Microstructure, Mechanical Properties, and Corrosion Behavior of Ultra-Low Carbon Bainite Steel with Different Niobium Content

Abstract

Four types of ultra-low carbon bainite (ULCB) steels were obtained using unified production methods to investigate solely the effect of niobium content on the performance of ULCB steels. Tensile testing, low-temperature impact toughness testing, corrosion weight-loss method, polarization curves, electrochemical impedance spectroscopy (EIS), and the corresponding organizational observations were realized. The results indicate that the microstructure of the four steels comprise granular bainite and quite a few martensite/austenite (M/A) elements. The niobium content affects bainite morphology and the size, quantity, and distribution of M/A elements. The elongation, yield strength, and tensile strength of the four types of ULCB steels are above 20%, 500 MPa, and 650 MPa, respectively. The impact toughness of the four types of ULCB steels at −40 °C is lower than 10 J. Steel with Nb content of 0.0692% has better comprehensive property, and maximum charge transfer resistance in 3.5 wt.% NaCl solution at the initial corrosion stage. The corrosion products on the surface of steel with higher niobium content are much smoother and denser than those steel with lower niobium content after 240 h of corrosion. The degree of corrosion decreases gradually with the increase of niobium content at the later stage of corrosion.

Research on the Chloride Ion Corrosion Resistance of Cu-Sb-Added Low-Carbon Steel

“…in the steel having a better corrosion resistance [12][13][14]. It can be seen from Table 2 that the 1# specimen with a Cu-Sb composite added to it had the lowest capacitance value and the highest Rf value, thus indicating that its resistance to electrochemical corrosion increased after low alloying [15].…”

“…This indicates that the selected equivalent circuit was effective in fitting the elements. The size of the impedance arc represents the ease of the charge transfer, with a larger diameter indicating a higher R f value (suggesting that the corrosion reaction is less likely to occur), which thus results in the steel having a better corrosion resistance [12][13][14]. It can be seen from Table 2 that the 1# specimen with a Cu-Sb composite added to it had the lowest capacitance value and the highest R f value, thus indicating that its resistance to electrochemical corrosion increased after low alloying [15].…”

Effect of Microstructure on Corrosion Resistance of Ultralow‐Carbon Bainitic Steel

“…The corrosion behavior of the ferrite–bainite dual‐phase steel is associated with the volume fraction of each phase. Zong et al [ 18 ] reported that Nb microalloying affects the bainite morphologies and the corrosion behavior. It is well known that martensite, bainite, and ferrite have the similar crystal structure (i.e., body‐centered cubic structure), but have different dislocation density, carbon content, and morphology.…”

Fatigue Tests and Analysis on Welded Joints of Weathering Steel

“…The introduction of those alloying elements can facilitate the formation of a dense and strongly adherent rust layer during wet/dry cycles. Compared to plain carbon steels (CS), the corrosion resistance of WS is enhanced due to the protective rust layer [ 1 , 2 , 3 , 4 ]. This contributes to the application for WS in bridge structures (e.g., orthotropic steel decks) ( Figure 1 ).…”