Residual stresses originating from weld induced thermal variations and metallurgical phase transformations have a negative influence on the fatigue performance of welded components and structures. A normal way to get rid of these and to decrease their negative influence on fatigue endurance is the application of post weld heat treatment. However, this method have a number of disadvantages among others: costs, difficulties when dealing with big steel structures, damaging of strength/toughness properties of parent plate if not accurate temperature and time sequences are applied among others. High-strength steels are tempered at certain temperature and if that specific temperature is exceed the parent plate properties could be damaged so it is paramount that PWHT temperature keep under strict control.