轴承钢中大尺寸夹杂物的特征、来源及改进工艺

doi:10.13228/j.boyuan.issn1006-9356.20200329

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Abstract Based on the BOF-ARS(argon stirring)-LF-RH-CC process of bearing steel production in Shaoguan Steel Plant, the characteristics and sources of large size inclusions were explored through the method of water immersion ultrasonic test combined with metalloscope, scanning electron microscope and the systematic sampling during the metallurgical-continuous casting process, and the improved process was proposed. Results showed that there were mainly two kinds of large inclusions, one was low-melting CaO-MgO-Al₂O₃-SiO₂ inclusion from 6% to 7% SiO₂(mass percent), whose size was from 50 to 500 μm, and the other was CaO-MgO-Al₂O₃ without SiO₂, whose size was larger than 500 μm. The source of the former was the slag entrapment caused by the uneven slagging, which was the result of the combined charge of low basicity slag with high viscosity and high melting point lime during steel tapping. The latter was induced by the charge of large bulk of calcium-aluminate slag during the refining process, which was difficult to be melted rapidly and was entrapped into steel. Therefore, the design of refining slag and the optimization of the slagging process were the key points to decrease the large size inclusions. The improved slagging technology was applied by feeding the large bulk of calcium-aluminate slag during tapping in advance, instead of the low-basicity slag, and the addition amount of other slag was reduced during LF refining process. The basicity of refining slag (w(CaO)/w(SiO₂)) was controlled in the range from 5 to 9, and the mass percent of Al₂O₃ was from 23% to 28%. After the improvement, the fluidity of slag was good, and nozzle clogging was reduced. The main inclusions in the products were micro MgO-Al₂O₃ spinel and composite sulfides. The qualified rate of bearing steel products evaluated by ultrasonic test was significantly improved.

Key words： bearing steel ultrasonic test large size inclusions refining slag cleanliness

Received: 02 June 2020

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	Articles by authors
	LONG Hu
	CHENG Guo-guang
	QIU Wen-sheng
	ZENG Ling-yu
	YU Da-hua
	LIU Dong

Cite this article:

LONG Hu,CHENG Guo-guang,QIU Wen-sheng等. Characteristics, sources analysis of large size inclusions and technical improvement during bearing steel production[J]. China Metallurgy, 2020, 30(9): 53-59.

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http://www.zgyj.ac.cn/EN/10.13228/j.boyuan.issn1006-9356.20200329 OR http://www.zgyj.ac.cn/EN/Y2020/V30/I9/53

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