Effects of RE-Sb on Gray Cast Iron

ＥｆｆｅｃｔｓｏｆＲＥ－ＳｂｏｎＧｒａｙＣａｓｔＩｒｏｎＸｉｏｎｇＺｈｏｎｇ－Ｍｉｎｇ（熊仲明）；ＺｈａｎｇＳｕｏ－Ｍｅｉ（张锁梅），ＳｈｉＤｏｎｇ－ｙａ（石东崖）；ＳｏｎｇＷｅｉ－Ｘｉ（宋维锡）（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｔａｉｌｕｒｇｙ，Ｕｎｉ...     

球墨铸铁微观组织形成的数值模拟

基于结晶动力学理论,建立了球墨铸铁凝固过程各阶段微观组织形成形核和长大的数学模型;根据该结晶动力学模型,编制了球铁微观组织形成模拟软件FTStructure．该软件可以预测球铁凝固过程中各相的形成以及固态转变中铁素体和珠光体的形成,并进而预测铸态力学性能．模拟了阶梯形试块的冷却曲线、微观组织和布氏硬度．模拟与实测结果符合较好．     

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。     

Investigation into the Microstructure and Mechanical Properties of Thin Wall Austempered Gray Cast Iron (TWAGI)

The main aim of this investigation is to assess the mechanical properties of thin wall (3 mm thickness) copper alloyed gray cast iron. Thin wall alloyed gray cast iron specimens are subjected to austempering heat treatment at six different temperatures for four different time periods. As a result, these samples develop an ausferrite matrix with excellent mechanical properties. The resulting microstructures have been evaluated and characterized by means of optical microscope and scanning electron microscope (SEM) and X-Ray diffraction analysis. The hardness and tensile properties of all these specimens are determined and correlated with the microstructure. The hardness, tensile strength and ductility initially increase, and thereafter it decreases on longer periods of austempering. On the other hand, hardness and tensile strength decreases with increasing austempering temperature, while ductility increases.     

Numerical and Experimental Study on Residual Stress in Gray Cast Iron Stress Lattice Shape Casting

The prediction of residual stress in a stress lattice shape casting (stress lattice) has been conducted and discussed by some researchers via the Finite Element Method (FEM). However, most of the previous studies used the first-order tetrahedral element, which has poor analysis accuracy in problems including bending. The use of the first-order tetrahedral element makes the verification of these studies uncertain because the bending deformation essentially occurs in the stress lattice casting. This study first shows that the thermal stress analysis for the stress lattice should use the element that can represent the bending deformation in principle for bending of the thin parts. Second, the simulated residual stress was compared with the measured value. The thermal stress analysis successfully predicted the residual stress of the stress lattice casting with and 11 pct difference. In addition to the prediction of the residual stress, it is important from the viewpoint of the productivity of castings to reveal the effect of the shake-out temperature on the residual stress. However, in the previous studies, conclusions concerning the effect of the shake-out temperature on the residual stress were not consistent (i.e., the one study said the higher shake-out temperature decreased the residual stress, and another study said a higher shake-out temperature increased the residual stress). Therefore, the current study first discusses the reason for the inconsistent conclusions in the previous studies. Second, stress lattice castings were cast and shaken out at various shake-out temperatures. Then, the current study validated the effect of the shake-out temperature on the residual stress. Consequently, the experimental results supported the conclusion of Kasch and Mikelonis that the shake-out at higher temperature contributed to the increase of the residual stress in the casting.     

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.     

Thermodynamics and Kinetics Study on Improving the Microstructure of High Chromium Cast Iron by Multi-Alloying

The effects of multi-alloyings(V,Ti and Nb)on carbides precipitation and as-cast microstructure of eutectic high chromium cast iron containing 2.8 wt.%carbon and 31.0wt.%chromium were investigated.The results showed that with the increase in the amount of alloy elements,the cast microstructure of 2.8C-31Cr high chromium cast iron changed gradually from refinement to coarsening and the total volume fraction of carbides decreased.When the addition of alloy was0.4V-0.40Ti-0.40Nb-0.35Mo,the solidification microstructure was largely improved,the distribution of carbides was reasonably uniform.The existence form of strong carbides forming elements(V,Ti,Nb)and the reasons of rnicrostructure change were investigated from thermodynamics and kinetics considerations.     

铁对镍基铸造高温合金组织和性能的影响

本文着重研究了0~25%铁对Ni-Cr-Mo-Al-Ti型镍基铸造合金组织及性能的影响。研究表明,随含铁量增加合金中γ'数量减少,尺寸变小,形态由立方状变为球状;MC量增多,而M₂₃C₆及M₃C₂量减少;铁明显地改变合金元素在γ-γ'中的分配关系,并提高合金的平均电子空位数$\\bar N$v_v,从而促进σ相析出。随含铁量增加,合金中有害微量元素增加,铁严重地降低持久强度,但对拉伸强度影响较小,铁高时合金塑性下降。     

Relationship Between Inoculants and the Morphologies of MnS and Graphite in Gray Cast Iron

The influence of oxides and sulfides in gray cast iron on the growth morphologies of MnS and on the nucleation of graphite was experimentally investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) analysis with evidences that shows the possible nucleation sites for graphite nucleation. Thermodynamic studies have been done on the influence of varying sulfur concentrations on the nucleation of MnS in the melt and during solidification. The consumption of dissolved oxygen and sulfur in the melt during the cooling process was analyzed and we explored how this influenced the nucleation process of oxides and sulfides. A sequential nucleation concept of oxides and MnS is proposed in relation to the growth morphology of MnS and graphite with respect to the mechanical properties of cast iron. The nucleation of new oxides and sulfides was analyzed using thermodynamics and compared to our experimental results. Graphite nucleation on substrates other than MnS, such as MoS₂ oxides and (Mo,Cr)S, was experimentally analyzed along with the influence of the substrates on graphite nucleation and growth morphology.     

Reduction in Liquid Segregation and Microstructure Improvement in a Semisolid Die Casting Process by Varying Injection Velocity

To investigate die filling from a semisolid melt, a die was designed to cast a two-part test sample with restrictions in one part and steps of different thicknesses in the other. Several defect types were observed including surface eutectic segregation, gas holes with eutectic segregation, oxide flaws, and shrinkage porosity. The effect of melt injection velocity on liquid segregation in the cast parts was investigated using macro–microstructural observation and computer simulation. Process parameters to reduce liquid segregation were obtained by computer simulation. The effect of injection speed of the plunger tip on liquid segregation was most significant after the semisolid material had filled the runner. According to experimental and simulation results, liquid segregation could be removed by controlled high plunger speed (more than 0.3m/s).     

合金元素对奥氏体-贝氏体型球墨铸铁组织和性能的影响

根据不同的合金元素对球墨铸铁基体组织的影响，将锰、钼、镍和铜的含量合理搭配，以岩棉为冷却介质，在连续冷却过程中获得了性能较好的奥氏体-贝氏体型球墨铸铁，HRC可达33～48，αk可达26～48J／cm^2。     

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

ＥｆｅｃｔｏｆＲａｒｅＥａｒｔｈｓａｎｄＮｉｔｒｏｇｅｎｏｎＧｒａｐｈｉｔｅＳｔｒｕｃｔｕｒｅｏｆＧｒａｙＣａｓｔＩｒｏｎＺｈａｉＱｉｊｉｅ（翟启杰），ＺｅｎｇＱｉ（曾奇）（ＦｏｕｎｄｒｙＩｎｓｔｉｔｕｔｅ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａ...     

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.     

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.     

Nd-Fe-B系铸锭显微结构的研究

研究了不同Dy取代量的Nd31.0-xDyxNb1.0Al0.3Cu0.3B1.03Fe余(x=0,1.0,2.0)系合金铸锭在均匀化处理前后显微结构的变化。发现添加少量Dy有利于减少铸锭中α-Fe相的数量。适当的均匀化处理可以减少或消除α-Fe相,但晶界相大量聚集,T1相(Nd2Fe14B相)晶粒显著长大。     

Solidification and Room Temperature Microstructure of a Fully Pearlitic Compacted Graphite Cast Iron

Compacted graphite cast irons are rapidly developing for they have better mechanical properties than lamellar graphite cast irons and present less porosity than spheroidal graphite cast irons. For many applications, an as-cast fully pearlitic matrix would be desired which can hardly be achieved when graphite is compacted. Addition of manganese, copper and tin are thus made as these elements are known to be pearlite promoters. However, their amount should be limited so as to avoid detrimental effects amongst which are heterogeneities in the matrix properties which impede easy machining. In the present work, a compacted graphite cast iron containing 0.3 wt% Mn, 0.8 wt% Cu and 0.1 wt% Sn was cast in sand mould and in standard thermal analysis cup. The cup sample showed a nearly fully pearlitic matrix and was selected for further study. The characterization consisted of measuring and correlating the distributions of pearlite interlamellar spacings and microhardness values. An attempt was made to look for the effect of solidification microsegregation on microhardness which did not reveal any trend.     

Analysis of Graphite Morphology of Gray Cast Iron in Pulse Magnetic Field

Theelectromagneticrefinementofmetalsolidi ficationstructureisanewlydevelopedtechnique. Themagneticfieldcanrefinethesolidificationstruc turebyactingupontheliquidmetal,suchasvibra tionandstirring.Atpresent,suchtechniquesare mainlyappliedtoalloyswithlower…     

脉冲电流对过共晶灰口铸铁凝固组织的影响

采用储能电容为1200uF的脉冲电源，在不同的充电电压下，对过共晶灰口铸铁进行电脉冲处理。结果表明：脉冲电流能够明显细化和改善过共晶灰口铸铁的凝固组织，使石墨由粗大的长片状变为小块状或小片状，石墨的分布更加均匀，而且尖角钝化甚至呈近似球形。脉冲电压的升高和脉冲频率的增大都有利于过共晶灰口铸铁凝固组织的细化和改善。