多品种铸件湿型砂生产控制工艺探讨

在湿型砂铸造过程中，型砂性能优劣直接影响到铸件的品质。针对由于型砂控制工艺比较单一，造成型砂性能波动大、铸件表面质量差、铸造缺陷增多等问题，通过试验摸索出分机型制定不同型砂物料加入量和旧砂除尘量，以稳定型砂中有效成分含量，使型砂性能波动减小，最终达到减少铸造缺陷的目的。     

湿型砂造型中型砂质量的控制

介绍了湿型砂各组分的作用.论述了型砂性能与其组分的关系,并指出控制好有效膨润土量和有效添加剂量是控制型砂质量的关键,结合生产实例阐述了型砂质量的控制要点.指出提高型砂质量控制水平、生产优质铸件和实现铸造生产循环用砂是铸造生产节能减排的有效方法.     

湿型砂造型中型砂质量的控制

介绍了湿型砂各组分的作用,论述了型砂性能与其组分的关系,认为控制好有效膨润土量和有效添加剂量是控制型砂质量的关键,结合生产实例说明了型砂质量的控制要点;指出提高型砂质量控制水平、生产优质铸件和实现铸造生产循环用砂是铸造生产节能减排的根本方法之一。     

消失模铸造砂处理系统的设计与应用

根据选矿和化工热交换原理，设计了一套适合于负压实型铸造的砂处理系统。该系统设备投资少、生产运行成本低，既可满足消失模铸造型砂的各项技术指标要求，还可根据生产铸件的特殊要求，灵活地调节型砂使用温度，从而满足产品的质量要求。该系统可解决消失模铸造砂处理系统中普通存在的投资大、能耗高、噪音大、维修量大且维修不方便的弊端。     

湿型用防粘砂、抗夹砂附加物的研究

煤粉是湿型铸造时常用的防止铸件粘砂、夹砂，提高铸件表面质量的附加物。但是，由于煤粉危害环境，损害型砂的某些性能，所以国内外相继开展了煤粉代用材料的研究。本文采用差热分析及光亮碳生成率的测试方法对所收集的几十种材料进行了试验，从中优选出了三种，即R1，R2，R3。其中R1和R2具有高的光亮碳生成率，R3可减小型砂的热彭胀。分别测试了这三种材料加入型砂中后对型砂性能的影响，分析结果可知：它们都提高了型砂的热湿拉强度，延长了型砂的爆热开裂时间，减小了型砂的热压应力，提高了型砂的抗夹砂能力。同时它们并不降低型砂的其它性能。用单纯型重心设计，优选出了这三种材料之间最合适的搭配方案。结果表明；对于手工和普通机器造型，由于膨润土加入量较少（5－6％），采用三组之混合物，即R1、R2和R3，在型砂中加入量为1．5～1．7％，而对于气冲和高压造型，膨润土加入量较多（8～10％），仅R1就可满足要求，在型砂中加入量为0．8～1％。     

薄壁缸体常见铸造缺陷浅析及对策

介绍了生产典型薄壁缸体铸件的技术要求,针对生产过程中先后遇到的冷芯缸体内腔与外表铸造缺陷及防止措施进行了阐述。对于水套内腔局部断芯,可通过使用特种砂替代硅砂,改进水套砂芯涂料工艺,严格控制原砂需酸值,保证砂芯足够强度来防止;对于水套外壁夹砂缺陷,采用天然钠土,减少上箱水套外壁热辐射时间,减少砂芯发气量来防止;对于表面粘砂缺陷,通过细化型砂粒度,增加砂型孔隙阻力,增加砂型气体背压,阻止金属液侵入砂型孔隙,控制旧砂温度与水分,减少铸件热粘砂,调整型砂参数来防止;对于烧结缺陷,减少装配螺钉尺寸,使用特种混合砂,降低油道芯烘干温度,减少油道芯的圆角半径,更改涂料配方来防止。     

环境温度和旧砂温度对生产线用粘土型砂性能的影响

稳定地保证粘土型砂的性能和质量是生产线用粘土砂型铸造生产中的关键问题之一。影响型砂性能的因素很多,其中环境温度和旧砂温度对生产线用粘土型砂性能的影响较大。从江铃铸造厂某造型生产线上现场的环境温度和旧砂温度和型砂性能的检测数据入手,对比分析了生产线上环境温度和旧砂温度变化与型砂性能的关系,跟踪了环境温度和旧砂温度变化对铸件缺陷率的影响;根据该造型生产线目前存在的旧砂温度过高、铸件缺陷率较大现状,提出了改进型砂质量和减少铸件缺陷的建议。     

日本的几种旧砂干法再生装置

一、概况在铸造生产过程中,型砂在高温金属的作用下必然产生下述的变化和带来不良的结果: 1.高温金属的热作用使型砂温度升高而成为热砂(温度超过室温20℃的型砂称为热砂)。热砂中的水分分布不均匀;在输送中产生灰尘;使铸件产生结疤、夹砂以及表面粘砂等缺陷。     

高密度造型型砂的管理

介绍了高密度造型砂处理系统旧砂的质量要求及砂量、微粉、膨润土、旧砂温度和水分等的管理经验 ,阐述了通过型砂组分和型砂性能控制的品质保证方法。     

用染色法检查型砂和旧砂中有效粘土含量的研究

一、绪论铸工车间的旧砂中都含有相当数量的细粉,被烧损的粘土(又称死粘土)、被烧损的煤粉或其他附加物。在旧砂回田时这些粉尘物质就都掺杂在型砂之中,虽然这些粉尘本身不产生粘结力,但是却能使型砂的湿态抗压强度提高。一般湿型铸造生产中都是根据型砂的湿态抗压强度高低而控制粘土加入量。如果型砂中含粉尘量多而含有效粘土量少也仍然显得湿态抗压强度较高,这就会使型砂中含有效粘土的数量过少,型砂的性能变脆,起模性能变     

Influence of metal ions on the formation of artificial zinc rusts

The artificial rust particles were prepared from ZnCl₂ solutions dissolving Al(III), Fe(III), Fe(II), Ni(II), Co(II) and Mg(II) at different atomic ratios from 0 to 0.3 in metal/Zn. With increasing metal/Zn the crystal phases of the products turned following as ZnO → a mixture of ZnO and Zn₅(OH)₈Cl₂ · H₂O (ZHC) → ZHC. Al(III) most facilitated the formation of ZHC but Mg(II) and Fe(III) produced no ZHC. The morphology of the formed particles varied following as agglomerate → fine → rod → sheet → irregular with the increase of metal/Zn. The sheet and irregularly shaped particles were identified as ZHC and the other particles as ZnO.     

Effect of dislocation density on the low temperature aging behavior of an ultra low carbon bake hardening steel

Strain aging was studied in an ultra low carbon (ULC) steel with a total carbon content of 20 ppm (wt.%) in order to identify the process stages and mechanism of bake hardening in this type of steel. The effects of dislocation density, varied by means of uniaxial tensile prestraining (1–10%) on the aging kinetics were investigated within an aging temperature range of 50–170°C. The aging was evaluated by means of strength measurements and the determination of interstitial carbon content after aging using a piezoelectric composite oscillator operating at 40 kHz. The interaction between interstitial carbon and dislocations was examined through amplitude dependent internal friction measurements. The influence of dislocation density on the aging behavior have been discussed with reference to the kinetics and mechanism of the aging process.     

A corrosion study of the main constituent phases of AZ91 magnesium alloys

The different constituents of an AZ91 alloy (α,β, and MnAl phases) were synthesized and their corrosion resistance was studied by electrochemistry in ASTM D1384 water, pH 8.3. The pure phases were characterised through the corrosion potential, the polarisation resistance, and polarisation curves, then systematically coupled to assess the galvanic corrosion occurring in the AZ91 alloy. The aluminium content of the oxide film was obtained by X-ray photoelectron spectroscopy measurements. The corrosion rate of the α solid solution alloys depends closely on their Al content. Aluminium enhances the corrosion resistance of the α-phase through the formation of an Al enriched superficial layer. The β-phase is 150 mV nobler than the α-phase, but their corrosion rates are similar. The galvanic currents are low (below 20 μA cm⁻²) whatever the implemented couples and close to the corrosion current previously measured for the AZ91 alloys.     

Effect of solution heat treatment on galvanic coupling between intermetallics and matrix in AA7075-T6

Susceptibility to localised corrosion is strongly affected by heat treatments performed on Al-Zn-Cu-Mg alloys. In order to study how galvanic coupling between intermetallics and matrix is affected by solution heat treatment, AA7075-T6 and solution heat treated AA7075 have been characterised by means of scanning electron microscopy and scanning Kelvin probe force microscopy. Solution heat treatment strongly increased the Volta potential difference between the intermetallics and the surrounding matrix showing a strong increase in galvanic coupling. This is explained by Zn and Mg enrichment of the matrix caused by dissolution of strengthening particles during solution heat treatment.     

硬质合金Hc、Com、D、HV_3的初步探讨

通过研究硬质合金的矫顽磁力、钴磁、密度和硬度,阐述了这些性能之间的相互关系,以及影响这些性能的主要原因,说明了其对生产实践中质量控制的重要意义。     

Characterizing corrosion behavior under atmospheric conditions using electrochemical techniques

AC and DC electrochemical experiments were performed as a function of humidity and contaminant concentration in an effort to identify the range of atmospheric environments where corrosion processes could be detected and possibly quantified. AC measurements exhibited two time constants at 25% relative humidity (RH), possibly indicating the ability to resolve both electrolyte resistance and interfacial impedance. Galvanic current measurements were sensitive to the presence of Cl_2(g) at 30% RH and electrochemical transients were detected at both 30% and 50% RH levels, also indicating sensitivity to interfacial processes. Higher humidity levels allowed better quantification due to decreasing electrolyte and interfacial impedances.     

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr-Pd and Zr-Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr₇₀Pd₃₀ and Zr₈₀Pt₂₀ alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H₂SO₄ and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H₂SO₄, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.     

A study on the deactivation of an IrO2–Ta2O5 coated titanium anode

The deactivation of an IrO₂–Ta₂O₅ coated titanium anode was studied during an accelerated life test at 2 A cm⁻² in 1 mol dm⁻³ H₂SO₄ solution using CV, EIS, SEM and EDX. The changes of voltammetric charge, double layer capacitance, oxide film resistance and charge transfer resistance of oxygen evolution with time during the electrolysis were monitored. The morphology and surface composition of the oxide anode before and after electrolysis test were analysed. A comprehensive process of deactivation of the oxide anode was proposed based on the test results and analysis.     

加速发展我国的快速成形技术

介绍了第二届北京国际快速成形及制造会议概况，分析了快速成形（RP）技术的发展趋势，指出RP技术研究领域的重大进展及学科发展的主攻方向是：由RP向快速制造（RM）发展，由RP向快速模具（RT）发展，RP技术在生物医学领域的应用。     

Corrosion behaviour of powder metallurgical and cast Al-Zn-Mg base alloys

The behaviour of Al-Zn-Mg base alloys produced by powder metallurgy and casting has been studied using potentiodynamic polarisation in 0.3% and 3% NaCl solutions. The influence of alloy production route on microstructure has been examined by scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectrometry. An improvement in performance of powder metallurgy (PM) materials, compared with the cast alloy, was evident in solutions of low chloride concentration; less striking differences were revealed in high chloride concentration. Both powder metallurgy and cast alloys show two main types of precipitates, which were identified as Zn-Mg and Zr-Sc base intermetallic phases. The microstructure of the PM alloys is refined compared with the cast material, which assists understanding of the corrosion performance. The corrosion process commences with dissolution of the Zn-Mg base phases, with the relatively coarse phases present in the cast alloy showing ready development of corrosion.