湿砂型铸铁件的砂孔和渣孔缺陷--湿砂型铸铁件缺陷讲座(二)

湿砂型铸铁件产生砂孔和渣孔缺陷的主要原因是：(1)芯头或砂台的间隙偏小；(2)浇注时铁液清渣不良；(3)砂型：表面耐铁液冲刷性能较差；(4)脱模剂使用不当；(5)手工开挖浇注系统；(6)型砂强度和韧度欠佳。对影响型砂强度和韧度的因素进行了分析，并提出改进方向。     

铸铁件粘砂缺陷的研究

按合金种类研究铸件缺陷可深化研究内容；深入研究铸铁粘砂缺陷肯定化学粘砂不会在铸件上出现。机械粘砂的主要影响因素是接触角和砂型空隙尺寸。铸铁件粘砂可以预测，从而在工艺设计中拟具措施防止。     

水玻璃砂生产高铬铸铁件粘砂之成因和消除

用水玻璃砂生产高铬铸铁件产生的粘砂主要是机械粘砂，其主要原因是：高铬铸铁流动性好，浇注压头高；铁水保持高温液态时间长；砂粒粗，孔隙大。水玻璃砂中添加细粉状附加物，是消除粘砂的有效措施。     

电饼铛发热盘渣孔缺陷的控制

通过目测铸件产生的缺陷与渣孔的理论特征对比,确认了电饼铛发热盘的缺陷为渣孔.结合现场实际操作并逐一分析,确定了产生的原因,采取了控制措施,消除了缺陷.结果表明:充分精炼、变质处理和挡渣浇注是消除离心铸造铸铝件渣孔的根本措施.     

水玻璃砂生产高铬铸铁件粘砂之成因和消除

用水玻璃砂生产高铬铸铁件产生的粘砂主要是机械粘砂，其主要原因是：高铬铸铁流动性好，浇注压头高；铁水保持高温液态时间长；砂粒粗，孔隙大。水玻璃砂中添加细粉状附加物，是消除粘砂的有效措施。     

湿型铸铁件生产中一些与型砂有关的问题解答(三)--与气孔、砂孔、渣孔缺陷有关的问题

1．某厂用挤压造型线生产铸铁小件．用冲天炉熔化铁液．浇包中使用干砂作为聚渣剂，铸件表面有米粒状砂孔（渣孔？）废品较多．请问如何解决？ 铸铁件产生砂孔、渣孔和气孔是比较常见的。气孔的孔洞基本上是空的，而砂孔和渣孔中间有砂子和渣子充满。只有当孔眼较大，凭眼睛观察孔眼中夹杂物的色泽才有可能分辨出来是砂子还是渣子。浇包中不可避免会有炉渣漂浮在铁液面上。     

微型汽车发动机曲轴箱砂孔缺陷的分析与消除

砂孔是发动机曲轴箱的主要缺陷之一,常见于曲轴箱的下箱,内腔亦有少部分。以LJ465Q-1A曲轴箱毛坯为例,分析了砂孔的成因及采取的措施。     

用钛渣砂做大型铸钢件抗粘砂材料的研究

钛渣是以Ａｌ２Ｏ３为主要成分的冶钛残渣，具有很好的高温化学稳定性，与金属液的润湿角以及其线膨胀系数、导热系数、蓄热系数等热物理参数均与铬铁矿砂相似，电镜照片显示，浇注后的钛渣砂与金属液接触表面会出现一层极薄、极稠的富集液相，能堵塞住砂粒间缝，阻止金属液向砂型内渗透，起到抗粘砂作用。生产应用表明，钛渣砂成本低，是一种具有开发价值的较为理想的大型铸钢件生产用的抗粘砂材料。     

湿砂型铸铁件的夹砂缺陷--湿砂型铸铁件缺陷讲座(三)

介绍夹砂缺陷的特征及其形成机理。防止夹砂缺陷的主要措施是降低型砂的膨胀应力和提高型砂的热湿拉强度。介绍活化膨润土的简易鉴别方法和膨润土的活化技术。     

湿砂型铸铁件的粘砂缺陷--湿砂型铸铁件缺陷讲座(一)

介绍湿砂型铸铁件机械粘砂和化学粘砂的区分方法，各种因素对机械粘砂的影响，包括：砂型紧实度、浇注温度、型砂的粒度和透气性、砂型涂料等。煤粉是防止粘砂和改善表面光洁度的主要型砂加入物。对煤粉的质量、有效煤粉含量、煤粉的代用品以及煤粉的补加量等问题进行了详细的的分析讨论。     

Grey cast iron cast in shell and sand moulds: relationship between tensile and wedge strengths

The tensile strength S_t of grey cast iron can be calculated from measurement of wedge strength S_c by using a linear relation between both variables: S_t = AS_c-B. The coefficients A and B depend on the casting process, the geometry of wedge penetration tool and specimen, and also on the device used to perform the wedge penetration test. Low alloyed grey cast irons of FL15, FL20, FL25 and FL30 basic materials have been cast in shell and sand moulds, at two different pouring temperatures and with and without inoculation. These changes in the process produce large variations in the structure and mechanical strength of the materials. Although these variations are important, the relationship between tensile and wedge strengths can be well described by an equation of the above mentioned type with a unique pair of values for coefficients A and B. IJCMR/453     

Post-perforation external corrosion of cast iron pressurised water mains

The corroded external surfaces of older cast iron water mains buried in soils for many decades usually show a rough undulating topography. Sometimes, there also are areas of relatively smooth topography similar to uniform corrosion but over undulating surfaces. Investigations show this pattern is associated with localised pipe-wall perforation and sometimes pipe fracture. It is proposed that corrosion pitting from the outside surface of the pipe perforates the pipe-wall, allowing fresh oxygenated drinking water from inside the pipe to effuse through the orifice. This then causes a high rate of localised general corrosion under the graphitised layer. The resulting thinning of the pipe-wall may then lead to pipe fracture under high water pressure.     

Carburiser properties transfer into the structure of melted cast iron

Heredity in the microstructure of cast iron produced solely from scrap (synthetic cast iron) was considered experimentally. The carbon deficiencies were adjusted using anthracite, synthetic graphite and petroleum coke as carburisers. The small flakes of anthracite resulted in smaller graphite flakes in the final microstructure, proving that heredity is affected by the carburiser as much as by the particular “pig iron-steel scrap-cast iron” combination.     

Kinetics of graphite expansion during eutectic solidification of cast iron

The paper introduces a new linear displacement analysis (LDA)/thermal analysis (TA) experimental device for measuring linear displacement during the solidification of cast iron. The experimental device comprises a sand mould encased in a steel shell that prevents mould wall movements. Thus, only the linear displacement caused by the shrinkage or expansion of the metal is recorded by the transducers. Two quartz rods introduced directly at different heights into the liquid metal and connected to two transducers record the linear displacement during the liquid–solid transformation and subsequent cooling. Two thermocouples positioned at the same height with the quartz rods allow for the concomitant TA and LDA and thus for the direct correlation between expansion/contraction and the temperature change during solidification events such as graphite formation. The LDA device was used to study the differences in the solidification mechanisms of irons with different graphite morphologies (lamellar, compacted/vermicular and spheroidal) at carbon equivalent in the range of 3·7–4·4%. The analysis included the LDA and TA curves and full metallographic characterisation of the cast irons. In general, graphite expansion increased as the graphite shape changed from lamellar, to compacted and then to spheroidal. The most important process variables are the magnesium and carbon contents. Higher Mg residual and C in the iron produced more graphite expansion. Compacted graphite (CG) iron was particularly sensitive to the Mg residual. Indeed, the high Mg CG irons exhibited similar graphite expansion to that of spheroidal graphite (SG) iron, while the low Mg CG iron expansion was closer to that of the lamellar graphite (LG) iron. Graphite expansion increased for all data with the time interval over which graphite expansion occurred. It also increased with both carbon and carbon equivalent. The time for graphite expansion increased noticeably with the carbon content of the iron. It did not depend on the graphite shape. By combining TA and LDA, it was possible to plot the evolution of graphite expansion as a function of the fraction solid and thus to understand the kinetics of graphite expansion. The amount of expansion available at the end of solidification was quantified. Such data, when correlated with process variables, will be useful in decreasing microshrinkage and in producing riserless compacted and SG irons.     

Continuously cast ductile iron: Processing, structures, and properties

Ductile iron billets were continuously cast using a horizontal casting machine. The billets were cast successfully, and the overall quality of the billets was acceptable. The as-cast microstructure consisted of eutectic carbide, chunky carbide and graphite nodules in a pearlite matrix. The amount of carbide was relatively large compared with that in traditional sand castings. Graphite nodularity decreased as the melt was held for longer periods of time before casting after inoculation and nodularisation treatments. The fading effect was significant when the melt was held for 6 min and longer. Graphite nodularity was found to affect the tensile strength and elongation, but not hardness, of the billets. The surface quality of the billets was fair, although light waves and drawal marks were clearly visible. The billets had good roundness. The tensile strength was found to be between 410 and 550 MPa; the elongation was 2.5-4.0%; and the hardness was 520-550 HB. Possible approaches to improving the as-cast structure and the implications of this research are discussed.     

Pitting corrosion of older underground cast iron pipes

Major water supply distribution networks in many cities consist of buried cast iron pipes. Often the pipes are internally cement-lined. For these the most severe external pitting corrosion is important because this may cause leakage and eventual structural failure. Herein representative data is reported for 10 pipes, ranging in age from 34 to 129 years and from 200 to 600?mm diameter that are part of a larger data set. The pipes examined were selected by the water utilities from several critical locations. Pit depths over 1–2?m lengths of pipes were measured and examined and soil properties measured. The morphologies of pitting around the pipes were found to be very different, with often much greater pit depths and larger pit areas at the base of the pipes. There were also considerable differences along the length of individual parts of pipes. When plotted on a Gumbel plot for the maximum pit depths, the deepest pits showed a different Gumbel trend compared with the majority of pit depth maxima. Theoretically, this indicates that different pitting mechanisms are involved. This possibility is explored by reference to earlier work on the long-term pitting corrosion of steels in sea water. Comments are made also about empirical fitting with other extreme value distributions, as sometimes suggested.     

树脂砂生产铸铁件裂隙状氮气孔及其防止

随着铸造生产的发展,采用呋喃树脂砂等有机树脂砂造型已越来越普遍。然而,有些丁厂被一种裂隙状皮下气孔所困扰,感到束手无策。作者在日本进修铸造技术期间曾碰到和解决过此种缺陷。作者认为,这种裂隙状皮下气孔产生的主要原因是由于有机树脂的含氮量过高而引起的。     

Empirical models for long-term localised corrosion of cast iron pipes buried in soils

ABSTRACT

Empirical models are proposed for the progression of maximum depth of localised corrosion of cast iron pipes, based on data for pipes buried in 67 different backfill clay and sandy soils for up to 129 years. Early corrosion increases with increased inhomogeneity of the backfill soil and with greater availability of free water at the soil–pipe wall interface. Longer term corrosion is correlated with free water availability and occurs at a much slower rate. In most cases, the free water is fresh, oxygenated rainwater, known to be corrosive, but may also include some groundwater. Statistical uncertainty in pit depth is estimated and factors are proposed to allow for different annual rates of precipitation.     

铸铁产品如何在云平台中实现虚拟制造

主要描述了在网络云端搭建虚拟制造系统平台,利用系统平台管控铸铁产品的设计流程与方案。同时,系统平台中的虚拟制造模块将设计方案转化为现场可执行的制造方案指导现实制造,并利用反馈的现实制造数据,在系统平台中经分析总结形成典型工艺,实现铸铁产品的智能设计。