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Title

EFFECT OF COILING TEMPERATURE ON THE MECHANICAL PROPERTIES OF HOT ROLLED MULTI PHASE 800 MPA STEEL

Authorship

Marques, Luciano Santos; Melo, Túlio Magno Fuzessy de; Buono, Vicente Tadeu Lopes

Marques, Luciano Santos

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Melo, Túlio Magno Fuzessy de

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Buono, Vicente Tadeu Lopes

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DOI

10.5151/9785-9785-32435

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Abstract

The influence of the coiling temperature after hot strip rolling on the microstructure and on the tensile and hole expansion properties of a 800 MPa multiphase steel was investigated. For the temperatures between 150°C and 600°C the microstructure consisted of a ferritic matrix with a dispersion of fine martensite-austenite (MA) and regions of degenerated upper bainite. In all cases the ferrite presented a heterogeneous mixture of polygonal, quasi-polygonal and acicular grains. The yield and tensile strengths showed a tendency of decreasing with the increasing coiling temperature, probably because of the larger fraction of MA particles at lower temperatures and higher fraction of quasi-polygonal ferrite at higher temperatures. The elongation was not significantly affected by the variation of coiling temperature. The average hole expansion ratio showed a maximum of 80% for the material coiled at 400°C and fell below 50% only for the coiling temperature of 150°C, probably due to the larger hardness difference between the ferrite matrix and the MA particles.

Keywords

Complex Phase; Hole Expansion Ratio; Hot Rolled.