Influence of boron on ferrite formation in copper-added spheroidal graphite cast iron

This paper reviews the original work of the authors published recently,describing the influence of B on the matrix of the Cuadded spheroidal graphite cast iron.The effect of Cu has been corrected as a ferrite formation promoter in the matrix of the grey cast iron by the usage of high-purity material.Also,this paper focuses on the ferrite formation and the observation of the Cu distribution in the B-added and B-free Cu-containing spheroidal graphite cast iron.The Cu film on the spheroidal graphite can be successfully observed in the B-free sample using a special etching method.However,in the B-added sample,no Cu film could be found,while the secondary graphite was formed on the surface of the spheroidal graphite.The interaction between B and Cu is stressed as a peculiar phenomenon by the employment of a contrast experiment of B and Mn.The heat treatment could make Cu precipitate more significantly in the eutectic cells and in the matrix in the form of large Cu particles because of the limited solubility of Cu.

Numerical Simulation of Shrinkage Cavity Formation in Spheroidal Graphite Iron Castings Based on Micro Modeling

A micro-modeling method (MM) for the quantitative prediction of the shrinkage cavity formation in SGiron castings is proposed. The mathematical models describing the volume changes during the solidification ofspheroidal graphite cast iron are established based on the models of solidification kinetics. The shrinkage cavityformation of T-shaped SG iron castings is calculated with MM method. The calculated results are compared with theexperimental results. It is shown that the predicted size, shape and distribution of shrinkage cavity by MM methodare in good agreement with the measured results.

Eutectic solidification mode of spheroidal graphite cast iron and graphitization

The shrinkage and chilling tendency of spheroidal graphite (abbreviated SG) cast iron is much greater than that of the flake graphite cast iron in spite of its higher amount of C and Si contents. Why? The main reason should be the difference in their graphitization during the eutectic solidification. In this paper, we discuss the difference in the solidification mechanism of both cast irons for solving these problems using unidirectional solidification and the cooling curves of the spheroidal graphite cast iron. The eutectic solidification rate of the SG cast iron is controlled by the diffusion of carbon through the austenite shell, and the final thickness is 1.4 times the radius of the SG, therefore, the reduction of the SG size, namely, the increase in the number, is the main solution of these problems.

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.

Cerium Distribution in Spheroidal Graphite of Cast Iron

Six thin sections of spheroidal graphites in cast iron have been investigated by TEM and SEM.The spheroidal graphites consist of two or three layers and have nuclei which are composed of Ce_2O_2S and Ce_2O_3. Cerium is existed ont only in nuclei,but also in central layer and middle layer of graphite.

Numerical simulation of microstructure evolution on near eutectic spheroidal graphite cast iron

A multiphase cellular automaton model was developed to simulate microstructure evolution of near eutectic spheroidal graphite cast iron(SGI) during its solidification process, and both dendritic austenite and spheroidal graphite growth models were adopted. To deduce the mesh anisotropy of cellular automaton method, the composition averaging and geometrical parameter were introduced to simulate the spheroidal graphite growth. Solute balance method and decentered square algorithms were employed to simulate austenite dendrites growth with different crystallographic orientations. The simulated results indicate that the graphite nodule grows in a spherical morphology when the surrounding environment of a single graphite nodule is same. However, for two adjacent graphite nodules, the environment is different. The higher the carbon concentration, the faster the growth of graphite. By comparison with experimental results, it is found that the microstructure evolution of near eutectic spheroidal graphite cast iron during solidification process can be reproduced quantitatively by numerical simulation with this model.

Thermomechanical Testing of GGG 40 Spheroidal Graphite Cast Iron Alloy

Spheroidal graphite cast iron GGG 40 was thermo-mechanically tested using thermo-mechanical simulator Gleeble-3500. Three deformation steps were successively applied on test-specimen at temperatures namely;900°C, 850°C and 750°C within the austenitic zone, at the same strain rate of 0.1 s-1. No cracks were observed, up to 50% deformation, after successive deformation steps. Stress-strain relationship obtained is correlated with previous work on SGCI with a different carbon equivalent. It was found that by decreasing the deformation temperature;for the same CE, young’s modulus, yield strength and strain hardening exponent increase. Microstructure of the deformed zone, for a specimen quenched after the final deformation step, reveals fine elongated ferrite and pearlite, as well as elongated graphite. While microstructure of the non-deformed zone subjected to the same treatment, includes coarser ferrite and pearlite with graphite spheres embedded in the matrix.

Impact Properties of Austempered Spheroidal Graphite Cast Irons

This study aims to clarify the influence of external notch on impact characteristics of high toughness ductile cast irons prepared by austempering heat treatment. We produced ductile cast irons samples with various matrix microstructure tested by Charpy impact within five kinds of external notches whose stress concentration factors (α), with values taken from 1.0 (Un-notched) to 4.8. In addition, to clarify the initiation process of impact characteristics, we observed the evolution of microstructure surface during bending tests with a slow loading speed for the un-notched and the notched impact samples. The results showed that the impact fracture energy decreases strongly in the range of α from 1 to 2.3 but decreases slightly for α larger than 3. Moreover, the impact value of samples with austempered microstructure is sensitive to the external notch shape. The impact transition temperature increases with increasing the stress concentration factor. The fracture energy is decreasing with the external notch from the impact test since the crack initiation energy is directly affected by this later. This work contributes to get a better understanding in the basic theories of external notch effect on impact characteristics of austempered spheroidal graphite cast irons (ADI).

GB/T 24733—2023《等温淬火球墨铸铁件》国家标准修订解读

介绍了GB/T 24733—2023《等温淬火球墨铸铁件》修订过程,论述了标准的主要修订内容,解读了与原标准和ISO 17804:2020《铸造奥铁体球墨铸铁分类》的主要技术差异和修订缘由,指出了新标准的特点和应用范围。

铸造冷铁布置原则的研究及验证

借助铸造数值模拟技术对球墨铸铁件冷铁设置的部分原则及要求进行了研究及验证。研究了冷铁铺设厚度对铸件激冷效果的影响,验证了冷铁最大效用的“二分之一原则”;同时也研究了铸件的直角两侧面同时铺设冷铁的距离控制问题,确定直角两边同时铺设冷铁的最小控制距离,为今后的冷铁工艺设计提供指导。

Influence of Si,Ce,Sb and Sn on chunky graphite formation

The thirteen mother alloys,C%+1/3Si%=4.45%,differing in their Si,Ce,Sb and Sn contents,were prepared.Seventy grams of these alloys was remelted in a high purity alumina crucible at 1,450oC under an Ar atmosphere,and then cooled at 30 K/min for obtaining their cooling curves.Their graphite morphologies were observed using an optical microscope and an SEM.Their three-dimensional graphite shapes were observed by the SEM using the samples whose matrices were etched off with an acid-aqua solution,to confirm the chunky graphite.For discussing the influence of the Si and Ce contents on the chunky graphite formation,two experiments were carried out.In the first one,the Si contents were changed from 0 to 4% in the 0.15%Ce alloys,and for the second one,the 3.5%Si and 4%Si samples that differed in the Ce contents of 0.1 and 0.2% were used.In the third experiment,the influence of Sb and Sn on the chunky graphite formation was investigated by using the 4%Si and 0.1%Ce samples.The results showed that with the increase of the Si content,the volume fraction of the chunky graphite increases,while the volume fraction of the ledeburite decreases,and the chunky graphite volume fraction in the 0.2%Ce samples is higher than that of the 0.1%Ce samples.The effect of the Sb and Sn additions on the prevention of chunky graphite formation cannot be confirmed due to their high Si contents.Therefore,further studies will be needed in this field.

Wear Behavior and Mechanism of Spheroidal Graphite Cast Iron

Wear behavior and mechanism of spheroidal graphite cast iron were studied on a pin on-disk elevated tem- perature wear tester. The phase and morphology of worn surfaces were examined by X ray diffraction and scanning electron microscopy. Results show that with an increase of load, wear rate of spheroidal graphite cast iron gradually increases under low loads, rapidly increases or potentially increases under high loads; wear rate increases with in- creasing ambient temperature. At 25 200 ℃, adhesive wear prevails; oxidative wear and adhesive wear coexist at 400 ℃. As load surpasses 150 N at 400 ℃, extrusive wear appears. The elevated-temperature wear of spheroidal graphite cast iron is a physical and chemical process including the following reactions： xFe＋y/2O2-FexOy , 2C＋ O2- 2CO and Fex Oy ＋yCO-xFe＋yCO2. Hence, at 400 ℃, the amount of graphite and tribo oxides are substan- tially reduced because of reductive function of graphite. It can be suggested that wear reduced effect of graphite and tribo-oxides is impaired.

基于ProCAST的制动铸件精确成形数值模拟与工艺提升

目的针对排气制动阀铸造工艺控制不当会产生缺陷这一问题,结合模拟分析,提出合理的铸造工艺方案,以减少铸件缺陷。方法基于ProCAST软件对蝶阀阀体铸造工艺进行模拟,研究阀体铸件在充型、凝固过程中的速度场、温度场、固相率分布和缺陷分布,并根据模拟结果对工艺进行优化。结果添加侧冒口和冷铁后,阀体的缩松缩孔缺陷得到了有效控制,缺陷体积减少了95%以上,获得了完整铸件。结论通过铸造模拟有效指导了排气制动用蝶阀的生产实践,优化了生产工艺,节约了生产成本。

活性屏离子渗氮处理对球墨铸铁力学性能的影响

活性屏离子渗氮(ASPN)处理可以扩大球墨铸铁的用途,处理后的球墨铸铁有望在特殊载荷条件下使用。研究了ASPN处理对球墨铸铁力学性能的影响。利用ASPN处理,在样品表面上形成氮化物层,并且能在氮化物层内部进一步形成扩散层。ASPN处理中氮化层的厚度随着处理温度的升高而增加,球墨铸铁的硬度、耐磨性和疲劳强度也随着处理温度升高而提高。

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。

铁素体对蠕墨铸铁力学性能和导热性的影响

蠕墨铸铁制动盘要求其材料兼具良好的力学性能和导热性以获得高的耐热疲劳和耐磨损性能。本文通过改变蠕墨铸铁中Sn和Mo元素的含量,研究了铁素体含量及其固溶强化程度对抗拉强度、布氏硬度和导热系数的影响。实验结果表明,Sn元素显著改变了蠕墨铸铁中铁素体与珠光体的比例,并具有明显的固溶强化效果。Mo元素同样具有固溶强化效果,但对铁素体含量影响较小。铁素体含量及其固溶强化程度对蠕墨铸铁力学性能和导热性的影响是互为矛盾的关系,因此提高铁素体含量的同时,通过固溶强化可以调控蠕墨铸铁的力学性能和导热性能以实现二者的平衡。

《压缩天然气发动机用耐热疲劳铁素体蠕墨铸铁件》团体标准解读

《压缩天然气发动机用耐热疲劳铁素体蠕墨铸铁件》T/CFA020101071-2022标准是我国首次制定的推荐性团体标准。介绍了该标准起草的主要过程,对该标准的适用范围、引用文件、材料牌号、技术要求、生产方法、试验方法、检验规则与判定以及标识、参考化学成分、热疲劳耐久试验要求进行了探讨,以便于该标准的推广应用。

基于多重分形理论的球铁石墨颗粒分散均匀性的分析

为了描述球墨铸铁中石墨颗粒的分散均匀性,提出了基于多重分形的描述方法,该方法采用Matlab分形工具箱提取石墨颗粒分布密度的分形特征来定量描述石墨分布的不均匀性,其多重分形谱的宽度以及最大最小概率子集维数之间的差别反映了石墨分布的不均匀性。不同Ce含量的球铁石墨图像的分析结果表明了该方法的有效性和实用性。

铸铁件工艺CAD系统的研究与开发

利用ＶｉｓｕａｌＣ++６．０和ＡｕｔｏＣＡＤ的二次开发工具ＯｂｊｅｃｔＡＲＸ开发了灰口铸铁、球墨铸铁铸造工艺二维ＣＡＤ系统，它可实现计算机辅助设计和绘图。根据铸铁特点对浇冒口模块进行了重点设计。系统主要功能包括：通用铸造工艺参数设计、实用冒口设计、浇注系统设计等。并结合工厂管卡零件进行了铸造工艺辅助设计。

强磁场对球墨铸铁退火处理的影响

研究了强磁场对退火处理球墨铸铁力学性能以及渗碳体分解、碳扩散的影响.在平行试样方向上施加强磁场进行退火处理后,球铁的拉伸强度、硬度降低,延伸率、断面收缩率升高.SEM分析表明,施加强磁场能够显著地提高渗碳体分解和碳扩散的速度.磁化力F是加速渗碳体溶解和碳扩散的驱动力,通过推导可以得出单位体积力F的表达式.