过热对铁液质量和激冷铸铁凸轮轴组织的影响

研究了1t中频炉铁液过热对铁液质量和激冷铸铁凸轮轴组织的影响。结果表明:随着过热时间的延长,化学成分中碳的烧损严重,其余元素变化不大,铁液白口倾向加大;铸件D、E型石墨数量增多,基体碳化物含量增多。在实际生产过程中,适宜的过热温度为1550℃以下,过热时间应控制在1h内,超过1h需采用补加生铁或增碳剂来增碳、降低白口倾向。     

工频电炉熔化冷硬铸铁轧辊铁液的工艺探讨(摘要)

与冲天炉熔炼相比，工频炉熔炼可能遇到的问题是：（１）熔化在氧化气氛中进行，当过热时间长时，会发生脱碳，影响铁液的白口倾向。（２）高温铁液长时间与炉衬接触会导致炉衬中ＳｉＯ２，被还原出Ｓｉ，后者进入铁液，提高其含Ｓｉ量而减弱冷铁的白口倾向。（３）铁液过热时间比冲天炉熔炼长，过热温度亦较高，容易破坏原生铁的激冷遗传性。（４）有降硫倾向，对铁液白口倾向亦有影响。为此应注意：１）应采用激冷性较好的炼钢生铁；２）应采用小块料，一次加满炉膛，熔化开始后要勤加料，避免铁液早期过热、脱碳、增硅；３）为减少降硫，…     

共晶度对灰铸铁组织和性能的影响

研究了铸件壁厚为２５ｍｍ时，共晶度及碳当量对铸件抗拉强度、硬度及珠光体含量的影响。结果表明，在共晶度为０．９０７～０．９７５范围内，抗拉强度、硬度及珠光体含量均随共晶度增大而降低。建立了抗拉强度——共晶度及硬度—共晶度的回归方程。     

熔体温度处理对Al-25%Si合金凝固特性及组织的影响

研究了熔体温度处理对Al-25%Si合金形核温度、结晶潜热和凝固组织的影响。结果发现:随熔体过热温度的升高,Al-25%Si合金的初生相转变温度和共晶相转变温度逐渐降低;合金总的潜热值和初生硅颗粒平均尺寸随过热温度的升高先增大后减小,在960℃达到最大值。熔体过热温度不超过960℃时,初生硅颗粒平均尺寸和总的潜热值随保温时间的延长而增大,并且其小平面生长特征增强;反之,熔体过热温度超过960℃时,两者都随过热温度的升高和保温时间的延长而减小,并且初生硅的小平面生长特征减弱。     

通过加增碳剂方法生产HT250铸铁

为降低生产成本,稳定生产HT250材质的机床铸件,采用了一种不经孕育处理的生产工艺.通过调整碳量、控制铁液的化学成分,将碳含量控制在3％～3.6％之间,提高铁液温度及保温时间,过热温度在1 450℃以上时,保温时间控制在15 min以内,可以保证试样抗拉强度在250 MPa以上.经生产验证,不经孕育处理的HT250材质铸铁的铸造性能及加工性能都很好,完全满足技术要求,且降低了成本.     

康明斯凸轮轴国产化的试验

０引言在生产凸轮轴的众多方法中，冷硬铸铁具有成本低，工序少，加工周期短，零件使用寿命长等优点，但冷硬铸铁生产有一定的难度，它要控制白口层冷硬深度、冷硬层内渗碳体量及形态分布，还有非冷硬部分的加工性能，因此需选择一个最佳的控制范围。为了达到康明斯技术条件，必须合理地选择化学成分，加强孕育、控制浇注温度、浇注时间和铁液停留时间，选用冷硬效果好的材料，优化设计冷铁尺寸、结构等。１合理地选择化学成分为了获得较高的白口层硬度，碳含量应为３．２０－３．６％。硅对白四层硬度无明显影响，随含硅量提高硬度稍有下降…     

过热温度和保温时间对镍硬白口铸铁组织的影响

通过对化学成分（WB／％）为：C3．0～3．5，Si0．5～1．0，Mn0．5～1．0，Ni4．0～4．5，Cr1．0～2．0，Mo0．2～1．0的镍硬白口铸铁铁液进行过热和保温，研究过热温度和保温时间对该材料的石墨数量和碳化物数量的影响。试验结果表明：（1）石墨含量的变化规律：在1460℃的温度下，保温30min，组织中含有1％的石墨；在1480℃的过热温度下，随着保温时间的延长，组织中的石墨逐渐消失；在1500℃及以上的过热温度下保温时，组织中没有石墨出现；（2）碳化物含量的变化规律：随着过热温度从1460℃到1480℃、1500℃、1520℃碳化物数量逐渐增加，在1500℃以上过热保温时，碳化物数量保持不变。     

共晶碳化物对白口铸铁热塑性的影响

通过对白口铸铁锻造裂纹的断口分析及锻造温度范围内不同温度下水淬白口铸铁宏观硬度及组织变化的研究,对共晶碳化物在不同锻造温度下形态、数量的变化对白口铸铁的热塑性的影响规律进行了探讨。结果表明,共晶碳化物是影响白口铸铁热塑性的主要因素;白口铸铁加热至950℃时,共晶碳化物开始大量分解固溶,导致高温下白口铸铁具有极为良好的塑性,可进行大变形量的锻轧加工。     

120t转炉冶炼枪位的探讨与实践

通过理论分析与工业试验研究硅含量、碳含量以及铁液温度等对120 t转炉炼钢枪位的影响。结果表明,对转炉冶炼枪位影响最大的因素是铁液中的原始硅含量。一般情况下,铁液中原始硅含量越高,过程枪位控制就越高。铁液中的碳含量和铁液温度对枪位也有影响,高碳铁液冶炼枪位比低碳铁液枪位要高出100 mm左右。如果铁液前期温度低,并且硅含量偏低前提下,4 min之前需要降枪至1 600 mm,否则渣中FeO过高,在5 min左右炉内会发生喷溅事故。     

工频电炉熔炼冷硬轧辊的实践与认识

用工频电炉替代冲天炉大批量生产合金冷硬轧辊 ,改变炉料配比 ,获得低硅铁液 ;严格控制铁液温度 ,防止温度过高和延长保温时间 ;熔炼后期在铁液中加入冷料 ,对铁液进行孕育 ,终于攻克工频电炉生产冷硬轧辊白口难以控制的难题     

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.     

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.