Papers by Keyword: ADI

Abstract: In this investigation, the characteristics of bulky retained austenite in an austempered ductile iron are evaluated in two tempered conditions. which were intially tempered at 200oC for 1h before cooling to room temperature, and then tempered at 350oC for 1h. The result shows that the hardness within retained austenite areas is distributed unevenly with a range from 423 HV to 897 HV, which is attributed to the transformation from austenite to martensite during austempering. Also, the mechanism regarding the quenched marteniste formation is discussed. The poor fatigue resistance of ADI is hypothesized to be due to the amount of austenite transformed to martensite.

Abstract: The contribution deals with the evaluation of tribological properties of materials: isothermally heat-treated cast iron ADI, heat-treated cast iron with globular graphite HTDI with sorbitic structure of the basic metal matrix and heat-treated steel C45. The aim of the research is to gain another knowledge for the application of materials in the condition where the loss of mechanical energy and the loss of material caused by parts wear are being appeared.

Abstract: Machine and equipment safety is the most essential factor that determines the choice of a particular material used in the construction phase. Failure analyses in engineering praxis demonstrate that nearly 90 % of all cases of failures are caused by fatigue. For popular technical applications such as cars and trains, the durability expected for some components ranges from 10⁸ to 10¹⁰ loading cycles. However, only few studies have been carried out for more than 10⁷ cycles. The SN curve in the ultra-wide life region must be determined in order to ensure actual fatigue strength and safety of these components. This paper presents the results obtained from fatigue tests carried out by means of a high-frequency fatigue testing machine for the three grades of ductile iron: with ferritic-pearlitic matrix (GGG50), with pearlitic-ferritic matrix (GGG60) and ADI cast iron in the range from 10⁶ up to 10¹⁰ cycles.

Abstract: This paper discusses utilizing Austempered Ductile Iron (ADI) to manufacture driving/driven spiral bevel gears for big-horsepower (under 350 Hp) heavy truck rear axles, which is a breakthrough in China. Through the carry out of focused research and experiments on main craft process key points of the components, and with all-round analysis to technical/quality outcome achieved, the authors have finally developed this new generation copper-niobium alloy ADI main/sub spiral bevel gear that is suitable for heavy truck (under 350 HP) rear axle uses. While being able to replace 22CrMo and 18CrMnTi alloy forged steels in use, this new gear has also achieved replacing forging & steel with casting & iron. Cutting of two main process steel-making and steel-rolling has not only raised production efficiency, but also lowered the its cost. At current, rear axle spiral bevel gears for automobiles in China are manufactured through forging, with 40Cr18CrMnTi22CrMo as key materials; cemented quenching and tempering techniques are applied in the production process.This method is also used in manufacturing of driving/driven spiral bevel gears for trucks rear axles. Such combination of high-quality steel and forging means high material cost, complicated process, and production inefficiency.

Abstract: select ADI commonly used in engineering, set 15 sets of austempering parameters and research on the rules of their influence on the tensile strength and elongation of ADI. Through the tensile test, use ANSYS Workbench to simulate the process of tensile measurement and compare the experimental data. The results show that: longer austenitizing time leads to smaller tensile strength, whereas the elongation remains unchanged. The tensile strength reduces linearly as the austempering temperature rises while the elongation first increases and then reduces as the austempering temperature rises and peaks at 350°C. The austempering time has little influence on elongation.

Abstract: Austempered Ductile Iron (ADI) is a type of nodular, ductile cast iron subjected to heat treatments - austenitising and austempering. Whilst machining is conducted prior to heat treatment and offers no significant difficulty, machining post heat treatment is demanding and often avoided. Phase transformation of retained austenite to martensite leading to poor machinability characteristics is a common problem experienced during machining. This case study explains the effect of feed rate on machinability of ADI using cutting force analysis and tool failure analysis. The experimental design consists of conducting drilling trials on grade 1200 and 1400 at constant depth of cut, 25mm; constant speed, 45m/min; no coolant and variable feed rates from 0.2 to 0.35 mm/rev (increment of 0.025mm/rev). Metallography and X-ray diffraction technique was carried out in order to identify and quantify the microstructural phases before and after drilling. The results from the trial infer that the best way to machine ADI efficiently without tool failure is using low feeds and high speeds and without coolant.

Abstract: This work proposes a mechanistic model to predict the cutting forces during machining of low machinability materials such as austempered ductile irons (ADI). For these cases, commonly used models are not accurate due to high rates of wear and a new coefficient is necessary to correctly estimate the cutting forces against time. As well, ceramic inserts are applied for the first time in dry turning of ADI.

Abstract: In this research wear mechanism of ADI under different intensity of loading with different hardness have been investigated. To study of wear behavior, a series of austempered specimens with optimum mechanical properties were used for wear tests. Dry sliding wear tests were carried out in pin-on-ring wear tester machine at speed of 0.5 ms-1 and loaded with normal loads of 100,200,300 and 400 N. Scanning electron microscopy for microstructure and wear surface analysis was used. To determine the austenite volume fraction and the percentage of carbon content in austenite, X-ray diffraction analysis was used. Results show that the role of retained austenite at wear properties of ADI is dependent on loading intensity and austenite carbon content.

Abstract: Ductile cast iron was quenched at different austempering temperatures with different isothermal time, so there were austempered ductile iron (ADI) materials with nine different mechanical properties. Their metallographic structures were qualitatively and quantitatively analyzed with scanning electron microscope and X-ray diffraction method. Curves of the relationships between heat treatment parameters, content of retained austenite and carbon content in retained austenite were studied respectively. Models that showed their relationships were built in the base of fuzzy subtractive clustering method to research the rules of isothermal temperatures and time affecting the microconstituent of ADI. The results show that the metallographical matrix structures of ADI become ausferrite, and its mechanical properties are strengthened notably. From the curves and fuzzy models, we knew that the effect of austempering temperature on the component content of ADI was predominant, and austempering time was inferior. Thus, as the temperature increased, the content of retained austenite, carbon content in retained austenite increased markedly. Keywords: ADI, heat treatment parameters, retained austenite, carbon content of retained austenite, fuzzy subtractive clustering model

Abstract: Elements such as Mn and Mo may be added to ductile iron to improve its hardenability and mechanical properties, but segregation of these elements could result in the reduction of mechanical properties and must therefore be considered during the manufacturing of thick section ductile iron. In this research the microstructures of cast specimens containing 2% Mn were studied by optical microscopy and scanning electron microscopy. Results showed that manganese segregates in the intercellular areas while silicon segregates in the regions around graphite nodules. Partial Melting Homogenization (PMH) was carried out on the samples to reduce segregation. Analysis of the results showed that homogenization has been done successfully and segregation in the ductile iron matrix was significantly reduced. The successful effect of homogenization was also studied on austempered samples. PMH prior to austempering resulted in a very uniform bainitic microstructure. Tensile tests were carried out on the samples which showed improved mechanical properties due to combined PMH process and austempering process.