Continuous reduction of the oxide scale of hot-rolled steel strip in hydrogen

Abstract

The continuous reduction in the oxide scale of hot-rolled steel strip in H 2 -N 2 atmosphere was simulated in laboratory. Scale specimens were reduced in 20% H 2 -N 2 or 50% H 2 -N 2 atmosphere. The sample weight losses were measured after soaking at 550, 700 and 800°C. In both atmospheres, specimen reduced at 700°C showed the minimum weight loss after soaking for 240 s. At 700 and 800°C, higher hydrogen concentration accelerated the reaction in the beginning of soaking, but had little effect once the dense-reduced iron layer formed. While at 550°C, the reduced iron kept growing in porous structure and the weight loss rate increased significantly in higher H 2 concentration.

Effect of Temperature on Reduction Behaviors and Microstructural Changes of Magnetite with H2 Under Fluidized Bed Conditions

“…The metallization degree was only 23.94% at 670 °C, which was even lower than that at 470 °C. According to the thermodynamic analysis, [ 20,28 ] the increase in temperature was conducive to the transformation of magnetite to metallic iron. However, the metallization degree decreased significantly when the temperature exceeded 570 °C, which indicated that the reaction kinetics conditions had changed and hindered the reduction of magnetite to metallic iron.…”

“…Once the dense iron layer was formed, the reaction was controlled by solid‐state diffusion, and the reaction rate dropped down quickly. [ 28 ] Therefore, there was an anomalous temperature effect, which led to a decline in the metallization degree.…”

“…Further research revealed that when magnetite was used as raw materials, there was a retardation phenomenon of the reduction. [ 26–28 ] Thus, directly using magnetite powder in the ironmaking process has been challenging. Moreover, iron ore is usually reduced at high temperatures (700~1200 °C) to ensure the reduction efficiency, and there have been few studies on the reduction of magnetite during hydrogen induction at a lower temperature (<700 °C).…”

Kinetics and Microstructure Transformations of Oxide Scale on Hot Rolled Steel Strip for Hot‐Dip Galvanizing during Reduction Annealing in 30% H2–N2 Atmosphere

“…According to Equation (4), the Arrhenius plot of and is a linear relationship, and values of E a can be obtained from the gradient of the fitted experimental data at each temperature. Guan [ 27 ] obtained values of E a from reduction data at 20% H 2 –Ar over 370–550 °C. Li [ 28 ] calculated the E a values of two types of oxide scales over 450–550 °C.…”

Effect of Cold Rolling before Hydrogen Reduction on Reduction Behavior and Morphologies of Oxide Scale on Hot-rolled Low-carbon Steel

“…Nevertheless, the reduction reaction efficiency was slow owing to the low concentration of hydrogen. Guan et al 10) experimentally evaluated the reduction of oxide scale on hot-rolled steel strips by 20 and 50% H 2 with N 2 balance at 550, 700 and 800°C for 4 min, and suggested that the rate of reduction became fast with the increase of reduction temperatures and hydrogen concentration. The results of previous researches indicated hydrogen has a strong edge on energy efficiency and environmental protection as the reactant compared with carbon monoxide.…”