Continuous Cooling Transformation Temperature and Microstructures of Microalloyed Hypereutectoid Steels

Elwazri, A.M.; Wanjara, P.; Yue, Steve

doi:10.2355/isijinternational.46.1354

Cited by 11 publications

(5 citation statements)

References 21 publications

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“…[5] The microalloying element vanadium that has been used [13] in combination with silicon to facilitate the fragmentation of grain boundary cementite also refines the pearlite structure. [14,15] Leseur [6] compared the additions to UHCS of 1.2 wt pct Si with that of 1.6 wt pct Al and found that the interlamellar spacing was finer in the latter. Aluminum addition has also been shown [16] to refine the microstructure of high carbon bainite.…”

Section: Introductionmentioning

confidence: 97%

Effect of Aluminum Content on the Microstructure and Mechanical Properties of Hypereutectoid Steels

Jang

Phaniraj

Kim

et al. 2010

Metall Mater Trans A

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Hypereutectoid steels with 0, 0.69, 1.29, and 1.95 wt pct aluminum were prepared. The samples were hot rolled at 1100°C followed by cooling in air. The microstructure of the as-rolled samples was characterized using field emission-scanning electron microscopy (FE-SEM). The electron backscattered diffraction (EBSD) technique was used to identify the grain boundary phases. The steels have a pearlitic microstructure with different amounts of grain boundary cementite. A continuous grain boundary cementite network is present in the 0 wt pct Al steel. Grain boundary cementite formation is completely suppressed in the 1.29 wt pct Al steel. Phase diagram calculations show that aluminum increases the eutectoid temperature. However, the interlamellar spacing and pearlite colony size decrease with increase in aluminum content. Dilatometry measurements show that aluminum addition increases the undercooling below the eutectoid temperature. The yield strength increases with the decrease in interlamellar spacing and colony size. Very high ultimate tensile strengths (1200 to 1400 MPa) and improved elongations to failure (7 to 9 pct) are achieved in the as-rolled condition.

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Section: Introductionmentioning

confidence: 97%

Effect of Aluminum Content on the Microstructure and Mechanical Properties of Hypereutectoid Steels

Jang

Phaniraj

Kim

et al. 2010

Metall Mater Trans A

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“…As important is the mechanical properties of final hot rolled steels that referred to the phase transformation behavior, in order to design the suitable cooling schedule after rolling, it is necessary to investigate the effects of various process parameters on austenite to ferrite and ferrite to pearlite transformation. Under industrial processing conditions the austenitic phase is subjected to continuous cooling (or heating), the transformation to pearlite usually differs from equilibrium and is retarded to lower start and finish temperatures [2].…”

Section: Introductionmentioning

confidence: 99%

Phase Transformation Behavior of Niobium Containing Microalloyed Steel with Predeformation and Continuous Cooling

She

Zhang

et al. 2014

MSF

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The continuous cooling phase transformation behavior of niobium microalloyed steel was studied by Thermecmastor-Z thermomechanical simulator; the continuous cooling transformation curves (CCT) were established. The change of microstructure under different cooling rates was observed, and the influence of deformation in austenite non-recrystallization region on transformation was discussed. Based on these work, it was possible to know that the phase transformation is retarded and the ferritic grain is refined dramatically as the cooling rate increasing. The deformation in austenite non-recrystallization region caused deformation stored-energy, which improved the grain refinement of transformation to some extent, but not significant.

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“…It has been reported previously that this can be due to a higher fraction and retarded dissolution of precipitates and also to a possible vanadium solute drag effect. 4,17) As a consequence, the S V value increased from 62 mm Ϫ1 (steel 10V) to 95 mm …”

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confidence: 97%

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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Continuous Cooling Transformation Temperature and Microstructures of Microalloyed Hypereutectoid Steels

Cited by 11 publications

References 21 publications

Effect of Aluminum Content on the Microstructure and Mechanical Properties of Hypereutectoid Steels

Effect of Aluminum Content on the Microstructure and Mechanical Properties of Hypereutectoid Steels

Phase Transformation Behavior of Niobium Containing Microalloyed Steel with Predeformation and Continuous Cooling

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

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