Growth Rate of Copper Sulfide Precipitates in Solid Low Carbon Steel

Abstract

The kinetics of copper sulfide growth has been investigated using low carbon steel samples such as Fe-0.3mass%Cu-0.03mass%S-0.1mass%C and Fe-0.1mass%Cu-0.01 mass%S-0.1mass%C. The samples were heat-treated at 1 273, 1 423 and 1 573 K for 100 s -14.4 ks for precipitation of copper sulfides and then subjected to observation by a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to measure the size of copper sulfides precipitated in the samples. The growth kinetics of copper sulfides has been found to be well described by the Ostwald ripening model, as follows:where Rt and R0 are the radii of copper sulfide precipitates, respectively, at t = t and t = 0 where t is time, kO is the rate constant in this model and T is thermodynamic temperature. The diffusion coefficients and activation energy derived from values of kO are close to those of copper in austenitic iron. On the basis of the growth kinetics, it has been proposed that the heat-treatment for as-cast strip steel should be conducted at around 1 273 K, at which the size of copper sulfide precipitates can be controlled to be as small as 20-30 nm in several tens of minutes.

Development of Analysis Method for Sulfide in Steel with Chelating Agent of Copper

“…[2][3][4][5][6][7][8][9] Several authors reported that when steels were rapidly cooled from a high temperature of 1 473 to 1 573 K, and observed after the SPEED etching, copper sulfides were found abundantly precipitated. [10][11][12] This temperature range was higher than the precipitation temperature (about 973 K) predicted by thermochemical calculation programs such as FactSage. 13) In other words, the calculation results did not agree with the experimental results.…”

High-temperature oxidation kinetics of Cu bearing carbon steel

“…EDS analysis showed copper segregation along with sulfur content. The thermodynamic point of view states sulphur affinity of copper is higher than iron [20]. Inner oxide particles could be seen below the surface and copper segregation.…”