Effect of processing parameters on the microstructure and properties of an Nb microalloyed steel

Bakkaloğlu, Adem

doi:10.1016/s0167-577x(02)00440-8

Cited by 60 publications

(32 citation statements)

References 9 publications

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“…The UTS gradually decreased with a decrease in the finish deformation temperature (Table II), which corresponds to some earlier published results [7,36] , although other studies [6,9,10,37] showed an increase in UTS with a decrease in the finish deformation temperature. This discrepancy in UTS behavior can be related to the variation in temperature range which was applied during finish rolling.…”

Section: B Effect Of Tmp On Mechanical Propertiessupporting

confidence: 90%

“…This discrepancy in UTS behavior can be related to the variation in temperature range which was applied during finish rolling. When hot rolling was carried out below the austenite-to-ferrite transformation temperature A r3 , a decrease in the finish deformation temperature resulted in the UTS increase, [6,9,10,37] due to an increase in work hardening (formation of deformation bands and dislocation pile-ups) with a decrease in temperature. However, when hot rolling was completed above A r3 temperature, similar to this work, the UTS decreased with a decrease in the finish deformation temperature.…”

Section: B Effect Of Tmp On Mechanical Propertiesmentioning

confidence: 99%

“…Low-temperature precipitation results in precipitation strengthening [3] and may stimulate dislocation generation which enhances work hardening. [4,5] Following TMP, the steel strength usually increases with (1) an increase in reheating temperature, [6,7] which can be attributed to particle dissolution, further precipitation during rolling at a finer scale, stronger grain boundary pinning, and grain refinement; (2) an increase in deformation strain, [6,8] due to grain refinement, work hardening (dislocation density increase), and strengthening by strain-induced precipitates; (3) a decrease in finish rolling temperature, [7,[9][10][11] due to grain refinement, work hardening (especially if deformation is carried out in two-phase a + c region), and transformation strengthening (formation of bainite or acicular ferrite); and (4) an increase in cooling rate, [10] due to grain refinement and transformation strengthening. Although these qualitative trends of microstructure property development during TMP are well understood, comparative contributions of each of the strengthening mechanisms (grain refinement, solid solution strengthening, precipitation strengthening, and work hardening) and their variations with steel composition and TMP parameters still require clarification.…”

Section: Introductionmentioning

confidence: 99%

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Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Kostryzhev

Marenych

Killmore³

et al. 2015

Metall Mater Trans A

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The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075 °C to 825 °C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly. The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075°C to 825°C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly.

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Section: B Effect Of Tmp On Mechanical Propertiessupporting

confidence: 90%

Section: B Effect Of Tmp On Mechanical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Kostryzhev

Marenych

Killmore³

et al. 2015

Metall Mater Trans A

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“…2) indicate that depending on the initial microstructure three different processes may occur at short reheat: (1) the dissolution of cementite with a formation of secondary austenite around cementite particles in the interior of ferrite grains and its transformation to secondary martensite at cooling, (2) the formation of inserts (grains) of secondary martensite at triple points and boundaries of ferrite grains and (3) the decomposition of primary martensite. [27]. In this investigation the trend in shift in the transition temperature was observed.…”

Section: Resultsmentioning

confidence: 50%

Effect of heat treatment on Charpy impact energy of microalloyed steel

et al. 2016

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Original scientific paper In this paper the microalloyed high-strength low-alloy (HSLA) Niomol 490K steel with an addition of niobium (0,032 wt. %) has been investigated. Heat treatment of the steel consisted of austenitisation at 1250 °C for 3 minutes and reheating up to 750 °C for 5 s. After austenitization the quenching was carried out in water with temperature of 70 °C and then in a lead bath up to 400 °C following cooling on the air. It was found that Charpy impact energy is higher and the transition temperature is lower for the transformation of austenite to bainite than to martensite microstructure. Experimental results showed that different fracture surface was observed. It is shown that preferred cleavage fracture occurred in the lattice plane (001) Utjecaj toplinske obrade na Charpy energiju udara mikrolegiranog čelikaIzvorni znanstveni rad U ovom radu istraživan je niskolegirani visokočvrsti čelik Niomol 490K koji sadrži dodatak niobija (0,032 mas. %). Toplinska obrada čelika se sastojala od austenitizacije pri 1250 °C u trajanju od 5 minuta i ponovnog zagrijavanja do 750 °C u trajanju od 5 s. Nakon austenitizacije provedeno je kaljenje u vodi kod temperature od 70 °C i u olovnoj kupci do temperature od 400 °C uz naknadno hlađenje na zraku. Utvrđeno je da je Charpy energija udara viša, a prijelazna temperatura niža za transformaciju austenita u bainit nego kod transformacije austenita u martenzitnu mikrostrukturu. Eksperimentalni rezultati su pokazali različite prijelomne površine. Pokazano je da je preferentno cijepajući prijelom zapažen po ravnini rešetke (001), neovisno o mikrostrukturi.

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“…Additionally, grain refinement improves weldability and segregation in hot rolled steel strips because of less carbon and reduced alloying elements in a given grade of steel. [1][2][3][4][5][6] Although extremely fine ferrite grain size of ~1 μm can be obtained at the laboratory scale, it is difficult to obtain on an industrial scale. 5,6) The common route to refine the ferrite grain size of C-Mn steel is accelerated cooling after controlled rolling.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Microstructural Control and Mechanical Properties in Hot Rolled Plain C–Mn Steel during Controlled Cooling

Yuan

et al. 2015

ISIJ Int.

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In this study, plain C-Mn steels with different ferrite grain size were obtained through various thermomechanical processing. Fast cooling suppressed ferrite transformation at high temperature, but promoted ferrite nucleation at low temperature and restricted ferrite grain growth. The microstructure and mechanical properties were governed by the combined effects of cooling rate and cooling temperature. A new thermo-mechanical controlled processing (TMCP) based on ultra fast cooling (UFC) technology was adopted to increase the strength of plain C-Mn steel strips. The new TMCP approach involving UFC enabled significantly finer grain size to be obtained in relation to conventional TMCP. The grain size of Fe-0.17C-0.33Mn steel strips obtained by the new TMCP was refined to ~3-4 μm, and both yield strength and tensile strength were increased by 60-100 MPa over the conventional TMCP.

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Effect of processing parameters on the microstructure and properties of an Nb microalloyed steel

Cited by 60 publications

References 9 publications

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

Effect of heat treatment on Charpy impact energy of microalloyed steel

Mechanism of Microstructural Control and Mechanical Properties in Hot Rolled Plain C–Mn Steel during Controlled Cooling

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