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
Super duplex stainless steel (SDSS) is considered as a composite formed from a microstructure of an approximately equal mixture of two primary constituents (γ-austenite and α-ferrite phases) and the secondary precip...Super duplex stainless steel (SDSS) is considered as a composite formed from a microstructure of an approximately equal mixture of two primary constituents (γ-austenite and α-ferrite phases) and the secondary precipitates (sigma, chi, alpha-prime, etc.). While the formation of these phases affects the properties of SDSS, however there are no rules that govern the relationship. In this work, the relationship between toughness as well as corrosion behavior of SDSS (UNS 32760) and the microstructure constituents has been experimentally investigated, and analyzed in view of the composite principles. Another two stainless steels namely;fully austenitic SASS (UNS N08367) and fully ferritic FSS (UNS S42900) are considered to simulate the constituent’s primary components in the composite which are austenite γ and ferrite α phases respectively. Samples of the composite and constituent’s steels are first subjected to solution annealing, where the composite steel has a microstructure of γ austenite and α ferrite grains. They were then subjected to similar different isothermal heat treatment cycles, for the formation of secondary phase precipitations within the transformation temperature ranges of each of γ and α primary grains. Impact toughness and corrosion (specific weight loss) tests were conducted on the annealed and isothermally treated samples. The composite rule of the mixtures (ROM) is used to analyze the relationship between the toughness and corrosion properties in the composite SDSS and the SASS and FSS constituent’s steels. The analysis indicates that in case of toughness, ROM applies well on the composite and constituents’ steels in the solution annealed and in isothermal treatment conditions, where better matching between experimental and calculated results is observed. When applying ROM for corrosion weight loss, a great difference is found between the experimental and calculated results, which is much reduced for solution treated samples ferritic and austenitic temperature ranges of 480℃ - 500℃ and 700℃ - 750℃ as for ferrite and austenite respectively.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Super duplex stainless steel (SDSS) is considered as a composite formed from a microstructure of an approximately equal mixture of two primary constituents (γ-austenite and α-ferrite phases) and the secondary precipitates (sigma, chi, alpha-prime, etc.). While the formation of these phases affects the properties of SDSS, however there are no rules that govern the relationship. In this work, the relationship between toughness as well as corrosion behavior of SDSS (UNS 32760) and the microstructure constituents has been experimentally investigated, and analyzed in view of the composite principles. Another two stainless steels namely;fully austenitic SASS (UNS N08367) and fully ferritic FSS (UNS S42900) are considered to simulate the constituent’s primary components in the composite which are austenite γ and ferrite α phases respectively. Samples of the composite and constituent’s steels are first subjected to solution annealing, where the composite steel has a microstructure of γ austenite and α ferrite grains. They were then subjected to similar different isothermal heat treatment cycles, for the formation of secondary phase precipitations within the transformation temperature ranges of each of γ and α primary grains. Impact toughness and corrosion (specific weight loss) tests were conducted on the annealed and isothermally treated samples. The composite rule of the mixtures (ROM) is used to analyze the relationship between the toughness and corrosion properties in the composite SDSS and the SASS and FSS constituent’s steels. The analysis indicates that in case of toughness, ROM applies well on the composite and constituents’ steels in the solution annealed and in isothermal treatment conditions, where better matching between experimental and calculated results is observed. When applying ROM for corrosion weight loss, a great difference is found between the experimental and calculated results, which is much reduced for solution treated samples ferritic and austenitic temperature ranges of 480℃ - 500℃ and 700℃ - 750℃ as for ferrite and austenite respectively.
