呋喃树脂砂和油——尿烷树脂砂的常温性能和高温性能

本报告介绍两种自硬粘结剂的比较结果。(低氮呋喃树脂和油—尿烷树脂)。讨论的中心是不同的砂子,热压强度和发气性问题。控制催化剂的加入量,使自硬砂的起模时间在45—60分钟的范围内,然后测定它们24小时的抗压强度。与尿烷树脂相比,呋喃树脂能在它和砂子的交界面上产生较高的粘结力,而且比较容易润湿砂子的表面。为了减少树脂的加入量,树脂砂使用的原砂,建议采用一种干式再生砂,这种干式再生砂在砂子的表面上残留一层光滑的树脂膜。根据树脂在1000℃分解之后的残留含炭量,可以推测尿烷树脂的热强度比较低。残留含碳量是根据树脂在1000℃分解生成的气体组成中计算出来的。与尿烷砂芯相比,呋喃砂芯含水分较高,(推算50％),氢气和碳氢化合物在分解气体中的含量较低。在1200℃时,尿烷树脂砂芯在4分钟内的发气量为总发气量的90％,而呋喃树脂砂芯在4分钟内的发气量的50％。在400℃时,尿烷树脂砂芯在8分钟内的发气量只有总发气量的40％,而呋喃树脂砂芯在8分钟内的发气量达总发气量的80％。     

响应面法优化3D打印呋喃树脂砂工艺条件

呋喃树脂砂的工艺性与3D打印复杂砂型的性能直接相关。在单因素试验的基础上,确定了树脂加入量、固化剂加入量、固化温度和固化时间4个因素的水平范围,选择呋喃树脂砂的抗拉强度作为响应值,通过响应面分析(RSA)优化呋喃树脂砂的工艺条件。预测结果表明,呋喃树脂砂的最佳工艺条件:树脂加入量为3.6%,固化剂加入量为27%,固化温度为120℃,固化时间为61min。试验证明,优化工艺条件下呋喃树脂砂的抗拉强度为1.59MPa,与预测值接近。     

固化剂自动控制仪在自硬砂造型线上的应用

在酸硬化呋喃树脂砂造型线上配置固化剂自控仪，再生砂的树脂加入量为砂质量的0．65％-0．85％，A＋B固化剂加入量为树脂质量的30％～40％，解决了自硬砂造型中再生砂砂温对固化速度影响的问题，保证了铸型和砂芯的品质。     

自硬呋喃树脂残留抗压强度的试验研究

通过试验研究确定了呋喃树脂残留抗压强度试样的制备方法,并取少量呋喃树脂进行热重-质谱联用检测,得出DTG曲线和MS曲线,进而研究温度对呋喃树脂残留抗压强度的影响规律.结果表明:呋喃树脂固化过程的剧烈热效应是其难以制样的原因,可以采用冰水冷却处理的方法对其进行制样;在不同温度下测量呋喃树脂的残留强度,发现呋喃树脂的残留抗...     

日本对呋喃树脂再生砂的日常管理

呋喃树脂砂由于树脂加入量少，浇注时被烧去一部分树脂以及树脂固化膜的抗剪强度不高，因此可比较容易地用气流对抗、气力浮动、粒间摩擦、砂轮研磨、磨盘研磨等多种形式的砂处理设备进行干法再生，再生率可达９０％～９７％，再生砂树脂加入量可降至０．６％～１．６％。...     

水玻璃砂添加剂对溃散性及铸钢件粘砂缺陷的影响

为了改善CO2水玻璃砂溃散性差、铸件粘砂等问题,研制了一组添加剂,并采用了自制的吹气装置。结果表明:在水玻璃砂中加入配制好的添加剂后,溃散性得到明显改善,各温度下的残留强度较未加入添加剂情况下有了大幅下降,尤其是600℃以上高温残留强度改善更为明显。另外,此添加剂还可促使铸钢件与砂型界面发生适度烧结,形成易于剥落的烧结壳,有利于获得表面光滑不粘砂的铸件。     

木质素改性呋喃树脂性能研究

研究对比了木质素改性呋喃树脂与传统呋喃树脂的性能差异。结果表明,木质素改性呋喃树脂砂与传统呋喃树脂砂的24 h终强度和发气量相近,且木质素改性呋喃树脂砂在低固化剂含量下即可获得较高强度,减少了固化剂的用量,改善了车间环境,适宜进行生产应用。     

聚氨酯砂改性工艺研究

采用红外光谱技术研究了聚氨酯砂的固化反应机理, 通过向聚氨酯砂中加入呋喃树脂砂进行改性处理, 并采用热失重及扫描电子显微分析技术研究了聚氨酯砂的改性机理。结果表明, 聚氨酯砂中加入呋喃树脂砂以后, 由于在高温下树脂膜分解速度下降, 高温强度得到提高。呋喃树脂砂合适加入量为１０ ％ , 改性聚氨酯砂具有良好的综合性能     

原砂粒度、树脂加入量对呋喃树脂砂强度的影响

树脂砂强度直接影响到铸件品质。树脂砂强度受到多种因素影响,其中,原砂粒度、树脂加入量对呋喃树脂砂的强度有着非常强烈的影响。通过对不同树脂固化剂加入量以及不同原砂粒度的试样强度进行分析,同时利用扫描电镜分析树脂砂粘结、断裂机理,研究了上述因素对呋喃树脂砂强度的影响。结果表明,粘结桥间的气孔将直接影响到树脂砂强度,树脂添加量在1.25%~1.75%时,树脂砂强度较好。原砂粒度较小时,粘结桥容易与原砂发生剥离,降低树脂砂强度。     

苏州市兴业化工厂

本厂最新推出的高科技产品——高强度环保型自硬呋喃树脂具有6大优势。1 可降低树脂加入量，使铸件生产成本大幅度降低 高强度环保型自硬呋喃树脂采用全新工艺合成，强度大幅提高，在保诋砂型（芯）同等强度前提下，可降低树脂加入量10％-20％；同时由于该新型树脂固化速度快，可减少固化剂的加入量。因此使用该树脂能大幅度降低铸件的生产成本。     

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.