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Laser welding of hardenable steel
2010 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the present work a novel idea based on nucleation and growth applied to an induction heat treatment of a laser welded component is presented. With this new concept, the microstructure and hardness of hardenable steel SS142225 with a thickness of 12 mm are believed to be improved by prolonging the cooling time after laser-welding and decreasing the preheat temperature. Initially, a simple analytical model was used to calculate thermal cycles. This knowledge then was used to programme a weld thermal simulator. A number of Gleeble tests were then performed in order to study the resulting microstructure. In these tests, important parameters such as pre-heating temperature, cooling time after welding, post weld heat treatment temperature were varied. After that and in order to compare the results obtained from the simulated specimens, real weldments were produced at Ferruform with the same parameters. After welding, the samples were prepared for microscopy and hardness examinations. The metallurgical phases are analyzed and described. A comparison between Gleeble samples and Ferruform samples is made. Both Gleeble and Ferruform results show that, it is possible to get microstructures that do not contain any untempered martensite in the heat affected zone. A reduction in the hardness values of the SS142225 hardenable steel was achieved in most of the experiments. A microstructure consisted of a mixture of bainite, tempered martensite and some ferrite and a duplex microstructure constituted by tempered martensite and bainite were obtained as two of the most promising results.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Laser welding, hardenable, steels, gleeble, induction heat, treatment
Keyword [sv]
URN: urn:nbn:se:ltu:diva-49692ISRN: LTU-PB-EX--10/026--SELocal ID: 701c91a6-fbd5-43e0-ac9d-a6594b9e1e15OAI: diva2:1023039
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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