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3D study of non-metallic inclusions by EEmethod and use of statistics for the estimationof largest size inclusions in tool steel.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Applied Process Metallurgy)
2010 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The control of non-metallic inclusions is very important for the improvement of

performance during the application of tool steel. This present study was performed to

see the effect of changing of some process parameters during the vacuum degassing of

the melt and how these changing parameters affects the characteristics of inclusions in

tool steel. The main parameters that were changed during the vacuum degassing were

the change of induction stirring, argon flow rate from both the plug 1 and 2 and

different ladle ages for different heat. Electrolytic extraction method was used to

observe the morphology and characteristics of inclusions as a 3 dimensional view in

tool steel. Four lollipop samples from four different heats were used for the

experiment and all the samples were after vacuum (AV) degassing. In this study four

different types of inclusions were found and they are classified as type 1, 2, 3 and 4.

Of them type 1 inclusion was the major one with mostly spherical shaped. This study

shows that among the three parameters, induction stirring has the biggest effect for the

total number of inclusions per volume in the sample than the other two parameters

Heat 4A showed the lowest number of inclusions per volume comparing with the other

heats. The main reason behind this can be said that the induction stirring was the

lowest comparing with the other heats with moderate argon flow and ladle age of 12.

Extreme value analysis was used in this study to predict the probability of getting

largest size inclusions in a certain volume of the metal. For the prediction of the

largest inclusion size, both the electrolytic extraction (3D) and cross-sectional (2D)

method was used. Later in this study comparison was done to determine the accuracy

of both the methods and it is concluded that for the type 1 inclusions electrolytic

extraction method shows almost similar trend with cross-sectional method and

electrolytic extraction method shows better accuracy for the prediction of largest size

inclusions than the cross-sectional method. Electrolytic Extraction method is also

applicable for the prediction of largest size inclusions for multiple types of inclusions.

Place, publisher, year, edition, pages
2010. , 48 p.
Keyword [en]
Tool Steel, Electrolytic Extraction, Vacuum degassing, Non-metallic inclusions, Induction stirring, Argon flow rate, Ladle age, Extreme value analysis.
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-93770OAI: diva2:523803
Subject / course
Materials and Process Design
Educational program
Master of Science - Materials Science and Engineering
2010-06-24, Conference Room N111, Brinellvägen 23, Stockholm, 14:00 (English)
Available from: 2012-08-10 Created: 2012-04-26 Last updated: 2012-08-10Bibliographically approved

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