How to improve low temperature impact toughness of 12Cr1MoV seamless steel tube

12Cr1MoV seamless steel tube is a kind of low alloy high strength steel. The metallographic structure often has banded structure. The effect of banded structure on impact toughness of 12Cr1MoV seamless steel tube is obvious. The banded structure is ferrite and pearlite. As the ferrite is soft and the toughness is poor, the impact toughness is low. How to improve the toughness of 12Cr1MoV seamless steel tube at low temperature?

The raw material 12Cr1MoV seamless steel tube is delivered at normalizing state, and the maximum impact energy of - 40 degree is only 12J. After observing the metallographic structure ferrite + pearlite + ribbon, two process adjustments have been made to raise normalizing temperature and prolong holding time, which can greatly improve low temperature impact toughness of 12Cr1MoV seamless steel tube.

1, high temperature quenching + high temperature tempering, band is not obvious. -40 degree impact energy of 12Cr1MoV seamless steel tube is 56J-67J, 12Cr1MoV tube tensile strength is 550MPa.

2, low temperature quenching and high tempering, the band will decrease but not decrease. -40 degree impact energy of 12Cr1MoV seamless steel tube is 90J-127J, 12Cr1MoV tube tensile strength is 485MPa.

In order to improve the low temperature impact property of 12Cr1MoV seamless steel tube, the quenching and tempering method is more effective, and the low temperature impact property of 12Cr1MoV seamless steel tube after quenching and tempering can reach more than 100. The positive adoption of heat treatment in following may be more effective.