Solving the cracking issue of grade ۷۲۲۵D sizes ۴۰ to ۶۵millimeters

There is an agreement that the ۷۲۲۵D steel is amongst the most applicable steel grades in theworld, as when it is lower in diameter, the cooling rate is sufficiently high. Steel with a diameterless than ۴۰ mm is usually quenched in an oil medium while sizes bigger than ۶۵ mm are oftenwater-quenched. However, the main concern is the diameter sizes between ۴۰ to ۶۵ mm. Thisis the critical diameter range which means if water quenched, they are prone to cracking and ifoil cooled, their tensile strength is below average. The proposed solution to this issue was twostepquenching so that firstly the material was water-quenched up to the nose in its TTTdiagram and then oil-quenched. Another way is limiting the composition range and dopingaluminum with a smaller grain size and typically higher impact energy to the alloy. Finally,the application of polymers rather than water has completely overcome this issue.

Keywords:

۷۲۲۵D steel , cooling rate , two-step quenching , composition range , polymer