LF精炼时间对帘线钢夹杂物成分影响

Effect of the LF refining time on the composition of inclusions in tire cord steels

针对国内某钢厂生产帘线钢LF精炼时间过长的缺点,在LF精炼过程进行密集取样,系统分析了钢中氧氮含量变化、夹杂物成分演变、数密度、面积百分比以及尺寸变化等,确定了合适的LF精炼时间。研究指出:氧化物夹杂集中分布于轧材中心和边缘部位,部分夹杂物实现了塑性化控制;LF精炼过程,钢中w(T.O)逐渐降低稳定在20×10-6,由于扒渣操作,钢液发生二次氧化,精炼开始阶段钢中w(N)迅速增大,逐渐稳定在22×10-6;当钢中w(Ca)>1.1×10-6时,夹杂物中Ca O逐渐生成,其类型由Si O2-Mn O向Ca O-Si O2-Al2O3转变;夹杂物中Al2O3主要来源于合金及脱氧剂等辅料,Mg O来源于钢包内衬耐材;基于Mg O-Ca O-Si O2-Al2O3-(Mn O)系夹杂物平均成分演变、尺寸所占比例变化以及夹杂物面积百分比变化等,建议将LF精炼过程软吹时间缩短20 min,即整个精炼时间控制在96 min最佳。

In the current study,the effect of LF refining time on the composition of inclusions in tire cord steel was investigated to optimize the LF refining time of a domestic steel plant. Steel samples were taken during LF refining. The evolution of total oxygen and nitrogen contents, and the composition,number density,area fraction,and size of inclusions in steel samples were systematically analyzed to determine an appropriate refining time. It was found that the oxide inclusions were concentrated in the center and edge of the cross section of rolled products and the composition of part of inclusions were controlled in the region of low melting temperature. The total oxygen mass fraction gradually decreased during LF refining and then reached stable to 20 × 10- 6. Due to the operation of slagging-off after tapping of BOF,the molten steel was oxidized by air,resulting in the rapid increase of nitrogen content at the initial stage of LF refining. The nitrogen mass fraction was then reached a stable value of 22 × 10- 6during the refining process. When the calcium mass fraction in the molten steel was larger than 1. 1 × 10- 6,the Ca O in inclusions was gradually generated and the type of inclusions were transformed from Si O2-Mn O to Ca O-Si O2-Al2O3. The Al2O3 in inclusions mainly came from raw materials such as alloy and deoxidizer. Besides,the Mg O in inclusions came from ladle lining. Based on the variation of average composition, size fraction and area fraction of Mg O-Ca O-Si O2-Al2O3-（ Mn O） inclusions,the soft blowing time during the current LF refining was suggested to shorten 20 min and the appropriate refining time was proposed as 96 min.