冷却速率对450 MPa级铁路货车耐候钢相变行为的影响

doi:10.13251/j.issn.0254-6051.2026.02.009

摘要/Abstract

摘要： 以鞍钢某厂生产的Q450NQR1钢连铸坯为研究对象,利用Gleeble-3800热模拟试验机对Q450NQR1钢的相变行为进行了研究,并绘制了动态CCT曲线,分析了冷却速率对其微观组织和硬度的影响。结果表明,Q450NQR1钢在较低冷却速率(0.2~1 ℃/s)下主要形成铁素体和珠光体,随着冷速增大,钢中珠光体减少,铁素体由块状转变为条状;继续增大冷却速率至3 ℃/s,钢中开始形成贝氏体,当冷速为5 ℃/s时,珠光体消失;随着冷速进一步增大至30~50 ℃/s,贝氏体逐渐增多,晶粒细化,残留奥氏体的分布逐渐弥散。Q450NQR1钢的显微硬度随冷却速率呈幂函数趋势增加。在较低的冷却速率下,组织主要为铁素体和珠光体,硬度较低,提高冷速后发生贝氏体转变,从而提高了硬度。当冷速在30~50 ℃/s时,组织构成无明显变化,仅发生晶粒细化,硬度提升缓慢。

关键词: 耐候钢, CCT曲线, 冷却速率, 相变行为, 硬度

Abstract: Phase transformation behavior of Q450NQR1 steel continuous casting billet produced by a certain factory of Ansteel was investigated by using Gleeble-3800 thermal simulation testing machine, and the dynamic CCT curve was drawn to analyze the effect of cooling rate on its microstructure and hardness. The results indicate that the Q450NQR1 steel mainly forms ferrite and pearlite at lower cooling rates (0.2-1 ℃/s). As the cooling rate increases, the pearlite fraction in the steel decreases, and the ferrite transforms from blocky to strip-shaped. Continuing to increase the cooling rate to 3 ℃/s, bainite begins to form in the steel, and when the cooling rate reaches 5 ℃/s, pearlite disappears. As the cooling rate further increases to 30-50 ℃/s, bainite fraction gradually increases, grain refinement occurs, and the distribution of retained austenite gradually disperses. The microhardness of the Q450NQR1 steel increases exponentially with cooling rate. At lower cooling rates, the structure is mainly composed of ferrite and pearlite, with lower hardness. Increasing the cooling rate leads to bainite transformation, thereby increasing the hardness. When the cooling rate is between 30-50 ℃/s, there is no significant change in the microstructure, only grain refinement occurs, resulting in a slow increase in hardness.

Key words: weathering steel, CCT curve, cooling rate, phase transformation behavior, hardness

中图分类号:

TG142.1

孙继鸿, 刘志众, 佟欣儒, 张瑞琦, 刘志伟, 孙傲. 冷却速率对450 MPa级铁路货车耐候钢相变行为的影响[J]. 金属热处理, 2026, 51(2): 61-66.

Sun Jihong, Liu Zhizhong, Tong Xinru, Zhang Ruiqi, Liu Zhiwei, Sun Ao. Effect of cooling rate on phase transformation behavior of 450 MPa railway freight car weathering steel[J]. Heat Treatment of Metals, 2026, 51(2): 61-66.

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