改变铸造用酚醛树脂流动性的研究

树脂流动性是影响树脂覆膜的关键因素。为改变铸造用酚醛树脂的流动性能，研究以润滑剂为改性的酚醛树脂，使树脂的流动性由原来的40～60mm提高到80～110mm，同时，减少树脂用量，达到树脂比强度提高和覆膜砂发气量及灼减量降低的目的。     

铸造用高强度改性酚醛树脂覆膜砂的研制

叙述了添加己内酰胺改性剂的树脂合成工艺,测得改性酚醛树脂性能为:软化点85～90℃,聚速50～60 s,游离酚＜6%,粘度40～45 s.介绍了热法覆膜工艺,用SWY型液压强度试验机测定了覆膜砂的抗拉强度和抗弯强度,结果表明:在相同的树脂加入量下与采用未改性的树脂比较,覆膜砂的抗拉强度提高15%,抗弯强度提高20%以上,同时型砂的溃散性得到改善,发气量也降低.     

铸造用改性高强度酚醛树脂的研究

针对目前国内生产的酚醛树脂覆膜砂强度低，树脂用量大的现状，进行了在酚醛树脂中加入以已内酰胺为改性剂和以硅烷为偶联剂的改性实验。结果表明，改性后的酚醛树脂，可以使覆膜砂的强度提高３０％，覆膜砂的韧性也有所提高，并改善其溃散性     

改性苯并恶嗪树脂制备铸造用覆膜砂的研究

合成了改性苯并恶嗪树脂,用其代替酚醛树脂制备铸造用覆膜砂,优化树脂合成和混砂条件,并筛选了六种固化剂。结果表明:苯并恶嗪树脂的最佳改性工艺为添加3%的水杨酸和4%的3-氨基丙基三乙氧基硅烷,ZnCl_2为最佳固化剂;改性后树脂聚合速度是56 s;覆膜砂在230℃下固化4 min时覆膜砂性能最好,其中热态抗拉强度达到0.45 MPa,常温抗拉强度达到1.85 MPa,强度与酚醛树脂混制的覆膜砂相当,且烟小味小。     

原材料对酚醛树脂覆膜砂性能的影响

研究了热塑性酚醛树脂和原砂对覆膜砂性能的影响.结果表明,改性树脂能够大幅度提高覆膜砂的强度;相比于大林砂,宝珠砂能够改善覆膜砂的性能,其冷态比抗拉强度和比抗弯强度分别达到3.16MPa/1%和4.35MPa/1%.适合于高性能覆膜砂的制备;而相比于锆英砂,采用宝珠砂混制覆膜砂具有良好的经济性.     

覆膜砂用酚醛树脂/MMT纳米复合材料制备与性能研究

利用己内酰胺同时作为热塑性酚醛树脂内增韧和蒙脱石（MMT）有机改性剂，通过一步原位插层法制备了改性酚醛树脂／MMT纳米复合材料。结果表明，酚醛树脂能较好地插层至4MMT的片层，用于覆膜砂时，由于树脂强韧性和耐热性的综合改善，覆膜砂的综合性能得到明显提高，特别是当MMT加入量为4％左右时，覆膜砂冷态抗拉、抗弯强度分别提高了25％和30％以上。     

铸造用高强度改性酚醛树脂的研究

目前，部分醋酸树脂覆膜砂强度较低，树脂加入量高，覆膜砂发气量大，壳芯脆性大，薄的复杂壳芯易损坏，不仅成本高，同时也影响铸件质量。为降低树脂使用量，提高覆膜砂的强度，笔者研究了以己内酸胺为改性剂的酚醒树脂，覆膜后壳芯韧性好，抗弯强度高，型砂的溃散性也得到了改善．再在改性树脂中加入偶联剂后，壳芯砂的抗拉、抗弯强度有进一步提高。1改性酚醛树脂且．l原材料工业用苯酚，熔点40．2℃；工业用甲醛，含量为36．6％；工业用盐酸，含量为五％；改性剂为己内酸胺；偶联剂为Allll。1．2树脂合成工艺在低温下将熔化的苯酚投入三…     

覆膜砂性能影响因素的探讨

通过对覆膜过程的分析和工艺试验对比，提出覆膜砂性能的主要影响因素有覆膜设备、原材料（原砂、树脂、固化剂、附加物）及覆膜工艺参数（原砂加热温度、混砂时间、加固化剂时的混合料温度等），提出了用不同软化点树脂按一定的比例混合，用复合固化剂和增塑剂及多筛制砂作原料，可以提高覆膜砂性能的观点。     

原砂及树脂加入量对覆膜砂性能的影响

以硅砂和宝珠砂为原砂、酚醛树脂为粘结剂制备覆膜砂,研究了原砂种类、粒度以及树脂加入量对覆膜砂性能的影响.试验结果表明:在原砂粒度为50～200目范围内,制备条件相同条件下,覆膜宝珠砂的强度是相同粒度覆膜硅砂的1.2～1.6倍;原砂太粗或者太细,覆膜砂强度一般,100/50目的覆膜砂强度相对较高;当树脂加入量为0.8％～...     

湿态覆膜砂壳型铸造曲轴粘砂的防止

分析了湿态覆膜砂壳型铸造曲轴粘砂的原因,确定该粘砂缺陷主要为机械粘砂。通过将射砂压力从0.2～0.25 MPa提高至0.3～0.4 MPa;控制成型性指数在93%～97%,调整流动性到15～22 g以提高湿态覆膜砂的充型能力;调整制壳温度为220～250℃;调整挡砂板与射砂板的间隙为8～12 mm使射砂过程更流畅;加强对覆膜砂原砂和树脂质量的控制等措施后,解决了湿态覆膜砂壳型曲轴的粘砂问题。     

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.     

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.