Charakterystyka bainitycznej stali 7CrMoVTiB10-10 (T24)

Microstructure and Mechanical Properties of a Similar T24 Steel Welded Joint After Service

“…The additional material with a chemical composition similar to CrMo steel probably has better ductility as compared to the additional material for T24 steel welding. This limits the tendency to hot cracking in T24 steel welded joints [1,6,10,15]. However, this material has a lower creep resistance as compared to the T24 steel [1,10].…”

“…The manufacturer's optimistic assumptions regarding the weldability of the T24 steel were quickly verified by industrial practice, which revealed significant problems during welding, assembly and use of this steel. These problems were mainly DOI: 10.32730/imz.0137-9941.18.2.04 related to the cracking of welded joints in power units, which involved high costs of repairs of these units and financial losses caused by their stoppage [1,5,6].…”

“…The main cause of the failure were transverse cracks in welded joints in tight walls, as welds connecting a flat bar with a tube, forming radiant tubes. The main mechanism causing the formation of cracks were hot cracks, and their further development occurred in the form of cold delayed cracks [1][2][3][5][6][7][8][9][10]. The hot cracking of the T24 steel joints was related to its very high strength properties in the state without heat treatment as compared to the properties of the tube and flat bar.…”

The Effect of Heat Treatment on the Structure and Hardness of Welded Joints in Steel 7CrMoVTiB10-10

“…Steel 7CrMoVTiB10-10 was launched on the market (and used primarily in the production of waterwalls) as a result of power engineering development, to address issues related to the retrofit of power generation equipment necessitated by an increase in generated power as well as to improve mechanical properties and eliminate the necessity of heat treatment. The steel was obtained through the modification of the chemical composition of steel 10CrMo9-10 (T22), involving the addition of microagents including vanadium, titanium, boron and nitrogen [1,3,4,6,7]. Assumedly, a decreased carbon content in the steel should translate into significantly better weldability and lower hardness, whereas the presence of microagents such as boron, titanium and vanadium should improve creep strength.…”

“…Welds made in the steel contained numerous hot, cold and relaxation cracks. Such a situation could be ascribed to the presence of numerous welding imperfections (of acceptable size), subsequently leading to the propagation of cracks as well as to the negative effect of secondary hardness resulting from the steel composition, the wide range of brittleness temperature, significant deformations of welds as well as the negative effect of hydrogen, present both during the process of welding and during the operation of welded structures [1][2][3][4][5][6][7][8].…”