Effect of Welding Heat Input on Microstructure and Toughness of Heated‐Affected Zone in Steel Plate with Mg Deoxidation

Wang

2018

Metals

Self Cite

The effects of Al content on inclusions, microstructures, and heat-affected zone (HAZ) toughness in a steel plate with Mg deoxidation have been investigated by using simulated high-heat-input welding and an automated feature system. The studies indicated that the main kind of oxysulfide complex inclusions in two steels without and with Al addition were both MgO-MnS. The number densities and mean sizes of inclusions were 96.65 mm−2 and 3.47 μm, 95.03 mm−2 and 2.03 μm, respectively. The morphologies of MgO-MnS complex inclusions in steel were changed obviously with the addition of Al. When containing 0.001 wt.% Al, they consisted of a central single MgO particle and outside, the MnS phase. When containing 0.020 wt.% Al, they comprised several small MgO particles entrapped by the MnS phase. Because the former could nucleate intragranular acicular ferrites (IAFs) and the latter was non-nucleant, the main intragranular microstructures in HAZs were ductile IAFs and brittle ferrite side plates (FSPs), respectively. Therefore, HAZ toughness of the steel plate without Al addition after high-heat-input welding of 400 kJ/cm was significantly better than that of the steel plate with Al addition.

Section: Introductionmentioning

confidence: 99%

Influence of Al Content on the Inclusion-Microstructure Relationship in the Heat-Affected Zone of a Steel Plate with Mg Deoxidation after High-Heat-Input Welding

Wang

2018

Metals

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“…[6] Xu et al reported that Mg addition to a shipbuilding steel can significantly induce the formation of the interlocking intragranular acicular ferrite (IAF), which has an excellent strength-toughness combination. [7,8] Wang et al highlighted the positive effect of Ti-Zr deoxidation in a low-alloy steel, revealing great improvement in intragranular transformation and strong prevention of coarse intergranular structures. [9] Yamamoto et al summarized the formation mechanism of IAF in HSLA steels noting that MnS forms a Mn-depleted zone at the Ti 2 O 3 /austenite interface, thus increasing the chemical free energy change for ferrite nucleation, and TiN decreases the interfacial energy for ferrite nucleation.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Impact Toughness of the Welding Heat-Affected Zone in High-Strength Low-Alloy Steels through Ca Deoxidation

Zhang

Liu

et al. 2021

Metall Mater Trans A

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Thick high-strength low-alloy (HSLA) steel plates with excellent large heat input welding properties are increasingly demanded to build super-large container ships for the globally flourishing marine trade. This article describes the effect of Ca content on the TiN particles, microstructure and impact toughness of the simulated coarse-grained heat-affected zone (CGHAZ) in HSLA steels after large heat input welding at 400 kJ/cm. The quantitative analyses on TiN particles demonstrate that the number densities of the submicron-and nano-scale particles increase with increasing Ca content, but the particle sizes appear to be independent of the Ca content. The prior austenite grains in the CGHAZs of the HSLA steels are comparably coarse, including a small number of extremely large grains, except for 25Ca steel, whose grains are relatively fine and uniform. Moreover, only the impact toughness of the CGHAZ in 25Ca steel is satisfactorily improved with a small test variability, and this could be attributed to the improved precipitation of the submicron-scale TiN particles that effectively refine the grains. Based on the experimental and thermodynamic results, it is strongly recommended to increase the Ca content to > 0.0019 wt pct for the related HSLA steel system in the future steel optimization.

“…[ 1 ] During the HHIW process, the microstructures in the coarse‐grained heat‐affected zone (CGHAZ) are coarsened, giving rise to the deterioration of the HAZ toughness. [ 2,3 ] Therefore, it is of considerable importance to improve their HAZ toughness after HHIW.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Fracture Characteristics of Heat‐Affected Zone in Shipbuilding Steel Plates with Mg Deoxidation after High Heat Input Welding

Pan

Zhang

2021

steel research int.

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To clarify the microstructure and fracture characteristics of heat‐affected zone in shipbuilding steel plates with Mg deoxidation after high heat input welding, two steels with 0.0002 (2Mg) and 0.0049 (49Mg) wt% Mg are prepared and investigated with metallography and crystallography. Compared with 2Mg, TiN particles are incrementally refined in 49Mg, making the prior austenite grain (PAG) size decrease. In the large‐sized grains of 2Mg, there are preferentially formed coarse grain boundary ferrites (GBFs) and ferrite side plates (FSPs), followed by intragranular bainite ferrites (IBFs). The small PAGs of 49Mg make fine‐grained polygonal ferrites (PFs) dominate the microstructure. With Mg addition, the effective grain with θ > 50° refines and the high‐angle grain boundary density increases. The brittle transgranular fracture occurs around little‐deformed coarse GBFs, FSPs, and IBFs with θ < 15° in 2Mg, showing the weak crack resistance. However, in 49Mg, the ductile fracture occurs around fine PFs and IAFs with large plastic deformation. Although there is transgranular fracture in coarse PFs, it can be soon deflected and arrested by small‐sized PFs with θ > 50° in 49Mg. Thus, for 49Mg, the crack initiation and propagation energies increase with the toughness at −40 °C increasing from 20 to 167 J.