7CrMoVTiB10-10 (T24) steel as an example of examinations, which evaluate the implementation of new materials and technologies for ultra-supercritical boilers (PPT)

摘要

Cracking mechanism is a brittle, trans-crystalline one. The causes of cold cracking include: weld joint discontinuities in form of micro-cracks, microporosity, micro-blisters, high level of stress in weld joints without PWHT, presence of hydrogen during welding, in boiler water and during acid cleaning, weld metal including martensite structure . Delayed, cold cracking develops in weld joint root towards the weld joint face and, through HAZ, to tube material. Fatigue cracking occurs gradually during boiler manufacture, transport, erection, pressure testing, acid cleaning and operation.