两相区QT工艺对低屈强比890 MPa级高强钢组织与性能的影响

doi:10.13251/j.issn.0254-6051.2024.11.013

摘要/Abstract

摘要： 研究了低屈强比890 MPa级高强钢在两相区QT处理中组织转变及其对力学性能的影响。通过扫描电镜对热处理态组织进行观察,并结合力学性能与XRD位错密度计算分析回火温度对组织性能的影响,进一步通过Gleeble热模拟试验结果分析淬火温度对组织性能的影响。结果表明,两相区QT处理态组织为铁素体+回火板条状组织。随回火温度升高,板条形态逐渐分解,位错强化增量降低,使得抗拉强度降低;软硬相间的协调变形作用使得屈服强度先升高,后随整体位错密度降低而降低,整体波动不大,从而屈强比升高。随淬火温度升高,位错强化增量升高,抗拉强度升高;相变过程中的膨胀量变化升高,软相铁素体占比降低,使得屈服强度升高,屈强比升高;硬相回火板条状组织占比增加,低温韧性降低。

关键词: 低合金高强钢, 低屈强比, 两相区QT处理, 位错密度, 热模拟试验

Abstract: Microstructure transformation of a low yield ratio 890 MPa grade high strength steel during intercritical QT (quenching and tempering) treatment and its effect on mechanical properties were investigated. The heat-treated microstructure was observed by scanning electron microscope, and the effect of tempering temperature on microstructure and properties was analyzed via mechanical properties and XRD dislocation density calculation. The effect of quenching temperature on microstructure and properties was further investigated by Gleeble thermal simulation experiment. The results show that the intercritical QT treated microstructure is ferrite and tempered lath structure. With the increase of tempering temperature, the lath structure gradually decomposes, and the dislocation strengthening increment decreases, which lead to the decrease of tensile strength. The yield strength increases firstly under the coordination deformation effect of soft and hard phases, and then decreases with the decrease of overall dislocation density. The yield strength changes a little leading to the increase of yield ratio. With the increase of quenching temperature, the dislocation strengthening increment increases and the tensile strength increases, the dilation change during phase transition increases, the proportion of soft phase ferrite decreases, which leads to the increase of yield strength and yield ratio. The increasing proportion of hard phase tempered lath structure makes the low-temperature toughness decrease as the quenching temperature rises.

Key words: low alloy high strength steel, low yield ratio, intercritical QT treatment, dislocation density, thermal simulation experiment

中图分类号:

TG156.31

郭呈宇, 张弛, 代春朵, 侯华兴, 李江文, 张哲. 两相区QT工艺对低屈强比890 MPa级高强钢组织与性能的影响[J]. 金属热处理, 2024, 49(11): 91-98.

Guo Chengyu, Zhang Chi, Dai Chunduo, Hou Huaxing, Li Jiangwen, Zhang Zhe. Effect of intercritical QT process on microstructure and properties of a low yield ratio 890 MPa grade high strength steel[J]. Heat Treatment of Metals, 2024, 49(11): 91-98.

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