Foundry technology and its applications of ductile iron castings produced by water-cooled copper alloy Mold

The high efficiency mechanized foundry technology of castings produced by using water-cooled copper alloy permanent mold has been systematically studied. Through the researching a Cu-Cr-Mg alloy with high conductivity and good combined mechanical properties used for making permanent mold was developed, and the basic design principles of the water-cooled permanent mold along with the control-range of relevant foundry processing parameters were also established. A cast production line equipped with water-cooled copper alloy mold was designed and fabricated for production of ductile iron automobile gear castings, This production line can consistently make automobile gear castJngs Jn QT500-15 and QT600-5 (Chinese Standard) grades of ductile iron with up to 95% casting success rate.

Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron castings were discussed. Finally, two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

Microstructure of coupled Al/gray cast iron obtained by molding and its effect on mass loss

This study aims to consolidate the surface of gray cast iron with aluminum deposition by developing a method that combines the preparation and surface treatment in a single operation. The effect of the wall thickness of the castings on the microstructure of the formed layers was studied, and two thicknesses, 8 mm and 25 mm, were studied. The formation of a continuous and homogeneous rich aluminum layer on the surface of the cast iron was observed. The formed layer is composed of two successive zones identified as two proeutectoid phases FeAl+FeAl/FeAl2 and single-phase FeAl, which significantly increases the surface hardness. Furthermore, this change in surface composition makes it possible to reduce the mass of the immersed samples in a 1 M hydrochloric acid solution during different exposure times(1 to 4 days). Consequently, a clear improvement in the corrosion resistance of the treated layers is highlighted.

通过优化偶联剂含量改善磁粉芯综合性能

磁粉芯在工程应用中会遇到体积变化引起的开裂、磁性能低等问题,目前未见关于这方面的研究。通过在羰基铁粉磁粉芯(包含磁环、磁片和一体成型电感)中加入不同含量KH550硅烷偶联剂,研究其成型性、磁性能和力学性能,并利用SEM、TMA和LCR等测试分析偶联剂对磁粉芯性能影响的作用机理。研究表明偶联剂能将树脂“约束”在磁粉表面,并在固化过程中带动磁粉颗粒重排,从而增加磁粉芯的膨胀系数。添加0 wt.%和0.1 wt.%偶联剂的磁粉芯具有负的膨胀系数,容易收缩开裂。当偶联剂含量达到0.3 wt.%、0.5 wt.%和0.7 wt.%时,树脂固化过程中磁粉芯的膨胀系数升高,从而增加磁粉芯的体积,有效抑制磁粉芯的开裂倾向。但是,体积的增加会降低磁粉芯的密度、磁导率、Q值和力学性能,增加损耗。综合考虑磁粉芯的成型性和其他性能,偶联剂添加的最佳比例是0.3 wt.%。揭示了偶联剂对磁粉芯膨胀系数等综合性能的影响规律,可为高性能磁粉芯的工程化应用提供重要理论依据。

合金灰铸铁玻璃模具开裂失效分析及改进措施

分析了合金灰铸铁玻璃模具开裂失效的原因,从模具的铸造工艺和热处理工艺上进行了改进试验。通过采用降低合金元素和多次孕育的工艺,组织的均匀性明显提高,通过提高高温石墨化温度,增加二次石墨化保温时间,得到全铁素体基体组织,模具组织的均匀性得到极大的改善。最后指出:(1)模具组织中的网状碳化物以及退火残存的珠光体是裂纹产生的主要原因;(2)提高高温石墨化温度,增加二次石墨化保温时间,有利于得到高温下稳定的全铁素体组织,模具组织的均匀性得到极大的改善。

采用3D打印技术生产灰铸铁叶轮铸件

介绍了灰铸铁小型单吸叶轮铸件的结构及技术要求,详细阐述了该铸件的生产工艺。为了减少造型工时,降低铸造成本,提高尺寸精度,尽量减少砂型、砂芯数量,运用3D打印砂型工艺,采用叠箱的浇注工艺及特殊的砂型分型方案。生产结果显示:铸件尺寸合格,外观质量良好,披缝少,叶片壁厚均匀,且均为未出现冷隔、穿皮、气孔、缩陷、浇不足等缺陷,满足客户需求。最后指出:运用3D打印砂型技术,结合独特的叠箱铸造工艺方案,可以提高铸件出品率,降低砂铁比,节省生产成本,简化造型浇注操作流程,提高生产效率。

CAE技术结合测温试验在树脂砂实型铸造中的应用

在呋喃树脂砂实型铸造的基础上,通过对铸件凝固过程中铸件—型砂界面处测温得到温度变化曲线,结合ADSTEFAN数值模拟软件的反算功能优化热物性参数,并验证其在实际生产中的有效性,以达到提高CAE计算精度的目的,为铸造工艺优化提供更精准的参考依据。其次用数值分析软件拟合出温度曲线及函数表达式,可以探究实际生产条件下厚大断面铸件的温度变化曲线特征以及本体金相状态与冷却速率之间的关系,为铸件局部位置提升珠光体含量的研究提供参考和新思路。

消失模铸造球墨铸铁减速机壳体皱皮及缩孔缺陷研究

消失模铸造生产的球墨铸铁减速机壳体,在生产过程表面出现了皱皮和缩孔缺陷。通过优化浇注系统,由顶注式改为底注式,有效减少了浇注过程铁液的紊流,解决了减速机壳体表面皱皮;探索出散热新工艺,解决了铸件热节区域的缩孔缺陷。试验结果表明,浇注系统改为底注后彻底解决了铸件表面皱皮缺陷;散热新工艺解决了缩孔缺陷,并且工艺简单,工艺出品率高。

铁型覆砂灰铸铁件氮气孔缺陷分析与改善措施

针对铁型覆砂铸造工艺生产灰铸铁件时产生的氮气孔缺陷,通过使用EDS能谱仪对氮气孔缺陷进行定性和定量分析,并结合铸件生产工艺对氮气孔的形成原因进行分析,通过在原材料上更换覆膜砂、提高新砂加入量、分开管理壳型线和铁型线回用砂,生产工艺上采取增加排气塞和提高铁型温度、固化时间、浇注温度等措施降低缺陷风险。改进后的工艺连续生产超过10万件产品,未再出现氮气孔缺陷。

Application of 3-D numerical simulation software SRIFCAST to produce ductile iron castings

Based on a method using numerical simulation equations and their solution schemes for liquid metal flows andheat transfer during mold filling and the solidification process of casting, 3-D numerical simulation software SRIFCAST wascreated. This includes enmeshment of casting; velocity and temperature fields calculation; displaying iso-temperature lines;velocity vectors and 3-D temperature fields on a Windows 9x operating system. SRIFCAST was applied to produce soundcastings of automobile and diesel engines, and also to connect with microstructure simulation for ductile iron castings.

Mechanical properties of thixo-formed austempered ductile iron

Semi-solid processing of metallic materials has been investigated for some time;however,this innovative production process has not fully established for ferrous alloys like ductile cast iron in the industry yet.Ferrous alloys-specially ductile cast ironbecause of increasing complexity due to high temperature processing and some other limitations have been allocated a small share of this useful forming process to themselves.However,this work describes that thixo-forming of ductile iron despite all of the limitations is possible even for thin sections(less than 1 mm).Die temperature and injection velocity are the most effective parameters to thixo-forming particularly for high melting point materials such as ductile cast iron.Filling behavior,shape factor of graphites and fluidity of thixo-formed specimens were characterized.In addition,defects as well as shrinkage and cold laps were examined to achieve sound specimen.Subsequence to successful thixo-forming,two step austempering was performed to accomplish a uniform structure with minimum untransformed austenite volume(UAV).Following austempering,tensile test was carried out and the results show good combination of tensile strength and elongation for treated specimens(1 137 MPa strength and 12% elongation in best situation).

A Mathematical Model for Predicting Shrinkage Defect of Ductile Iron Castings

The shrinkage defect of a ductile iron casting is attributed to the volume variations occurring in solidification, which consist of liquid contraction, solidification shrinkage, graphitization expansion, and mold cavity enlargement. Based on this understanding, a mathematical model for predicting the shrinkage defect of the casting is developed, in which the volume variations of the casting in soli- dification are numerically simulated, especially, the mold cavity enlargement is quantitatively calculated. Moreover, the reliability of the model is verified in production and experiment.

直压硫化工艺金属内模电磁感应加热均匀性的试验研究

研究导磁体长度和截面尺寸对直压硫化金属内模电磁感应加热均匀性的影响。结果表明:减小导磁体的长度可使得鼓瓦两端磁力线密度下降,使电磁感应加热更均匀,但会导致鼓瓦的加热功率下降,当导磁体长度为170 mm时,直压硫化金属内模电磁感应加热的均匀性最好;增大导磁体的截面尺寸虽然会使得电磁感应加热均匀性有所降低,但可以减小导磁体的涡流损耗和功率损耗,有效解决了导磁体铁损的问题,当导磁体的截面尺寸为20 mm×15 mm时,直压硫化金属内模电磁感应加热效果最好。

梯度石墨铸铁玻璃模具液态模锻模拟与仿真

为解决传统砂型铸铁玻璃模具铸件工艺出品率低、缩孔缩松等问题,采用液态模锻工艺成型,通过不同的冷却条件实现铸件石墨形态呈梯度分布。利用Procast对液态模锻过程的温度场和凝固场模拟,对缩孔缩松缺陷进行了预测,对浇注温度、冷却方式、浇口尺寸等关键工艺参数进行了调整优化,并根据热分析观点对铸件不同部位组织进行预测。结果表明,液态模锻可以有效减少缩孔缩松等铸造缺陷。

陶瓷颗粒增强铁基表面复合材料的研究进展与展望

研发长寿命、轻量化锭模是硅铁企业实现机械自动化浇铸的关键。陶瓷表面层铁基复合材料具有金属材料和陶瓷的双重优点,是实现硅铁锭模寿命倍增和轻量化的有效途径。本文综述了陶瓷颗粒增强铁基复合材料可行的工业化制备工艺及其性能,介绍了几种重要的陶瓷颗粒增强体,并给出了选取原则。基于陶瓷/灰铸铁复合锭模对硅铁液的优良抗熔损性,概述了其制备方法,并提出未来的研究重点。

铁-球墨系金属抗铝热熔损性能及腐蚀机理研究

以经孕育/球化处理、石墨球密度数可调的铁-球墨系金属为研究对象,借助扫描电子显微镜、超声热熔损失重等分析手段,系统研究了不同球墨密度对铁-球墨系金属热熔损性能的影响规律。结果表明,随着球墨密度的增大,铁-球墨系金属热熔损失质量逐渐下降,铁-球墨系金属的抗铝液腐蚀性能与H13钢相比有明显的提升。铁-球墨系金属浸铝热熔损试验后,Fe-Al反应生成物层的厚度与球墨密度成反比,间距小、大比表面积的石墨球阻碍铝液与基体接触和铝液的扩散,从而抑制熔融铝液对基体的腐蚀。铁-球墨系金属表现出更优异的抗铝熔体腐蚀性能。

高强韧珠光体球墨铸铁的研究

在球墨铸铁成分优化基础上,用万能材料试验机、布氏硬度计和金相分析显微镜研究了球墨铸铁经多元合金化、型内孕育处理和等温正火后的组织和和性能。结果表明:经Cu、Mo、Sb多元合金化和型内孕育处理的球墨铸铁,其铸态和等温正火处理后的组织明显改善,共晶团数目增加,基体组织细化,石墨球形态圆整、细小,珠光体数量增多,比例均大于90%,力学性能显著提高。与未合金化的球墨铸铁比,Cu,Mo,Sb多元合金化的球墨铸铁,其铸态和等温正火处理后的屈服强度R_(0.2)、抗拉强度R_(m)和硬度HB分别提高了25%、20%,47%、17%,41%、11%,达到502、620 MPa,811、975 MPa,256HB、298HB,伸长率A均大于6%。

球墨铸铁轮毂典型生产工艺的对比

介绍了粘土砂手工造型、微震压实造型,水平无箱自动化造型、静压自动化造型、覆砂铁型及消失模工艺的几种典型铸造成形工艺,阐述了基于轮毂铸件的质量提升需要、行业规范发展的推动、各成形工艺技术的突破和装备技术的发展以及各种工艺的局限性及优势。最后指出:汽车轮毂铸件的几种典型成形工艺各有其工艺优势和一定的局限性,企业采用何种适宜的生产方式,需依据生产需求、自身条件、行业和技术发展趋势做综合评定。

厚大断面球墨铸铁齿轮铸件的研制

为获得厚大断面球墨铸铁齿轮铸件,生产时进行分段制造。借助数值模拟软件模拟仿真优化,采用优质生铁、纯净的废钢及强化孕育,获得了合格铸件,为生产同规格球墨铸铁齿轮积累了宝贵的经验。