SHORT-TIME AGEING OF MS350 MARAGING STEEL WITH AND WITHOUT PLASTIC DEFORMATION

The age hardening behaviour of MS350 maraging steel both in undeformed specimens and in specimens deformed immediately after ageing was studied. Experiments of short-time (15, 30 and 60 s) ageing at temperature up to 600 degrees C were performed. It was found that after ageing at 480-500 degrees C for 15-60 s without deformation the hardness reached the 450-525 HV. The time of ageing at 600 degrees C to reach hardness 600 HV was 15 seconds. No precipitation in specimen aged at 500 degrees C for 60 s was found in TEM and HRTEM investigations. Deformation immediately after ageing intensifies the process of hardening caused by temporary increase of temperature and increase of dislocation density. The hardness of specimens aged for 30 s and then deformed at 480-550 degrees C was similar to the hardness at peak aged conditions (480 degrees C/4h) and reached 600-630 HV. Material produced in industrial trials of cold forward flow forming and following laboratory ageing was analyzed. Increase of hardness from 370 HV to 590-630 HV for specimens taken from thin walled flow formed tube as a result of ageing at 460-490 degrees C for 30 minutes occurred.