Sammendrag
The influence of post weld heat treatment on the HAZ mechanical prope rties and microstructure of a supermartensitic stainless steel contai ning 12.6% Cr, 6.4% Ni and 2.0% Mo has been studied. HAZ weld simulat ions were performed with a peak temperature of roughly 1350 0C and a cooling time between 800 0C and 500 0C of 5 seconds. Post weld heat t reatment was performed both in the weld simulator, for 5 and 10 minut es, and in an electrical furnace, for 30 minutes, 1 and 10 hours. The post weld heat treatment resulted in a small (15 % at maximum) hardn ess reduction in the coarse-grained HAZ. At higher temperatures the m aximum hardness reduction was reached after 1 hour of annealing, afte r which the hardness started to increase again. The toughness of the material increased during tempering up to 1 hour holding time, but fo r longer annealing times the toughness again decreased, and for all t emperatures it reached a value close to that in as weld condition aft er 10 hours. The lowest annealing temperature gave the strongest incr ease in toughness. A change in dislocation density with time was obse rved to take place during tempering, the progress with time being dep endent on temperature. At all temperatures molybdenum containing carb ides were formed throughout the tempering sequence.
Vis fullstendig beskrivelse
