Effect of B Segregation at Prior Austenite Grain Boundaries on Microstructures and Toughness in the Heat‐Affected Zone of Mg‐Deoxidized Shipbuilding Steel Plates

Self Cite

The inclusions, microstructures, and toughness in heat‐affected zone (HAZ) of the shipbuilding steel plates with Mg deoxidation and the different Ti/N ratios are studied after the high heat input welding of 400 kJ cm−1. With increasing the Ti/N ratio from 3.00 to 5.67, the average size of inclusions increases, the mass fraction of total TiC inclusions increase from 2.8% to 5.0%, and the average size of MgO–TiN–MnS increases from 2.82 to 5.49 μm, while the number density that can induce intragranular acicular ferrite (IAF) nucleation decreases from 87 to 62 mm−2. These changes in inclusions are detrimental to induce the IAF nucleation. The HAZ microstructures are composed of the IAFs, polygonal ferrites, and upper bainites (UBs). With increasing the Ti/N ratio, the area fraction of the IAFs decreases from 44% to 14%, and the area fraction of UBs increases from 1.8% to 9.5%. The HAZ fracture mode changes from ductile fracture to brittle fracture after the high heat input welding of 400 kJ cm−1, and the HAZ toughness decreases from 183.3 to 48.7 J at −20 °C.

Section: Introductionmentioning

confidence: 99%

Influence of Ti/N Ratio on Inclusions, Microstructures, and Toughness in Heat‐Affected Zone of Shipbuilding Steel Plates with Mg Deoxidation after High Heat Input Welding

Zhang,

Yang

et al. 2023

Self Cite

“…[3] Besides, the coarse grains and brittle microstructures will be formed in the coarse-grained heat-affected zone (CGHAZ) during welding process of steel plates, which can deteriorate the HAZ toughness. [5,6] Therefore, improving the welding HAZ toughness is an important factor to obtain high-performance offshore engineering steels.…”

Section: Introductionmentioning

confidence: 99%

Effect of Si Content on the Microstructures and Toughness in Heat‐Affected Zone of Offshore Engineering Steels with Mg Deoxidation

Pan

Yang

Zhang

et al. 2022

Self Cite

Herein, the effect of Si content on the microstructures and toughness in the heataffected zone (HAZ) with the heat input of 100 kJ cm À1 for Mg-deoxidized offshore engineering steels is presented. For the matrix, increasing Si content coarsens the lath bainites (LBs) in HAZ due to the higher A r3 and lower A r1 . Thus, the highangled grain boundary density (HAGBD) decreases from 0.88 to 0.53 μm À1 , and the effective grain size increases from 10.6 to 18.3 μm. M-A constituents are transformed from dotted and filmed ones to the stringer and blocky ones, with the area fraction increasing from 2.9% to 5.6%. Among them, the stringer M-A particles are likely to debond from the matrix, while the blocky M-A particles tend to initiate cracks because the interfacial energy of stringer particles is lower than that of blocky ones. Accordingly, increasing Si content from 0.0003 to 0.120 wt% results in both the increased crack initiation probability by more M-A constituents with the larger size and the lowered crack propagation barrier by the smaller HAGBD, thereby reducing the HAZ toughness at À40 °C from 202 to 58 J.

Impact of Permanent Magnet Stirring on Inclusion Evolution, Solidification Structure and Mechanical Properties of AH32 Shipbuilding Steel

Liao,

Yang,

et al. 2024

An experimental investigation has been conducted with respect to the effect of permanent magnet stirring (PMS) under different rotation speeds (0, 60, 180 rpm) on the solidification of AH32 shipbuilding steel by analyzing the inclusion evolution, solidification structure, and mechanical properties. As the rotation speed increased from 0 to 180 rpm, the mean size of inclusions (Al2O3, MnS, and Al2O3–MnS) reduced significantly from 6.23 to 2.92 μm, their number increased from 49 to 82 n mm−2 and the ratio of complex inclusions increased from 30.6% to 75.6% in the AH32 steel ingot. Besides, the increasing number of small complex inclusion promotes the formation of acicular ferrite in steel, resulting in an elevation of the area ratio from 10.5% to 27.8%. Furthermore, under a rotation speed of 180 rpm, the mean grain size decreased to 99.4 μm and the frequency of high‐angle grain boundaries (HAGBs) increased to 86.1%. In addition, the as‐cast AH32 steel exhibited an optimized ultimate tensile strength of 532.0 MPa and an improved elongation of 24.2% after an enhanced PMS, which was attributed to more acicular ferrite, higher HAGBs ratio, and refined grain size.