Development of NbTiB Microalloyed HSLA Steels for High-Strength Heavy Plate

Meuser, Heike; Grimpe, F.; Meimeth, S.; Heckmann, C.J.; Träger, C.

doi:10.4028/www.scientific.net/msf.500-501.565

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…The addition of 0.001 % B lead to reduction in A r3 by approximately 25°C, which is in line with reported values of 50°C decrease per 40 ppm B. 40) This decrease is caused by segregation of B to the austenite grain boundaries, 41,42) which reduces the number of preferred ferrite nucleation sites and lowers the grain boundary energy. B also lowers the selfdiffusion coefficient of iron on the grain boundaries.…”

Section: Effect Of Tmcp and Chemistry On T Nr And A R3supporting

confidence: 74%

Thermomechanical Processing of Pipeline Steels with a Reduced Mn Content

Schambron

Phillips

O’Brien³

et al. 2009

ISIJ Int.

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Lowering the Mn content of hot rolled pipeline steel can economise the steel making process by eliminating costly desulphurisation and at the same time improve product properties, particularly toughness, by reducing the formation of MnS inclusions. Lower Mn contents, however, have significant implications for austenite recrystallization and austenite (g) to ferrite (a) transformation behaviour. This study compares the recrystallization start (T nr ) and g to a transformation (A r3 ) temperatures of two low Mn steels to those of a commercial steel with a conventional Mn content. Simulations of thermomechanical processing were carried out using a Gleeble 3500 testing machine. The T nr for the low Mn alloy design were found to be ϳ25°C higher than for the high Mn steel, while the A r3 of the low Mn steel were some 50°C higher. The higher A r3 promotes the formation of coarse ferrite grains, thus reducing the strengthening and toughening benefits of a fine grain size. However, this could largely be overcome by maximising the degree of deformation performed between T nr and A r3 and maintaining a combination of high cooling rates and low stop cooling temperatures below A r3 , thus providing a high density of nucleation sites and promoting high nucleation rates. Production trials validated the results from the Gleeble tests.KEY WORDS: pipeline steel; high strength low alloy; manganese; hot rolling; non-recrystallization temperature; thermo-mechanical control process.

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Section: Effect Of Tmcp and Chemistry On T Nr And A R3supporting

confidence: 74%

Thermomechanical Processing of Pipeline Steels with a Reduced Mn Content

Schambron

Phillips

O’Brien³

et al. 2009

ISIJ Int.

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“…[10] The microstructural bands are coarse bainitic phases formed in a uniform matrix of ferrite and are transformed from coarse austenite grains, which are developed when conditions favor abnormal grain growth or strain-induced grain boundary migration in the rolling passes. [11,12] It is also possible to have inappropriate austenite refinement before strain begins accumulating, in some cases, as a consequence of a low soaking temperature [13] or in others due to microalloying segregation. [14] Also, in thin slab direct rolling technologies, the refinement and conditioning of austenite prior to transformation may be limited.…”

Section: Introductionmentioning

confidence: 99%

Effect of Composition and Deformation on Coarse-Grained Austenite Transformation in Nb-Mo Microalloyed Steels

Isasti

Jorge-Badiola

Taheri

et al. 2011

Metall Mater Trans A

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Thermomechanical processing of microalloyed steels containing niobium can be performed to obtain deformed austenite prior to transformation. Accelerated cooling can be employed to refine the final microstructure and, consequently, to improve both strength and toughness. This general rule is fulfilled if the transformation occurs on a quite homogeneous austenite microstructure. Nevertheless, the presence of coarse austenite grains before transformation in different industrial processes is a usual source of concern, and regarding toughness, the coarsest high-angle boundary units would determine its final value. Sets of deformation dilatometry tests were carried out using three 0.06 pct Nb microalloyed steels to evaluate the effect of Mo alloying additions (0, 0.16, and 0.31 pct Mo) on final transformation from both recrystallized and unrecrystallized coarse-grained austenite. Continuous cooling transformation (CCT) diagrams were created, and detailed microstructural characterization was achieved through the use of optical microscopy (OM), field emission gun scanning electron microscopy (FEGSEM), and electron backscattered diffraction (EBSD). The resultant microstructures ranged from polygonal ferrite (PF) and pearlite (P) at slow cooling ranges to bainitic ferrite (BF) accompanied by martensite (M) for fast cooling rates. Plastic deformation of the parent austenite accelerated both ferrite and bainite transformation, moving the CCT curves to higher temperatures and shorter times. However, an increase in the final heterogeneity was observed when BF packets were formed, creating coarse high-angle grain boundary units.

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“…It is estimated that taking full advantage of the potential offered by controlled processing and replacement of traditional steels with microalloyed grades can give saving up to 40% of the total production costs. Therefore, although used for decades now, improvements in cotrolled processing technologies are still a subject of numerous projects and research, concerning emerging grades of steels [4,5,6], new applications [7÷10] and/or innovative realisation techniques [11,12].…”

Section: Introductionmentioning

confidence: 99%

Automated Determination and On-Line Correction of Emissivity Coefficient in Controlled Cooling of Drop Forgings

Skubisz

Micek

Sińczak

et al. 2011

SSP

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The paper presents the methodology of determination of emissivity coefficient of steel in the direct cooling temperature range, which allow self-definition of this parameter in automated temperature control system used for direct cooling of drop-forged parts. Based on the actual temperature of the surface of the workpiece, the system automatically adjusts the velocity of fan-forced air to produce desired cooling rate and course of cooling curves. To enable automatic correction of cooling rate, the system must rely on exact remote temperature measurements. This is conditioned by correct definition of emissivity in pyrometer gauge system. Traditionally, pyrometers use presets of a constant value, selected as to get optimum consistency for the temperature range concerned. As the emissivity is time-dependent, the idea of the approach presented in the paper is to use time dependent characteristics, to attain the minimum discrepancy between actual and measured values during the whole cooling cycle.

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Development of NbTiB Microalloyed HSLA Steels for High-Strength Heavy Plate

Cited by 5 publications

References 6 publications

Thermomechanical Processing of Pipeline Steels with a Reduced Mn Content

Thermomechanical Processing of Pipeline Steels with a Reduced Mn Content

Effect of Composition and Deformation on Coarse-Grained Austenite Transformation in Nb-Mo Microalloyed Steels

Automated Determination and On-Line Correction of Emissivity Coefficient in Controlled Cooling of Drop Forgings

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