Properties and Structure of High-Silicone Austempered Ductile Iron

Krzyńska, A.; Kochański, Andrzej

doi:10.2478/afe-2014-0043

Cited by 8 publications

(6 citation statements)

References 2 publications

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“…The strengths are on similar or higher level compared to the results presented for conventional silicon concentration ADI austempered in similar temperatures [1,2,12]. The current results match well with gained previously with silicon solution strengthened austempered ductile irons despite the difference in austenitisation temperature [7,9].…”

Section: Discussionsupporting

confidence: 89%

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Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron

Soivio

2018

MSF

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Austempered ductile iron provides a feasible way to produce high strength components. However, in heat treatments resulting in highest strengths some of the ductility is lost due to formation of bainitic carbides. The role of silicon in inhibiting the formation of iron carbides in as-cast ductile irons as well as its solution strengthening effect is well known and acknowledged in industry. The effect of silicon on austemperability, resulting microstructures, and mechanical properties of austempered ductile irons with silicon contents with 3.4-3.8 w-% was researched. Quenching and austempering heat treatments were carried out for production grade silicon solution strengthened ductile irons EN GJS 500-14. Results indicate, that it is possible to manufacture a fully ausferritic structure into a silicon solution strengthened matrix and indeed good ductility can be achieved in combination with ultimate tensile strength of 1600 MPa. Segregation of silicon reduces the solubility of carbon into the matrix especially close to the graphite nodules which reduce the stability of carbon stabilized austenite and leads into compromised machinability.

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Section: Discussionsupporting

confidence: 89%

“…There is divergence between the presented equation and equilibrium diagrams. Previous austempering experiments with silicon solution strengthened ductile irons have used austenitising temperature of 900 °C [7,9]. As Larker presented in his invention, high enough austenitising temperature should be used.…”

Section: Introductionmentioning

confidence: 99%

Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron

Soivio

2018

MSF

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“…In Figure 4b it can be noted how in the sample treated at 290 • C for 90 min, α ac needles converge at the same nucleation site, giving the appearance of α ac needle bundles. Another type of α ac needle arrangement consists of clusters, as observed in the sample treated at 320 • C for 90 min in Figure 4c, which is composed of parallel α ac needles separated by γ hC , similar to results of other researchers [40][41][42][43]. Meanwhile, Figure 4d,e illustrate the two types of α ac needles, fine (lower ausferrite) and feathery (upper ausferrite), respectively, within the samples treated at 290 and 380 • C for 60 min, as reported by Putantunda and Olawale [19,44].…”

Section: Microstructural Analysis and Hardnesssupporting

confidence: 89%

Statistical Data-Driven Model for Hardness Prediction in Austempered Ductile Irons

Rodríguez-Rosales

Montes-González

Gómez-Casas

et al. 2022

Metals

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This research evaluates the effect of temperature and time austempering on microstructural characteristics and hardness of ductile iron, validating the results by means of a statistical method for hardness prediction. Ductile iron was subjected to austenitization at 950 °C for 120 min and then to austempering heat treatment in a salt bath at temperatures of 290, 320, 350 and 380 °C for 30, 60, 90 and 120 min. By increasing austempering temperature, a higher content of carbon-rich austenite was obtained, and the morphology of the thin acicular ferrite needles produced at 290 °C turned completely feathery at 350 and 380 °C. A thickening of acicular ferrite needles was also observed as austempering time increased. An inversely proportional behavior of hardness values was thus obtained, which was validated through data analysis, statistical tools and a regression model taking temperature and time austempering as input variables and hardness as the output variable, which achieved a correlation among variables of about 97%. The proposal of a mathematical model for the prediction of hardness in austempered ductile iron represents a numerical approximation which validates the experimental results at 95.20%.

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“…The adopted model has the following form: HB (τ) = ΔHB * EXP (-(τ-2) / t) + HBmin (1) where: τ -sample holding time [h], t -time constant of the process [h], HB -hardness. The time constant of the process T should be understood as the time which it takes for the phases present in the alloy to achieve the state of dynamic equilibrium in respect of each other as a result of the different rates of diffusion stabilized at an equal level.…”

Section: Test Resultsmentioning

confidence: 99%

Prediction of Microstructure in ADI Castings

Guzik

Sokolnicki

Królikowski

et al. 2016

Archives of Metallurgy and Materials

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Tests were carried out on samples of low-alloy ductile iron with additions of Ni, Cu and Mo, subjected to austempering heat treatment. The samples were austenitized at 850, 900 and 950 °C, and then austempered at T = 210, 240, 270, 300 and 330 °C. The ausferritizing treatment was carried out in a salt bath for the time τ = 2 - 8 hours. Additionally, tests and studies covered samples subjected to the ausferritizing treatment at 270 °C with the time of holding castings in a bath from 2 to 24 hours. Evaluation covered the results of the ADI microstructure examinations and hardness measurements. The ADI matrix morphology was identified counting the average number of ausferrite plates and measuring their width and spacing. The regression equations HB = f (τ, T) and τ = f (HB, T) were derived to establish the, so-called, “process window”, allowing obtaining a priori the required microstructure of ADI and, consequently, the required mechanical properties, mainly hardness, shaping the functional properties of castings, abrasion wear resistance – in particular.

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Properties and Structure of High-Silicone Austempered Ductile Iron

Cited by 8 publications

References 2 publications

Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron

Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron

Statistical Data-Driven Model for Hardness Prediction in Austempered Ductile Irons

Prediction of Microstructure in ADI Castings

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