Nb、Al复合微合金化对Mn-Cr齿轮钢高温渗碳晶粒度的影响

doi:10.13251/j.issn.0254-6051.2026.02.022

摘要/Abstract

摘要： 设计了Mn-Cr系Nb和Nb+Al微合金化齿轮钢,通过模拟热锻-正火-伪渗碳工艺,分析了试验钢热锻变形后冷却过程中的相变行为、正火工艺对组织的影响以及高温渗碳时的抗晶粒粗化能力,并基于ThermoCalc软件计算了Nb(C, N)和AlN的析出动力学。结果表明,Nb钢在余热正火条件下可满足960 ℃×4 h渗碳的晶粒度要求,但等温正火时铁素体+珠光体组织细化,导致在960 ℃×4 h伪渗碳时发生了奥氏体异常晶粒长大。Nb+Al钢可同时满足960 ℃×4 h、980 ℃×4 h渗碳的晶粒度要求,未产生混晶缺陷。相对于Nb钢,Nb+Al钢在伪渗碳时表现出更佳的抗晶粒粗化或混晶能力,且与模拟锻造后的冷却速率关联性不强,这主要来源于其碳氮化物的体积分数更高以及碳氮化物析出行为对锻后冷却的适应性。

关键词: 齿轮钢, 伪渗碳, 异常晶粒长大, 微合金化, Nb(C, N), AlN

Abstract: The Mn-Cr series gear steels microalloyed with Nb and Nb+Al respectively were designed. By simulating the processes of hot forging, normalizing and blank carburizing, all of the phase transformation behavior of the two experimental steels during cooling after hot forging deformation, the effect of normalizing process on the microstructure, and the resistance to grain coarsening during high-temperature carburizing were analyzed. Furthermore, the precipitation kinetics of Nb(C, N) and AlN were calculated based on the ThermoCalc software. The results show that the Nb microalloyed steel can meet the grain size requirement of carburizing at 960 ℃ for 4 h when subjected to residual-heat normalizing, but the ferrite+pearlite microstructure is refined when subjected to isothermal normalizing, resulting in abnormal austenite grain growth during blank carburizing at 960 ℃ for 4 h. The Nb+Al microalloyed steel can meet the grain size requirements of carburizing at 960 ℃ and 980 ℃ for 4 h, respectively, and no mixed grain defects are produced. Compared with the Nb microalloyed steel, the Nb+Al microalloyed steel exhibits better resistance to grain coarsening or mixed grain during blank carburizing. Moreover, this performance has weak correlation with the cooling rate after simulated forging, which is mainly attributed to the higher volume fraction of carbonitrides and the adaptability of carbonitride precipitation behavior to post-forging cooling.

Key words: gear steel, blank carburizing, abnormal grain growth, microalloying, Nb(C, N), AlN

中图分类号:

TG156.32

李海洋, 郭子强, 秦萱, 张东, 周蕾, 邓伟. Nb、Al复合微合金化对Mn-Cr齿轮钢高温渗碳晶粒度的影响[J]. 金属热处理, 2026, 51(2): 145-152.

Li Haiyang, Guo Ziqiang, Qin Xuan, Zhang Dong, Zhou Lei, Deng Wei. Effect of Nb-Al combined microalloying on austenite grain size of high-temperature carburized Mn-Cr gear steel[J]. Heat Treatment of Metals, 2026, 51(2): 145-152.

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