Copper Enrichment Behaviours of Copper-containing SteelsIn Simulated Thin-slab Casting Processes

Abstract

The copper enrichment behaviours of several copper-containing steels under conditions similar to those in the thin-slab casting processes are examined. Formation of a molten copper phase at the scale-steel interface can be avoided when the substrate phase is occluded in the scale during steel oxidation. Significant enrichment of nickel in the surface layer of the substrate is a necessary condition for the occlusion of the substrate phase into the scale before the precipitation of a molten copper phase. The critical nickel content above which the occlusion mechanism would be operative is between 0.02 % and 0.07 %. The critical temperature above which the occlusion mechanism becomes operative in the high nickel steels differs when the isothermal oxidation step, following continuous cooling in ambient air, is conducted in different atmospheres. When conducted in ambient air, this temperature is between 1 150°C and 1 230°C, whereas when conducted in moist air or in simulated furnace atmospheres, it is lowered to between 1 100°C and 1 150°C. Preferential oxide growth along the grain boundaries of the substrate is another important occlusion mechanism, however, the deep oxide penetrations in the substrate may lead to descaling difficulty.

The Effect of Silicon on the High Temperature Oxidation Behavior of Low-carbon Steels Containing the Residual Elements Copper and Nickel

“…The planar interface reduces the amount of material that can be occluded into the oxide. 9) As mentioned above, the decrease in oxidation rate due to internal oxidation of silicon reduces the amount of separated copper-rich liquid which should promote interface perturbations and occlusion. The measured interface lengths support this hypothesis, since the interface lengths increase in the steels containing copper, nickel, and silicon compared to the iron-copper-nickel alloy, see Figs.…”

“…In addition to nickel, some effects of silicon on occlusion have been previously observed. Chen and Yuen 9) found iron-silicon oxide particles and suggested that they aided occlusion. Copeland and Kelley 11,12) have also observed the benefits of silicon additions (greater than 0.3 wt%).…”

Effect of Arsenic and Copper+Arsenic on High Temperature Oxidation and Hot Shortness Behavior of C–Mn Steel

“…23) has reported that back diffusion rate of copper would reach its enrichment rate level when oxidation temperature is over 1 050°C, especially in the temperature range of 1 100°C-1 200°C. In addition, occlusion mechanism begins to operate at the high temperature if the steel contains silicon as indicated by Chen R. Y. et al 21) As presented in Fig. 13, a large number of particles containing arsenic and copper + arsenic are occluded into scale at 1 150°C.…”

“…This temperature is lower than melting point of pure copper (1 084.87°C 18) ) and the penetration temperature range of copper-rich liquid phase (1 100°C-1 150°C) suggested by many studies. [19][20][21][22] The reason is considered that the presence of arsenic, determined by EDS as revealed in Fig. 12, decreases melting point of copper-rich phase and thus contributes to penetration of copper-rich liquid phase into grain boundaries at the lower temperature.…”

Effect of Atmospheric Conditions on Copper Behaviour during High Temperature Oxidation of a Steel Containing Copper

“…[1][2][3][4] The addition of nickel above a critical level also has the effect of copper occlusion in the scale. 5) Moreover, the addition of silicon has also has been beneficial with this problem 6,7) This addition reduces the likelihood of hot shortness 6) and decreases the amount of precipitated copper by the occlusion of copper in the oxide scale. 7) Meanwhile, it is reported that the addition of phosphorus, carbon, and boron are favourable elements for hot shortness, since these elements are thought to change the distribution of liquid copper in the scale, steel grain size, and the toughness of the steel grain boundary for the crack propagation.…”