The influence of thermomechanical processing on the surface quality of an AISI 436 ferritic stainless steel

Show simple item record Uananisa, H.J. Siyasiya, Charles Witness Stumpf, Waldo E. Papo, M.J. 2016-04-22T07:43:58Z 2016-04-22T07:43:58Z 2015-10
dc.description.abstract The need to reduce weight while maintaining good mechanical properties in materials used in the automotive industry has over the years seen an increased exploitation of various steels to meet this new demand. In line with this development, the ferritic stainless steel family has seen a wide application in this industry, with the AISI 436 type increasingly being used for automotive trims and mufflers for exhaust systems, as well as a significant part of this steel’s application being for the manufacture of wheel nuts and wheel nut caps in trucks, mainly through the deep drawing process. However, there have been reports of some poor surface roughening of this material during deep drawing, with tearing and/or cracking also reported in some instances. This has been suspected to possibly be associated with some local differences in localized mechanical properties between grains and grain clusters of the rolled and annealed material. In order to investigate the poor surface roughness exhibited by AISI 436 ferritic stainless steel (FSS) during deep-drawing, Lankford values (Rmean and Δr), grain size, and microtextures of various sheet samples from this steel were studied. The chemical composition range for the samples was 0.013–0.017% C, 17–17.4% Cr, 0.9–1% Mo, and 0.4–0.5% Nb. The steels were subjected to various hot and cold rolling processing routes i.e. involving industrial direct rolling (DR) or intermediate annealing rolling (IR), and the drawability and final surface qualities of the steels were compared. It was found that the DR route gave an average R-mean and Δr value of 1.9 and -1.4 respectively, while the IR route yielded an average Rmean and Δr value of 1.6 and 0.52 respectively. The high Δr value for the DR processing route had a substantial adverse effect on the drawability. IR samples exhibited a smoother surface finish on visual inspection, while clear flow lines were visible on the DR samples, despite the fact that DR is the preferred industrial processing route due to the reduced production costs it offers. This observation was also confirmed through SEM examinations. The difference in the surface quality was attributed to microtexture. However, the mechanism responsible for this difference still needs to be identified. en_ZA
dc.description.department Materials Science and Metallurgical Engineering en_ZA
dc.description.librarian am2016 en_ZA
dc.description.sponsorship The authors gratefully acknowledge the financial contribution provided by the Advanced Metal Initiative (AMI) of the Department of Science and Technology (DST) through the Ferrous Metals Development Network (FMDN), and Columbus Stainless (Middelburg, South Africa). en_ZA
dc.description.uri en_ZA
dc.identifier.citation Uananisa, HJ, Siyasiya, CW, Stumpf, WE & Papo, MJ 2015, 'The influence of thermomechanical processing on the surface quality of an AISI 436 ferritic stainless steel', Journal of the Southern African Institute of Mining and Metallurgy, vol. 115, pp. 981-986. en_ZA
dc.identifier.issn 0038-223X (print)
dc.identifier.issn 2225-6253 (online)
dc.identifier.other 10.17159/2411-9717/2015/v115n10a13
dc.language.iso en en_ZA
dc.publisher Southern African Institute of Mining and Metallurgy en_ZA
dc.rights © The Southern African Institute of Mining and Metallurgy en_ZA
dc.subject Ferritic stainless steel en_ZA
dc.subject Formability en_ZA
dc.subject Microtexture en_ZA
dc.subject Electron backscatter diffraction (EBSD) en_ZA
dc.title The influence of thermomechanical processing on the surface quality of an AISI 436 ferritic stainless steel en_ZA
dc.type Article en_ZA

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