Three-Dimensional Morphology and Growth Behavior of Acicular Ferrite in Low Carbon Steel Weld

In this work, a high strength, high toughness low carbon steel weld was developed by controlling the contents of B and Ti which are the minor but critical elements to the weld microstructure. The weld with the low B - Ti content exhibited the high strength close to 1 GPa and the excellent toughness over 70 J at 40 °C. The weld microstructure consisted of the multiphase which composed acicular ferrite, bainite, martensite, under welding condition. A weld with the high B - Ti content was fully martensite and exhibited the high strength over 1 GPa but the poor toughness below 15 J at 40 °C. The present results inform that, when the low carbon steel weld contains the substantial amount of various alloying elements to obtain the high strength, the B content should be low as possible so that a substantial amount of acicular ferrite is ensured by screening the hardenability improving effects from other elements. The Ti content was found to affect the size of the multi-component oxides such that the less the Ti content, the smaller the oxide size which is critical to the acicular ferrite nucleation.

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Microstructural refinement by the formation of acicular ferrite on Ti–Mg oxide inclusion in low-carbon steel

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141795 ◽

2021 ◽

pp. 141795

Author(s):

Fangce Liu ◽

Jiawang Li ◽

Qi Wang ◽

Yandong Liu ◽

Yang Bai ◽

...

Keyword(s):

Carbon Steel ◽

Acicular Ferrite ◽

Oxide Inclusion ◽

Low Carbon Steel ◽

Low Carbon ◽

Microstructural Refinement

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In situ observation of growth behaviour of acicular ferrite in low-carbon steel containing 13 ppm magnesium

Ironmaking & Steelmaking ◽

10.1080/03019233.2017.1364035 ◽

2017 ◽

Vol 46 (2) ◽

pp. 176-183 ◽

Cited By ~ 2

Author(s):

Chi-Kang Lin ◽

Yan-Chi Pan ◽

Weng-Sing Hwang ◽

Ying-Chien Fang ◽

Yen-Hao Su ◽

...

Keyword(s):

Carbon Steel ◽

Acicular Ferrite ◽

Low Carbon Steel ◽

In Situ Observation ◽

Low Carbon ◽

Growth Behaviour

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The Effect of Severe Plastic Deformation on the Brittle-Ductile Transition in Low Carbon Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.633-634.471 ◽

2009 ◽

Vol 633-634 ◽

pp. 471-480

Author(s):

Masaki Tanaka ◽

Kenji Higashida ◽

Tomotsugu Shimokawa

Keyword(s):

Fracture Toughness ◽

Carbon Steel ◽

Grain Boundaries ◽

Three Dimensional ◽

Low Carbon Steel ◽

Dislocation Dynamics ◽

Strain Rates ◽

Low Carbon ◽

Dislocation Source ◽

Brittle Ductile Transition

Brittle-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various temperatures and strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the controlling process of the BDT was not changed by the deformation with the ARB process. It was deduced that the decrease in the BDT temperature by grain refining was not due to the increase in the dislocation mobility controlled by short-range barriers. Quasi-three-dimensional simulations of dislocation dynamics, taking into account of crack tip shielding due to dislocations, were performed to investigate the effect of a dislocation source spacing along a crack front on the BDT. The simulation indicated that the BDT temperature is decreased with decreasing in the dislocation source spacing. Molecular dynamics simulations revealed that moving dislocations were impinged against grain boundaries and were reemitted from there with increasing strain. It indicates that grain boundaries can be new sources in ultra-fine grained materials, which increases toughness at low temperatures.

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