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| 低碳含铌建筑结构用钢动态 CCT曲线及冷却工艺研究 |
| Dynamic CCT curve of and cooling process for low-C Nb-containing building structural steel |
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| DOI： |
| 中文关键词: 低碳含铌钢 CCT曲线 冷却工艺 相变 微观组织 |
| 英文关键词: low-C Nb-containing steel CCT curve cooling process transformation microstructure |
| 基金项目:广西科技重大专项 (桂科 AA19254009)；柳州市科技重大专项( 2019AC10602).作者简介:邹佳辉( 1999-)，男，武汉科技大学硕士生 . E-mail: 1411760707@qq.com通信作者:田俊羽( 1992-)，男，武汉科技大学讲师，博士 . E-mail: tianjunyu@wust.edu.cn |
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| 中文摘要: |
| 采用 Gleeble-3500热模拟实验机，对低碳含铌建筑结构用钢进行了动态过冷奥氏体连续冷却转变 (CCT)实验研究，结合不同冷却速度下实验钢的膨胀曲线、显微组织和显微维氏硬度，绘制了实验钢动态 CCT曲线。结果表明，随着冷却速度的提高，连续冷却相变温度区间向低温方向移动，促进铁素体晶粒形核，有效细化铁素体晶粒尺寸。此外，结合动态 CCT曲线，设置了不同冷却工艺参数，确定冷却速度和空冷开始温度对实验钢相变和组织的影响。结果表明，为空冷开始温度设定为 550、600℃时，室温组织主要为铁素体和粒状贝氏体。同一空冷温度下，随着冷速的增加，铁素体含量减少，贝氏体含量增加；而在相同冷速下，降低空冷温度会导致铁素体含量增加。当空冷开始温度设定为 650 ℃时，无论冷速是 5 ℃/s还是 10℃/s，室温组织主要为铁素体和珠光体，且随着冷速的提升，铁素体含量因相变时间的缩短而降低。 |
| 英文摘要: |
| Dynamic continuous cooling transformation(CCT)experiments of a low-C Nb-containing structural steel were performed on the Gleeble-3500 thermal simulation test machine. Based on the dilatometric curves，microstructure and Vickers microhardness of samples treated by different cooling rates，the corresponding dynamic CCT curves were plotted. The results indicate that with the increase of cooling rate，the temperature for continuous cooling transformation shifts towards lower range，promoting the nucleation of ferrite grains and effectively refining the size of ferrite grains. Moreover，by integrating the dynamic CCT curves with various cooling process parameters，the effects of cooling rate and air cooling start temperature on the phase transformation and microstructure of the tested steel were determined. The results show that at air cooling onset temperatures of 550 ℃ and 600 ℃，the room-temperature microstructure is predominantly ferrite and granular bainite. At a constant air cooling temperature，increasing the cooling rate reduces the ferrite content and raises the bainite content; whereas decreasing the air cooling temperature at the same cooling rate results in a higher ferrite content. At an air cooling onset temperature of 650 ℃，irrespective of the cooling rate(whether 5 ℃/s or 10 ℃/s)，the room temperature microstructure consists mainly of ferrite and pearlite，with ferrite content decreasing as the cooling rate increases due to the shortened phase transformation time. |
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