Microstructures and Mechanical Properties of a New As-Hot-Rolled High-Strength DP Steel Subjected to Different Cooling Schedules

Hu, Jun; Du, Linxiu; Wang, Jianjun; Gao, Chen; Yang, Tong-Zi; Wang, An-Yang; Misra, R.D.K.

doi:10.1007/s11661-013-1839-z

Cited by 40 publications

(20 citation statements)

References 31 publications

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“…18 compares the mechanical properties of the present samples with DP steels that have been conventionally processed. It can be seen that the UTS and YS of the studied DP steel are lower than those of hot rolled ones, while the total elongation is relatively higher [2,10,13,27,[33][34][35][36][37][38][39]. The product of UTS × total elongation is relatively lower than that of hot rolled ones, which suggests a lower toughness in the studied steel compared to the reference steels.…”

Section: 2mentioning

confidence: 98%

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

et al. 2015

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Conventional dual phase (DP) steel (0.08C-0.81Si-1.47Mn-0.03Al wt.%) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117. ±. 44. μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40-90%, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461-623. MPa and a corresponding total elongation in the range of 0.31-0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite. Abstract: Conventional dual phase (DP) steel (0.08C-0.81Si-1.47Mn-0.03Al wt. %) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117±44 μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40-90 %, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461 -623 MPa and a corresponding total elongation in the range of 0.31 -0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite. Disciplines Engineering | Science and Technology Studies

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Section: 2mentioning

confidence: 98%

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

et al. 2015

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“…The M/A constituents was systematically studied by Misra and co-wokers. [19] During the slow cooling process, the undercooled austenite first transforms to ferrite and the untransformed austenite becomes C rich. When C-rich austenite is cooled to a temperature below M s , it is partially or totally transformed to martensite and forms M/A constituent.…”

mentioning

confidence: 99%

The Determining Role of Finish Cooling Temperature on the Microstructural Evolution and Precipitation Behavior in an Nb-V-Ti Microalloyed Steel in the Context of Newly Developed Ultrafast Cooling

Wang

Deng

et al. 2016

Metall Mater Trans A

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We have studied here the impact of finish cooling temperature on the microstructural evolution and precipitation behavior in Nb-V-Ti microalloyed steel through thermo-mechanical simulation in the context of newly developed ultrafast cooling system. The microstructural evolution was studied in terms of morphology and crystallography of precipitates using high-resolution transmission electron microscopy. At finish cooling temperature of 933 K and 893 K (660°C and 620°C), the microstructure primarily consisted of polygonal ferrite, together with a small amount of wedge-shaped acicular ferrite and lamellar pearlite, while, at 853 K and 813 K (580°C and 540°C), the microstructure consisted of lath bainite with fine interlath cementite and granular bainite with martensite/ austenite (M/A) constituent. In all the finish cooling temperatures studied, the near-spherical precipitates of size range~2 to 15 nm were randomly dispersed in ferrite and bainite matrix. The carbide precipitates were identified as (Nb,V)C with NaCl-type crystal structure. With a decrease in the finish cooling temperature, the size of the precipitates was decreased, while the number density first increased with a peak at 893 K (620°C) and then decreased. Using Ashby-Orowan model, the contribution of the precipitation strengthening to yield strength was~149 MPa at the finish cooling temperature of 893 K (620°C).In the last few decades, high-strength low-alloy (HSLA) steels have been widely used in buildings, bridges, and ships because of their potential to obtain high strength-toughness combination. [1] Superior mechanical properties were obtained through optimization of alloy design in conjunction with thermo-mechanical processing (TMCP). [2][3][4][5] The improvement in mechanical properties was a consequence of grain refinement together with microstructural control and precipitation strengthening. The carbide-forming elements include titanium and niobium that facilitate grain refinement and contribute to dispersion hardening through carbide precipitation in the matrix. The relative contribution of the microalloying elements is determined by the solubility of carbides in the microstructure. Titanium is beneficial because it combines with nitrogen at relatively high temperature, preventing grain growth, while niobium can effectively retard recovery and recrystallization during hot rolling leading to grain refinement. Moreover, these two elements can precipitate as carbides from the supersaturated ferrite solid solution or precipitate as interphase precipitates during austenite-to-ferrite transformation increasing strength. Vanadium is less effective in grain refinement but contributes to strength via precipitation hardening because of higher solubility in austenite as compared to niobium, leading to precipitation at lower temperature. [6] TMCP involving ultrafast cooling (UFC) technology developed by our laboratory is being currently applied to industrial production, [7][8][9] with the aim to reduce the consumption of alloying elements and make the s...

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“…Saai et al 14) proposed that the volume fraction and distribution of martensite in the soft ferrite phase is responsible for strain localization and fracture in DP steels. While the strengthening effect of hard phases, such as martensite in DP steels 15) and δ-ferrite in duplex stainless steels, 16) are extensively investigated, there are few studies on the interactions between α-ferrite and austenite during hot deformation, where α-ferrite is the softer phase and austenite is the harder.…”

Section: Correlation Of Strain Accommodation Factor With the State Ofmentioning

confidence: 99%

Correlation of Strain Accommodation Factor with the State of Microstructural Components in a Multiphase Steel

2015

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Microstructures and Mechanical Properties of a New As-Hot-Rolled High-Strength DP Steel Subjected to Different Cooling Schedules

Cited by 40 publications

References 31 publications

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

The Determining Role of Finish Cooling Temperature on the Microstructural Evolution and Precipitation Behavior in an Nb-V-Ti Microalloyed Steel in the Context of Newly Developed Ultrafast Cooling

Correlation of Strain Accommodation Factor with the State of Microstructural Components in a Multiphase Steel

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