汽车排气歧管用球墨铸铁的显微组织和抗生长性

通过LOM、XRD、SEM和EDS等手段分析了汽车排气歧管材料的组织构成。高温工作后两种材料尺寸的变化随工作温度的升高逐渐增大,但高硅钼球墨铸铁的尺寸增幅明显大于高镍球墨铸铁的增幅。由于镍和锰能有效提高球墨铸铁的抗氧化性和相变温度,所以高镍球墨铸铁的抗生长性优于高硅钼球墨铸铁的抗生长性。     

稀土对Ni-Cr-Cu合金铸铁组织及耐碱腐蚀性能的影响

设计了不同含量的稀土镍-铬-铜合金铸铁,采用光学显微镜观察组织,用失重法测定合金铸铁在动态、高温、高浓度碱液中的腐蚀速率。结果表明,添加稀土可以改善合金铸铁中石墨的形态及分布,使之由长条形逐渐球化;并且随着稀土含量的增加,石墨数量增加,合金铸铁的耐蚀性增强。但稀土过量会使得合金铸铁的耐蚀性减弱。     

硼对耐磨球墨铸铁组织和力学性能的影响

研究了不同硼含量对含碳3．4％－3．8％、含硅2．0％－3．0％,含锰2．0％－＝3．0％的球墨铸铁铸主热处理态组织和力学性能的影响。结果表明：随着硼含量的增加,铸态组织中的碳化物数量增加,硬度提高,冲击韧性下降,当硼含量大于0．010％时,铸态组织中出现了明显的网状或断网状碳化物,冲击韧性下降幅度较大,经淬火、回火后、碳化物发生不同程度的溶解。当硼含量为0．003％－0．0105时,热处理后碳化物基本消失,硬度保持在HRC50左右,冲击韧性达到或超过9J／cm^2;当硼含量超过0．010％时,热处理后仍存在断网状或条块状碳化物,硬度稍有增加,冲击初性明显下降。     

Nucleation of Bainite in Bainite Ductile Cast Iron

The bainite ductile cast iron with given comppasition was quenched to get bainite strueture. The nucleating position of bainite and the distrihution of alloying elements in the matrix were measured. The results show thai the bainite nucleates at the interface between graphite and austenite during quenching. Based on the experimental results and thermodynamics, the nucleating tnechanism of bainite in ductile iron was analyzed.     

钒对中铬白口铸铁组织和性能的影响

研究了钒对中铬白口铸铁的组织与性能的影响.采用SEM与EDS对试样进行了组织与成分分析,并测定了试样的冲击韧性、硬度等力学性能.结果表明:随着V含量的增加,中铬白口铸铁的组织得到细化,冲击韧性得到改善;当V的加入量增加至4%(质量分数)时,基体上弥散分布大量VC颗粒,使得材料有潜在的良好的耐磨性能.     

激光重熔球墨铸铁基陶瓷复合层的金相组织

采用金相显微镜、扫描电子显微镜等测试手段,分析了激光重熔球墨铸铁及球墨铸铁基陶瓷复合层的金相组织形貌,探讨了其形成机理。     

Effect of Mold Hardness on Microstructure and Contraction Porosity in Ductile Cast Iron

  The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated. Molds with different hardnesses (041, 048, 055, 062 MPa) and a sand mold prepared by Co2 method were used. The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated. The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases; therefore, the possibility of achieving a sound product without using any riser increases.     

铸铁中开花状石墨的微观结构

用透射电子显微镜和扫描电镜研究了铸铁中开花状石墨的微观结构,结果表明,开花状石墨是石墨沿[0001]方向生长速率增大的过程。因而它是1种过球化石墨,而不是铸铁过程中球化不良造成的。     

Microstructure and Mechanical Properties of Ductile Cast Iron in Lost Foam Casting with Vibration

The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm 2 of the specimens produced by LFC without vibration to 334 mm^-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the ＂crystal shower＂ caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and Dearlite colonv, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.     

稀土对高Ni-Cr铸铁石墨的变质作用

采用金相和电镜等手段对稀土在高Ｎｉ－Ｃｒ铸铁中的行为进行了研究。结果表明：稀土可以改善高Ｎｉ－Ｃｒ铸铁石墨的形态及分布，使之由长条状向短厚状过渡。并且随着稀土加入量增多，石墨数量增加。     

The Microstructure of Graphite Spherulites in Cast Iron

The microstructure of graphite spherulites （G.S.） in Ce addition ductile cast iron was carried out using transmission electron microscopy （TEM） techniques. The structral characterization of the graphites is as following: there are platelets growing along the periphery as well as fan-like structure formed from platelet aggregates in the diameter section of spherulite, in which most of the platelets are with sizes ranging from several to tens nm in radial; the [001] direction of the platelets would have a tend to parallel to radial of the G. S. and meanwhile, they also a small misorientation deviated from the radial among the platelets each other. It shows that the anisotropy of graphites has been restrained by adding Ce element in cast iron and the structural characterization of the G. S. is consistent with the Double’ s model of the conical helixes formed in helical growing and branching.     

DN800mm球墨铸铁管的生产

DN800mm管退火后存在延伸率低,合格率低的问题,经分析,退火炉轧道变形、铸态管本身椭圆及加热时间不够等是导致管子变形的主要原因。为此,高速铁水化学成分和浇注工艺参数,对退火炉炉底及轧道进行改造,并采用“高温快速”的退火工艺,从而提高了管子的圆整度和生产效率,退火合格率达到了100％。     

铈对中铝耐热铸铁组织和力学性能的影响

中铝耐热铸铁因其脆性大使用受到限制。研究了Ce对中铝耐热铸铁的组织及力学性能的影响。结果表明:Ce可使中铝耐热铸铁的石墨球化,组织细化,力学性能得到明显改善。     

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

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稀土对Fe－C－Al－Si铸铁组织和性能的影响

本文研究了稀土对Ｆｅ－Ｃ－Ａｌ－Ｓｉ铸铁的石墨形态，基体组织，力学性能及激冷倾向的影响。随１~＃稀土量增加，石墨由片状向蠕虫状转变较快，但由蠕虫状向球状转变很慢，故具有较大的蠕化范围。铸铁的强度在０．３～１．２％１~＃稀土范围内随稀土的增加而增加，但在１．２～２．０％范围内稍有下降。稀土具有较强的促进激冷倾向的能力，而铝具有抑制或消除激冷倾向的作用。孕育能显著降低激冷倾向，且其效果比普通铸铁更明显。并对有关机理进行了讨论。     

Thermal Fatigue Behavior and Cracking Characteristics of High Si-Mo Nodular Cast Iron for Exhaust Manifolds

 The thermal fatigue cracking behavior of high Si-Mo nodular cast iron (NCI) is investigated by means of optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscope (EDS), in order to find a new material used in exhaust manifolds in First Automotive Works (FAW). Nodular cast irons with silicon content about 4. 7%, in combination with up to 1. 1% molybdenum, were produced by Jilin University and FAW. The repeated heating/cooling test was performed under cyclic heating at various maximum heating temperatures (Tmax) ranging from 800 to 900 ℃. Experimental results indicate that the thermal fatigue cracking resistance of high Si-Mo NCI decreases with increasing the maximum heating temperature. The periods for crack initiation are 24-36, 40-50 and 70-90 times associated with heating temperature of 900, 850 and 800 ℃, respectively, when the holding time is about 10 min at Tmax. When thermal fatigue cracking occurs, the cracking always initiates at the bigger surface of specimen. The major positions of cracks propagation are generally at the eutectic oxide boundary region and the region of the graphite disappearance. At the same time, the oxidation may accelerate crack initiation and propagation. On the other hand, micro-crack number varied from large to little because of shielding effect. As exhaust manifolds, the reasonable working temperature of high Si-Mo NCI is no more than 840 ℃ by test and analysis.     

铸态高韧性球墨铸铁的研制和应用

对铸态直接获得高韧性球铁进行了研究。试验表明,在保证石墨球化良好的情况下,硅、锰含量是影响铁素体量和延伸率δ%的主要因素,δ%值随着硅的增加和锰的降低而相应地提高,在Si(2.90~3.20)%、Mn(0.15~0.40)%范围内,δ%值可达(19~21)%。这种铸态高韧性球铁成功地用于生产厚大断面和薄壁铸件。     

轻稀土镁复合球化、孕育处理工艺在轧辊生产中的应用

叙述生产轧辊类超厚大断面球墨铸铁件所用的轻稀土镁球化剂、孕育剂和复合球化、孕育处理过程及其对原铁水的要求,同时介绍了所生产轧辊的组织、性能和良好的使用效果。     

Effect of Microstructure on Impact Fatigue Resistance and Impact Wear Resistance of Medium Cr-Si Cast Iron

 A great amount of iron grinding balls in tube mills have been consumed. Under this impact abrasive wear working condition, the failure of wear resistant alloying white irons grinding balls is mainly caused by fatigue spalling. The impact wear resistance of martensitic high chromium cast iron (Cr of 15%) is not high sometimes, but its cost is not low. Thus, medium Cr Si wear resistant cast iron is recommended. The influence of the iron on impact fatigue resistance and impact wear resistance is pronounced. Ball on ball impact fatigue test and high stress impact wear test of the grinding balls have been carried out. The results show that the impact fatigue resistance (IFR) and impact wear resistance (IWR) of medium Cr Si cast iron are superior to those of martensitic high chromium cast iron (Cr of 15%). The main reasons are that (1) the stress in medium Cr Si cast iron is released in the as cast state; (2) the matrix is fine pearlite with better toughness and plasticity; (3) the pearlite is more stable compared with a retained austenite under repeated impact load and less phase transformation can take place; (4) high silicon content improves the morphology of eutectic carbide; (5) there is no secondary carbide which results in less crack sources. All these factors are beneficial to improvement of impact fatigue spalling resistance. The eutectic carbide M7C3 is the main constituent to resist wear.     

Microstructure and Mechanical Properties of Nodular Cast Iron Produced by Melted Metal Die Forging Process

 The microstructure and mechanical properties of nodular cast iron produced by the melted metal die forging process (MMDF for short) were experimentally researched. The main obtained results are: the nodular cast iron produced by this process can be machined as easy as traditional one only if holding at the remained temperature for 4 h; its strength and plasticity are obviously higher than those of traditional ones; the graphite size arrived at grade 8, and the graphite spheroidizing arrived at grade 1 or 2, but a streamline molded distribution of the graphite slightly appeared. Both of the strength and plasticity increased with the pressure when the pressure holding time was larger than its critical value. A new way to produce high properties nodular cast iron was provided.