低碳钢中高密度超细纳米第二相粒子的快速获取

Acquiring high density of ultrafine second-phase nanoparticles quickly in low-carbon steel

一般熔炼过程中,非金属化合物以夹杂物的形式存在,对钢的力学性能和寿命都会有损害.当夹杂物尺寸小到纳米量级,从而在钢中形成高密度分布的纳米第二相颗粒却能够有效同时提升钢的强度和韧性.本文通过在熔炼过程中施加动态磁场,制备了Fe–0.04C–1.5Mn–0.5Ti–0.5Al_(2)O_(3)(Fe–TAMO)钢,然后通过轧制和退火处理实现对Fe–TAMO钢的晶粒尺寸优化和等轴化.透射电镜观察发现铸态组织中弥散分布着纳米第二相粒子,密度为3.3×10^(15)m^(-2),颗粒的平均直径为2.75±0.803 nm.通过EDS能谱分析,第二相颗粒为Ti–Al–Mn氧化物.利用万能试验机分别测试了铸态、轧制态以及退火态Fe–TAMO钢的压缩力学性能,铸态Fe–TAMO钢的晶粒尺寸为143μm,抗压屈服强度为150 MPa,约为铸态纯铁素体钢的2倍.经过轧制和退火处理,Fe–TAMO钢的晶粒尺寸减小为64μm,抗压屈服强度为334 MPa.该方法极大简化了工艺流程,实现了在短时间(约3 min)内将超细的纳米第二相粒子均匀分散在钢基体中,密集分布的第二相纳米颗粒有效提高了钢的强度,并且通过后续热处理能进一步提升钢的力学性能,为大批量生产高性能钢提供了一个新思路.

In the general smelting process,nonmetallic compounds manifest as inclusions.These inclusions,typically larger than 5μm,can significantly reduce the strength,toughness,and processability of steel.More critically,they pose a threat to the service life of steel.To mitigate these adverse effects,the practice of inclusion modification has been developed.Typically,calcium and magnesium elements are employed for this purpose.However,despite these efforts,the size of modified inclusions often remains at the micron level.Although there is some improvement in mechanical properties,the presence of these inclusions still compromises the steel matrix.Therefore,controlling the size,quantity,and distribution of nonmetallic inclusions during steel manufacturing becomes imperative.When inclusions are reduced to nanometer size,the formation of a high density of nanosized second-phase particles can substantially improve the strength and toughness of the steel.In this study,we prepared Fe–0.04C–1.5Mn–0.5Ti–0.5Al_(2)O_(3)(Fe–TAMO)steel by applying a dynamic magnetic field during the smelting process.This was followed by grain size optimization and equiaxed optimization through rolling and annealing processes.Transmission electron microscopy revealed that the second-phase particles were uniformly dispersed within the as-cast Fe–TAMO steel matrix.The density of these particles reached 3.3×10^(15) m^(−2),with an average diameter of 2.75±0.803 nm.Energy-dispersive x-ray spectroscopy analysis identified these particles as oxides of Ti–Al–Mn.The compressive mechanical properties of Fe–TAMO steel,in its as-cast,as-rolled,and as-annealed states,were evaluated using a universal testing machine.The grain size of the as-cast Fe–TAMO steel is 143μm,with a compressive yield strength of 150 MPa,approximately double that of as-cast pure ferritic steel.After rolling,the grain size decreased to 119μm,and the compressive yield strength increased to 484 MPa.Following annealing,the grain size was further reduced to 64μm,with a compressive yield strength of 334 MPa.These results demonstrate that the applied method effectively minimizes the size of the second-phase particles,with most controlled within 5 nm.The densely distributed second-phase nanoparticles significantly improve the steel strength,while subsequent heat treatments allow for adjustments in grain size to further enhance mechanical properties.This method streamlines the process flow to a single step,achieving uniform dispersion of ultrafine nanosized second-phase particles in the steel matrix in about a mere 3 minutes.Moreover,it holds great potential for industrial production,offering a new avenue for the mass production of high-performance steel.