20CrMnTi热轧棒材铁素体-珠光体带状组织控制

controlling the ferrite and pearlite banded of 20CrMnTi hot rolled bar

  • 摘要: 本文对20CrMnTi棒材在轧制线不同位置的铁素体-珠光体带状取样分析,结果表明:越靠近轧制末端,带状越严重,且钢材的带状组织从表面到芯部逐渐加重。通过实验对比不同的终轧温度和轧后冷却速度的带状,当终轧温度≥905℃时,棒材的带状满足≤2.5级。当终轧温度≥915℃,能够满足带状组织≤2.0级,提高终轧温度,促进奥氏体原位发生相变,减少铁素体的塑性变形,有利于带状级别的降低。提高轧后的冷却速度,能够有效抑制C、Mn和Cr元素贫化区与富化区间的扩散,有利于带状的减轻。对热轧和退火两种状态的20CrMnTi棒材试样进行扫描分析,结果表明:对热轧棒材进行退火热处理会加重带状组织,严重的带状组织使得C、Mn和 Cr元素分布不均匀,但对Si和Ti元素的分布的均匀性无明显影响。

     

    Abstract: The sampling of ferritic-pearlite banded of 20CrMnTi bar at different positions in the rolling line, the result shows that the closer the rolling end, the more serious the banded is, and the banded structure of steel is gradually aggravated from the surface to the core. By comparing the banded of different final rolling temperature and cooling rate after rolling, when the final rolling temperature is over 905℃, the banded structure of the bar can be less of 2.5 level. When the final rolling temperature is over 915℃, the banded structure can less of 2.0 level, and the banded grade gradually decreases with the increase of the final rolling temperature. Increasing the final rolling temperature can promote the transformation of austenite in situ and reduce the plastic deformation of ferrite, which is conducive to the reduction of band grade. Increasing the cooling rate after rolling can effectively inhibit the diffusion of C. Mn and Cr elements from the depleted zone to the enriched zone, which is conducive to the reduction of the strip. The scanning analysis of the samples of 20CrMnTi bars in hot rolled and annealed states shows that the annealing treatment of hot rolled bars will aggravate the zonal structure, which makes the distribution of C, Mn and Cr elements uneven, but has no obvious effect on the distribution uniformity of Si and Ti elements.

     

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