Influence of Vanadium Microaddition on the Microstructure and Mechanical Properties of High Strength Large Diameter Wire-Rods

Mendizábal, Lucía; Iza-Mendia, A.; López, Beatriz; Rodríguez-Ibabe, J.M.

doi:10.4028/www.scientific.net/msf.500-501.761

Cited by 8 publications

(5 citation statements)

References 15 publications

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“…(5)- (7) and the experimental values from Fig. 4, Table 3, some previous results obtained for the plain C-Mn2 steel 12) in Table 1 and those obtained with steel 11VN in Ref. 13), the following expression was obtained for the f treat term of Eq.…”

Section: Effect Of Process Parameters On Hardnesssupporting

confidence: 54%

“…11) for an eutectoid Nb microalloyed steel, whereas in Ref. 12), where several V microalloyed steels were studied, it was observed that the application of the above criterion led to an "orientation unit" mean size larger than the "facet size" measured on fracture surfaces. In the latter a 12°misorientation criterion provided better results.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Influence of Thermomechanical Processing on the Austenite–Pearlite Transformation in High Carbon Vanadium Microalloyed Steels

et al. 2010

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Multipass torsion tests were carried on with several V-microalloyed high carbon steels, using different deformation sequences in order to modify the austenite state prior to transformation. Both recrystallized and deformed austenite microstructures were studied. After deformation, different cooling rates were applied. The results show that accumulating strain in the austenite before transformation seems to slightly increase the interlamellar spacing for a given cooling rate, this increase being related to the pearlite transformation taking place at higher temperatures because of the increase in the austenite grain boundary area per unit volume (S V ). On the other hand, the retained strain significantly contributes to a refinement of the "ferrite units", this effect being more significant as vanadium and nitrogen contents rise. A relationship between the mean "ferrite unit" size with S V and cooling rate was determined. Similarly, empirical expressions to predict strength as a function of vanadium microalloying addition, S V and cooling rate were derived.KEY WORDS: eutectoid steel; pearlite transformation; vanadium microalloying; thermomechanical processing.tion. This means that when defining the "ferrite unit" the misorientation criterion used is an important factor. A 15°m isorientation criterion was used in Ref. 11) for an eutectoid Nb microalloyed steel, whereas in Ref. 12), where several V microalloyed steels were studied, it was observed that the application of the above criterion led to an "orientation unit" mean size larger than the "facet size" measured on fracture surfaces. In the latter a 12°misorientation criterion provided better results.In a recent paper Jorge-Badiola et al. evaluated the beneficial effect of combining strain induced vanadium nitride precipitation in austenite with proper deformation schedules to accumulate strain in the austenite in eutectoid steels.13) As occurs in low carbon steels, the accumulation of strain produces a significant refinement in the austenite, this leads to high values in the specific grain boundary area (S V ) which may produce, after transformation, a refinement in the "ferrite unit" in pearlite. In the aforementioned paper the work was mainly focused on analyzing the relevance of VN precipitation on austenite conditioning and the subsequent influence on the size of "ferrite units" obtained after transformation compared with a plain C-Mn steel.The precipitation of VN in austenite and the subsequent grain size refinement will affect the CCT curve and consequently, the resulting interlamellar spacing as well as the V(C, N) precipitation hardening can be modified for a given cooling schedule. This paper attempts to evaluate the interaction between these factors considering the influence of different vanadium and nitrogen contents in eutectoid steels. Experimental ProcedureThe composition of the vanadium microalloyed eutectoid steels used in this study are indicated in Table 1. Steels 5V and 10V were provided in the form of 16 mm diameter bars forged from laborat...

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Section: Effect Of Process Parameters On Hardnesssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 98%

Influence of Thermomechanical Processing on the Austenite–Pearlite Transformation in High Carbon Vanadium Microalloyed Steels

et al. 2010

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“…Cementite orientation can change inside a single unit [3] which is composed of ferrite regions with nearly the same crystallographic misorientation [86][87][88][89]. Different critical misorientation angle criteria have been adopted in bibliography [90], ranging from 10 o misorientation criterion in plain eutectoid steels by Park and Bernstein [91], to 15 o in Nb-microalloyed steels [81] and 12 o in the case of V eutectoid steels [92].…”

Section: Crystallographic Unit Size and Toughnessmentioning

confidence: 99%

Niobium in Microalloyed Rail Steels

Ray

Bhadeshia

2015

HSLA Steels 2015, Microalloying 2015 &Amp; Offshore Engineering Steels 2015

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Rail steels rely primarily on possessing adequate wear and rolling contact fatigue resistance. These properties, together with the toughness, can in principle be optimized by implementing thermomechanical processing assisted by controlled niobium additions. The purpose of the current work is to develop a Nb-microalloying strategy in the context of high-carbon pearlitic and cementite-free bainitic steels. The conventional methods do not leave the critical regions of a rail section in a suitably processed state. An attempt has been made for the first time, to create a pancaked austenite grain structure, with an examination of the consequences on the final Declaration This dissertation is submitted for the degree of Doctor of Philosophy at the University of Cambridge. The research reported was conducted under the supervision of

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“…However in Ref. 10), when several V microalloyed steels were studied, the application of the above criterion led to an "orientation unit" mean size larger than the "facet size" measured on fracture surfaces. In this case a 12°misorientation criterion brought better results.…”

Section: Pearlite Microstructurementioning

confidence: 99%

“…Among other aspects (such as the cleanness of the steel), the toughness of pearlitic steels is mainly controlled by the size of the "ferrite unit" and the refinement of this microstructural feature is the only way to improve toughness. [8][9][10] Taking into account how the austenite/pearlite transformation occurs, lowering of the "ferrite unit" size requires the refinement of the austenite microstructure.…”

Section: Introductionmentioning

confidence: 99%

Role of Vanadium Microalloying in Austenite Conditioning and Pearlite Microstructure in Thermomechanically Processed Eutectoid Steels

Jorge-Badiola¹,

Iza-Mendia²,

López³

et al. 2009

ISIJ Int.

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Multipass torsion tests were carried out with two eutectoid steels, one microalloyed with vanadium, using different deformation sequences. The aim of the study was to investigate the potency of vanadium in the retardation of recrystallization for accumulating strain in the austenite. The study showed that at certain deformation conditions well defined non-recrystallization temperatures (T nr ) were observed in the vanadium microalloyed steel. As a consequence, an increase in the austenite grain boundary area per unit volume (S V ) was obtained which led to a refinement of the "ferrite unit" size in the pearlite.KEY WORDS: eutectoid steel; vanadium microalloying; austenite conditioning. 1615© 2009 ISIJ proved toughness.Nevertheless, there is a lack of knowledge concerning the potential use of vanadium for the accumulation of strain in eutectoid steels and the optimum deformation conditions to achieve this. This paper attempts to analyze the potency of vanadium to accumulate strain in the austenite through the application of thermomechanical treatments. Experimental ProcedureTwo eutectoid steels were considered for this study: a plain carbon one and another microalloyed with vanadium, both having the same base composition. The C-Mn steel was commercially produced in bar shape, while the C-Mn-V was cast in the laboratory by adding vanadium after remelting the above C-Mn steel. Afterwards the resulting slabs were hot worked to square ingots. The compositions of the materials are indicated in Table 1.Multipass torsion tests were carried out to determine the non-recrystallization temperature (T nr ). Specimens, having a gauge length of lϭ12 mm with a diameter of 2rϭ6 mm, were reheated for 15 min at 1 200°C. After reheating the samples were deformed applying 24 passes at decreasing temperature in the range 1 150-800°C. The measured torque G and the twist q were converted to von Mises equivalent stress (s) and strain (e) with the help of these equations:.................... (1) The tests were performed using different pass-strains: eϭ 0.2-0.3-0.4. The strain-rate used in all the tests was e˙ϭ 1.5 s Ϫ1, and the interpass time at each deformation stage was 10 s. During deformation a cooling rate of 1.5°C/s was applied. In a particular test, the strain per pass, strain-rate and interpass time were held constant. The values of the T nr were calculated by using the method proposed by Bai et al.,12) from the graphic representation of the mean flow stress (MFS) versus the inverse absolute temperature for each one of the passes.The initial austenite grain size prior to deformation was determined in specimens directly quenched after reheating treatment. In most tests, the specimens were also directly quenched after deformation for the analysis of the austenite microstructure. Some additional tests were carried out applying natural cooling (ϳ3°C/s) after deformation for the study of the pearlite microstructure.The metallographic observation of the samples was done on a surface parallel to the torsion axis at a distance close to ...

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Influence of Vanadium Microaddition on the Microstructure and Mechanical Properties of High Strength Large Diameter Wire-Rods

Cited by 8 publications

References 15 publications

Influence of Thermomechanical Processing on the Austenite–Pearlite Transformation in High Carbon Vanadium Microalloyed Steels

Influence of Thermomechanical Processing on the Austenite–Pearlite Transformation in High Carbon Vanadium Microalloyed Steels

Niobium in Microalloyed Rail Steels

Role of Vanadium Microalloying in Austenite Conditioning and Pearlite Microstructure in Thermomechanically Processed Eutectoid Steels

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