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| Improvement of reheat-cracking susceptibility and microstructure of T23 steel |
| ZHOU Ren-yuan1, ZHU Li-hui1, LI Shi-xian1, ZHAI Guo-li2 |
1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China;
2. Central Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 201900, China |
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Abstract The high reheat-cracking susceptibility of T23 severely endangers the safety of Ultra-super critical power plants. In order to decrease the reheat-cracking susceptibility of T23,the mass percent of elements such as C and W was optimized. The simulated coarse-grained heat-affected zone (CGHAZ) in T23 and modified T23 was produced via thermal simulation of welding,and the reheat-cracking susceptibility was evaluated by isothermal slow strain rate tensile test on Gleeble. The microstructure of CGHAZ in T23 and modified T23 was investigated by optical microscope (OM),scanning electron microscope (SEM) and transmission electron microscope (TEM). The effect of microstructure on the reheat-cracking susceptibility of modified T23 was discussed. The result shows that the reheat-cracking susceptibility of modified T23 is greatly decreased,and the mechanical properties meet the requirements of ASME specification. Compared with T23,there are less intergranular M23C6 precipitates and intragranular MX particles in modified T23. At the same time,the mass percent of C and W in the grain interiors is decreased in modified T23. Therefore,the difference between intergranular and intragranular strength is small in modified T23,leading to the improved reheat-cracking susceptibility. In addition,smaller grains and fewer M-A constituents in modified T23 help to decrease the reheat-cracking susceptibility. The decreased number of M23C6 at grain boundaries slows down the micro-void connection and crack propagation. The composition of modified T23 steel can provide reference for further improving the reheat-cracking susceptibility of T23 steel.
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Received: 11 June 2019
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2020, Vol. 55 
