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 spheroids 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.

多级孔铁氮掺杂生物炭催化剂的制备及性能

在水稻秸秆基铁氮掺杂生物炭粉末催化剂的基础上,制备了多级孔铁氮掺杂生物炭成型固体催化剂,探讨了其成型工艺,对其进行了表征,并对其活化过硫酸盐降解有机污染物的性能进行了评价,为铁氮掺杂生物炭催化剂的工业放大提供参考。该方法制备的成型球体催化剂具有良好的力学性能、丰富的多级孔结构、极低的铁离子浸出,可在宽pH范围内有效去除实际废水COD以及三氯苯酚(TCP)、双酚A(BPA)等有机污染物,可通过浸渍和热处理再生。吸附60 min、降解100 min后,COD、TCP、BPA的去除率分别可达46.85%、63.62%、90.18%。Fe^(2+)、Fe^(0)能够活化过硫酸盐产生·OH、SO_(4)^(-)·、·O_(2)^(-)和^(1)O_(2)降解有机污染物,Fe—N、C=O、O=C—OH和π→π^(*)位点作为电子供体,氧化态N作为电子受体。

覆砂铁型工艺生产制动鼓的过程质量控制

介绍了使用覆砂铁型铸造工艺生产汽车制动鼓铸件的优缺点,详细阐述了覆砂铁型铸造生产线各工序过程质量控制要点,列举了多种覆砂铁型铸造生产线生产的汽车制动鼓铸件的铸造缺陷,对缺陷产生的原因进行了初步分析并制定了相应的防止措施。最后指出:细节决定质量,生产中要严格控制原材料质量、操作质量、过程参数以及工艺细节制定等内容,从而获得稳定的高质量铸件。

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。

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。

电梯轮毂铸件的EPS壳型工艺开发

针对采用呋喃自硬树脂砂、静压造型成形工艺生产的铸件在环状厚大部位中心处存在较严重的缩孔、缩松问题,提出了壳型精密成形工艺方案,基于高密度EPS雕刻白模,涂覆数层无机浆料和骨料,经烘干焙烧,制成强度高、内壁洁净、轮廓完整的壳型,埋置于陶粒砂中,在负压紧实状态下浇注金属液,提高金属液充型、凝固及补缩能力,得到了组织致密、外观光洁的精密铸件。壳型精密成形工艺采用物理条件控制和无粘结剂陶粒砂,过程易于控制,稳定可靠,循环使用,绿色环保,保证产品质量,综合效益显著。

超细铁粉在金刚石工具胎体中的应用

为了降低成本,采用国内两家公司的两种超细铁粉。文章对两种粉末的粒度、形态、氧含量等进行了检测,对粉末压制成型性能、烧结性能进行了对比,并对粉末在烧结金刚石锯片配方中的使用量进行了对比试验。对产品硬度、抗弯强度、切割性能等进行了测试,结果表明在金刚石锯片胎体中应用超细铁粉,产品锋利度、寿命均有较好的效果;而组合使用不同超细铁粉,发挥各自的优点,应用效果更佳。

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。

熨烫处理对3D打印成型件表面特性的影响

为了有效提高3D打印成型件的表面质量和美观度,通过熔融沉积成型(FDM)3D打印机挤出头对成型件表面进行熨烫处理,采用表面粗糙度测试、光泽度测试、颜色属性测试评价了熨烫处理对FDM成型件表面特性的影响。粗糙度测试结果表明,熨烫处理后FDM成型件的轮廓算术平均偏差Ra和轮廓最大高度Rz平均值分别降低了46.18%和37.36%;光泽度测试结果表明,熨烫处理后FDM成型件在20°,60°,85°入射角下的光泽度平均值分别提高了45.65%,31.63%,20.34%;颜色属性测试结果表明,熨烫处理后FDM成型件的色相H平均值基本保持不变,明度L*、彩度C*平均值分别增大了7.25%和6.14%。对比工业显微镜拍摄的细节放大图可见,与熨烫处理前较粗的表面纹理相比,熨烫处理后FDM成型件的表面纹理更加细密,质感更显光滑,其表面的凸起物得到有效去除,“缺陷”基本消失,光泽度有所提升,颜色显得更加明亮、鲜艳。因此,熨烫处理可以有效改善FDM成型件的表面特性,具有较高的应用推广价值。

风机轮毂用一体式模具的设计与应用

针对现有大型风机轮毂铸件模具生产过程中劳动强度高、产品精度差、壁厚尺寸不稳定及浮渣多等问题,通过采用一体式砂芯造型工艺,更改浇注系统等方式,设计出减少间隙数量、提高铸造尺寸精度、降低劳动强度并且保证产品质量的模具产品,在实际生产中得到较好的应用。

冷冻砂型对铸铁合金凝固行为及组织性能影响规律研究

采用冷冻砂型铸造铸铁合金,界面换热系数是反映冷冻砂型与铸铁合金换热程度的重要参数,对于分析铸铁合金组织性能具有重要意义。研究测定了合金的界面接触温度随时间的变化规律,在此基础上分析了界面换热特征,获得了界面换热系数随初始界面温度变化的函数式,同时分析了冷冻砂型中铸件凝固的铸态微观组织及力学性能。结果表明:界面换热系数随着冷冻砂型初始温度的增加而降低,随含水率的减少而升高。当含水率为6%(质量分数,下同)时,在-35℃、-30℃、-25℃初始冷冻温度条件下,铸型铸件界面换热系数峰值分别是195663W/(m^(2)·K)、147933W/(m^(2)·K)、120836W/(m^(2)·K);当含水率为5%时,在-35℃、-30℃、-25℃初始冷冻温度条件下,铸型铸件界面换热系数峰值分别是209257W/(m^(2)·K)、176878W/(m^(2)·K)、134472W/(m^(2)·K)。相同含水率下初始冷冻温度越低,珠光体晶粒越细,石墨化程度越高,抗拉强度也越高。

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。

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。

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.

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。