Thermodynamic consideration on selective surface oxidation of high strength steels prior to hot-dip galvanizing

Abstract

The galvanizability of high strength steel is dependent on the surface selective oxidation of alloy elements during intercritical annealing. First, this study reviewed the selective oxidation of Mn, Si, Al, Cr, and their possible products. Then we applied three sets of elemental activity data, i.e., calculated from ThermoCalc, molar fraction, and a M (M = Mn, Si, Al, Cr) = 1 to calculate the equilibrium oxygen partial pressure of each oxidation reaction. It was found that there is a significant deviation among the results calculated from different data. Finally, this study established the stabilities and precipitation sequences of Mn-Si, Mn-Al and Mn-Cr mixed oxides, and proposed a new Mn-Cr rule to predict the oxides formed on the surface of Mn-Cr steel.

Experimental study and thermodynamic analysis on the selective oxidation of DP1180 dual‐phase steel

“…The calculation results show that Mn 2 SiO 4 has the largest initial reaction driving force. However, according to literature reports, 32 these complex oxides are generally formed by simple oxide reactions. The actual situation may be that SiO 2 or MnO was precipitated first, and then Mn 2 SiO 4 and MnSiO 3 were formed.…”

Effect of Dew Point and Gas Flow Rate on the Surface Oxidation of Advanced High Strength Steels

“…[3][4][5][6][7][8][9][10][11] To identify ways to reduce surface oxides, studies were carried out in various annealing conditions; such as the influence of oxygen partial pressure or H 2 /N 2 ratio in atmosphere, Si/Mn ratio or trace elements in steel compositions etc. Most of these investigations were focused on the reaction of metals with oxygen in atmospheres that were assumed to be under (or near) thermodynamic equilibrium conditions wherein the oxygen partial pressure in atmosphere was determined by gas phase equilibrium.…”

Insight into selective oxidation of dual‐phase steel after annealing in pure H2 atmosphere at different heating rates and temperatures

“…Also, in the annealing atmosphere, due to the low oxygen pressure (reduction atmosphere), the alloy elements in the substrate, such as Mn, Si, Cr, Al, and so on, tend to diffuse and segregate on the surface. [4] According to Ellingham's diagram, the alloying elements described above will be oxidized and form a distribution at different positions due to their stronger affinity than iron, such as localizing at the steel surface (external oxidation) or beneath the steel surface (internal oxidation). [4][5][6][7][8][9][10][11] The segregation and oxidation of alloying elements on the surface are very complex.…”

“…[4] According to Ellingham's diagram, the alloying elements described above will be oxidized and form a distribution at different positions due to their stronger affinity than iron, such as localizing at the steel surface (external oxidation) or beneath the steel surface (internal oxidation). [4][5][6][7][8][9][10][11] The segregation and oxidation of alloying elements on the surface are very complex. And they are often considered to be closely related to the following factors: Annealing parameters (temperature, heating rate, annealing atmosphere, [12,13] and annealing time), alloying elements, [14] and the matrix microstructure as well as its surface morphology.…”