Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel

Sas, Ján; Kvačkaj, Tibor; Milkovič, Ondrej; Zemko, Michal

doi:10.3390/ma9120971

Cited by 9 publications

(11 citation statements)

References 18 publications

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“…[1][2][3][4][5][6][7] This has been shown to occur throughout the austenite phase field. 8,9) In earlier publications, the present authors have reported that the amounts of ferrite formed per pass increase with decreasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Retransformation Behavior of Dynamically Transformed Ferrite during the Simulated Plate Rolling of a Low C and an X70 Nb Steel

2017

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Plate rolling simulations were carried out on an X70 Nb and a low C steel by means of torsion testing. A seven-pass rolling schedule was employed where the last pass was always applied above the respective Ae 3 temperature of the steel. Interpass intervals of 10 and 30 s were employed, which corresponded to cooling rates of 1.5 and 0.5 C/s. The mean flow stresses (MFS`s) applicable to each schedule increased less rapidly than expected from the decreases in temperature due to the dynamic transformation (DT) that took place during straining. The amounts of ferrite that retransformed into austenite during holding were determined by optical metallography. These increased with length of the interpass intervals and were reduced in the X70 steel due to the presence of Nb. The holding times after rolling required to increase the amount of austenite available for microstructure control on subsequent cooling were also determined for the two steels.

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Section: Introductionmentioning

confidence: 99%

Retransformation Behavior of Dynamically Transformed Ferrite during the Simulated Plate Rolling of a Low C and an X70 Nb Steel

2017

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“… plastic deformation conditions realized in monophase austenite region at deformation temperatures. spontaneous recrystallization of austenite—RCR [ 62 , 63 , 64 ] produced polycrystalline austenitic grains with diameter dγ ≈ 50–80 μm, which transformed to polycrystalline ferrite grain with diameter dα ≈10–30 μm, non-recrystallization austenite region—CR [ 56 , 63 ] (narrowly raised Ar3 temperature) formed deformation-elongated austenitic grains with an effective ferritic nucleation surface calculated from grain boundaries and deformation bands Sv(gb+db) ≈ 25–500 1/mm [ 56 ]. This corresponds to the corrected diameter grains of austenite d γ, cor ≈ 4–70 μm) transformed to polycrystalline ferrite with diameter d α ≈ 2–10 μm.…”

Section: Introductionmentioning

confidence: 99%

“…This corresponds to the corrected diameter grains of austenite d γ, cor ≈ 4–70 μm) transformed to polycrystalline ferrite with diameter d α ≈ 2–10 μm. dual-phase (γ+α) region—CR [ 55 , 63 ] (non-recrystallized austenite–deformed ferrite) bellow Ar3 temperatures with Sv(gb+db) ≈1000 1/mm, corresponding to d γ, cor ≈ 2 μm with subsequent transformation to ferrite (non-recrystallized austenite, to polycrystalline ferrite–deformed ferrite, to ferrite subgrains) with diameter d α ≈ 1–2 μm. …”

Section: Introductionmentioning

confidence: 99%

“…spontaneous recrystallization of austenite—RCR [ 62 , 63 , 64 ] produced polycrystalline austenitic grains with diameter dγ ≈ 50–80 μm, which transformed to polycrystalline ferrite grain with diameter dα ≈10–30 μm,…”

Section: Introductionmentioning

confidence: 99%

“…non-recrystallization austenite region—CR [ 56 , 63 ] (narrowly raised Ar3 temperature) formed deformation-elongated austenitic grains with an effective ferritic nucleation surface calculated from grain boundaries and deformation bands Sv(gb+db) ≈ 25–500 1/mm [ 56 ]. This corresponds to the corrected diameter grains of austenite d γ, cor ≈ 4–70 μm) transformed to polycrystalline ferrite with diameter d α ≈ 2–10 μm.…”

Section: Introductionmentioning

confidence: 99%

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Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Kvačkaj

Bidulská

Bidulský³

2021

Materials

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This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

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Influence of Finish Rolling Temperature and Molybdenum Addition on Strengthening of Low Carbon Niobium Steels—A Computational and Experimental Study

Chakraborty

Primig

2021

steel research int.

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Low C microalloyed steels have widespread applications in contemporary construction and transportation applications owing to their unique combination of high strength and ductility. [1,2] The addition of microalloying elements such as Nb, Ti, and V in the presence of ultralow C contents imparts effective strengthening by precipitation and grain size refinement under controlled thermomechanical processing (TMP) conditions. [3][4][5] Several studies have investigated the role of microalloying and TMP routes on the evolution of harder (nonequilibrium) phases as matrix microstructures, such as acicular ferrite, bainite, and martensite, for high-strength plate and pipeline applications. [6][7][8][9][10][11][12][13] However, a harder phase matrix microstructure suffers from poor stretch flangeability (formability) due to its poor local elongation abilities near higher stress concentration zones along the soft/hard interfaces, leading to premature microvoid crack initiation and failure in thin-sheet applications. [14,15] This explains interest in softer equilibrium phases as matrix microstructures such as ferrite. Ferritic steels offer better stretch formability and are, thus, more suitable for thin sheet applications, e.g., in the automotive industry. Funakawa et al. [16] developed a TiC precipitation-strengthened ferritic steel with a yield strength of 734 MPa, a total elongation of 24%, and a hole expansion ratio around 120% for a 0.047C-0.082Ti-0.2Mo (wt% in the following) hot-rolled steel. A higher ferritic yield strength of 760 MPa in a multicomponent microalloyed 0.04C-0.08Ti-0.011Nb-0.015V-0.18Mo steel was reported by Shen et al. [17] due to a mix of finely dispersed TiC and coarser grain boundary (GB) M 23 C 6 precipitates. Single-hit deformation and aging experiments at 650 C by Mukherjee et al. [18] highlighted the effect of Mo on initiating extremely stable Ti(Mo)C (α/γ) interphase nanoprecipitates in ferrite in a 0.04C-0.05Ti-0.22Mo steel for aging durations between 300 and 3600 s, leading to an average ferrite hardness of 250 vickers hardness number (VHN). In addition, they also observed fine TiC solute clusters during shorter aging periods. The beneficial role of Mo in the presence of Ti in lowering of austenite to ferrite transformation temperature upon continuous cooling and delaying precipitate coarsening while aging during ferritic transformation is also well established. [19][20][21][22][23] While it is evidently clear that microalloying in the presence of Mo improves the yield strength of ferritic steels, deformation at lower temperatures in the two-phase austenite þ ferrite (γ þ α) region, also known as intercritical or warm deformation, [24][25][26][27][28] remains another strategic option to exploit. An average ferrite grain size of 1.3 μm in a C-Mn steel was achieved using large strain warm deformation processing. [28] A comprehensive review by Song et al. [29] examined the influence of both severe plastic deformation and advanced thermomechanical strategies on processing of ultrafine ferrite gr...

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Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel

Cited by 9 publications

References 18 publications

Retransformation Behavior of Dynamically Transformed Ferrite during the Simulated Plate Rolling of a Low C and an X70 Nb Steel

Retransformation Behavior of Dynamically Transformed Ferrite during the Simulated Plate Rolling of a Low C and an X70 Nb Steel

Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Influence of Finish Rolling Temperature and Molybdenum Addition on Strengthening of Low Carbon Niobium Steels—A Computational and Experimental Study

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