高速重轨钢采用无铝脱氧工艺,但是钢中常发现大颗粒纯的MgO-Al2O3夹杂物,严重影响产品质量。为了明确高速重轨钢中尖晶石夹杂物的来源,进一步控制重轨钢中夹杂物,通过对重轨钢拉伸断口进行分析,结合水口结瘤物分析、热力学计算及典型夹杂物分析,系统研究了高速重轨钢中尖晶石夹杂物的形成机理。结果表明,重轨钢中的尖晶石夹杂物分为单独存在的尖晶石和钙铝酸盐包裹的尖晶石两类。其中钙铝酸盐包裹的尖晶石为CaO-SiO2-Al2O3-MgO复合夹杂物在降温冷却过程中析出,析出温度与夹杂物中Al2O3和MgO质量分数有关;单独存在的小尺寸尖晶石夹杂物为钢液凝固冷却过程中析出,与钢液成分有关。此外,研究还表明,水口结瘤也是重轨钢中出现大颗粒镁铝尖晶石夹杂物的重要原因之一。因此,严格控制合金辅料中Mg、Als等杂质元素质量分数,防止钢液发生二次氧化、降低耐火材料侵蚀等,尽可能降低夹杂物中的Al2O3和MgO质量分数,对控制重轨钢中尖晶石夹杂物,提高产品质量至关重要。
Abstract
Large particles of pure MgO-Al2O3 inclusions are often found in high-speed heavy rail steel, which affects the quality of products seriously. To clarify the source of spinel inclusions in high-speed heavy rail steel for better inclusion controlling, the formation mechanism of spinel inclusions in high-speed heavy rail steel is systematically studied through tensile fracture analysis, combined with nozzle clogging analysis, thermodynamic calculations and typical inclusion analysis. The results show that the spinel inclusions in the steel can be classified into two types: single spinel inclusions and spinel inclusions wrapped by calcium aluminate. The spinel inclusions wrapped by calcium aluminate is caused by the self-precipitation of CaO-SiO2-Al2O3-MgO composite inclusions during the cooling process, and the precipitation temperature is related to the content of Al2O3 and MgO in inclusions; smaller single spinel inclusions in the steel are precipitated during the solidification and cooling process, which depends on the chemical composition of the steel. In addition, the study also shows that nozzle nodulation is one of the important reasons for the occurrence of larger spinel inclusions in heavy rail steel. Therefore, strictly controlling the content of impurity elements such as Mg and Als in alloys and raw materials, preventing secondary oxidation, and reducing the corrosion of refractories and the content of Al2O3, MgO in inclusions as much as possible are very important for controlling spinel inclusions and improving products quality.
关键词
高速重轨钢 /
尖晶石 /
非金属夹杂物 /
水口结瘤
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Key words
high speed heavy rail steel /
spinel /
non-metallic inclusion /
nozzle clogging
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脚注
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基金
国家自然科学基金资助项目(U1860206,51725402); 中央高校基本科研业务费专项资金资助项目(FRF-TP-17-001C2)
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