20G硬度与球化关系研究及寿命评估新方法

通过采用高温加速时效的方法模拟20G炉管珠光体球化的演变过程并测试不同球化程度下的硬度,结合现场检测对电站锅炉20G炉管进行硬度和球化程度分析。基于Matlab软件模拟建立硬度与珠光体球化之间的关系模型,提出20G珠光体的球化与温度和时间之间的关系公式,进而提出一种简捷有效的电站锅炉炉管寿命评估方法。     

20g钢珠光体球化过程的分析

以广泛应用的20g钢为例,采用高温加速球化法模拟该钢的球化过程,使用"原位"观测法对既定的珠光体区域进行连续观察,并对珠光体球化变化的过程进行了微观机理分析和能量角度分析。实验结果表明了珠光体在球化过程中的自相似性和能量变化特点。     

15CrMo钢珠光体球化对性能的影响

采用高温加速时效的方法模拟15CrMo钢珠光体球化的演变过程,测试了不同球化等级15CrMo钢的室温及高温力学性能。结果表明,在高温时效过程中,随着保温时间增加,珠光体球化程度提高,使材料的抗拉强度和屈服强度降低;球化减少了铁素体基体的固溶元素,使材料硬度降低。     

15CrMoG钢管的寿命评估新方法

采用高温加速时效的方法模拟15CrMoG钢管珠光体组织球化的演变过程并测试不同球化程度下的布氏硬度,结合现场检测对电站锅炉15CrMoG钢管进行硬度和球化程度分析。基于Matlab软件模拟建立硬度与珠光体球化之间的关系模型,提出15CrMoG珠光体组织的球化与温度和时间之间的关系公式,即温度和时间对组织球化进程的影响,进而提出该钢管寿命评估的新方法。     

12Cr1MoVG钢硬度与球化关系研究及其寿命评估

采用高温加速时效的方法模拟12Cr1MoVG钢管珠光体(贝氏体)组织球化的演变过程并测试不同球化程度下的布氏硬度,结合现场检测对电站锅炉12Cr1MoVG钢管进行硬度和球化程度分析.基于Matlab软件模拟建立硬度与珠光体(贝氏体)球化之间的关系模型,提出12Cr1MoVG珠光体(贝氏体)组织的球化与温度和时间之间的关系公式,进而提出该钢管寿命评估的新方法.     

高温条件下20G炉管材质的性能研究

采油注汽锅炉是油田开采稠油的专用注汽设备,其炉管材质常用20G耐热钢。为了预防采油注气锅炉爆管事故的发生,对炉管材料20G钢在高温使用过程中的组织和性能进行研究。利用20G试件在不同温度下退火试验,分析20G在高温下长时间使用过程中的组织和硬度变化特点,研究其球化状态与硬度与劣质化程度的关系,从而有效控制20G钢的工作环境,保证它的有效寿命。     

长时运行高温过热器12Cr1MoV钢寿命评估

以长时运行高温过热器12Cr1MoV钢为研究对象,采用金相检验、扫描电镜、硬度和拉伸性能测试等手段对其组织形貌、化学成分和力学性能进行分析。结果表明,长期高温服役的取样管珠光体球化达到4.5级,碳化物呈链状聚集分布,存在蠕变孔洞和沿晶裂纹,微观组织劣化严重。微观组织劣化越严重,硬度越低,抗拉强度越低,综合力学性能越差。内壁氧化层厚度与微观组织劣化程度无关。运行过程中取样管的当量温度已接近该材质规定的上限温度,取样管剩余蠕变寿命均大于40 000 h。     

软化处理对ZG95Cr17Ni2不锈钢组织及硬度的影响

利用扫描电镜、能谱分析、洛氏硬度计等测试手段,研究了ZG95Cr17Ni2马氏体不锈钢在普通退火、等温球化退火、高温回火+等温球化退火种处理工艺下组织及硬度的变化。结果表明,3种处理后的组织均由珠光体+莱氏体+碳化物组成,其中前两种处理后的基体主要由片状或不均匀粒状珠光体组织组成;而经高温回火+等温球化退火处理后的基体主要由均匀细小的粒状珠光体组成。采用普通退火、等温球化退火后的ZG95Cr17Ni2不锈钢硬度(HRC)为36～46,经过高温回火+等温球化处理后的硬度降至29。     

中碳碳素结构钢S55C的球化退火工艺

对S55C钢进行了不同工艺的球化退火处理,研究了所获得的组织和硬度.结果表明,S55C钢经740℃保温5 h,以≤20℃/h的冷速缓冷至700℃保温5 h,再以≤40℃/h的冷速缓冷至680℃保温5 h后空冷,得到的组织为球状珠光体,珠光体球化率≥90％,硬度值165 HBW,符合客户使用要求.     

铬含量对中碳锰铬钢珠光体相变组织和性能的影响

采用热膨胀仪测定了含Cr量分别为1 mass%和2.5 mass%的中碳锰铬钢55Mn2Cr、55Mn2Cr3的过冷奥氏体连续转变曲线,结合组织观察、硬度测定、动力学分析、热力学计算等研究了Cr元素含量对中碳锰铬钢珠光体相变过程、组织和硬度的影响。研究表明,55Mn2Cr3钢较高的淬透性和较大珠光体球化倾向缩小了其片状珠光体转变区;55Mn2Cr钢能在较宽冷速范围内、较低温度下获得细片珠光体,硬度330 HV左右。     

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。