Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Nandi, Somnath; Tewary, N.K.; Saha, J. K.; Ghosh, S. K.

doi:10.1080/1478422x.2016.1141744

Cited by 13 publications

(42 citation statements)

References 43 publications

(60 reference statements)

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“…The addition of V slightly reduces ferrite grain size from 7 to~4.5µm. However, in a rather small volume fraction, upper bainite appears in the microstructure of the core zone and it has been indicated that the breaking cementite lamellar into a small fragment is mainly due to a decrease in transformation temperature [30].…”

Section: Outer Surface (Rim)mentioning

confidence: 99%

Microstructure and Mechanical Properties of V-Alloyed Rebars Subjected to Tempcore Process

Ahmed

Ibrahim

Galal³

et al. 2021

Metals

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Two B400B-R and B500B grade rebars were industrially produced through a Tempcore process. The standard chemical composition of B500B grade was additionally alloyed with 0.067 wt.% V to enhance its mechanical properties. A set of optimized processing parameters were applied to manufacture two different diameters D20 (Ø 20 mm) and D32 (Ø 32 mm). The microstructure -mechanical properties relationships were evaluated using optical and scanning electron microscopes, hardness, and tensile testing. In addition, a thermal model was developed to define the thermal cycle evolution during cooling in the quenching & tempering box (QTB) to simulate the kinetics of V(C,N) precipitation. The microstructure observations showed a typical graded microstructure consisting of ferrite-pearlite core and outer tempered martensite ring for both grades of both diameters. The optimized processing parameters for B400B-R of D32 (compared with D20) resulted in softening of the core (from 160 to 135 HV10) and tempered martensite surface (from 220 to 200 HV10) as well as in decreasing the yield strength (from 455 to 413 MPa) and tensile strength (from 580 to 559 MPa). On the contrary, an increase in hardness of the core (from 165 to 175 HV10) and the outer tempered martensite (from 240 to 270 HV10), in addition to an increase in yield strength (from 510 to 537 MPa) at almost the same level of tensile strength of 624–626 MPa are observed for B500B grade D32 compared with D20. The modeling and simulation calculations suggest that the manufacturing D32 rebars of B500B grade involves longer quenching time in the QTB which allow deeper tempered martensite surface along with a relatively higher core temperature that renders faster kinetics and larger volume fraction of V(C,N) precipitates. The current study demonstrates that the full potential of V-alloying can be exploited when a sufficient quenching time at the equalization temperature is achieved, which is valid for D32 rebars.

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Section: Outer Surface (Rim)mentioning

confidence: 99%

Microstructure and Mechanical Properties of V-Alloyed Rebars Subjected to Tempcore Process

Ahmed

Ibrahim

Galal³

et al. 2021

Metals

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“…It has been already reported that an increase in yield strength of reinforcing bars occurs by raising carbon as well as manganese content or by microalloying. It is also true that higher carbon content may cause lower weldability and ductility [13,16,23]. It is worth mentioning here that all the steel rebar samples selected in the present investigation contain a lower amount of carbon since a higher amount of carbon can cause harmful carbide formation and pearlite formation in the as-rolled steels thereby causing micro-galvanic corrosion [23,33].…”

Section: Alloy Compositionmentioning

confidence: 87%

“…However, encountering chloride solution in this structure causes the breakdown of this passive layer. In the coastal and marine areas, excessive level of chloride causes problems of chloride-induced corrosion, thereby creating problems in corrosion resistance of the TMT rebars in the concrete [23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Study on the Perspective of Mechanical Properties and Corrosion Behaviour of Stainless Steel, Plain and TMT Rebars

Dey¹,

Manna²,

Yadav³

et al. 2022

Stainless Steels

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In the present research, the effects of various alloying elements and microstructural constituents on the mechanical properties and corrosion behaviour have been studied for four different rebars. The microstructures of stainless steel and plain rebar primarily reveal equiaxed ferrite grains and ferrite-pearlite microstructures, respectively, with no evidence of transition zone, whereas tempered martensite at the outer rim, followed by a narrow bainitic transition zone with an internal core of ferrite-pearlite, has been observed for the thermomechanically treated (TMT) rebars. The hardness profiles obtained from this study display maximum hardness at the periphery, which decreases gradually towards the centre, thereby providing the classical U-shaped hardness profile for TMT rebars. The tensile test results confirm that stainless steel rebar exhibits the highest combination of strength (≈755 MPa) and ductility (≈27%). It has been witnessed that in Tafel plots, the corrosion rate increases for all the experimental rebars in 1% HCl solution, which is well expected because the acid solutions generally possess a higher corrosive environment than seawater (3.5% NaCl) due to their acidic nature and lower pH values. However, all the experimental results obtained from Tafel and Nyquist plots correlate well for both 1% HCl and 3.5% NaCl solutions.

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“…The results obtained in this research suggest that the corrosion resistance of TMT bars could be higher than that of conventional hot rolled reinforcing bars. Another corrosion study with TMT bars also reports weight losses in NaCl solutions [4]. Recent preliminary results on about the effect of the galvanic connection between TMT and conventional reinforcement steels on their corrosion performance in simulated pore solutions have also been published [16].…”

Section: Introductionmentioning

confidence: 98%

“…Moreover, the stresses in the microstructure of cold rolled bars can make them more prone to corrosion [3], and they present offer worse after-fire mechanical properties [1,2]. To increase the mechanical properties of hot rolled carbon steel bars, the addition of microalloying elements as well as thermomechanical treatment (TMT), can be used [4]. The addition of carbon in amounts ranging between 0.3 and 0.5% hardens the steel, but its bendability and weldability decrease [5].…”

Section: Introductionmentioning

confidence: 99%

Influence of the microstructure of TMT reinforcing bars on their corrosion behavior in concrete with chlorides

Bautista

Pomares

González

et al. 2019

Construction and Building Materials

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Thermomechanically treated (TMT) carbon steel bars, often known as "TempCore" bars, are commonly used as reinforcements in concrete structures. TMT causes the formation of a martensite case in the outer surface of the bars, increasing their hardness, while the remaining ferritic-perlitic core maintains the typical ductility of hot rolled bars. In this work, the effect of this TMT induced microstructure on the development of pitting attacks in chloride media has been analyzed in depth. Electrochemical impedance spectroscopy (EIS) measurements and polarization curves have been carried out in simulated pore solutions to understand the effect of the presence of different phases in the microstructure and to quantify the strength of the galvanic couple that the outer martensite can form with the inner core. Moreover, accelerated corrosion tests in chloride contaminated concrete slabs have also been performed. Bars from six different slabs where corrosive attack has been forced for different times have been studied. The shape of the main pits in the bars corroded in concrete has been analyzed through optoelectronic microscopy and the results obtained prove that the depth of the attack is related to the microstructure of the TMT bars.

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Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Cited by 13 publications

References 43 publications

Microstructure and Mechanical Properties of V-Alloyed Rebars Subjected to Tempcore Process

Microstructure and Mechanical Properties of V-Alloyed Rebars Subjected to Tempcore Process

Study on the Perspective of Mechanical Properties and Corrosion Behaviour of Stainless Steel, Plain and TMT Rebars

Influence of the microstructure of TMT reinforcing bars on their corrosion behavior in concrete with chlorides

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