Effect of Heat Treatment in Pipe Processing Stage on Corrosion Resistance of Micro-Alloyed Steel Hot-Rolled Products

The effect of heat treatment on corrosion resistance of low-alloy pipe steels is investigated in relation to oilfield pipeline operating conditions. It is established that after pipe bulk heat treatment at 720 °C metal corrosion resistance increases, but at a lower temperature of 680 °C no significant change is detected. Analysis of the corresponding structural changes is performed and the main factors facilitating an increase in corrosion resistance are determined: cementite component spheroidization in the areas of pearlite or degenerated pearlite, and a reduction in dislocation density. The role of nanoscale precipitate type on pipe corrosion resistance is noted. It is established that at a higher processing temperature there is a larger fraction of ferritic precipitates. In contrast to interphase precipitates these particles do not adversely affect steel corrosion resistance.