无定形石墨砂特性及其在铝合金铸造中的应用

研究了天然无定形石墨砂热物理特性，试验结果表明，与硅砂相比，石墨砂有较好的激冷性，可提高合金组织的致密度，改善其力学性能。将无定形石墨砂用于铸铝合金铸件生产，可有效防止铸件产生针孔、缩松等缺陷，降低废品率，提高产品质量。用石墨砂代替铝冷铁，可提高劳动生产率。     

凝固模拟所用砂型热物性参数的测定和研究

采用反算法对砂型的热物性参数进行实验研究，并用自制的实验测温装置对工厂实际生产的硅砂的热物性参数进行测量，测量值得到模拟结果的验证；为本厂生产汽车后制动鼓铸件进行数值模拟，提供了实用和可靠的热物性参数。     

石墨化膨胀引起制动鼓粘砂缺陷的防止措施

介绍了制动鼓铸件的生产情况,对冒口下部铸件表面粘砂缺陷的原因进行了分析。采用MAGMA软件对凝固过程进行模拟,结果显示:冒口颈凝固早于铸件最大热节,冒口颈邻近的铸件表层开始凝固时间与铸件最大热节接近,该处的表层强度不足以抵抗热节中心石墨化膨胀产生压力,而且冒口与铸件之间的型砂强度较低,以上情况导致铁液从铸件热节溢出进入砂层而形成粘砂缺陷。防止措施为:加大冒口颈厚度,让铸件热节石墨膨胀压力释放到冒口中。生产结果显示:铸件不再产生上述粘砂,铸件返修率下降至零。     

球墨铸铁数字化铸造技术及应用

介绍了铸造CAE技术、热物性参数反求技术、计算机微断层成像技术等数字化技术在球墨铸铁生产中的应用,并给出相应的应用实例。说明了铸造CAE和热物性参数反求技术的应用能够提高缺陷的预测精度,同时缩短工艺设计周期,有效地提供优化的工艺方案,直接指导实际生产,提高球墨铸铁件的生产水平。计算机微断层成像技术的应用突破了传统球墨铸铁中对二维石墨形态的分析,实现了对石墨三维形态的直接分析,拓展了对球墨铸铁的认识水平。     

无定形石墨砂在铜合金铸造中的应用研究

石墨砂是一种新型的铸造用砂，研究了石墨砂对铸铜合组织与性能的影响，并将石墨将应用于青铜阀体铸件生产中，取得了良好的效果。     

铝电解槽用石墨化阴极炭块热物性测试的研究

对热物性测试方法——Angstroms法的测试原理进行深入分析和研究，针对实验模型和石墨化阴极炭块材料性能的特点，利用精密的电子仪器及先进的数据采集设备，设计开发了一套铝电解槽用阴极炭块热物性测定装置。实验采用的纵向周期热流法可以直接测定材料的导温系数，在已知密度和比热参数的情况下可以计算出导热系数。在20～300℃的范围内，测定装置操作方便、可行，数据可靠，测试精度较高。     

蠕墨铸铁制动盘表面片状石墨层及其控制的研究

针对蠕铁制动盘表面片状石墨恶化层缺陷,分析了片状石墨的形成原因及机理,发现砂型中S含量高是形成片状石墨的主要原因,而砂型中硫主要来自再生砂,少量来自固化剂。通过试验,研究了型砂中再生砂添加比例及硫含量对蠕铁片状石墨层深度的影响。结果表明:低硫固化剂+防渗硫涂料+30%以上的新砂的呋喃树脂砂工艺,或控制再生砂硫含量≤0.11%,最终型砂硫含量≤0.14%,可降低盘面片状石墨恶化层深度在工艺允许范围内。     

铁神一号净化剂对铸态球铁金相组织和力学性能的影响

采用中频感应电炉熔炼球墨铸铁,水玻璃砂造型,浇注Y型试块及热分析试样,研究了铁神一号净化剂对球墨铸铁组织和力学性能的影响。试验结果表明,加入净化剂可以获得理想的球化效果,使石墨球数增加,石墨球直径减小,改善石墨球分布状态,力学性能有所提高;可以降低磷含量,钒钛含量有所增加。净化剂对球墨铸铁的共晶过冷度和白口倾向影响不大。     

用铁墨砂作外冷铁

通过试验证明、用铁屑、石墨、桐油配制的芯砂,用在油砂芯局部地方作外冷铁,对消除球墨铸铁、普通铸铁件局部热节处的缩孔、     

V、Ti合金化对玻璃模具材料抗氧化及耐热疲劳性的影响

通过测试不同V/Ti比条件下蠕墨铸铁玻璃模具材料的抗氧化及热疲劳性能,研究了蠕墨铸铁的钒、钛合金化工艺,并探讨了影响这些性能的因素.结果表明,在V、Ti变化范围内,V/Ti比为1.63时蠕墨铸铁具有较均匀的铁素体基体+蠕虫状石墨组织,以及良好的热物性.     

造型材料表观热物性的测定

为精确地模拟铸件的凝固过程和进行铸造工艺的计算机辅助设计,采用浇注法对粘土砂和水玻璃砂的表观热物性进行了研究。实验表明,型砂的表观导热系数、表观导温系数及表观蓄热系数均随着原砂粒度的增大而增大,也随着粘结剂的含量(陶土或水玻璃)增加而增大,但达到一定程度后则趋于恒定。     

砂芯对缸盖组织的影响

在对渗漏缸盖的分析解剖中，时常发现一些壁薄部位的石墨和基体组织异常。采用Cu－Sn合金强化措施，只是消除了部分壁薄部位的基体组织异常。本文分析了缸盖组织异常产生的原因，确认砂芯变形或砂芯下不到位引起铸件壁薄，砂芯壁薄和热效应导致石墨和基体组织异常。     

热处理对不同冷速Al合金共晶相形貌及含量的影响

选取成分为Al-5.17Cu-2.63Si(合金A)、Al-4.29Cu-1.09Mg(合金B)和Al-2.09Si-1.66Mg(合金C)三元铝合金,分别进行不同冷速下的凝固实验。对比研究不同凝固速率下得到的共晶相形貌与含量在接近各合金体系三元共晶温度下热处理前后的变化行为。结果表明:同一合金冷速越慢,得到的原始组织二次枝晶间距越大,合金A的石墨型、砂型、保温型冷却组织的二次枝晶间距分别为24.17、63.32和99.88μm,合金B的二次枝晶间距分别为24.35、82.78和139.42μm。均匀化热处理的热扩散过程可以明显地溶解非平衡共晶相,由于原始组织的尺度不同,共晶相所处的溶解阶段与溶解程度不同。合金A的石墨型、砂型、保温型组织热处理后与热处理前的共晶相含量比值分别为0.44、0.49和0.68,合金B的共晶相含量比值分别为0.084、0.30和0.38。     

镁合金应用石墨砂湿型铸造的实践

总结了采用石墨砂湿型铸造镁合金的经验，分析了镁合金铸造的特点。介绍了湿型砂各组分的性能及配比。实践证明，由石墨砂和阻燃剂R-SO4N3，H3BO3等配制成的粘土湿型砂能生产内外质量都良好的镁合金铸件。     

The Influence of Processing Variables on the Dimensional Integrity of Spheroidal-graphite Iron Castings

Abstract

This investigation was carried out to identify the major factors and their degree of influence on the dimensional accuracy of spheroidal-graphite iron castings produced in chemically- bonded sand moulds. Test castings were poured into furan-resin-bonded zircon sand and silica sand moulds and sodium silicate/ CO₂ bonded silica sand moulds. A comparison of casting sizes with those of the mould cavity into which they were poured showed considerable scatter and overlap. From these data the size that each casting would have had, had it solidified without graphite formation, was calculated and found to depend on mould cavity size for each type of mould. By isolating the differences in casting size due to graphite it was possible to identify the influencing factors. Thus castings poured into furan-resin-bonded zircon sand have the highest contraction and their size depends primarily on the amount of graphite present. The dimensions of castings poured into silica sand moulds show more variation and depend not only on the amount of graphite present and the structure of the metal but also on the thermal expansion of the silica sand moulds.     

Effect of cooling rate and of titanium additions on the microstructure of thin-walled compacted iron castings

This article addresses the effect of cooling rate and of titanium additions on the exhibited microstructure of thin-walled compacted graphite iron (TWCI) castings as determined by changing moulding media, section size and ferrotitanium. Various moulding materials were employed (silica sand and insulating sand ‘‘LDASC’’) to achieve different cooling rates. This study shows that the cooling rates exhibited in the TWCI castings varies widely (70–14 °C/s) when the wall thickness is changed from 2 to 5 mm. In turn, this is accompanied by a significant variation in the compacted graphite fraction. The resultant cooling rates were effectively reduced by applying an insulating sand in order to obtain the desired graphite compactness. Ti additions in combination with LDASC sand moulds were highly effective in promoting the development of over 80% compacted graphite in castings with wall thicknesses of 2–3 mm as evidenced by quantitative metallographic analyses.     

Effect of temperature field on solidification structure of pure Al under pulse magneto-oscillation

This article discusses the effect of temperature field on the Pulse Magneto-Oscillation (PMO) induced solidification refinement of pure aluminiurn to provide more information for the industrial application of the PMO solidification technology. The temperature field is altered mainly by applied variable cooling conditions and pulse parameters. Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate, however, in the alternative case, the sand mould whose sand bottom was replaced by a graphite block is favorable to the survival of equiaxed nucleus. The refinement mechanism is discussed in terms of the relationship between temperature field and the formation process of solidified structure.The formation or survival of nucleus depends on both temperature field and Joule heat produced by PMO, both low pulse frequency and high pulse current were experimentally confirmed to be effective; and PMO was demonstrated high potential in industrial application.     

Adhesion, hardness and structure of thermal sprayed Al/SiC composite coat on graphite

Combustion powder spraying has been used in the coating of graphite by a layer of Al and SiC composite utilizing the Box-Wilson design that fixes the optimum spraying parameters of Al/SiC wt.% composition, substrate temperature and spraying distance. Graphite substrate surface was conditioned by subjecting to sand blast roughing and nitrogen flushed furnace treating. Under the spraying conditions considered, a single spraying pass attains a coating layer 65 ± 15 µm of average thickness. Two optimum spraying conditions that concern adhesion of coating to graphite and its hardness are obtained. Upon spraying for adhesion purpose, the coat/graphite adhesion strength is found to depend mainly on graphite surface conditioning, but for hardness purpose, it is found to depend mainly on SiC wt.% composition.Microstructure of transversal coating section indicates that adhesion efficiency is due to physical interlocking of molten sprayed materials on the roughened and treated graphite surface. Phases identified from fractured coatings by XRD analysis show individual phase of Al, SiC and graphite in addition to small amount of new extra phases that combine the three constituents such as Al₄C₃ and Al₄Si₂C₅. These phases play a role with the good physical interlocking in achieving adhesion strength that exceeds that of graphite.     

石墨砂型铸渗机理的研究

通过热力学、动力学分析计算，结合倾倒试验结果，对石墨砂型铸造渗碳过程的渗碳机理进行了研究，首次明确提出了石墨砂型铸渗机理。研究认为，石墨在钢液中的直接溶解及碳在钢中的扩散是产生石墨砂型铸渗效果的主要原因