风电轮毂用低温球墨铸铁的疲劳性能研究

通过控制铁水成分配比并采用脱氧工序,试制了一种可用于风电机轮毂的非标低温球墨铸铁。研究了基体组织和石墨形态对该球铁疲劳强度和断裂韧度的影响。结果表明,该球铁的这两种性能均达到了QT400-18球铁的水平;该球铁能达到符合要求的疲劳性能的显微组织为:珠光体含量<5%的铁素体基体,Ⅵ型球状石墨+Ⅴ型团絮状石墨,石墨尺寸≥6级,石墨球化级别≤3级。     

基于石墨畸变机理的大断面球墨铸铁断口形貌及组织结构分析

以大断面球铁铸件为研究对象,研究了石墨的畸变机理。分析了电炉熔炼大断面球铁试样的化学成分和显微组织结构。结果表明,基体上白色异性相为氧化物夹杂,该氧化物夹杂可能会引起晶间断裂,降低大断面球铁铸件的力学性能。     

用超声波试验评价铸铁

铸铁的机械性能和显微组织可以用超声波测量和图象分析仪测定。超声速度随着石墨从球状演变到片状而降低。区分高强度铸铁(如球铁、具有球墨的蠕铁)与灰铁以及典型蠕铁的速度值约为5300米/秒,在声速≥5300米/秒,石墨形状系数K≥35%的情况下,声速与石墨形状系数之间存在着线性关系,如基体中珠光体数量不变,机械性能与超声速度之间也存在着精确的线性关系。具有相同石墨形状的铸铁,其基体中的珠光体数量可以通过硬度试验来检查。超声速度测量和硬度试验结合对间接测量不同石墨和基体结构的高强度铸铁的抗拉强度来说是最满意的方法。     

铸态S195柴油机球铁曲轴的生产和使用可靠性

获得珠光体球铁有效而简便的方法是添加稳定珠光体的合金元素。我们曾在实验室中研究了铜、锑和锰对铸态球铁机械性能和基体组织的影响。铜(0.3～0.4％)均匀地分布在基体组织中,能稳定珠光体又不促进碳化物的形成,既提高球铁的强度和硬度,又不致引起脆性,对石墨球化亦无影响     

低蠕化率蠕铁与球化不良及衰退球铁的区别

详细介绍了低蠕化率蠕铁、球化不良球铁及球化衰退球铁的区别。金相组织的区别是:低蠕化率蠕铁的球状石墨圆整,蠕虫状石墨粗短,只有极少量的团絮状石墨,没有片状石墨,基体组织细密;球化衰退的球铁石墨形态恶化,开花状石墨和团絮状石墨较多,严重时有片状石墨,组织粗大;球化良好的铸铁,球墨圆整,极少团絮状和蠕虫状石墨,没有片状石墨,组织细密。力学性能的区别是:球化衰退球铁的力学性能已明显下降,低蠕化率蠕铁的力学性能则远高于规定要求,如果采用适当的热处理方法,在冷热交变环境下服役能显示优异性能,因此,不能笼统地将其判为废品。     

铸态珠光体球铁QT800—2的试制研究

经过工艺性试验,提出了获得QT800—2铸态珠尤体球铁的成份和工艺,并研究了二者对其组织、性能的影响;另外,还对铸态QT800—2材质的断裂韧性KIc进行了测量和评价,采用俄歇电子探针分析揭示了铜、锡在球铁基体与石墨球界面的分布.     

高硅铁素体球墨铸铁的组织及性能

制备了含硅量达到4.0％以上的高硅铁素体球墨铸铁,采用光学显微镜及电子万能拉伸试验机研究了其显微组织及力学性能,并通过X射线衍射仪(XRD)半宽高法测定了其铁素体基体的晶格常数.结果表明:含硅量为4.0％～4.1％时,高硅铁素体球铁的基体组织为全铁素体,石墨数量多、石墨球细小圆整;球铁的抗拉强度达到608～626 MP...     

稀土镁球墨铸铁问答(三)

六、球铁热处理是怎么回事?问:您再说说,提高球铁机械牲能,需要从那方面入手?答:前面谈过,铸铁中的一对主要矛盾是基体与石墨。灰茬铁中由于片状石墨影响性能是主要的,石墨是矛盾的主要方面。球铁中石墨呈球状以后,基体对球铁性能的影响是矛盾的主要方面。所以,提高球铁性能须从石墨和基体两方面下功夫。     

硬环组织球墨铸铁

近几年,呼吁改善球铁的强韧性,就石墨组织而论,虽然研究了球墨数量和球径的影响;在基体组织方面,虽然研究了合金元素的影响,贝氏体化,通过热处理获得微细双相混合组织的强化法,但尚未见到考虑降低强度低的石墨相的补强方法。作者从与以往完全不同的观点出发,研究了比基体组织硬而强的第二相,成环状地包围石墨,通过补     

稀土球铁中Ce的分布及作用

用定向凝固和电解萃取—放射性同位素测量技术,分析了球化剂Ce在球铁各相中的分布;配合测量石墨球化率,确定了球铁含Ce量与石墨球化程度的关系,结果表明:Ce在球铁中主要以合金化Ce的形式存在,但石墨相Ce含量是石墨球化程度的表征值;只有当石墨相Ce含量高于一定值时,石墨才能完全球化。     

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.