Microstructure of high strength niobium-containing pipeline steel

Shanmugam, S.; Misra, R.D.K.; Hartmann, J.E.; Jansto, Steven G.

doi:10.1016/j.msea.2006.08.017

Cited by 114 publications

(59 citation statements)

References 40 publications

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“…[9][10][11][12][13][14] It is conjectured that the absence of Nb(C,N) precipitation in the as-cast and hot-rolled steels is due to the fast cooling rates (60 to 80 K/s upon water cooling) applied in the CASTRIP process. Consequently, the Nb atoms are essentially retained in a supersaturated ferritic solid solution.…”

Section: B Effect Of Microalloying With Nbmentioning

confidence: 99%

“…In respect to the effect of Nb microalloying on high-strength low-alloy steels, many studies have been carried out. [9][10][11][12][13][14][15] An important and widely reported effect in both theoretical and experimental studies is the decrease in the transformation start temperature, thus favoring the formation of low-temperature transformation products such as acicular ferrite and bainite. It also has been demonstrated that Nb precipitates strongly retard austenite recrystallization.…”

Section: Introductionmentioning

confidence: 99%

“…[15,16] Furthermore, Nb additions are known to impart improved strength to these steels through the formation of nanoscale NbC or Nb(NC) precipitates, which retard the movement of dislocations within the grains during deformation. [9][10][11][12][13][14] In this research, we provide the first comprehensive evaluation of the effects of hot rolling and Nb microalloying on the detailed microstructure-property relationships in UCS steels.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Xie

Yao

Zhu

et al. 2011

Metall Mater Trans A

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The microstructure and corresponding tensile properties of both plain and Nb-microalloyed grades of ultrathin cast strip (UCS) low alloy steel produced using the CASTRIP Ò process were studied. Both as-cast and hot-rolled strip cast steels with various levels of Nb microalloying were manufactured and investigated in this study. Hot rolling had little effect on the yield strength of Nb microalloyed UCS specimens for a given chemical composition, but resulted in a slightly finer microstructure. The effect of Nb microalloying was significant, and this is attributable to the promotion of finer, tougher austenite transformation products such as bainite and acicular ferrite at the expense of large polygonal ferrite grains. A fine dispersion of Nb solute clusters was observed in all Nb-containing steels following hot rolling, and it is suggested that this also contributes to the observed strengthening.

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Section: B Effect Of Microalloying With Nbmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Xie

Yao

Zhu

et al. 2011

Metall Mater Trans A

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“…In the thermo-mechanically controlled processing (TMCP) of pipeline steels, different combinations of microstructures can be obtained, such as ferrite-pearlite, bainitic ferrite, bainitic ferritebainite, polygonal ferrite-bainitic ferrite etc [18][19]. It has been reported that the efficiency of trapping tends to increase in the following order: small second phase particles, coarse pearlite, fine pearlite, bainite, martensite and acicular ferrite [15,20].…”

Section: Introductionmentioning

confidence: 99%

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Hejazi

Haq

Yazdipour

et al. 2012

Materials Science and Engineering: A

117

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The influence of composition and microstructure on susceptibility to hydrogen induced cracking (HIC) was investigated in high strength pipeline steels, with Mn contents of 1.2% (standard, X70), and 0.5% (medium, MX70). The HIC resistance of the simulated coarse grained heat affected zone microstructures and normalized X70 transfer bar was also investigated. Notched and fatigue pre-cracked samples were charged with hydrogen prior to three point bend tests. The conditional fracture toughness JQ was determined. The results are discussed in relation to grain size, microstructure, composition and the type and distribution of non-metallic inclusions and precipitates. Published as "Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking" AbstractHydrogen, even in very low concentrations, can diffuse to regions of high stress concentration resulting in a degradation of mechanical properties. However, the transport of hydrogen depends on the interaction between hydrogen atoms and microstructural traps which, in turn, is related to microstructure. The influence of composition and microstructure on susceptibility to hydrogen embrittlement was investigated by selecting pipeline steels with different Mn contents, i.e., standard Mn (X70) and medium Mn (MX70) strips. The HAZ (heat affected zone) microstructures of these strips as well as a normlised transfer bar (TB) were also investigated. HAZ simulations were conducted using Gleeble thermo-mechanical machine to simulate a thermal cycle typical of inservice repairs. Notched and fatigue pre-cracked samples were subjected to electrochemical hydrogen charging using a solution of H 2 SO 4 and NaAsO 2 to achieve 2 and 4 ppm hydrogen content. Three point bend tests were conducted on as-received and hydrogen-charged samples. The X70 strip exhibited a higher J Q than the MX70 strip before and after charging, whereas the TB displayed the lowest J Q . The fracture performance of both steels deteriorated almost linearly with an increase in the hydrogen content. Because of their coarser prior austenite grain sizes and the presence of relatively hard bainitic-ferrite structure with martensite/austenite islands, the simulated HAZ microstructures of the two steels demonstrated significantly lower fracture resistance both with and without hydrogen. The results obtained were compared and discussed in relation to the grain size, microstructure, composition and the type and distribution of precipitates in the samples.

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“…It is the result of effect of heat flow and the cooling rate of steel during welding process. For example, in this case of multilayer welding the deposition of each layer includes heating of underlaying microstructure [11]. Difference in transition temperature of HAZ of weldments of structural steels is explained with the effect of local brittle zones (LBZ) [12,13].…”

Section: Introductionmentioning

confidence: 99%

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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Microstructure of high strength niobium-containing pipeline steel

Cited by 114 publications

References 40 publications

Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Effect of Nb Microalloying and Hot Rolling on Microstructure and Properties of Ultrathin Cast Strip Steels Produced by the CASTRIP® Process

Effect of manganese content and microstructure on the susceptibility of X70 pipeline steel to hydrogen cracking

Effect of heat treatment on Charpy impact energy of microalloyed steel

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