Effect of steel-drawing-sheet annealing conditions on surface carbon combustion rate

Abstract

The level of surface‐carbon contamination exerts an adverse influence on the subsequent coating process such as phosphating and painting. In evaluating quantitatively surface carbon by the combustion technique, the temperature programmes adopted do not exceed 500°C in the case of sheet produced by continuous annealing system and 600°C for batch‐annealed sheet, this to avoid matrix‐carbon combustion. In this paper two hypotheses are discussed, concerning the reasons why evolution of the matrix carbon occurs at different temperatures in the two types of steel products. It is shown that different grain sizes generated by the batch and continuous annealing processes induce diversity in the different surface reactivities, in fact, grain size and hence the concentration of surface grain boundaries increases the oxidation rate of carbon.