Internal stresses during heat treatment of large forgings
Internal stresses, caused by each heat treatment, influence the service performance of parts. For large forgings these residual stresses can not be determined by tests because of the high cost involved. The stresses of a test cylinder of 970mm diameter and 3.300mm length after defined heat treatments were calculated for air cooling and spray cooling from 900 C, oil quenching from 1100 C with subsequent air cooling and spray cooling from 900 C and compared with the measured results. After air cooling the residual tension stresses at the surface in tangential direction were measured as 240 to 315 N/mm2 while the calculated value was 332 N/mm2. The measured residual stresses in the longitudinal direction were between 136 and 208 N/mm2 and the calculated value was 336 N/mm2. For oil quenching with subsequent air cooling, tangential pressure residual stresses were found to be between -500 and - 600 N/mm2, the calculated value being - 519 N/mm2. The pressure longitudinal residual stresses were found to be between -210 and -375 N/mm2, the calculated value being -424 N/mm2. The change in the sign of the residual stresses between air cooling and oil quenching was therefore calculated correctly.
Bibliographic Reference: EUR 12253 DE (1989) 89 pp., MF, ECU 4, blow-up copy ECU 11.25
Record Number: 199010342 / Last updated on: 1994-12-01
Original language: de
Available languages: de