Effect of Heat Treatment on Properties of Bainitic Steels
Viinanen, Noora (2016)
2016
Materiaalitekniikan koulutusohjelma
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2016-09-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201608254442
https://urn.fi/URN:NBN:fi:tty-201608254442
Tiivistelmä
The wear of drilling tools, for example the button bits, causes a significant share of the expenses of hard rock excavation. Therefore, research and development of more durable materials for rock drilling tools has great importance in achieving cost savings and in enhancing the drilling performance.
Button bits are drill bits that are used in percussive drilling of rock. Button bits consist of a steel body and of embedded cemented carbide buttons. This thesis is a part of the research work aiming at quality improvement of button bit bodies. The aim of this thesis is to understand how different heat treatment processes affect the properties of the steel that is used to manufacture the button bit body, and to optimise the heat treatment process based on the done research.
The theory part of this thesis gives information that helps to understand the results of the experimental part. In the experimental part, different heat treatment processes and their effects on the properties of specific steel were compared. The tested properties of the steel were hardness, impact toughness, strength, ductility and abrasive wear resistance. Also, the microstructures of the samples and the quality of the holes drilled for the buttons were inspected. In addition, phase transformation diagrams were calculated with JMatPro® software.
The microstructure of the samples was either bainitic or tempered martensitic depending on the heat treatment. Most of the differences between the mechanical properties of the samples resulted from the differing heat treating temperatures and times, but the differing quenching media and cooling rates during the austempering heat treatments also induced differences.
It was not possible to optimise the heat treatment process of button bits based on the results of the experimental part, but the findings give a good base and direction for the future research work aiming at quality improvement of button bit bodies.
Button bits are drill bits that are used in percussive drilling of rock. Button bits consist of a steel body and of embedded cemented carbide buttons. This thesis is a part of the research work aiming at quality improvement of button bit bodies. The aim of this thesis is to understand how different heat treatment processes affect the properties of the steel that is used to manufacture the button bit body, and to optimise the heat treatment process based on the done research.
The theory part of this thesis gives information that helps to understand the results of the experimental part. In the experimental part, different heat treatment processes and their effects on the properties of specific steel were compared. The tested properties of the steel were hardness, impact toughness, strength, ductility and abrasive wear resistance. Also, the microstructures of the samples and the quality of the holes drilled for the buttons were inspected. In addition, phase transformation diagrams were calculated with JMatPro® software.
The microstructure of the samples was either bainitic or tempered martensitic depending on the heat treatment. Most of the differences between the mechanical properties of the samples resulted from the differing heat treating temperatures and times, but the differing quenching media and cooling rates during the austempering heat treatments also induced differences.
It was not possible to optimise the heat treatment process of button bits based on the results of the experimental part, but the findings give a good base and direction for the future research work aiming at quality improvement of button bit bodies.