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调质温度对超高强中锰钢微观组织和 力学性能的影响
Effect of Quenching Temperature on the Microstructure and Mechanical Properties of Ultrahigh Strength Medium Manganese Steel
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- DOI:
- 作者:
- 蒋家乐1，李云杰1，李小琳2，袁 国1
JIANG Jiale1, LI Yunjie1, LI Xiaolin2, YUAN Guo1
- 作者单位:
- 1. 东北大学轧制技术及连轧自动化国家重点实验室，辽宁沈阳110819；2.西北工业大学凝固技术国家重点实验室， 陕西西安710072
1. State Key Laboratory of Rolling and Automation Northeastern University, Shenyang 110819, China; 2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
- 关键词:
- 超高强钢；原始奥氏体；调质温度；残余奥氏体；力学性能
ultrahigh-strength steel; original austenite; quenching temperature; retained austenite; mechanical properties
- 摘要:
- 2000MPa级超高强钢是极端服役环境用的关键结构材料，面临严重的强塑性倒置、合金昂贵、生产制备工 艺复杂等难题。为此，设计了低成本C-Mn成分体系，研究不同调质温度对实验钢微观组织和力学性能的影响。结 果表明，随着调质温度的增加，实验钢的原始奥氏体由带状向等轴状转变，在780℃调质时，带状原始奥氏体晶粒宽约 4 μm、长约 14 μm，等轴状原始奥氏体晶粒宽约3μm、长约5μm。实验钢的位错密度随调质温度的增加，从6.87× 1015 m-2 降至 5.27×1015 m-2，再降低至 4.46×1015m-2。 实验钢室温下残余奥氏体(retained austenite, RA)的体积分数由 12.6% 降至10.2%再降至9.2%，变形前后RA的体积分数变化值由7.1%降至6.8%再升至7.1%。 样品Q780的综合力学性能 最好，其屈服和抗拉强度最大，分别为1665和2107MPa，均匀伸长率也相对较高，为8.9%。5mm厚V口Q780试样的 室温裂纹萌生能(9.8J)和裂纹扩展能(3.9J)也相对较高，使其室温冲击功最高为13.7J。 其优异性能归因于最大的位错 密度(6.87×1015 m-2)、最大的 RA 体积分数(12.6%)和最小的马氏体平均晶粒尺寸(0.77μm)。
2 000 MPa ultrahigh-strength steel is a key structural material for extreme service environments and faces serious problems such as strength-ductility inversion, expensive alloys, and complex production and preparation processes. To this end, a low-cost C-Mn composition system was designed, and the effects of different quenching and tempering temperatures on the microstructure and mechanical properties of the experimental steel were studied. The results show that with increasing quenching and tempering temperatures, the original austenite of the experimental steel changes from banded to equiaxed. When quenched and tempered at 780 ℃, the width and length of the banded original austenite grains are approximately 4 and 14 μm, respectively, and those of the equiaxed original austenite grains are approximately 3 and 5 μm, respectively. The dislocation density of the experimental steel also decreases from 6.87×1015 m-2 to 5.27×1015 m-2 and then to 4.46×1015 m-2 with increasing quenching and tempering temperatures. The volume fraction of retained austenite (RA) of the experimental steel at room temperature decreases from 12.6% to 10.2% and then to 9.2%. The variation in the volume fraction of RA before and after deformation decreases from 7.1% to 6.8% and then increases to 7.1%. Sample Q780 has the best comprehensive mechanical properties, with the highest yield and tensile strengths of 1 665 and 2 107 MPa, respectively, and also a relatively high uniform elongation of 8.9%. The room temperature crack initiation energy (9.8 J) and crack propagation energy (3.9 J) of 5 mm thick Q780 with a V-notch are also relatively high, making its room temperature impact energy as high as 13.7 J. The reasons for its excellent performance are that it has the largest dislocation density (6.87×1015 m-2), the largest RA volume fraction (12.6%) and the smallest average martensite grain size (0.77 μm).