Abstract
The Ti element plays a role in pinning grain boundaries but also has a good binding ability to C and N, forming large primary carbides. Therefore, the effect of Ti content on primary carbides’ behavior in H13 ingots was comprehensively studied. A non-aqueous electrolysis method was used to determine the three-dimensional (3D) characteristics of primary carbides. We found a great difference between the two-dimensional (2D) and the three-dimensional characteristics of primary carbides. When performing 2D analyses, the density of the primary carbides appeared high, while their size was small. The actual characteristics of primary carbides can be obtained only by 3D observation. The primary carbide showed a typical dendritic structure, whose center consisted of Ti–V-rich carbide wrapped by V-rich carbide. As the Ti content increased, the size of the primary carbide increased from 24.9 μm to 41.3 μm, and the number density increases from 25.6 per/mm2 to 43.9 per/mm2. The Ti4C2S2 phase precipitated first, then changed into Ti–V-rich carbide, and finally further partly transformed into V-rich carbide. The addition of elemental Ti promoted the precipitation and transformation of primary carbides, resulting in an increase of the number density and size.
Highlights
The microalloying element Ti has been widely applied to improve the properties of steel, especially for the heat-affected zone (HAZ) [1,2]
Elemental Cr, Mo, V, and C were rejected from the liquid and could be present in was the same for all samples
Fatigue strength size theprimary primary carbide decreased from 41.3 μm to 24.9
Summary
The microalloying element Ti has been widely applied to improve the properties of steel, especially for the heat-affected zone (HAZ) [1,2]. The addition of elemental Ti can form fine dispersion of TiN or TiC particles that can pin the prior austenite grain boundaries, preventing excessive grain growth because of their stability at high temperatures [3,4]. Maity found that the tensile and yield strength of 0.07 wt.% titanium low-alloy steel increases sharply compared to those of un-inoculated steel, 0.2 wt.% titanium, and 0.4 wt.% titanium steels, because finer Ti(C, N) particles are precipitated [5]. The TiN particles effectively promote intragranular ferrite nucleation in low-carbon steel. The TiN and TiN+oxide particles can act as the nucleation core of δ-phase during solidification, refining the solidification structure of ferritic stainless steel, especially increasing the fraction of equiaxed grains [9]. The appropriate addition of Ti can significantly improve the properties of materials
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