Thermal Simulation Study on the Solidification Structure and Segregation of a Heavy Heat-Resistant Steel Casting

The prediction and controlling of the solidification structure and macro-segregation in heavy steel casting, which is usually produced in limited quantities, was a conundrum in the foundry field. In this work, the cooling and solidification processes of a 16 t CB2 ferritic heat-resistant steel (FHRS...

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Published inMetals (Basel ) Vol. 9; no. 2; p. 249
Main Authors Wang, Biao, Zhong, Honggang, Li, Xihao, Wang, Xiebin, Wu, Tieming, Liu, Qingmei, Zhai, Qijie
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.02.2019
Subjects
Chemical precipitation
Chill casting
Chromium
Cold
Continuous casting
Cooling
Electron probes
Experiments
ferritic heat-resistant steel
Ferritic stainless steels
Heat
Heat resistant steels
heavy casting
Iron and steel making
Lasers
macro-segregation
Manganese
Micrometers
Molybdenum
Morphology
Niobium
Precipitates
Silicon
Simulation
Solidification
Steel
Temperature
Thermal simulation
China
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Summary:The prediction and controlling of the solidification structure and macro-segregation in heavy steel casting, which is usually produced in limited quantities, was a conundrum in the foundry field. In this work, the cooling and solidification processes of a 16 t CB2 ferritic heat-resistant steel (FHRS) valve casting were reproduced by studying the solidification behavior of three typical units through a thermal simulation method. The results indicate that the types of casting without chilling have the most uneven distribution of solutes and hardness, while those types of casting in which parts are solidified by chilling are much more uniform. The macro-segregation degrees of B, C, Nb, P, Cr, Mo, Si, V and Mn decrease gradually during heavy casting of CB2 ferritic heat-resistant steel. Of them, B, C, Nb, and P are solutes prone to segregation, and the maximum macro-segregation index of B can even reach 15. The macro-segregation tendencies of Cr, Mo, Si, V, and Mn are relatively small. Further studies on the last solidification portion of samples taken by electron microprobe reveal that large-sized precipitates such as MnS and NbxC are easily formed due to solute enrichment, and the sizes of these precipitates were distributed from dozens to hundreds of micrometers.
ISSN:2075-4701
2075-4701
DOI:10.3390/met9020249