预先Mn配分处理对Q&P钢中C配分及残余奥氏体的影响*
收稿日期: 2014-08-18
网络出版日期: 2015-07-23
基金资助
*国家自然科学基金项目51254004和51304186, 河北省自然科学基金项目E2014209191及河北省教育厅科研项目YQ2013003资助
EFFECT OF Mn PRE-PARTITIONING ON C PARTITIONING AND RETAINED AUSTENITE OF Q&P STEELS
Received date: 2014-08-18
Online published: 2015-07-23
Supported by
National Natural Science Foundation of China (Nos.51254004 and 51304186), Natural Science Foundation of Hebei Province (No.E2014209191) and Science Foundation of Department of Education of Hebei Province (No.YQ2013003)
以低碳Si-Mn钢为研究对象, 采用双相区保温-淬火(IQ)工艺研究预先Mn配分行为, 并对其配分现象进行表征, 采用淬火-配分(Q&P)及双相区保温-奥氏体化-淬火-配分(I&Q&P)热处理工艺, 探讨了预先Mn配分处理对低碳高强Q&P处理钢中C配分和残余奥氏体及力学性能的影响. 结果表明, 实验钢在双相区保温过程中C, Mn不断向奥氏体内扩散, 淬火处理后C, Mn在马氏体(原双相区奥氏体)内呈现明显的富集现象; 实验钢经I&Q&P工艺处理后, 室温组织中Mn富集现象依然很明显, C在马氏体板条间富集; 随着C配分时间的延长, 实验钢抗拉强度不断减小, 延伸率均呈先增加后降低趋势, 在C配分时间为90 s时, I&Q&P工艺下钢的强塑积达到23478 MPa·%; I&Q&P工艺中预先Mn配分处理, 使得实验钢在一次淬火时保留更多的奥氏体, 随后C配分促使更多的C原子扩散到这些奥氏体中, 从而二次淬火至室温获得更多残余奥氏体. I&Q&P工艺中C, Mn的综合作用稳定的残余奥氏体体积分数比相同条件下Q&P工艺中C配分稳定的残余奥氏体体积分数最大增多2.4%左右.
陈连生 , 张健杨 , 田亚强 , 宋进英 , 徐勇 , 张士宏 . 预先Mn配分处理对Q&P钢中C配分及残余奥氏体的影响*[J]. 金属学报, 2015 , 51(5) : 527 -536 . DOI: 10.11900/0412.1961.2014.00462
The chemical compositions of C and Mn have a strong influence on the stability of the metastable retained austenite at room temperature. In the intercritical annealing process, Mn element improves the stability of the austenite by partitioning from ferrite to austenite and the enrichment of Mn in austenite can also impact on the diffusion of C element from martensite to retained austenite in partitioning process. Based on C partitioning, Mn partitioning can further improve the product of strength and elongation, and has no negative effect on weldability of the low carbon high strength steel. Thus, it can effectively solve the contradiction between mechanical property and weldability of low carbon high strength steel in traditional quenching-partitioning (Q&P) process. In this case, it is of great significance to study the Mn pre-partitioning mechanism and its influence on C partitioning and retained austenite of the low carbon high strength steel. Therefore, one low alloy C-Si-Mn steel was studied in the present work. The Mn pre-partitioning behavior and its effect on C partitioning and the stability of the retained austenite were investigated by means of intercritical heating-quenching (IQ) process, Q&P and intercritical heatingaustenitizing-quenching-partitioning (I&Q&P) process. The results showed that during the process of phase transformation in the intercritical reheating, C and Mn elements constantly diffused from ferrite to austenite. When this process ended, C and Mn elements enriched in austenite. While Mn element in microstructure at room temperature was still enrichment and C element enriched regularly between the martensite laths in the I&Q&P treated steel. With the increase of C partitioning time in both Q&P and I&Q&P process, the tensile strength of steel was decreased constantly, while the elongation showed an increasing fristly and then decreasing trend. The product of strength and elongation of the steel treated by I&Q&P process reached 23478 MPa·% with the C partitioning time of 90 s. The more austenite in martensite phase would be obtained after the first quenching with the Mn pre-partitioning. It was important to prompt more C diffusing into austenite during C partitioning process to stabilize more retained austenite at room temperature of the steel after the second quenching. With the same experimental conditions, the retained austenite of the combined effects of C and Mn partitioning during I&Q&P process would be increased 2.4% than the effect of C partitioning during Q&P process.
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