共同作用导致应力腐蚀开裂的发生。对封头产生的高应力进行了分析,对大型复合钢板封头的选取及裂纹的处理提出了建议。     

SA516Gr70钢大型拼焊封头焊接工艺研究

介绍了SA516Gr70钢大型封头的拼焊工艺.研究了退火温度对力学性能的影响及焊接线能量对焊接接头韧性的影响,并对选用的SA516Gr70钢焊接材料进行了焊接接头的抗硫化物应力腐蚀开裂(SSC)试验及H2S环境氢致开裂(HIC)试验.通过SA516Gr70钢焊接试板试验,确定了SA516Gr70钢大型拼焊封头成型后正火...     

乙二醇装置蒸发器凝液罐封头腐蚀原因分析

某乙二醇厂乙二醇装置蒸发系统的封头直边处内、外表面出现大量裂纹。采用光谱仪、金相显微镜、扫描电镜和X射线衍射仪对该封头材料的成分、显微组织、腐蚀状况、裂纹进行了的分析。结果表明,封头材质为0Cr18Ni9不锈钢;内、外表面出现裂纹的原因是Cl-在封头直边处的形变马氏体组织中富集发生点蚀,进而引发材料的应力腐蚀开裂;马氏体的选择性溶解促进了裂纹扩展。据此提出了合理的热处理和选材建议。     

重油催化氨精制塔塔底封头失效分析

分析了重油催化装置的氨精制塔塔底封头开裂原因,发现母材３０４不锈钢由于冷却加工（旋压）工体相变,在湿硫化氢的环境下,含形变马氏体的３０４不锈钢发生了湿硫化氢应力腐蚀开裂（ＳＳＣＣ）,文中提出了防护措施。     

SYP-15液化罐封头冲压件开裂分析

本文利用断口扫描电镜分析、金相分析、微区成分分析、应力测试和金属薄膜透射电子显敞分析等方法对SYP-15液化罐封头(冲压件)开裂问题进行了系统分析,得出了该冲压件发生开裂的原因,并提出了改进的措施。     

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.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。