A reliable and consistent production technology for high volume compacted graphite iron castings

The demands for improved engine performance,fuel economy,durability,and lower emissions provide a continual challenge for engine designers.The use of Compacted Graphite Iron（CGI）has been established for successful high volume series production in the passenger vehicle,commercial vehicle and industrial power sectors over the last decade.The increased demand for CGI engine components provides new opportunities for the cast iron foundry industry to establish efficient and robust CGI volume production processes,in China and globally.The production window range for stable CGI is narrow and constantly moving.Therefore,any one step single addition of magnesium alloy and the inoculant cannot ensure a reliable and consistent production process for complicated CGI engine castings.The present paper introduces the SinterCast thermal analysis process control system that provides for the consistent production of CGI with low nodularity and reduced porosity,without risking the formation of flake graphite.The technology is currently being used in high volume Chinese foundry production.The Chinese foundry industry can develop complicated high demand CGI engine castings with the proper process control technology.     

Compacted graphite iron: Cast iron makes a comeback

Although compacted graphite iron has been known for more than four decades, the absence of a reliable mass-production technique has resulted in relatively little effort to exploit its operational benefits. However, a proven on-line process control technology developed by SinterCast allows for series production of complex components in high-quality CGI. The improved mechanical properties of compacted graphite iron relative to conventional gray iron allow for substantial weight reduction in gasoline and diesel engines or substantial increases in horsepower, or an optimal combination of both. Concurrent with these primary benefits, CGI also provides significant emissions and fuel efficiency benefits allowing automakers to meet legislated performance standards. The operational and environmental benefits of compacted graphite iron together with its low cost and recyclability reinforce cast iron as a prime engineering material for the future.     

The superior durability of chilled cast iron camshafts

The demands of the automotive industry for cost-effective valve-train components that will function well at high stress and offer extremely low wear resistance under marginal lubrication, with improved emissions, requires guaranteed high-performance materials behavior together with a robust and proven manufacturing technology to support high-volume, low-rejection-rate production. Chilled cast iron (CCI) camshafts and followers have long been successfully meeting these requirements in both European-and Japanese-designed gasoline and diesel internal combustion engines; recent studies extend the role of CCI to modern engine configurations employing roller followers and ceramic mating surfaces. Performance in these newer applications is discussed.     

发动机铸铁件新材料工艺探讨

随着国Ⅲ、国Ⅳ和国Ⅴ柴油机的研发,这些新型发动机都对其关键铸件如缸体、缸盖等的铸件材质提出了更高的要求。目前普遍采用的HT250牌号已经远远满足不了其材质可靠性要求。发动机铸件材质国内外在80年代走过了从HT200到普遍使用HT250的时代,已经进入了从HT250向高性能铸铁发展的时代。作为高性能铸铁。一个是以HT280为代表的高性能灰铸铁,另一个就是蠕墨铸铁。     

Analytical investigations concerning the wear behaviour of cutting tools used for the machining of compacted graphite iron and grey cast iron

Compacted graphite iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 L Audi V8 TDI and the 4.0 L BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount as decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools.     

Overview of thermal barrier coatings in diesel engines

An understanding of delamination mechanisms in thermal barrier coatings (TBCs) has been developed for diesel engine applications through rig tests, structural analysis modeling, nondestructive evaluation, and engine evaluation of various TBCs. This knowledge has resulted in improved TBCs that survive se-vere cyclic fatigue tests in high-output diesel engines. Although much conflicting literature now exists regarding the impact of TBCs on engine performance and fuel consumption, changes in fuel consumption appear to be less than a few percent and can be nega-tive for state-of-the-art diesel engines. The ability of the TBC to improve fuel economy depends on a num-ber of factors, including the fuel injection system, combustion chamber design, and initial engine fuel economy. Limited investigations on state-of-the-art diesel engines have indicated that surface- connected porosity and coating surface roughness may influence engine fuel economy. Current research efforts on TBCs are primarily directed at reduction of in-cylinder heat rejection, ther-mal fatigue protection of underlying metal surfaces, and possible reduction of diesel engine emissions. Significant efforts are still required to improve the plasma spray processing capability and the economics for complex-geometry diesel engine components.     

高性能灰铸铁发动机缸盖生产实践与研究

发动机动力的不断提升使得客户对发动机缸盖的力学性能要求大幅提升.针对客户对缸盖的本体抗拉强度大于320 MPa的需求,进行了高性能灰铸铁材料的研究及生产实践.通过严格控制废钢质量、炉料配比、成分控制、熔化工艺以及孕育过程,能够稳定生产高性能灰铸铁.     

Laser-assisted machining of compacted graphite iron

Compacted graphite iron (CGI) is a material currently under study for the new generation of engines, including blocks, cylinder liners, and cylinder heads. Its unique graphite structure yields desirable high strength, but makes it difficult to machine, thus resulting in a machining cost. Laser-assisted machining (LAM) is adopted to improve its machinability and hence machining economics. The machinability of CGI is studied by varying depth of cut, feed, and material removal temperature and then evaluating resultant cutting forces, specific cutting energy, surface roughness, and tool wear. At a material removal temperature of 400 °C and a feed of 0.150 mm/rev at a cutting speed of 1.7 m/s, it is shown that tool life is 60% greater than conventional conditions at a feed of 0.100 mm/rev. Surface roughness is improved 5% as compared to conventional machining at a feed of 0.150 mm/rev. CGI microstructure evaluated post machining by sectioning and polishing shows no change. An economic analysis shows that LAM can offer an approximately 20% cost savings for the machining of an engine cylinder liner.     

Mechanical properties of Solid Solution-Strengthened CGI

Despite the increased usage of pearlitic compacted graphite iron (CGI) in heavy vehicle engines, poor machinability of this material remains as one of the main technical challenges as compared to conventional lamellar iron. To minimise the machining cost, it is believed that solution-strengthened CGI material with a ferritic matrix could bring an advantage. The present study focuses on the effect of solution strengthening of silicon and section thickness on tensile, microstructure and hardness properties of high-Si CGI materials. To do so, plates with thicknesses from 7 to 75 mm were cast with three different target silicon levels 3.7, 4.0 and 4.5 wt%. For all Si levels, the microstructure was ferritic with a very limited pearlite content. The highest nodularity was observed in 7 and 15 mm plate sections, respectively, however, it decreased as the plate thickness increased. Moreover, increasing Si content to 4.5 wt% resulted in substantial improvement up to 65 and 50% in proof stress and tensile strength, respectively, as compared to pearlitic CGI. However, adding up Si content to such a high level remarkably deteriorated elongation to failure. For each Si level, results showed that the Young’s modulus and tensile strength are fairly independent of the plate thickness (30–75 mm), however, a significant increase was observed for thin section plates, particularly 7 mm plate due to the higher nodularity in these sections.     

等离子喷涂灰铸铁涂层的研究进展

在汽车上使用轻质铝合金发动机可以有效减少燃油消耗和环境污染,但铝合金的耐磨损性能较差,从而造成发动机工作过程中气缸壁面容易磨损。利用表面改性技术对铝合金表面进行强化处理,可以满足其作为滑动部件在高载荷条件下的使用要求。灰铸铁较低的成本和其中石墨的自润滑作用,使其成为铝合金发动机气缸表面保护涂层材料的首选。等离子喷涂技术以其高效率和灵活性在表面强化领域受到广泛应用。因此,利用等离子喷涂制备灰铸铁涂层成为改善铝合金发动机气缸表面耐磨性的有效方法之一。但是,由于等离子喷涂过程中熔滴冷却速度极快,等离子喷涂很难得到含大量石墨组织的灰铸铁涂层。以调控灰铸铁涂层中的石墨含量为目的,总结了等离子喷涂灰铸铁涂层的研究现状,以及基体温度、颗粒尺寸、添加合金元素等对熔滴冷却速度的影响,并以此为基础,结合凝固理论分析了在涂层中保留灰铸铁粉末中的石墨组织的可行性,同时分析了在铸铁涂层中保留石墨所面临的主要问题,并提出了解决这些问题的主要措施。最后就在等离子喷涂灰铸铁涂层中保留石墨的研究方向进行了展望。     

变质处理对高强度灰铸铁钻削加工性能的影响

目前,通常采用加Mo高强度灰铸铁生产本体抗拉强度大于250MPa的大马力发动机缸体,由于Mo-Fe价格一直居高不下,使生产成本提高。因此开发低成本、高强度、易加工的灰铸铁具有重大意义。采用变质处理方法,生产满足大马力发动机缸体性能要求的不含Mo高强度灰铸铁,对比研究了含Mo与变质处理不含Mo高强度灰铸铁在钻削加工过程中的钻削抗力、扭矩、钻头磨损形貌、钻屑特征及两种灰铸铁的石墨形态、尺寸、分布和基体珠光体片间距对钻削加工性能的影响规律。结果表明,变质处理可以获得细小、弯曲、均匀分布的片状石墨,能够改善灰铸铁的钻削加工性能,同时提高抗拉强度。这为灰铸铁大马力发动机缸体毛坯国产化生产奠定了基础。     

含磷蠕墨铸铁闸瓦的研制

本文研制了一种新型材质的闸瓦—含磷蠕墨铸铁闸瓦。试验结果证明,一定量的磷加入蠕墨铸铁中,其硬度、抗拉强度均满足闸瓦的使用要求而耐磨性可达到中磷灰铸铁闸瓦的2倍以上。磷加入蠕墨铸铁中使得蠕墨铸铁的磷共晶数量增加而石墨数量减小,因此使得其强度降低,硬度升高,闸瓦的耐磨性提高。     

Investigation of the wear mechanism of cubic boron nitride tools used for the machining of compacted graphite iron and grey cast iron

Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of compacted graphite iron (CGI). Comparative studies for tools used to machine grey cast iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.     

511球铁曲轴断裂分析

对大功率柴油机球墨铸铁曲轴进行了宏观、微观全面的理化检验及分析；球墨铸铁曲轴未经过氮化处理，表面疲劳强度低是导致曲轴断裂的原因。提出了相应的改进建议。     

Application of complex inoculants in improving the processability of grey cast iron for cylinder blocks

The automobile engine cylinder block made of gray cast iron has complicated shape and requires high performance, which has been drawing significant attention to producers and investigators for many years. Due to the conventional conception that gray cast iron had ideal process-ability in comparison to other cast irons, the research related to the process-ability of the gray cast iron was very limited. With the strengthening corporation between China and foreign countries in the recent years, t…     

Effects of Casting Size on Microstructure and Mechanical Properties of Spheroidal and Compacted Graphite Cast Irons: Experimental Results and Comparison with International Standards

The aim of this research was to investigate the effects of casting size (10-210 mm) on the microstructure and mechanical properties of spheroidal (SGI) and compacted (CGI) graphite cast irons. A comparison of the experimental mechanical data with those specified by ISO standards is presented and discussed. The study highlighted that the microstructure and mechanical properties of SGI (also known as ductile or nodular cast iron) are more sensitive to casting size than CGI (also known as vermicular graphite cast irons). In particular, in both types of cast iron, hardness, yield strength and ultimate tensile strength decreased, with increasing casting size, by 27% in SGI and 17% in CGI. Elongation to failure showed, instead, an opposite trend, decreasing from 5 to 3% in CGI, while increasing from 5 to 11% in SGI. These results were related to different microstructures, the ferritic fraction being more sensitive to the casting size in SGI than CGI. Degeneration of spheroidal graphite was observed at casting size above 120 mm. The microstructural similarities between degenerated SGI and CGI suggested the proposal of a unified empirical constitutional law relating the most important microstructural parameters to the ultimate tensile strength. An outstanding result was also the finding that standard specifications underestimated the mechanical properties of both cast irons (in particular SGI) and, moreover, did not take into account their variation with casting size, at thicknesses over 60 mm.     

Effect of V and Sn on microstructure and mechanical properties of gray cast iron

The cylinder liner is one of the important parts of a diesel engine. Gray cast iron is the main material for manufacturing cylinder liners due to its good casting performance, convenient processing performance, good wear resistance and low cost. In the present work, the effects of vanadium (V) and tin (Sn) on the microstructure and properties of gray cast iron were studied. Results show that increasing the contents of V and Sn can not only refine the graphite, but also reduce the pearlite lamellar space. The graphite size and lamellar spacing of pearlite are firstly reduced and then increased. Pearlite quantity reaches over 98% after adding V and Sn. Adding V and Sn can promote the precipitation and solid solution strengthening of gray cast iron, so as to improve the mechanical properties. The Brinell hardness reaches the peak of 424 HB at the contents of 0.21wt.% V and 0.06wt.% Sn, and the sample containing 0.11wt.% V and 0.08wt.% Sn shows the highest compressive strength and tensile strength of 1,699 MPa and 515 MPa, respectively. The main strengthening mechanism comes from the solid solution strengthening and fine grain strengthening of V and Sn.

     

铌微合金化船用柴油机硼铸铁缸套组织与性能研究

采用铸铁-水玻璃砂复合型负压铸造浇注铌微合金化6170和6190型柴油机硼铸铁缸套，并对不同Nb含量对铸铁组织、硬度和抗拉强度的影响进行了研究。结果铸件尺寸精确，无铸造缺陷。Nb能细化晶粒和石墨，明显提高强度和硬度。其强化机理主要是硬质相强化、固溶强化和晶粒细化强化。ω(Nb)的最佳量为0．25％。     

等离子喷涂高铬铸铁涂层的摩擦学性能

针对铝合金缸体内壁油性腐蚀环境中的摩擦工况,采用大气等离子喷涂制得了高铬铸铁涂层和316L不锈钢涂层,采用维氏显微硬度计、图像分析软件、台式扫描电子显微镜及热场发射扫描电子显微镜分别对显微硬度、孔隙率、涂层厚度及结构进行了测试和分析。采用球-盘式往复摩擦试验机对比研究了两种涂层与典型缸套材料HT200灰铸铁在大气环境、纯发动机油润滑环境和模拟发动机腐蚀性油润滑环境下的摩擦学性能。结果表明:高铬铸铁涂层在腐蚀性发动机油环境中表现出好的摩擦磨损性能。     

摩托车发动机用Ti-Al-Fe-Mo气门的制备及性能表征

以Ti粉和Al、Fe、Mo等元素粉末为原料,采用粉末冶金工艺制备了Ti-Al-Fe-Mo合金,并最终制成摩托车发动机用钛气门,研究了钛合金制备过程中的组织和性能演变规律,考察了钛气门的装机试验使用效果。结果表明,采用粉末冶金工艺制备的Ti-Al-Fe-Mo合金具有优良的综合性能,其抗拉强度为1232 MPa,屈服强度为1186 MPa,延伸率为6.5 %,硬度为49 HRC。在钛合金表面涂覆TiN硬质耐磨涂层后,制成的钛气门可满足摩托车发动机的装机测试要求。与使用钢制气门相比,使用钛气门可以使发动机的功率和扭矩提高约12%,油耗降低1%,并显著降低噪音。