To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Qu...To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.展开更多
Spheroidal graphite cast iron GGG 40 was thermo-mechanically tested using thermo-mechanical simulator Gleeble-3500. Three deformation steps were successively applied on test-specimen at temperatures namely;900°...Spheroidal graphite cast iron GGG 40 was thermo-mechanically tested using thermo-mechanical simulator Gleeble-3500. Three deformation steps were successively applied on test-specimen at temperatures namely;900°C, 850°C and 750°C within the austenitic zone, at the same strain rate of 0.1 s-1. No cracks were observed, up to 50% deformation, after successive deformation steps. Stress-strain relationship obtained is correlated with previous work on SGCI with a different carbon equivalent. It was found that by decreasing the deformation temperature;for the same CE, young’s modulus, yield strength and strain hardening exponent increase. Microstructure of the deformed zone, for a specimen quenched after the final deformation step, reveals fine elongated ferrite and pearlite, as well as elongated graphite. While microstructure of the non-deformed zone subjected to the same treatment, includes coarser ferrite and pearlite with graphite spheres embedded in the matrix.展开更多
Studying the thermo-mechanical behavior of ductile iron is necessary to develop the rolling process for ductile iron sheet/strip production, thus, extending its application by replacing steel in several fields such as...Studying the thermo-mechanical behavior of ductile iron is necessary to develop the rolling process for ductile iron sheet/strip production, thus, extending its application by replacing steel in several fields such as machine casing, constructional applications, etc. In order to predict the safe rolling conditions for producing sheets and strips, the thermo-mechanical behavior of a ductile iron alloy, with CE of 4.48, is studied by physical simulation of hot rolling process using Gleeble-3500 simulator. The test was conducted on specimens at a range of deformation temperatures from 800°C to 950°C while three different strain rates;namely 0.05, 0.1 and 0.5 s-1 were used. The results obtained, show minimum values of flow stresses at 850°C. By increasing the deformation temperature up to 900°C, the flow stresses increased to reach maximum values, beyond which the flow stress decreased again. A remarkable dynamic recrystallization is observed at the deformation temperatures of 850°C and 800°C with applied strain rates of 0.05 and 0.1 s-1. Gleeble test results are correlated with microstructure observations on samples quenched at their deformation temperatures, where the changes in structure and graphite morphology are reported. The deformation process at high temperatures namely 950°C and 900°C result in changing the graphite shape from a spheroidal-like to a saucer-like shape. However, by decreasing the deformation temperature to 850°C as well as 800°C, graphite with lamellar shape is observed. As a conclusion, ductile iron could be successfully deformed without cracking at the applied conditions.展开更多
文摘To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.
文摘Spheroidal graphite cast iron GGG 40 was thermo-mechanically tested using thermo-mechanical simulator Gleeble-3500. Three deformation steps were successively applied on test-specimen at temperatures namely;900°C, 850°C and 750°C within the austenitic zone, at the same strain rate of 0.1 s-1. No cracks were observed, up to 50% deformation, after successive deformation steps. Stress-strain relationship obtained is correlated with previous work on SGCI with a different carbon equivalent. It was found that by decreasing the deformation temperature;for the same CE, young’s modulus, yield strength and strain hardening exponent increase. Microstructure of the deformed zone, for a specimen quenched after the final deformation step, reveals fine elongated ferrite and pearlite, as well as elongated graphite. While microstructure of the non-deformed zone subjected to the same treatment, includes coarser ferrite and pearlite with graphite spheres embedded in the matrix.
文摘Studying the thermo-mechanical behavior of ductile iron is necessary to develop the rolling process for ductile iron sheet/strip production, thus, extending its application by replacing steel in several fields such as machine casing, constructional applications, etc. In order to predict the safe rolling conditions for producing sheets and strips, the thermo-mechanical behavior of a ductile iron alloy, with CE of 4.48, is studied by physical simulation of hot rolling process using Gleeble-3500 simulator. The test was conducted on specimens at a range of deformation temperatures from 800°C to 950°C while three different strain rates;namely 0.05, 0.1 and 0.5 s-1 were used. The results obtained, show minimum values of flow stresses at 850°C. By increasing the deformation temperature up to 900°C, the flow stresses increased to reach maximum values, beyond which the flow stress decreased again. A remarkable dynamic recrystallization is observed at the deformation temperatures of 850°C and 800°C with applied strain rates of 0.05 and 0.1 s-1. Gleeble test results are correlated with microstructure observations on samples quenched at their deformation temperatures, where the changes in structure and graphite morphology are reported. The deformation process at high temperatures namely 950°C and 900°C result in changing the graphite shape from a spheroidal-like to a saucer-like shape. However, by decreasing the deformation temperature to 850°C as well as 800°C, graphite with lamellar shape is observed. As a conclusion, ductile iron could be successfully deformed without cracking at the applied conditions.
