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Microalloyed steel

About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.


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Journal ArticleDOI
TL;DR: In this paper, a statically recrystallized fraction of low carbon microalloyed steels containing vanadium, niobium and titanium, respectively, has been determined for different temperatures and strains.
Abstract: Using torsion tests and applying the back extrapolation method, the statically recrystallized fraction of low carbon microalloyed steels containing vanadium, niobium and titanium, respectively, has been determined for different temperatures and strains. From the recrystallized fraction against time curves it is possible to draw precipitation-time-temperature (PTT) diagrams. These diagrams show that the strain does not affect precipitation kinetics in an independent manner, but that this influence is related with the microalloy content. The greater the strain applied, the shorter the incubation time of induced precipitation, but this influence diminishes as the microalloy content increases. It is also demonstrated that the incubation time is practically independent of the nature of the metal microalloy (V, Ti, Nb). In this sense, new expressions are proposed to relate the incubation and precipitation end times with the strain and the microalloy content. A model is also established for precipitation kinetics at the curve nose temperature.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the transformation behavior and microstructural characteristics of a low carbon high niobium-bearing microalloyed pipeline steel were investigated by deformation dilatometry and microstructure observation.
Abstract: The transformation behavior and microstructural characteristics of a low carbon high niobium-bearing microalloyed pipeline steel were investigated by deformation dilatometry and microstructure observation. The continuous cooling transformation curves of the test steel were constructed. The results showed that high niobium content and deformation enhanced the formation of acicular ferrite; the microstructures changed from polygonal ferrite, quasi-polygonal ferrite to acicular ferrite with increasing cooling rates from 0.5 to 50 °C/s and was dominated by acicular ferrite in a broadened cooling rate higher than 5 °C/s. The chaotic microstructure consisted of non-equiaxed ferrite and interwoven ferrite laths with high density dislocations and subunits. The results of isothermal holding treatment showed that acicular ferrite microstructure was formed at 550 — 600 °C and consisted of highly misoriented plate packets having internal low angle boundaries. With increasing the holding time or temperature, some low misorientation boundaries changed to high misorientation owing to the movement of dislocations and coarsening of grain.

22 citations

Journal ArticleDOI
TL;DR: In this article, the impact of tempering temperature and tempering time on the microstructure and mechanical property in a low carbon Nb-Cu microalloyed steel via a three-step heat treatment was described.
Abstract: We describe here the impact of tempering temperature and tempering time on the microstructure and mechanical property in a low carbon Nb–Cu microalloyed steel via a three-step heat treatment. After tempering process, the microstructure primarily comprised of ferrite, retained austenite and tempered bainite/martensite. The ferrite matrix with ultrafine grain size was film-like and enriched with nanometer-sized niobium-containing and copper precipitates. The volume fraction of ferrite increased with the increase in tempering temperature and tempering time. Retained austenite had average grain size less than 1 μm and was enriched with copper precipitates that contributes to enhance the stability of austenite. The retained austenite revealed high thermal stability and remained stable in the range of 20–30% when tempering temperature and time changed. High strength and good ductility were obtained in the tempering temperature range of 450–550 °C, or by prolonging tempering time at 500 °C, where the yield strength was ~750 MPa and the product of tensile strength and % elongation was ~32 GPa%, which is attributed to the cooperation of multiphase microstructure, stable retained austenite and nanometer-sized precipitates.

22 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that a small amount of Ti-bearing precipitates, consuming about 10% of the elemental Ti, were formed on dislocations after rough rolling and cooling to 900°C.
Abstract: Strain-induced precipitation kinetics and precipitates' characteristics in a Ti microalloyed steel subjected to a two-stage controlled rolling process, simulating rough and finish rolling process of industrial production, were quantitatively investigated by stress relaxation experiments and transmission electron microscopy (TEM), as well as inductively coupled plasma-atomic emission spectroscopy (ICP-AES). In the present work, precipitation during the cooling stage after rough rolling was taken into consideration for the first time. It was found that a small amount of Ti-bearing precipitates, consuming about 10% of the elemental Ti, were formed on dislocations after rough rolling and cooling to 900 °C. The obtained precipitation-time-temperature (PTT) curves exhibited a classic C shape with a nose temperature of 900 °C and the shortest incubation time of 60 s. The PTT curves moved to the lower left by the introduction of 20% deformation at 1050 °C, which was attributed to more nucleation sites for strain-induced precipitation and the decrease of Ti concentration in deformed austenite. During the stress relaxation stage, strain-induced precipitates preferentially nucleated on dislocations and sub-boundaries and were identified as TiC particles. The mean size of precipitated TiC particles increased from 10.2 ± 2.1 to 25.2 ± 2.8 nm, as the holding time was increased from 100 to 1800 s at 900 °C. When the holding time exceeded 600 s the migration of austenite grain boundaries could not be completely inhibited due to the coarsening of precipitates. Isothermal treatment at 900 °C with a holding time of 60–100 s is suggested here as a viable combination for the processing of the 0.05C-0.21Si-1.05Mn-0.13Ti (wt. %) steel due to the shortest incubation time period and effective pinning of grain boundaries by strain-induced precipitates.

22 citations

Journal ArticleDOI
TL;DR: In this article, an analytical model for predicting the austenite grain size in the heat affected zone was derived based on the experimental measurements, and the grain growth depends mainly on heat input and peak temperature as well as growth activation energy and exponent.
Abstract: Austenite grain sizes in the heat affected zone (HAZ) of a high heat input welded Zr-Ti bearing microalloyed steel are measured under different welding conditions simulated by a Gleeble-1500 thermal-mechanical simulator. The austenite grain growth is divided into two regimes in terms of temperature. When the temperature is lower than 1250 °C where the pinning effect of precipitates is strong, the austenite grain size increases slowly with increasing peak temperature, but it increases drastically when the temperature is higher than 1250 °C where the pinning effect of precipitates is weak. Based on the experimental measurements, an analytical model for predicting the austenite grain size in the heat affected zone is derived. Model predictions indicate that the initial grain size has little effect on the final one, and the grain growth depends mainly on heat input and peak temperature as well as growth activation energy and exponent. With the use of the model, the width of coarse grained heat affected zone (CGHAZ) for a thick plate is predicted.

22 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202288
202164
202090
201986
201888