Transformation of Inclusions in Linepipe Steels During Heat Treatment

Chu, Yanping; Li, Weifu; Ren, Ying; Zhang, Lifeng

doi:10.1007/s11663-019-01593-1

Cited by 46 publications

(26 citation statements)

References 36 publications

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“…silica) caused by fast diffusion and chemical reaction. The high quantity of inclusions in Billet 2 accelerated the element concentration and facilitated the formation of new inclusions [44][45][46]. The large-sized inclusions facilitated crack initiation, while the large volume fraction of inclusions accelerated the crack propagation along the grain boundary.…”

Section: Fracture Mechanisms In Cwrmentioning

confidence: 99%

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

et al. 2020

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Central cracking in cross-wedge-rolled workpieces results in high wastage and economic loss. Recent cross-wedge rolling tests on two batches of steel showed that one batch formed central cracks, while the other was crack-free. The batches were both nominally of the same chemical composition and thermomechanical treatment history. In addition, both batches had passed all the standard quality assessments set for conventional forging processes. It was suspected that the different cracking behaviours were due to differences in microstructure between the two as-received steel billets, and the material in cross-wedge rolling (CWR) was more sensitive to the initial microstructure compared with other forging processes due to its specific loading condition including ostensibly compression and large plastic strain. Nevertheless, no previous study of this important problem could be identified. The aim of this study is, therefore, to identify the key microstructural features determining the central crack formation behaviour in CWR. The hot workability of the as-received billets was studied under uniaxial tensile conditions using a Gleeble 3800 test machine. Scanning electron microscope with energy-dispersive X-ray spectroscopy and electron backscatter diffraction was applied to characterise, quantitatively analyse, and compare the chemical composition, phase, grain, and inclusions in these two billets, both at room temperature and also at the CWR temperature (1080°C). Non-metallic inclusions (oxides, sulphides, and silicates) in the billets were determined to be the main cause of the reported central cracking problem. The ductility of the steels at both room and elevated temperatures deteriorated markedly in the presence of the large volumes of inclusions. Grain boundary embrittlement occurred at the CWR temperature due to the aggregation of inclusions along the grain boundaries. It is suggested that a standard on specifying the inclusion quantity and size in CWR billets be established to produce crack-free products.

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Section: Fracture Mechanisms In Cwrmentioning

confidence: 99%

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

et al. 2020

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“…The schematic of experimental procedures is shown in Figure 2. steels transformed into Al2O3-CaS type after heat treatment in the range of 1273 to 1673 K [27,32]. Yang et al also investigated the transformation of inclusions in pipeline steels during solidification and cooling [33].…”

Section: Methodsmentioning

confidence: 99%

“…It was found that Al-Ca-O-S complex inclusions were the predominating particles in EH36 shipbuilding steels, but the TiN ones were profusely populated after being heated at 1473 K [30,31]. CaO-Al 2 O 3 type of inclusions in pipeline 2 of 21 steels transformed into Al 2 O 3 -CaS type after heat treatment in the range of to 1673 K [27,32]. Yang et al also investigated the transformation of inclusions in pipeline steels during solidification and cooling [33].…”

Section: Introductionmentioning

confidence: 99%

Transformation of Inclusions in Solid GCr15 Bearing Steels During Heat Treatment

Gong

Zhang

et al. 2019

Metals

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Laboratory heating experiments with a varied holding time of GCr15 bearing steels at 1498 K were performed to study the transformation of inclusions in solid GCr15 bearing steels during high temperature diffusion processes. Heating experiments at 1573 and 1648 K were also carried out to study the effect of these heating temperatures. Experimental results showed that inclusions transformed from Al2O3-CaO-(MgO) to Al2O3-CaS-(MgO-CaO) when the heat treatment was in the range of 1498 to 1648 K due to reactions between Al and S in the steel matrix and CaO in the inclusions. This is in good agreement with thermodynamic calculations. Moreover, the size of the inclusions hardly changed after heat treatment. The transformation rate of the inclusions depended strongly on both the heating temperature and the size of the inclusions. Kinetic analyses on the transformation of inclusions during heat treatment were performed based on a simplified analytical model. The mass transfer coefficients of CaO and CaS in inclusions were calculated, which ranged from 0.73 × 10−10 to 4.48 × 10−10 m/s.

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“…[6][7][8][9][10][11][12][13][14][15] However, little attention was paid to study the variation of inclusions in solid steels during heating and rolling so far. [16][17][18][19] Significant variation in the composition of inclusions from the molten steel of continuous casting tundish to continuous casting products was reported. [20] In the 1960s, Takahashi [21] reported the transformation of inclusions in 304 stainless steels from MnO-SiO 2 to MnO-Cr 2 O 3 during the heating of the steel, which was confirmed and deeply investigated by Shibata et al [22] and Ren et al [23] Li et al reported the transformation of inclusions in solid Al-Ti-deoxidized steels during heating.…”

Section: Introductionmentioning

confidence: 99%

“…[24] Wang et al [25] reported the crystallization of inclusions themselves that was the main reason for the transformation of inclusions in Al-Ca killed steels during heating. Chu et al [26] studied the transformation of inclusions in solid Al-killed Ca-treated linepipe steels during heating from CaO-Al 2 O 3 to Al 2 O 3 -CaS with CaS forming on the surface of inclusions and the total calcium and total oxygen (T.O) had a great influence on the transformation. Cheng et al [18] reported a similar phenomenon in a solid bearing steel.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Inclusions in a Complicated‐Deoxidized Heavy Rail Steels During Heating

Zhang

Chu³

et al. 2020

steel research int.

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The transformation of inclusions in a heavy rail steel during heating is investigated in laboratory experiments. When the steel is heated at 1000–1300 °C, inclusions of CaO–SiO2–Al2O3–MgO are transformed into CaS–MgO·Al2O3 ones and the contents of CaS and Al2O3 in inclusions increase, whereas those of CaO and SiO2 decrease. When the steel is heated at 1400 °C, the MgO·Al2O3 phase in inclusions precipitates, whereas CaS, CaO, and SiO2 still exist, which is caused by the lower thermodynamic driving force at high temperature. With the holding time increasing from 0 to 7 h, the composition of inclusions tends to the equilibrium value which is predicted using Factsage. The transformation phenomenon is validated using thermodynamic analysis and a kinetic model is established to predict the composition of inclusions during heating. The MgO·Al2O3 phase formed in inclusions in the steel during heating results in an exposure of MgO·Al2O3 spinel inclusions after rolling, which are rigid and harmful to the performance of steel rails.

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Transformation of Inclusions in Linepipe Steels During Heat Treatment

Cited by 46 publications

References 36 publications

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

Transformation of Inclusions in Solid GCr15 Bearing Steels During Heat Treatment

Transformation of Inclusions in a Complicated‐Deoxidized Heavy Rail Steels During Heating

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