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2 Journal of Achievements in Materials and Manufacturing Engineering

2 2015

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Laboratory melting, casting and forging of manganese TWIP steel

Martinek P., Podany P., Duchek M., Konopik P.

Journal of Achievements in Materials and Manufacturing Engineering

2015

Vol. 71, nr 1

39--44

Purpose: The article deals with the possibility of experimental melting, casting and forging of these kinds of steel in laboratory induction melting furnace Design/methodology/approach: The metallographic tests and Rastegaev compression test were made to describe microstructural properties and flow stress behaviour at different forging temperatures. Findings: Results of this test show the true stress - true plastic strain diagrams which can be used as a data input to the numerical simulation of forging for example in DEFORM 3D simulation software. Research limitations/implications: Microstructure analysis proved successful handling during all forging operations - no cracks and similar defects were observed in the microstructure. Practical implications: Transportation industry demands high strength steels with the possibility to absorb high energy in case of a sudden collision. In recent years, so-called TWIP steels are in the focus of research of materials with high strength suitable for car bodies. Originality/value: TFeMn TWIP is a high-strength steel concept with superior formability, which may be close to being produced industrially. High manganese TWIP steels are highly ductile, high strength Mn austenitic steels characterized by a high rate of work hardening resulting from the generation of deformation-nucleated twins.

Fracture toughness determination of P91 steel according to ASTM E1820 and ISO 12135

Konopik P., Viehrig H. W.

Journal of Achievements in Materials and Manufacturing Engineering

2015

Vol. 69, nr 2

64--68

Purpose: This paper attempts to discuss the problems associated with the determination of fracture toughness values for P91 steels according to the tests standards ASTM E1820 and ISO 12135. Design/methodology/approach: The most applied standards for fracture toughness values determination in the ductile region are ASTM E1820 and ISO 12135. Both standards are intended to determine fracture toughness values in the ductile region. However, there are remarkable differences which leads to different values of obtained fracture toughness parameters such as JIC or CTOD. Findings: Within this work the P91 steel was characterized by fracture mechanics and fracture toughness parameters according to the test standards ASTM E1820 and ISO 12135 were determined. It was shown that despite of the fact that both test standards are designed to provide engineering fracture toughness for ductile crack initiation the evaluated fracture toughness values differ strongly depending to the applied standard. Research limitations/implications: For establishing ultimate load limitations and assessing the integrity for a large number of engineering structures of multifarious types a fracture mechanic has attained a great attention. Originality/value: Fracture toughness is one of the most important mechanical properties.