低碳合金钢带状组织控制研究现状

A review of research on banded structure control in low carbon alloy steel

铁素体/珠光体带状组织是低碳合金钢热轧过程常见的组织缺陷,不仅恶化钢材横向塑性及韧性,而且严重影响后续加工零部件的使用寿命。近年来,带状组织的控制一直是高品质钢研究的重点之一。为了充分认识带状组织,综述了国内外关于带状组织形成机理、影响因素及控制方法的研究现状,指出了带状组织控制思路及方向,为今后学者研究提供一定的启发和参考。分析发现,合金元素偏析是带状组织形成的必要条件,而铁素体形核、长大以及碳元素的扩散是带状组织形成的决定条件。元素富集区和贫化区的铁素体形核速率差是影响带状组织形成的直接原因,提高热轧后冷却速率不仅可以降低不同区域铁素体形核速率差异,而且可以减少碳元素扩散距离,抑制带状组织的形成。此外,再结晶获得较大奥氏体晶粒尺寸,可以降低单位体积铁素体形核核心,阻碍铁素体生长平面形成,影响元素偏析带的连续性,进而破坏带状组织的形成。但是较快冷却速率下形成的魏氏体组织和较大奥氏体晶粒相变生成的粗大铁素体均不利于基体性能。固态相变过程中,利用氧化物冶金技术可以调控晶内铁素体形成和先共析铁素体的生长方向,改善微观组织和力学性能各向异性,实现带状组织的控制。

Ferrite/pearlite banded structure is a common structural defect in the low carbon alloy steel during hot rolling process,which not only deteriorates the transverse plasticity and toughness of steel,but also seriously affects the service life of subsequent processed parts.In recent years,the control of banded structure has been one of the focuses of high-quality steel research.In order to fully understand the banded structure,the research status of banded structure formation mechanism,influencing factors,and control methods at domestic and foreign were reviewed.The control thought and direction of banded structure are pointed out,which will provide some inspiration and reference for future research.It is found that alloy element segregation is a necessary condition for the formation of banded structure,while ferrite nucleation,growth and diffusion of element C are the decisive conditions for the banded structure formation.The difference of ferrite nucleation rate between the element enrichment zone and depletion zone is the direct reason affecting the formation of banded structure.Increasing the cooling rate after hot rolling can not only reduce the difference of ferrite nucleation rate,but also reduce the diffusion distance of element C and inhibit the formation of banded structure.Moreover,the larger austenite grain size obtained by recrystallization can reduce the unit volume ferrite nucleation site,hinder the formation of ferrite growth plane,affect the continuity of element segregation band,and then destroy the formation of banded structure.However,the formation of widmanstatten structure at a faster cooling rate and the formation of coarse ferrite grains by the larger austenite grains transformation are not conducive to the matrix properties.In the solid-state phase transformation process,oxide metallurgy technology can regulate the formation of intragranular ferrite and the growth direction of proeutectoid ferrite,improve the anisotropy of microstructure and mechanical properties,and realize the control of banded structure.