Effect of Aging Time on Microstructure and Mechanical Properties in a Cu-Bearing Marine Engineering Steel.

Mingxue Sun,Yang Xu,Jin Wang

doi:10.3390/ma13163638

Mingxue Sun, Yang Xu + Show 1 more

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https://doi.org/10.3390/ma13163638

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Abstract

This study elucidated the structure–property relationship in a Cu-bearing marine engineering steel that was water cooled and then aged at 500 °C for 0.5–3 h. The microstructural features, tensile properties and impact properties were comparatively investigated as a function of aging time. When the aging period was increased, the Cu precipitates underwent coarsening, and a stable face-centered cubic (fcc) formation occurred. Additionally, the tensile properties were significantly improved at the expense of low temperature toughness, which can be attributed to the presence of nano-sized Cu precipitates. The increment of yield strength mainly derived from Cu precipitate–dislocation interaction strengthening effects (232 MPa for 1 h and 199 MPa for 3 h.) during aging process. Therefore, optimization of mechanical properties was achieved by controlling the parameters of aging process. The peak age hardening condition (i.e., at 500 °C for 1 h) resulted in the yield strength of 755 MPa, tensile strength of 812 MPa, elongation of 26.3% and impact energy of 78 J at −80 °C.

Highlights

Cu-bearing high strength low alloy (HSLA) steels, which possess a desirable combination of strength, ductility, weldability and toughness, have drawn much attention in the construction of naval warships, offshore drilling platforms, oil pipelines and bridges [1,2,3,4]
A of bainitic ferrite (BF) structure, which is characterized by the presence of lath bainite morphology, small amount of bainitic ferrite (BF) structure, which is characterized by the presence of lath bainite was observed
The aging process was applied to a Cu-bearing marine engineering steel

Summary

Introduction

Cu-bearing high strength low alloy (HSLA) steels, which possess a desirable combination of strength, ductility, weldability and toughness, have drawn much attention in the construction of naval warships, offshore drilling platforms, oil pipelines and bridges [1,2,3,4]. To achieve good weldability and high impact toughness, the carbon content is kept below 0.08 wt% in Cu-bearing HSLA steels. Many research papers have been published on the quenching and aging conditions required for the development of Cu-bearing HSLA steels [11,12,13,14]. Dhua et al [11] investigated the effects of tempering temperature on the mechanical properties and microstructures of HSLA-100 type Cu-bearing steels. They noted that coarsening of Cu precipitates occurred when the tempering temperature was higher than 500 ◦ C. Hwang et al [12] utilized the direct quenching and tempering (DQ&T)

Methods

Discussion

Conclusion