Effect of Rare Earth Alloy Modification on High Carbon Equivalent Gray Cast Iron of Automotive Brake Drum

Effect of rare earth alloy modification on properties and microstructure of high carbon equivalent gray cast iron was investigated.The experimental results show that in the way of mechanical property,when the addition of rare earth alloy is 0.2% and 0.3%,the tensile strength of cast iron increases.In the way of microstructure,the addition of rare earth alloy increases the number of primary austenite dendrites,reduces secondary dendritic arm spacing,and changes the eutectic size and quantity.When rare earth alloy is added into gray cast iron,the morphology and quantity of graphite play a major role on the improvement of tensile strength.

Relationship between Primary Crystal Temperature and Carbon Equivalent in Cast Iron

CE （=%C＋（1/3）x（%Si）） does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperature （Tc） and carbon equivalent （CEL） was investigated. The results show that Tc （Celsius degree） = 1650-110 × （%C） -25 × （%Si）＋3 × （%Mn） -35 × （%P） -71 × （%5）-2 × （%Ni） -7 × （%Cr）; CEL=%C ＋ 0.23×（%Si）-0.03× （%Mn）＋0.32×（%P）＋0.64×（%S） ＋0.02×（%Ni）＋0.06×（%Cr）. That is, in hypo eutectic composition, carbon equivalent should be calculated with CEL=%C＋ 0.23×（%Si）, not with CE=%C＋（1/3） x（%Si）.

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.

Carbon Equivalent Fundamentals in Evaluating the Weldability of Microalloy and Low Alloy Steels

Understanding the weldability of steel in relation to the use of carbon equivalent is very necessary for the welding industry. The study was poised to unearth the fundamentals of carbon equivalent as applied in evaluating the weldability of steel. The study used a two-stage design approach to address the problem of carbon equivalence weldability of steel, thus, survey and experimental. Two different steels were tested to ascertain their chemical composition which could inform carbon equivalent calculation, and the results revealed microalloy and low alloy steels respectively. In subjecting the microalloy steel to carbon equivalent analyses of the AWS and IIW coefficients;revealed a value (CEV) = 0.11 each, suggesting that this microalloy steel has excellent weldability;no preheating is required. A successful welding operation on this steel does not depend on preheating. Also, the average results of the low alloy steel revealed a value (CEV) = 0.37 and 0.32 respectively, suggesting that this type of steel has very good weldability and may require to preheat. It is recommended that welders have a general idea about the weldability of steel with regard to carbon equivalent calculation. In addition, they should understand the chemical compositions of steels they are dealing with.

Effect of austenitization temperature on microstructure and mechanical properties of low-carbon-equivalent carbidic austempered ductile iron

The wear resistances of austempered ductile iron （ADI） were improved through intxoduction of a new phase （carbide） into the ma- txix by addition of chromium. In the present investigation, low-caxbon-equivalent ductile iron （LCEDI） （CE = 3.06%, and CE represents cax- bon-equivalent） with 2.42% chromium was selected. LCEDI was austeintized at two difl＇erent temperatures （900 and 975~C） a^ld soaked for 1 h and then quenched in a salt bath at 325~C for 0 to 10 h. Samples were analyzed using optical microscopy and X-ray diffraction. Wear tests were carded out on a pin-on-disk-type machine. The efl＇ect of austenization temperature on the wear resistance, impact strength, and the mi- crostructure was evaluated. A stxucture-property correlation based on the observations is established.

Precipitation and evolution of nodular graphite during solidification process of ductile iron

The quantity and morphology of spheroidal graphite have an important effect on the properties of ductile iron, and the characteristics of spheroidal graphite are determined by the solidification process. The aim of this work is to explore the precipitation and evolution of graphite nodules in hypoeutectic, eutectic, and hypereutectic ductile irons by thermal analysis, liquid quenching and metallographic technique. Results show that hypoeutectic ductile iron has the longest solidification time and the lowest eutectic temperature;eutectic ductile iron has the shortest solidification time;hypereutectic ductile iron has the highest eutectic temperature. After solidification is completed, hypoeutectic ductile iron has the lowest nodule count, nodularity and graphite fraction;eutectic ductile iron has the highest nodule count, nodularity and the smallest nodule diameter;hypereutectic has the highest nodule diameter and graphite fraction. The nucleation and growth of graphite nodules in hypereutectic ductile iron starts before bulk eutectic crystallization stage, however, the precipitation and evolution of graphite nodules of hypoeutectic and eutectic ductile irons mainly occur in the eutectic crystallization stage. The graphite precipitated in eutectic crystallization of hypoeutectic, eutectic, and hypereutectic ductile irons, are 61%, 68% and 43% of total graphite volume fraction, respectively. Simultaneously, there are plenty of austenite dendrites in hypoeutectic and hypereutectic ductile irons, which are prone to shrinkage defects. Therefore, the eutectic ductile iron has the smallest shrinkage tendency.

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.

Effects of Carbon Content and Solidification Rate on the Thermal Conductivity of Grey Cast Iron

The thermal conductivity/diffusivity of pearlitic grey irons with various carbon contents was investigated by the laser flash method. The materials were cast in controlled thermal environments producing three dissimilar cooling rates. The cooling rates together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent, and the fraction of the former primary solidified austenite transformed into pearlite. The results show that the optimal thermal transport properties are obtained at medium cooling rates. Equations are given for the thermal conductivity of pearlite, solidified as pre-eutectic austenite, and the eutectic of grey iron. The thermal conductivity of pearlitic grey iron is modelled at both room temperature and elevated temperatures with good accuracy.

Photochemical naphthylation at(α-carbon atom of carbonyl and its equivalences

The photostimulated reaction of halonaphthalene with a series of carbanions derived from, propionic acid derivatives in liquid ammonia led to the naphthylation at a-carbon of the carbanions in an isolated yield ranging from 25％ to 86％.In all cases,the dehalonaphthalenes were found to, be by-products and the reaction was inhibited by p-dinitrobenzere.An electron transfer from the carbanion to the halonaphthalene followed by ejection of halogen led to naphtbyl radical,as predicted by comparing the LUMOs of the carbanions and the halonaphthalenes,was involved in the process. Absence of the alkylnaphthalene and 1,2-dinaphthylalkane in the products indicates the smooth electron transfer between(Naph-Nu)^+ and Naph-X.C-vs.O-naphthylation is fully addressed in terms of MNDO calculations and acid-base principle.