THE EFFECT OF QUENCHING CONDITIONS ON THE HARDNESS OF N690 STEEL

Quenching is a commonly used method of heat treatment of steels with the objective of achieving the desired properties, most often increasing of hardness. To achieve the desired properties, it is important to correctly set the technological and process parameters, especially the correct quenching temperature, time endurance, the cooling rate and the quenching medium selection. The influence of the selected quenching conditions on the steel hardness modification is monitored in the submitted contribution. The hardness modification dependent on the variable quenching conditions is monitored during the heat treatment of N690 steel. The monitored parameters are the time endurance at the quenching temperature and the use of various quenching media. The time endurance at the quenching temperature was chosen to be 0 min., 10 min., and 17 min. The quenching media selected were water, Mogul TK 22 oil, and compressed air cooling. The results achieved show that the highest average hardness values were reached by N690 steel samples cooled in oil with an endurance time of 10 min.