Cast joining of cast iron to aluminium casting matrix

Abstract

The present study focused on reinforcing Al–Si–Cu alloy with a cast iron insert and using Zn–xAl–3Si–0·5Mg (wt-%) intermediate alloys by the cast joining technique to take advantage of lightness and stiffness of the hybrid structure. The experimental set-up consisted of coating the insert using hot dipping method followed by immersing the coated insert into the Al melt and allowing the system to cool down to the room temperature. The quality of Al–Fe joints in terms of morphology, thickness, chemistry and microhardness was evaluated as a function of coating composition and immersion time in the Al melt. Characteristics of reaction layer at the coating/insert interface and its effects on the joint properties were determined using microstructural analysis and thermodynamic calculations. Combination of a suitable coating containing 27 wt-%Al and optimised process parameters, including 1 min immersion time, resulted in the formation of an Al–Fe joint with promising characteristics.     

Experimental investigation on an adsorption system for producing chilled water

This paper describes a zeolite-water adsorption refrigeration system for producing chilled water, in which zeolite-13X-H₂O is used as a working pair and the exhaust gas from a diesel engine is utilized as a heat source. The system is to be used on a fishing boat for preserving aquatic products. The design of the system is given. The adsorption unit consists of many adsorption elements. The dynamic curve of the elements has been measured in a laboratory. A medium-size prototype of the adsorption chiller has been made, and its preliminary operating performance with an associated diesel engine is given. Further testing of its application is underway.     

Failure investigation of lime coated grey cast iron moulds at TEMCO ferroalloy smelter

This case study outlines an investigation to identify the root cause for the failure of casting machine moulds, manufactured from grey cast iron, at the TEMCO Ferroalloy smelter in Bell Bay, Tasmania. A preliminary stress analysis shows that the thermal stresses developed in the moulds during operation are insufficient to cause failure in a non-defective mould. The failure can instead be attributed to high temperature oxidation that results from a combination of high mould surface temperature, decomposition of the hydrated lime release coating and the grey cast iron structure. Preventing the oxidation reaction would eliminate this material damage and increase the service life of the moulds. The formation of the high temperature oxide can be prevented by reducing the maximum surface temperature of the mould, using a coating that does not release water at operating temperatures or using moulds manufactured from a different type of cast iron.     

Effect of heat treatment on ultrasonic velocity in ductile cast iron

Abstract

The measurement of the ultrasonic velocity is a common method in the foundry industry for the evaluation of the nodularity in ductile iron castings. Practical experience has shown that heat treatment can reduce the ultrasonic velocity compared to the as cast condition. Using ductile iron samples with different heat treatments in order to vary the ferrite and pearlite content respectively confirmed this decrease in the ultrasonic velocity compared to the as cast state. Further investigations showed that with all the heat treatments applied, irrespective of their effect on the microstructure, the density was decreased. The decrease in density correlated with the decrease in ultrasonic velocity for all heat treatments. The mechanisms involved in the reduction in the density are discussed.     

微量润滑条件下Si3N4陶瓷 白口铸铁的摩擦学性能研究

采用块 盘式摩擦磨损试验方法,在MG 200摩擦磨损试验机上对Si3N4陶瓷 白口铸铁摩擦副进行了微量润滑条件下的摩擦磨损试验,同时根据试件的SME照片和能谱成分分析了摩擦磨损机理,为陶瓷材料的制备及减少磨损提供理论依据。试验和分析结果表明：微量润滑条件下Si3N4陶瓷的磨损率和摩擦系数要比干摩擦条件下小得多;Si3N4陶瓷的磨损率随载荷的增大而增大,滑动速度对磨损率的影响要小于载荷对其的影响;Si3N4陶瓷 白口铸铁的摩擦系数随速度的增大而减小,载荷的变化对摩擦系数的影响不大;Si3N4陶瓷的磨损是化学磨损、机体物质脱落和磨粒磨损共同作用的结果,其中化学磨损起主导作用。     

Influence of chunky graphite on mechanical and fatigue properties of heavy-section cast iron

This research work aimed to find out the influences of the different amounts of chunky graphite on mechanical and fatigue properties of GJS 800 ductile cast iron. Chunky graphite has been a problem of heavy section thick-walled ductile cast iron components. Chunky graphite is branched and interconnected as a network within eutectic cells and has been observed to form in thermal centres of heavy ductile cast iron sections during solidification. This research work proved that chunky graphite in the microstructure decreases the ultimate tensile strength, the elongation to fracture and fatigue life significantly, but does not influence on the yield stress of ductile cast iron GJS 800 substantially. Low nodular count and nodularity rate also decrease the fatigue life of ductile cast iron, and the difference of fatigue life of specimens containing chunky graphite or having low nodular count and nodularity rate is not large. Influence of the amount of chunky graphite on fatigue life increases until 20% chunky graphite content, and above that the fatigue life does not decrease substantially.     

Influence of methane and carbon dioxide on in-flight particle behavior of cast iron powder by atmospheric plasma spraying

Graphite degradation in plasma sprayed cast iron coatings is a technological barrier for achieving superior wear resistant coatings. Therefore, there is a need to understand the in-flight particle behavior of cast iron powder. In this study, methane (CH₄) and methane/carbon dioxide (CO₂) mixture has been introduced into the plasma flame to decrease the in-flight particle temperature of cast iron powder in order to prevent the oxidation and dissolution of graphite as well as provide additional free carbon. It has been observed that, CH₄ and CH₄/CO₂ addition remarkably decreases the in-flight particle temperature as a result of the in-situ endothermic reactions. Also, results demonstrate that while CH₄ and CH₄/CO₂ addition does not alter the microstructure, it slightly increases the graphite content in cast iron coatings.     

Adhesion behavior of plasma sprayed thermal barrier coatings on Al-6061 and cast iron substrates

In this work an investigation was carried out on adhesion strength and micro-hardness of plasma sprayed coatings on Al-6061 and cast iron substrate materials. For the adhesion test, ASTM C633, and for the micro hardness, ASTM E384 standards were used. From the results obtained it was found that the main failure locations were in the bond coat-substrate interface, which is considered as adhesion strength. The various parameters affecting adhesion strength are also discussed.     

铸铁电火花沉积WC-8Co超细涂层的组织及性能

采用电火花沉积技术,在铸铁表面制备WC-8Co沉积涂层。利用XRD、SEM、显微硬度计、摩擦磨损试验机研究了涂层的微观组织及耐磨性能。结果表明,通过优化的沉积工艺参数可以获得组织均匀、致密且与基体呈冶金结合的沉积层。沉积层主要由Co3W3C、Fe3W3C、W2C和Fe7W6相组成;沉积层中弥散分布有大量的超细碳化物颗粒。沉积层的最高硬度为1512.1Hv,其耐磨性能是基体的2.3倍;沉积层的磨损机制主要是磨粒磨损和疲劳磨损。涂层中弥散分布的超细硬质相是沉积层硬度及耐磨性能提高的主要因素。     

离心式冷水机组大温差设计运行特性的实验研究

中央空调冷冻水系统大温差设计可以显著降低输配能耗,对系统节能具有重要意义.但随设计温差增大、冷冻水流速降低,蒸发器水侧传热系数逐渐减小,成为制约冷水机组能效的主要因素.本文基于蒸发器换热机理,理论分析了冷冻水大温差对蒸发器换热性能的影响,并通过离心式冷水机组串联运行的方案,实验对比了大温差工况下不同水路流程对整机性能的...     

超临界撞击流技术制备微胶囊工艺

将超临界流体与撞击流技术相结合,提出了一项新的包覆技术—超临界撞击流技术(SFIT)。以石蜡和玻璃微珠分别作为包覆模型材料的壁材和芯材,考察该技术的可行性和有效性;研究混合器内压力、温度、撞击釜内撞击距离以及膨胀前温度等因素对于微胶囊的表观包覆率和表观形态的影响。结果表明,在混合器内压力20MPa以上、温度75℃,且撞击距离70mm,膨胀前温度140℃时,得到的微胶囊团聚小,包覆均匀且效果较好。实验采用电子扫描电镜、激光粒度分布仪和差式扫描量热仪等检测方法从微胶囊的表观包覆率、粒径分布范围、表面形态等角度进行评价。从结果来看,超临界流体与撞击流技术相结合可以实现微胶囊的包覆且效果良好。     

Effects of process parameters on the microstructure of iron coating fabricated on pure aluminum by immersion plating

In this paper, an iron coating was designed to fabricate on the surface layer of pure aluminum. The effects of process parameters such as immersion plating method, durations and temperatures on the microstructure of iron coating were studied systematically. The experimental results showed that the quality of the iron coating fabricated on the sample by one-step immersion plating is better than that obtained by two-step immersion plating. The iron coating obtained by one-step immersion plating for 1 min is continuous and without obvious gaps and cavities. With the immersion time increased to 3 min and 5 min, the coating is uneven and easy to fall off from the surface of sample. Additionally, due to that the higher temperature increases the efficiency of displacement reaction, the quality of the coating obtained at 40 °C is better than that obtained at 55 °C and 65 °C. Consequently, the optimal immersion plating parameters were one-step immersion plating, 1 min, and 40 °C. This paper provides a novel method to prepare an iron coating as a pretreatment for electroplating of aluminum.     

Experimental investigation on process parameters of near-field deposition of electrospinning-based rapid prototyping

Near-field electrospinning (NFES) with its capability to produce a straight fine fibre has been integrated into additive manufacturing for the fabrication of scaffolds with controllable pattern structures. However, building the third dimension with NFES is not easy due to the unsolidified fibre while being deposited. Presented in this paper is an investigation on the influence of process parameters on achieving a small cylindrical fibre from the near-field fibre deposition of an electrospinning-based rapid prototyping. A set of experiments have been conducted on solutions of polycaprolactone (PCL) in N,N-dimethylformamide (DMF). Parameters of interest are voltage, standoff distance, polymer concentration, environmental condition and needle size. From the experimental results, polymer concentration, environmental condition and needle size had influence on achieving a small cylindrical fibre. Under near-field deposition, the concentration should be high, the needle should be small and the temperature should be maintained during the process.     

声波测井偶极子发射换能器性能的实验研究

多极子声波测井是新一代声波测井技术,偶极子发射换能器制作技术是其关键技术。本文报道了对自行研发的偶极子声波测井换能器的一致性、耐温、指向性等进行的测试分析结果。本文对三个压电弯曲振子的实验测量结果表明,将偶极子声波测井换能器置于硅油中测量的谐振频率要比在空气中测量的谐振频率降低约20％：在室温到150℃范围内,换能器的谐振频率随着温度的升高略有降低;在偶极子声波测井发射换能器的指向性测量曲线中,换能器辐射声波能量最强方向的声压值与其最弱方向的声压值的比值超过12dB;初步现场测量结果说明．本文研制的偶极子声波测井发射换能器能够测得满意的偶极子声波测井波形。     

不同温度下玻璃钢材料放气速率的试验研究

设计了一套基于压差流量法的试验装置来测量玻璃钢试样的放气速率。将试样的表面采用砂纸（500#）进行打磨，采用扫描探针显微镜对试样表面粗糙度进行测量。测量了不同温度下玻璃钢试样的放气速率。试验结果表明测量室温度越高，测量室的气体压力越高，玻璃钢试样的放气速率越大。     

Application of grey relational analysis based on Taguchi method for optimizing machining parameters in hard turning of high chrome cast iron

High chrome white cast iron is particularly preferred in the production of machine parts requiring high wear resistance. Although the amount of chrome in these materials provides high wear and corrosion resistances, it makes their machinability difficult. This study presents an application of the grey relational analysis based on the Taguchi method in order to optimize chrome ratio, cutting speed, feed rate, and cutting depth for the resultant cutting force (F_R) and surface roughness (R_a) when hard turning high chrome cast iron with a cubic boron nitride (CBN) insert. The effect levels of machining parameters on F_R and R_a were examined by an analysis of variance (ANOVA). A grey relational grade (GRG) was calculated to simultaneously minimize F_R and R_a. The ANOVA results based on GRG indicated that the feed rate, followed by the cutting depth, was the main parameter and contributed to responses. Optimal levels of parameters were found when the chrome ratio, cutting speed, feed rate, and cutting depth were 12%, 100 m/min, 0.05 mm/r, and 0.1 mm, respectively, based on the multiresponse optimization results obtained by considering the maximum signal to noise (S/N) ratio of GRG. Confirmation results were verified by calculating the confidence level within the interval width.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0231-z     

低温试验冷库制冷系统完善试验研究

针对一座试验冷库的实际需要,重新并人一套制冷系统,并通过试验分析降温特性,从经济性角度扩大原有冷库库内温度区域及下一步研究范围。同时对实际设计搭建过程中出现的问题进行探讨分析,以供设计参考。     

Experimental investigation on evolution of surface damage and topography parameters during rolling contact fatigue tests

Nowadays, micropitting is perceived as one of the prevalent wear mechanisms, which is responsible for the breakdown of high power density (power throughput/weight) machines. The current work demonstrates the evolution of surface damage and surface topography parameters during micropitting tests. The test surfaces are examined at different load stages utilizing 3D optical profiler, optical microscope, and scanning electron microscope. The effect of slide‐to‐roll ratio (SRR) on surface damage and topography parameters is also presented. It is observed that the severity of micropitting increases with an increase in the number of cycles. It is concluded that surface bearing index (Sbi), kurtosis (S_ku), maximum valley height (S_v), and autocorrelation length (S_al) are positively correlated with surface damage, whereas mean summit curvature (S_sc) and skewness (S_sk) are negatively correlated with surface damage. Surface texture ratio (S_tr) and power spectral density (PSD) of test surfaces are used for analysing surface texture, and it is found that deterioration in surface texture occurs after 6 million cycles. It is also concluded that geometrical isotropy increases with an increase in SRR.     

Experimental investigation of effects of build parameters on flexural properties in fused deposition modelling parts

Additive manufacturing is a group of fabrication techniques that is used to build components by depositing material in a layer-by-layer manner. Fused deposition modelling (FDM) is one of the additive manufacturing techniques which is widely used for prototyping and production applications of thermoplastic components. In load-bearing applications, flexural and compression forces often coexist. In order to avoid failure under these loads, it is essential to study the mechanical properties of FDM components. The main focus of this research is to study the flexural properties of FDM components and to comprehend their dependence on various build parameters. It has been observed from a series of flexural tests that FDM parts have anisotropic properties and this anisotropy was not due to the material in use, but due to the fabrication process itself. In this study Ultem 9085 is used as the material to fabricate coupons with variations in build parameters including build direction, raster angle and negative air gap. A full-factorial experimental design was used to study the individual and combined effects of these build parameters on the flexural properties of the coupons. Solid and sparse-build styles were used in the coupon fabrication. Flexural properties investigated include flexural yield strength, flexural modulus, flexural strength/mass ratio and flexural modulus/mass ratio. Qualitative observation and reasoning is used to comprehend how the flexural properties are affected by the build parameters.     

液氢温区脉动热管实验研究

为了研究脉动热管用于冷却Mg B——2超导磁体的可行性,对一台自行研制的液氢温区脉动热管实验台开展了实验研究工作。充液率为34.2%时,随着加热功率的增大,脉动热管经历了启动、脉动、极限3个阶段,启动阶段中脉动热管传热温差波动很大,传热性能差,而脉动阶段中脉动热管传热温差很小,传热性能好。脉动热管在加热功率为1.28 W时具有最高的有效热导率为19 k W/m·K,此时蒸发段与冷凝段温差为0.28 K。