IMPROVEMENT OF MECHANICAL PROPERTIES OF MARAGING STEELS USING ESR TECHNIQUE

Document Type : Original Article

Authors

1 Professor, Department of Steel Technology (STD), Central Metallurgical R&D Institute (CMRDI), Cairo, Egypt.

2 Professor, Department of Metallurgical Engineering, Faculty of Engineering, Cairo, University, Giza, Egypt.

3 Associate Professor, Department of Steel Technology (STD), Central Metallurgical R&D Institute (CMRDI) Cairo, Egypt.

4 Senior Researcher Assistant, Department of Steel Technology (STD), Central Metallurgical R&D Institute (CMRDI), Cairo, Egypt.

Abstract

Electroslag refining is a useful remelting process by which clean steels can be produced for sophisticated applications. In this investigation, maraging steels have been electroslag refined and the improvement in its ductility have been assessed using hardness, and tensile strength tests; electroslag refining has improved the ductility considerably. Results indicate that ESR obtains higher recovery of alloying elements under slag of high viscosity and low interfacial tension (slags 1 and 3). Results indicate that it should be possible to raise both strength and toughness for ESR ingot to much higher value using appropriate remelting condition and heat treatment. It is clear from experimental data that there is a steady rise in peak hardness level in the case of the three types of investigated slags for all steel under investigation. At the same time, there is a widening in the aging temperature at which peak hardness is attained in order ESR2, ESR3, ESR1. This result also clarifies that ESR steel has higher retained austenite content than IF heats, which depends mainly on its chemical compositions. In other hand, ESR process under any of the investigated fluxes leads to uniform distribution of austenite grain. The improvement in tensile properties in ESR steel has been attributed primarily to the removal of non-metallic inclusions, the reduction in sulphur content, fine and well distributed microstructure and sufficient austenite content.

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