Effect of Cooling Path on Microstructure Features and Tensile Properties in a Low Carbon Mo-V-Ti-N Steel

Xiao, X.P.; Shi, Genhao; Zhang, Shuming; Wang, Qingfeng

doi:10.3390/met8090677

Cited by 5 publications

(4 citation statements)

References 46 publications

(81 reference statements)

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“…[ 15,32,33 ] A notable increase of the dislocation density was also observed in the specimens isothermally transformed at the 590 °C temperature compared to the other CTs. These values were comparable with the low carbon Mo–V–Ti–N steels with a mixed microstructure of polygonal ferrite, acicular ferrite, granular bainitic ferrite, and a martensite–austenite constituent, [ 53 ] although the present steels were fully ferritic, as shown in Figure 1. Thus, the present results demonstrated that a significant difference between the dislocation densities can be achieved in the low‐carbon low‐alloyed steels by changing the CT.…”

Section: Resultssupporting

confidence: 83%

Evaluation of Strengthening Mechanisms in Novel Fully Ferritic Advanced High‐Strength Steels

Nousiainen,

Hannula,

Saukko

et al. 2023

steel research int.

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New steel alloying concepts were designed in order to produce a fully ferritic, low‐alloy steel with high (1 GPa) ultimate tensile strength. A simulated hot‐deformation process of the Ti‐Mo‐V‐Nb and Ti‐Mo‐V steels was designed for that purpose, and the strengthening mechanisms of the steels were evaluated after the isothermal dwell at three different temperatures (590 °C, 630 °C, and 680 °C). The tensile strength (TS) and the yield strength (YS) of the test alloys were estimated via hardness measurements. Results showed that the estimated tensile strength (TS) of over 1000 MPa and yield strength (YS) of over 900 MPa could be achieved in both steels, although the contribution of different strengthening mechanisms to the YS varied between the steels. The effect of the dislocation strengthening could especially compensate the reduced effect of the precipitation strengthening at all tested coiling temperatures (CT). Based on the results, a CT range of 590–630 °C with the 1800 s dwell time seemed to be a potential process window for the studied steels after the present TMCP route.This article is protected by copyright. All rights reserved.

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Section: Resultssupporting

confidence: 83%

Evaluation of Strengthening Mechanisms in Novel Fully Ferritic Advanced High‐Strength Steels

Nousiainen,

Hannula,

Saukko

et al. 2023

steel research int.

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“…Table 3 shows that the average dislocation density in the QF+GBF matrix of steels decreases with an increase in Si content, owing to the increased transformation temperature of QF+GBF. The contribution of dislocation enhancement (σ ρ ) to the YS can be estimated from the following equation [31,33,34]:…”

Section: Effect Of Si Content On the Tensile Propertiesmentioning

confidence: 99%

“…The contribution of precipitation strengthening (σ p ) to the YS can be estimated using Equation (6) [34][35][36][37], which is based on the fraction and average size of precipitates:…”

Section: Effect Of Si Content On the Tensile Propertiesmentioning

confidence: 99%

Influence of Si Content on the Microstructure and Tensile Properties of Weathering Bridge Steel Produced via Thermal Mechanical Control Process

Chen

Shi

et al. 2022

Metals

Self Cite

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In this study, the effects of Si on the microstructure and tensile properties of weathering bridge steel were elucidated. The thermal mechanical control process (TMCP), containing two stages of controlled rolling and accelerated cooling process, was simulated using a thermo-mechanical simulator for four experimental steels with varying Si contents (0.15–0.77 wt.%). Micro-tensile tests were performed, and the microstructures were observed via optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and electron back-scattered diffraction (EBSD). Furthermore, the tensile properties and microstructures of these steels were analyzed. The results show that a mixed microstructure comprising granular bainitic ferrite (GBF), quasi-polygonal ferrite (QF), and martensite/austenite (M/A) constituent was formed in each sample. With an increase in Si content, the GBF content decreased, QF content increased, mean equivalent diameter (MED) of the QF+GBF matrix increased, and the fraction and average size of the M/A constituent increased. With a rise in Si content from 0.15 to 0.77 wt.%, the contributions of dislocation strengthening, grain boundary strengthening, and precipitation strengthening decreased from 149, 220, and 21 MPa to 126, 179, and 19 MPa, respectively. However, the combined contribution of solution strengthening, lattice strengthening, and M/A strengthening increased from 41 to 175 MPa, which augmented the final yield strength from 431 to 499 MPa. The decreasing yield ratio shows that strain hardening capacity is enhanced due to an increase in the fraction of the M/A constituent as well as in the MED of the QF+GBF matrix. Furthermore, the mechanisms by which Si content controls the microstructure and mechanical properties of weathering bridge steel were also discussed.

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“…Application of TMCP leads to the decrease of the effective ferrite grain size and the increases of the dispersed precipitate and the dislocation density, which eventually resulted in the improvement of comprehensive properties such as strength, toughness and weldability. It also improves the morphology of MA (martensite-austenite) constituent, which lowered the yield ratio and, thereby, enhanced the capacity for strain hardening [15]. Microalloying elements can effectively control the microstructure of steel and improve its mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

Tian

Wang

et al. 2020

Materials

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Isothermal treatment affects the microstructural evolution and the precipitation behavior of high-strength low alloy (HSLA) steels. In this regard, thermal simulation of different isothermal treatment temperatures was adopted by using a thermomechanical simulator. The results showed that hardness reached the maximum value at 600 °C holding temperature, which was related to a finer grain structure and granular bainite. The strengthening effect of precipitates was remarkable due to the combination of small particle size and small interparticle spacing. It is presumed that the precipitation started after 600 s at 600 °C. Precipitation strengthening continued to exist, even though coarsening of ferrite grains led to softening phenomena when the specimen was isothermally held at 750 °C, which led to relatively high hardness. The precipitates were fcc (Ti, Nb) (N, C) particles, and belonged to MX-type precipitates. Average size of precipitates increased from 3.14 to 4.83 nm when the specimens were isothermally held between 600 °C and 800 °C. Interparticle spacing of precipitates also increased with increasing isothermal treatment temperatures. These led to a reduction in precipitation strengthening. At the same time the polygonal ferrite content increased and ferrite grain size got larger, such that the hardness decreased continuously.

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Effect of Cooling Path on Microstructure Features and Tensile Properties in a Low Carbon Mo-V-Ti-N Steel

Cited by 5 publications

References 46 publications

Evaluation of Strengthening Mechanisms in Novel Fully Ferritic Advanced High‐Strength Steels

Evaluation of Strengthening Mechanisms in Novel Fully Ferritic Advanced High‐Strength Steels

Influence of Si Content on the Microstructure and Tensile Properties of Weathering Bridge Steel Produced via Thermal Mechanical Control Process

The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

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