过热度对X65钢连铸板坯中心偏析的影响

Effects of superheat on the center segregation in continuous casting slab of X65 steel

研究了不同过热度下X65管线钢连铸板坯的中心偏析情况。工业试验的研究结果表明,在使用轻压下技术的前提下,低过热度浇铸时中心形成较宽的负偏析区,中心偏析影响的厚度范围较大;而适当提高过热度浇铸时,中心形成细窄的中心偏析线,中心偏析影响的厚度范围更小更集中。成分分析结果表明适当提高过热度浇铸(>25℃),X65管线钢碳和锰的平均最大偏析度分别由常规生产的1.20和1.04以上降低到1.10和1.02以下。将适当提高过热度配合使用轻压下技术的改进工艺应用于X65抗酸管线钢的生产后发现:碳和锰最大中心偏析度平均值分别由常规生产的1.18和1.04降低到了1.06和0.99,同时钢板的屈强比和冲击功平均值由常规生产的0.83和370J分别提高到0.92和430J。

The effects of superheat on center segregation in continuously cast slab of X65 pipeline steel were investigated. The results of macrostructure etching showed that center segregation was dispersed across the equiaxed zone and the negative segregation was thick, which results in the thick incidence of center segregation in the thickness direction of the slab. However, in high-superheat cast slab, the center segregation was compressed in a narrow range in the vicinity of slab center and formed the obvious centerline segregation which was thinner than that of low-superheat cast slab. It is revealed by the chemical analysis results that the fluctuation of element content across the thickness with low-superheat casting was larger than that of high-superheat casting. Compared to the low-superheat cast slabs, the average maximum segregation index of carbon and manganese was decreased from above 1.20 and 1.04 to below 1.10 and 1.02 respectively in high-superheat cast slabs. The above-mentioned results indicated that high-superheat with soft reduction was more effective to improve and control the center segregation in X65 pipeline steel. The application results of high-superheat （〉25 ℃） with soft reduction on X65 acid resistant pipeline steel showed that the average maximum segregation index of carbon and manganese was decreased from 1.18 and 1.04 to 1.06 and 0.99, while the yield ratio and impact toughness were increased from 0.83 and 370 J to 0. 92 and 430 J respectively.