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Protective Coatings on Steel for Hot Stamping
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

TL3 and TL4 are two steels coming from the same coil; these steels are used for the production of automotive components by hot stamping. Despite of the fact that the steels are the same, variations in the adhesion of the oxide scale after hot stamping are seen; on TL3 there is almost no visible flaking off when hot stamping between flat dies, while on TL4 the scale flakes off easily in many areas. Scaling during hot stamping is undesirable for several reasons; a loose scale on the tool dies lead to increased wear and thus higher maintenance. Alongside, it has a negative effect on the working environment in the plants due to the release of fine dust and finally the loose oxide on the produced parts must be removed through shot blasting, which is itself and undesirable process step. The steels were heat treated at 930° C with an oxygen potential of approximately 990 mV and a dwell time of 3 minutes at Gestamp Hardtech to evaluate the behaviour of the oxide scale produced. Microstructural characterization by means of SEM, LOM, GDOES, EDS, XRD and tape test, were performed on the scale and steel after heat treatment. Beforehand the steels in the as received condition (e.g. non heat-treated) were analyzed by LOM, SEM, GDOES, EDS and roughness. Differences in grain size were found between TL3 and TL4 before heat treatment, as well as divergence on the element distribution on the surface of both steels, mainly carbon and silicon. After heat treatment, the scale on TL4 was found to be somewhat thicker than TL3 and despite of the fact that the same constituents were found, the percentage on each of them were different. The interface was characterized by a narrow layer between steel and scale containing silicon rich nanoparticles, which seem to vary in terms of morphology and size between TL3 and TL4.

Place, publisher, year, edition, pages
2014. , 81 p.
Keyword [en]
Technology, hot stamping, oxide scale, SEM
Keyword [sv]
Teknik
Identifiers
URN: urn:nbn:se:ltu:diva-52446Local ID: 99199479-404d-426c-9da2-a4d79bcecc0eOAI: oai:DiVA.org:ltu-52446DiVA: diva2:1025816
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level
Supervisors
Note
Validerat; 20140825 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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