黄一君, 张麦仓, 谢锡善. 富Nb复合碳氮化物对22Cr15Ni3.5CuNbN奥氏体钢焊接模拟热影响区组织和性能的影响[J]. 工程科学学报, 2019, 41(7): 889-897. DOI: 10.13374/j.issn2095-9389.2019.07.007
引用本文: 黄一君, 张麦仓, 谢锡善. 富Nb复合碳氮化物对22Cr15Ni3.5CuNbN奥氏体钢焊接模拟热影响区组织和性能的影响[J]. 工程科学学报, 2019, 41(7): 889-897. DOI: 10.13374/j.issn2095-9389.2019.07.007
HUANG Yi-jun, ZHANG Mai-cang, XIE Xi-shan. A simulation of the effect of Nb-rich carbonitride on the structure and properties of weld HAZ of 22Cr15Ni3.5CuNbN austenitic steel[J]. Chinese Journal of Engineering, 2019, 41(7): 889-897. DOI: 10.13374/j.issn2095-9389.2019.07.007
Citation: HUANG Yi-jun, ZHANG Mai-cang, XIE Xi-shan. A simulation of the effect of Nb-rich carbonitride on the structure and properties of weld HAZ of 22Cr15Ni3.5CuNbN austenitic steel[J]. Chinese Journal of Engineering, 2019, 41(7): 889-897. DOI: 10.13374/j.issn2095-9389.2019.07.007

富Nb复合碳氮化物对22Cr15Ni3.5CuNbN奥氏体钢焊接模拟热影响区组织和性能的影响

A simulation of the effect of Nb-rich carbonitride on the structure and properties of weld HAZ of 22Cr15Ni3.5CuNbN austenitic steel

  • 摘要: 采用Gleeble热模拟的方法, 通过模拟焊接过程中快速加热和冷却的热循环过程, 得到1150~1300 ℃不同峰值温度下22Cr15Ni3.5CuNbN奥氏体钢扩大的热影响区组织, 并对其进行冲击性能分析. 对热影响区组织的研究表明, 实验钢的母材中存在一定量富Nb复合碳氮化物, 有效钉扎晶界, 且与大量位错缠结. 在焊接过程中, 该富Nb复合碳氮化物经历溶解与重新析出的复杂过程: 当峰值温度为1150 ℃时, 仅小颗粒的富Nb碳氮化物发生了溶解, 而峰值温度为1300 ℃时, 富Nb复合碳氮化物经历溶解与重新析出, 呈现网状的组织形貌, 且其整体尺寸增加. 富Nb复合碳氮化物的演化导致了冲击功的变化, 经历焊接热循环条件的实验钢较母材具有更高的冲击韧性, 随着峰值温度的升高, 冲击韧性呈现先升后降的趋势, 其中在峰值温度为1150 ℃时实验钢的冲击韧性最高.

     

    Abstract: Niobium is a strong carbonitride-forming element. The evolution of Nb-rich carbonitride in austenitic steels during welding has an important effect on the ductility of the heat-affected zone (HAZ). The new austenitic heat-resistant steel of 22Cr15Ni3.5CuNbN, a candidate material for ultra-super critical boiler superheater and reheater serviced at 620-650 ℃, contains 0.5% Nb, which will significantly affect the steel's weldability; therefore, it is necessary to study the microstructure and properties of the weld HAZ of the steel and provide a reference for the further applications of this new material. Because of the narrow weld HAZ of this material, the extended HAZ structure of 22Cr15Ni3.5CuNbN austenitic steel at different peak temperatures from 1150 ℃ to 1300 ℃ was obtained by Gleeble thermal physical simulation method in this study, aiming to simulate the thermal cycling process of the welding process, and impact performance tests were carried out. The results show that a certain amount of Nb-rich composite carbonitrides is present in the base metal of the experimental steel, which effectively pins the grain boundaries and entangl with a large number of dislocations. The Nb-rich composite carbonitride underwent a complex process of dissolution and re-precipitation during the simulated welding process. When the peak temperature was at 1150 ℃, only small particles of Nb-rich carbonitrides were dissolved, while when the peak temperature reached 1300 ℃, the Nb-rich composite carbonitride underwent dissolution and re-precipitation, showing a "mesh" structure, and its overall size increased. The evolution of Nb-rich composite carbonitrides led to changes in the impact energy of this steel. The impact toughness of the experimental steel subjected to welding thermal cycling condition was higher than that of the base metal. With the increase in the peak temperature, the impact toughness first increased and then decreased. The impact toughness of the steel reached the highest when the peak temperature was at 1150 ℃.

     

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