Title:	Effects of hot forging on the structural condition in HS 6-5-2 high-speed steel
Other Titles:	Vliv kování za tepla na strukturu HS 6-5-2 rychlořezné oceli
Authors:	Průcha, Vojtěch Benešová, Soňa Veselý, Vilém Kesl, Miloslav
Citation:	PRŮCHA, V., BENEŠOVÁ, S., VESELÝ, V., KESL, M. Effects of hot forging on the structural condition in HS 6-5-2 high-speed steel. In: IOP Conference Series: Materials Science and Engineering. Bristol: IOP Publishing Ltd, 2019. s. 1-9. ISSN 1757-8981.
Issue Date:	2019
Publisher:	IOP Publishing Ltd
Document type:	konferenční příspěvek conferenceObject
URI:	2-s2.0-85080949659 http://hdl.handle.net/11025/42746
ISSN:	1757-8981
Keywords:	Rychlořezná ocel;kování;austenitické zrno
Keywords in different language:	High-speed steel;forging;austenite grains
Abstract in different language:	Microstructure analysis was performed on rolled bars of high-speed steel after two and three forging cycles, each cycle comprising one upsetting and one drawing out operation. High-speed steels belong to difficult-to-form materials with a narrow forging temperature interval. Forging above the maximum forging temperature may lead to grain coarsening. Below the minimum forging temperature, deformation resistance of the material increases, and the workpiece may fail. Using numerical modelling, special forging dies were designed and effective strain distribution was calculated for an axial cross-section plane in specimens after two and three forging cycles. The purpose of the analysis was to identify the relationship between the amount of effective strain and the shape and size of austenite grain and the volume fraction and density of carbidesafter forging. The size of prior austenite grains was measured using the linear intercept method which is based on the Snyder-Graff method. Grain shapes were characterized in terms of circularity, which is the difference between the shape in question and a circle. With increasing amount of strain, the grains in the materialbecame finer, as undissolved carbides impeded grain growth. In as-received rolled condition, the austenite grain size was G9. After three forging cycles, it was smaller, G11 (the higher the number, the smaller the grains). Circularity characterizes the complexity of a grain shape.Micrographs of carbide particles were taken using a scanning electron microscope and examined with NISElements image analysis software. The majority of carbides were sized between 0.2 and 2μm.The carbides which are less than 1μm in size do not shrink in response to increasing strain and their quantity does not change appreciably. Carbides with a size of 1-2μm show a different behaviour. In the central region of specimens, where strain is the largest, their amounts are much larger than in less-worked regions.
Rights:	© IOP Publishing
Appears in Collections:	Konferenční příspěvky / Conference papers (KMM) OBD

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