Effect of Nb on Microstructural Evolution and Mechanical Properties of Hot-Rolled Quenching and Partitioning Steels Containing Bainite,Steel Research International

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Effect of Nb on Microstructural Evolution and Mechanical Properties of Hot-Rolled Quenching and Partitioning Steels Containing Bainite
Steel Research International ( IF 1.9 ) Pub Date : 2021-07-21 , DOI: 10.1002/srin.202100247
Zhisong Chai ₁ , Jun Hu ₁ , Chenchong Wang ₁ , Lingyu Wang ₁ , Weihua Sun ₂ , Sybrand van der Zwaag ₃ , Wei Xu ₁

Affiliation

Herein, the effect of Nb content on the phase transformation kinetics, microstructure, and mechanical properties of hot-rolled quenching and partitioning (Q&P) steel is investigated. The characteristics of three C–Mn–Si–Ti steels (0.18C, 2.0Si, 2.6Mn, and 0.015Ti) containing 0, 0.027, or 0.061 wt% Nb are compared. Results reveal that grain boundary pinning by precipitates and Nb solute drag effects refine the austenite grain size during the hot-rolling process; the microstructural refinement is carried over to the final microstructure subjected to the Q&P treatment. The remaining supersaturated Nb suppresses the bainite formation and decreases the final bainite fraction formed in the Q&P process. The microstructural evolution leads to an increase in the ultimate tensile strength (UTS) of the steel containing 0.027 wt% Nb from 1169 to 1228 MPa, while keeping the total elongation at 18%. When the Nb content is increased to 0.061 wt%, the UTS of the steel increases to 1313 MPa, but the elongation at break drops to 16%. The effect is due to the carbon consumption by the Nb precipitates, which causes a decrease in the stability of the retained austenite and reduces the strain hardening at high strain levels.

中文翻译：

Nb对含贝氏体热轧淬火隔断钢组织演变和力学性能的影响

在此，研究了 Nb 含量对热轧调质 (Q&P) 钢的相变动力学、显微组织和力学性能的影响。比较了三种含有 0、0.027 或 0.061 wt% Nb 的 C-Mn-Si-Ti 钢（0.18C、2.0Si、2.6Mn 和 0.015Ti）的特性。结果表明，在热轧过程中，析出物的晶界钉扎和Nb溶质拖曳效应细化了奥氏体晶粒；微观结构的细化被延续到经过 Q&P 处理的最终微观结构。剩余的过饱和 Nb 抑制了贝氏体的形成并降低了 Q&P 过程中形成的最终贝氏体分数。显微组织演变导致含有 0 的钢的极限抗拉强度 (UTS) 增加。027 wt% Nb 从 1169 到 1228 MPa，同时将总伸长率保持在 18%。当 Nb 含量增加到 0.061 wt% 时，钢的 UTS 增加到 1313 MPa，但断裂伸长率下降到 16%。其影响是由于 Nb 析出物消耗了碳，这会导致残余奥氏体的稳定性降低并降低高应变水平下的应变硬化。

更新日期：2021-07-21

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