Fuzzy neural network analysis on gray cast iron with high tensile strength and thermal conductivity

To develop a high performance gray cast iron with high tensile strength and thermal conductivity, multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned parameters consisted of graphite content, maximum graphite length, primary dendrite percentage and microhardness of the matrix. Under the superposed influence of various parameters, the relationships between thermal conductivity and structural characteristics become irregular, as well as the effects of graphite length on the strength. An adaptive neuro-fuzzy inference system was built to link the parameters and properties. A sensitivity test was then performed to rank the relative impact of parameters. It was found that the dominant parameter for tensile strength is graphite content, while the most relative parameter for thermal conductivity is maximum graphite length. The most effective method to simultaneously improve the tensile and thermal conductivity of gray cast iron is to reduce the carbon equivalent and increase the length of graphite flakes.

Research of Synthetic Rules with Mechanical Properties vs Inoculation Degree on Gray Cast Iron

To fit the special needs of gray cast iron as a new engineering material,i.e.,higher σ b and lower HB,or lower σ b and higher HB,using the method of heat analyzing and polyparameters analytic figures,the synthetic rules of carbon saturation degree,inoculation degree and mechanical properties can be exposed.The result shows that,according to the needs of the part′s mechanical properties,referring to the synthetic rules of gray cast iron,the corresponding technological measure and composition proportion can be defined,by which we will get the exact mechanical properties that could achieve the result expected completely.Thus,the casting for gray cast iron might be 'designed'from'selected'.

Effect of RE Complex Inoculation on the Fatigue Wear Behaviours of High Chromium Cast Iron

Inoculation of high chromium cast iron is made by RE complex inoculant. Influence of inoculating on rolling fatigue wear characteristics of high chromium cast iron is investigated. The experimental resutls indicate that high chromium cast iron inoculated by RE complex inoculation is improved in structure and properties, i. e. fatigue wear sevice life is prolonged and relative wear resistance is increased greatly.

Effect of Rolling Process on Microstructure and Wear Properties of High Carbon Equivalent Gray Cast Iron

Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.

Gray Cast Iron With Directional Graphite Flakes Produced by Cylinder Covered Compression Process

A new plastic deformation process for gray cast iron named cylinder covered compression （CCC） was developed. By CCC process, gray cast iron （GCI） specimens, which are embedded in steel cylinders, were hot compressed up to 80% reduction in height without the cracking problem. It was clearly observed that the uniform distribution of directional graphite flakes appeared after more than 45 % reduction hot compression. The strength, ductility, and microhardness of GCI after 80% reduction deformation were significantly enhanced： the tensile strength varied from 117 MPa to 249 MPa, while the total elongation varied from 0 to 5.2%, and the microhardness varied from 153 HV to 217 HV. It was shown that the tensile fracture surface presented ductility characters after more than 45% reduction hot deformation.

Effect of inoculating addition on machinability of gray cast iron

Gray cast irons were inoculated with FeSi75＋RE and FeSi75＋Sr inoculants. The changes of apex angle of the drills before and after being used were used to evaluate machinability of gray cast irons. Effect of FeSi75＋RE and FeSi75＋Sr inoculants on mechanical properties, machinability and sensibility of gray cast iron used in cylinder block were investigated. Experimental results showed that gray cast iron treated with 60%FeSi75＋40% RE inoculants exhibited tensile strength consistently at about 295 MPa along with good hardness and improved metallurgical quality. While gray cast iron inoculated with 20%FeSi75＋80% Sr inoculants exhibited the best machinability, the lowest cross-section sensibility and the least microhardness difference. The tool flank wear of the drill increased correspondingly with the increase of the microhardness difference of the matrix, indicating the great effect of homogeneity of the matrix on the machinability of gray cast iron.

Effect of Rare Earths and Nitrogen on Graphite Structure of Gray Cast Iron

By means of inoculating, the effects of rare earths, N and RE N joint inoculants on the content and surface morphology of graphite of high CE gray cast irons were studied The results indicate that RE, N, and especially RE N joint inoculants make the content of graphite decrease; N and RE N joint inoculants could make the surface of graphite rougher and the heads of graphite flake passive

Effect of Cu-Ni and Cu-Ni-Mn on the Microstructural and Mechanical Behaviour of As-Cast Non-Inoculated Hypereutectic Grey Iron

The hypereutectic region of grey cast iron has received very little attention especially for designing cast products by researchers. Due to its high carbon equivalence, hypereutectic grey iron poses some challenges especially its tendency for grey to white transition (GWT) at this level of carbon content. However, hypereutectic grey iron possesses inherent properties that could be easily utilized for improved performance in automobile engines and brake pad system. Significantly, they could be modified for superior hardness, strength and toughness. This study presents the effect of microalloying on the mechanical behaviour of hypereutectic grey cast iron with carbon equivalence above 4.5. The first part of this work presented in this paper considers the addition of Cu-Ni and Cu-Ni-Mn to series of as-cast hypereutectic grey cast iron and their hardness and tensile strength were studied and compared. A total of 33 cast samples were obtained with the control sample. The examination of the micrographs revealed that graphite eutectics cells of Type A and A + D were obtained in the resulting microstructure. Results analyses showed that the ferrite forming tendency of silicon was suppressed due to the high carbon content of the as-cast hypereutectic grey iron coupled with the absence of inoculation which plays a great role in the graphite flake type, network, size and distribution. Cu-Ni microalloying was also confirmed to promote hardness with the hardening effect limit of nickel observed at 1.3% composition. For Cu-Mi-Mn addition, excess and free sulphur in the hyper- eutectic grey iron results in reverse effect of manganese on strength, hardness, reduced graphite flake size and shape.

铸态QT700-2偏心体铸件的研发

本文介绍铸态QT700-2偏心体铸件的研发过程。在铸造工艺方案上采用分层浇注,在铸件热节部位使用冷铁,并且结合保温冒口工艺,使铸件达到均衡凝固,消除铸件的缩松、缩孔缺陷;在熔炼过程通过合金化,使用低稀土球化剂,采用多次孕育处理,消除了碎块状石墨、细化了石墨晶粒、稳定了珠光体含量,生产的铸态偏心体的性能满足客户要求。

6缸柴油机高强度球墨铸铁曲轴的研制

通过成分设计、凝固模拟、铁模覆砂铸造和等温正火复合新工艺应用,研制了一种高强度6缸柴油机球墨铸铁曲轴,分析了其内部质量、显微组织和力学性能.中试结果表明:采用复合新工艺研制的6缸球墨铸铁曲轴,其组织致密,没有内部铸造缺陷;与树脂砂铸造工艺相比,球墨铸铁曲轴的基体组织更均匀,共晶团数增多,晶粒显著细化,基体组织中索氏体比例大于90%,自由渗碳体比例小于1%.6缸球墨铸铁曲轴沿轴向不同位置的平均拉伸强度R_(m)、平均伸长率和基体平均硬度分别为946 MPa、5.6%和287 HB.负荷为2900N·m下,其弯曲疲劳试验加载次数达到10×10^(7)次而未出现裂纹和开裂现象,各项性能指标均超过L6R040301Q曲轴的技术要求,可代替现用的45锻钢和42CrMo锻钢曲轴,成本分别降低44.0%和66.2%.

钨极氩弧焊焊接粉末冶金高铬铸铁/低碳钢的焊接性能及组织演变

以粉末冶金高铬铸铁和低碳钢为原材料,采用多道次手工钨极氩弧焊,研究了焊接电流对焊缝组织演变和力学性能的影响,提出了焊接接头组织演化模型,并探讨了其断裂机理。结果表明,焊接接头的抗拉强度在焊接电流为140 A时达到538.1MPa,分别是烧结高铬铸铁和低碳钢抗拉强度的95.3%和97.4%。由于二次回火和合金元素扩散/偏析的作用,焊接接头的显微硬度在水平方向上由高铬铸铁一侧向低碳钢一侧逐渐降低,而在垂直方向则呈M形分布。当焊接电流为140 A时,焊缝的熔合区主要由奥氏体和回火马氏体组成,在熔合区与低碳钢母材之间存在一个单一奥氏体柱状晶区;在熔合区与烧结高铬铸铁母材之间,存在一个柱状高铬铸铁区域,该区域的碳化物为粗糙树枝状,沿基体晶界分布。

低碳当量对灰铸铁组织和性能的影响

随着柴油发动机功率的不断提高,对灰铸铁缸体材料提出了越来越高的性能要求。本文通过金相显微镜、扫描电子显微镜、布氏硬度计、电子万能试验机和激光导热仪对低碳当量(CE≤3.9%)灰铸铁的组织和性能进行研究。探究碳当量(3.2%~3.8%)对灰铸铁的显微组织、力学性能及导热性能的影响。结果表明:当碳当量由3.8%降至3.2%,石墨形貌变得细小弯曲,石墨长度降低;珠光体层片间距变得致密均匀,抗拉强度达到385.9MPa;随着碳当量降低,材料的导热性能对温度的依存性也逐渐降低。

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%。

微量Sb对高强度灰铸铁断面敏感性的影响

采用浇注阶梯试块、光学显微镜、硬度测试研究了锑对高强度灰铸铁不同厚度断面的显微组织及力学性能影响。结果表明:灰铸铁含锑量为0.02%时,石墨片得到适度细化,珠光体体积分数有所增加且含量在98%以上,但却不出现白口,硬度的平均值也显著提高;随着厚度的增大,石墨组织大小、数量以及形貌基本保持不变,基体组织也保持均匀性,而硬度减小明显缓慢,大大改善了高强度灰铸铁铸件的断面敏感性。

Influence of rare earth nanoparticles and inoculants on performance and microstructure of high chromium cast iron

The high chromium cast irons （HCCIs） with rare earth （RE） nanoparticles or inoculants were fabricated in the casting process. The phase compositions and microstructure were analyzed by X-ray diffraction （XRD） and optical microscopy （OM）, respectively. The hardness and impact toughness were tested by Rockwel-hardmeter and impacting test enginery. And then, the morphology of fracture was researched by scanning electron microscopy （SEM）. The results demonstrated that the phase compositions of HCCIs with addition of RE nanoparticles or inoculants which were M7C3 carbides ＋ α-Fe did not change obviously. However, the prime M7C3 carbides morphology had great changes with the increase of RE nanoparticles, which changed from long lath to granular or island shape. When the content of RE nanoparticles was 0.4 wt.%, the microstructure of high chromium cast iron was refined greatly. The microstructure of carbides was coarser when the addition of RE nanoparticles was higher than 0.4 wt.%. The hardness and impact toughness of HCCIs were improved by addition of RE nanoparticles or inoculants. The impact toughness of HCCIs was increased 36.4% with RE nanoparticles of 0.4 wt.%, but the hardness changed slightly. In addition, the adding of RE nanoparticles or inoculants could reduce the degree of the brittle fracture. Fracture never seemed regular, instead, containing lots of laminates and dimples with the increase of the RE nanoparticles. The results also indicated that the optimal addition amount of the RE nanoparticles was 0.4%, under this composition, the microstructure and mechanical property achieved the best cooperation. In addition, through the study of erosion wear rate, when adding 0.4% RE nanoparticles into the HCCIs, the erosion wear rate got the minimum 0.32×10-3 g/mm2, which could increase 51.5% compared with that without any RE nanoparticles.

不同孕育剂处理的高强度灰铸铁加工性能研究

为研究不同孕育剂对灰铸铁切削加工性能的影响,制备了高强度HT350材质的试样。对比研究了孕育剂75SiFe、SrSi、BaSi、SiS(r80%)+75FeS(i20%)处理的高强度灰铸铁的力学性能和切削加工性能。结果表明,SiS(r80%)+75FeS(i20%)复合孕育处理的灰铸铁较单一孕育处理的灰铸铁石墨细小弯曲,基体组织均匀性好,具有较高的硬度以及较小的切削抗力,但其断面敏感性较大。单一孕育剂中75SiFe孕育处理的灰铸铁具有较高的抗拉强度、较小的硬度以及较低的断面敏感性。灰铸铁中A型石墨越细小,基体组织越均匀,灰铸铁的加工性能越好,说明显微组织的均匀性对灰铸铁的加工性能具有较大影响。

复合孕育技术在高强度薄壁灰铸铁件上的应用研究

研究了几种复合孕育剂对较高碳当量 (CE =3 8%～ 4 1% )灰铸铁性能的影响 ,试验并经实际生产结果表明 ,选择 6 0 %SiBa + 40 %SiFe作为高碳灰铸铁件的复合孕育剂 ,其抗拉强度稳定在 2 5 0MPa以上 ,并能减小白口宽度和断面敏感性 ,满足实际生产要求。同时对其孕育机理进行了探讨。

高铬白口铸铁初生碳化物细化的研究进展

介绍了高铬铸铁初生碳化物细化的研究进展,综述了初生碳化物的结构、生长模式以及细化方法。稀土、K、Na、Zn、Mg、V、Ti、B等元素对初生碳化物有良好的细化作用,悬浮铸造和合金化也是细化初生碳化物的有效途径。

铸态高强度高伸长率球墨铸铁研究进展

铸态高强度高伸长率球墨铸铁是近年来铸铁材料研究的热点,其研究与应用有很大进展。本文概述了包括固溶强化铁素体基体、珠光体-铁素体基体、奥铁体基体的铸态高强度高伸长率球墨铸铁研究进展,介绍了它们的化学成分、生产工艺与性能特点,指出了生产应用中存在的问题,展望了其研究与发展前景。

孕育处理对薄壁高强灰铸铁件性能的影响

针对薄壁高强度缸体、缸盖的特点，结合国内现状，借助于正交设计，研究了复合孕育剂ＲＡＣ、ＲＴ４、ＲＣＣ、ＨＹ等对高强度薄壁灰铸铁件性能的影响。试验结果表明，对于高碳当量（ＣＥ＝４．１％～４．２％）低合金化的铁水，采用复合孕育剂，可使性能稳定地达到牌号ＨＴ２５０以上，并改善断面均匀性。对于ＣＥ＝４．０％～４．２％的铁水，若控制铁水质量，加大复合孕育剂用量，亦可获得ＨＴ２５０铸铁。结果适用于大、中、小工厂冲天炉熔炼。