Development of X80/X100 Linepipe Steels with High Strain Aging Resistance

摘要

Overview on the development of X80/X100 linepipe steels with high strain aging resistance was introduced. The effects of aging temperature and specimen dimension on the strain aging of pipes were examined. Also, the microstructure and thermal aging behavior of X80 and X100 steel have been investigated as functions of processing conditions. 1) The strain aging resistance of the coated pipe decreases as the increase of tensile pre-strain induced during pipe making. Also, it was found that strain aging behavior of pipe was different along the through thickness direction. Especially, the strain aging behavior of the whole pipe well corresponds to that of the pipe center position. 2) Thermal aging behavior of X80 steels manufactured by cooling from the y single phase region and the γ + α two phase region was studied. It was shown that austenite single phase cooed X80 steel pipe had the better strain aging resistance than the γ + α two phase cooled steel pipe, which was thought due to the formation of finer polygonal ferrite in the y single phase cooled steel. 3) Heavy reduction in non-recrystallization region and moderate cooling control was very effective in enhancing the strain aging resistance of the X100 steel pipe. X100 steel pipe manufactured by heavy reduction in non-recrystallization region and moderate accelerated cooling yielded by round house type yielding after aging at 250 ℃. Uniform elongation of the X100 pipe after coating simulation at 250 ℃ was 6.7%.