... tempering, ≥ 25Section shrinkage rate ψ (%): quenching and tempering, ≥ 55Impact energy Akv (J): quenching and tempering, ≥ 118Hardness: annealing, quenching and tempering, ≥ ≤ 200HB; 170HBThe ... slow cooling or about 750 °C fast cooling quenching; 2), 959 ~ 1000 °C cold oil; 3) 700 ~ 750 °C tempering soon ...