Abstract
Since hot-dip galvanizing causes a heat effect on cold-worked steel substrate and produces a coating layer comprised of distinct phases with varying mechanical properties, the fatigue mechanism of hot-dip galvanized steel is very complex and hard to clarify. In this study, AISI 1020 steel that has been normalized to minimize susceptibility to the heat effect was used to clarify the effect of the galvanizing layer on the tensile and fatigue properties. The galvanizing layer causes a reduction in the yield point, tensile strength, and fatigue strength. The reduction in the fatigue strength was more significant in the high cycle fatigue at R = 0.5 and 0.01 and in the low cycle fatigue at R = 0.5. The galvanizing layer seems to have very little effect on the fatigue strength at R = −1.0 in the low and high cycle fatigue. Since the fatigue strengths at R = 0.01 and −1.0 in the low cycle fatigue were strongly related to the tensile strength of the substrate, the cracking of galvanized steel was different than that of non-galvanized steel. The fatigue strength of galvanized steel at R = 0.5 dropped remarkably in the low cycle fatigue in comparison to the non-galvanized steel, and many cracks clearly occurred in the galvanizing layer. The galvanizing layer reduced the fatigue strength only under tension–tension loading. We believe that the findings in this study will be useful in the fatigue design of hot-dip galvanized steel.
Highlights
Published: 6 December 2021 hot-dip galvanized steel structures are gaining popularity in various industries, there are still some reservations about the use of hot-dip galvanized steel in some applications such as structural steel members in bridges due to limited knowledge of their fatigue behavior and design recommendations [1,2,3]
The microstructure of the plating layer from a conventional zinc bath is comprised of a thin gamma (Γ) phase, which forms an interphase with the steel substrate, followed by the delta (δ) phase, the zeta phase (ζ) phase, and the eta phase (η) made of pure zinc is at the outermost surface [6]
This experimental study was focused on determining the effect of hot-dip galvanizing on the fatigue strength of normalized AISI 1020 steel
Summary
Published: 6 December 2021 hot-dip galvanized steel structures are gaining popularity in various industries, there are still some reservations about the use of hot-dip galvanized steel in some applications such as structural steel members in bridges due to limited knowledge of their fatigue behavior and design recommendations [1,2,3]. Hot-dip galvanizing produces a coating layer comprised of different intermetallic phases of distinct mechanical properties [4,5]. The microstructure of the plating layer from a conventional zinc bath is comprised of a thin gamma (Γ) phase, which forms an interphase with the steel substrate, followed by the delta (δ) phase, the zeta phase (ζ) phase, and the eta phase (η) made of pure zinc is at the outermost surface [6]. Due to the many possible microstructures of the plating layer with the resulting mechanical properties and the requirement to preserve the mechanical performance of steel components after post-forming surface treatments such as galvanizing, the effect of the galvanizing layer on the fatigue strength of various steel types has been of much interest. Sirin [12] reported the formation of pre-cracks in the delta phase during solidification after hot-dip galvanizing and a reduction in fatigue strength
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