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金属学报  2019, Vol. 55 Issue (6): 783-791    DOI: 10.11900/0412.1961.2018.00485
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调质态含Cu高强钢的强化机理及钢中Cu的析出行为
张正延(),柴锋,罗小兵,陈刚,杨才福,苏航
钢铁研究总院工程用钢研究所 北京 100081
The Strengthening Mechanism of Cu Bearing High Strength Steel As-Quenched and Tempered and Cu Precipitation Behavior in Steel
Zhengyan ZHANG(),Feng CHAI,Xiaobing LUO,Gang CHEN,Caifu YANG,Hang SU
Department of Structural Steels, Central Iron and Steel Research Institure, Beijing 100081, China
全文: PDF(18289 KB)   HTML
摘要: 

对含Cu低合金高强度钢板淬火并经高温时效后,采用SEM、EBSD、HRTEM和APT等手段对其微观组织和纳米尺度Cu的析出相进行了表征,对其厚度截面的室温拉伸性能进行了测定,并对钢板厚度方向近表面和心部的强化机理进行了分析。结果表明,高温时效后钢中Cu的析出相尺寸在6~50 nm范围内,30 nm以内的为9R结构的短棒状或球状粒子,30 nm以上的为fcc结构的长棒状粒子,棒状粒子中微量的Mn、Ni在Cu粒子与基体界面上的偏聚更明显。在较高温度范围内进行时效后,钢的屈服强度随着时效温度的升高而呈大致线性下降趋势,钢的主要强化机制为细晶强化,其次为位错强化和析出强化,经计算,钢中每1% (质量分数)的Cu在过时效状态下能够产生约90 MPa的析出强化增量。钢板厚度截面存在强度差异,表面与心部强度相差约40 MPa,这主要是由于晶粒尺寸及位错密度差异所导致。

关键词 Cu合金化强化机理Cu析出相厚板强度差    
Abstract

High strength low alloy (HSLA) steels are widely used in the construction of ship structures, oil pipelines, offshore platforms and so on because of their good strength, toughness and weldability. HSLA steel is generally designed with low carbon and Cu alloying. Tempered lath bainite or martensite and nano-precipitate phase of Cu can be obtained by quenching and ageing process after rolling to ensure the excellent matching of strength, low temperature toughness and weldability of HSLA steel. At present, increasing attention has been focused on the precipitation behavior and strengthening mechanism of Cu particles in HSLA steel which was aged at the peak hardness of ageing curve. However, in practical engineering applications, overageing heat treatment is generally used to make HSLA steel achieve a good match of strength and toughness. In this work, the microstructure and nano-sized Cu precipitates of an industrial production HSLA steel plate with thickness of 35 mm were characterized by SEM, EBSD, HRTEM and APT. Meanwhile, the strengthening mechanism of the tested steel was investigated. The results show that Cu precipitates in the tested steel processed by overageing are mainly in the range of 6~50 nm, Cu particles exhibiting short rod or spherical shape within 30 nm are 9R structure, and other particles size larger than 30 nm exhibiting long rod or spherical shape are fcc structure. The segregation of trace Mn and Ni in rod particles on the interface between Cu particles and matrix is more obvious. After ageing at a higher temperature range, the yield strength of the tested steel decreases linearly with the increase of tempering temperature. The main strengthening mechanism of the HSLA steel is fine grain strengthening, followed by dislocation strengthening and precipitation strengthening. The calculated results show that every 1%Cu added in the tested steel can produce about 90 MPa precipitation strengthening increment under the condition of overageing heat treatment. The strength difference between the surface and the center of the tested steel plate is about 40 MPa, which is mainly due to the difference of grain size and dislocation density of steel.

Key wordsCu alloyed    strength mechanism    Cu precipitate    strength difference of thick plate
收稿日期: 2018-10-25     
ZTFLH:  TG142  
基金资助:国家重点研发计划项目(No.2017YFB0304501)
通讯作者: 张正延     E-mail: zhangzhengyan@cisri.com.cn
Corresponding author: Zhengyan ZHANG     E-mail: zhangzhengyan@cisri.com.cn
作者简介: 张正延,男,1986年生,博士,工程师

引用本文:

张正延,柴锋,罗小兵,陈刚,杨才福,苏航. 调质态含Cu高强钢的强化机理及钢中Cu的析出行为[J]. 金属学报, 2019, 55(6): 783-791.
Zhengyan ZHANG, Feng CHAI, Xiaobing LUO, Gang CHEN, Caifu YANG, Hang SU. The Strengthening Mechanism of Cu Bearing High Strength Steel As-Quenched and Tempered and Cu Precipitation Behavior in Steel. Acta Metall Sin, 2019, 55(6): 783-791.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2018.00485      或      https://www.ams.org.cn/CN/Y2019/V55/I6/783

图1  实验用钢在不同温度时效后的屈服强度和调质态钢板厚度截面硬度分布
图2  钢板厚度截面不同位置的SEM像
图3  实验钢板表面和心部的EBSD晶界分布图及晶界密度对比图
图4  钢的表面及心部位置析出相的TEM像及其EDS
图5  钢中析出的不同尺寸Cu粒子的HRTEM像
图6  660 ℃时效后钢中Cu析出物的APT像
图7  Cu粒子的APT像及其成分分析
图8  Thermo-Calc软件计算的Cu的析出量随时效温度的变化
图9  实验用钢表面与心部的强化方式叠加分析
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