Title

NEW FAST COOLING TECHNOLOGIES IN HOT STRIP MILLS

NEW FAST COOLING TECHNOLOGIES IN HOT STRIP MILLS

Authorship

LACROIX, J.; HERMAN, J-C.

LACROIX, J.

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HERMAN, J-C.

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DOI

10.5151/2594-5297-LA3495-11832

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Abstract

The "Transfer Bar Cooling" unit, placed after the last roughing stand of the Sidmar HSM (Arcelor), cools the transfer bar in a very fast and controllable way in order to fulfil the very diversified rolling thermal constraints as required for the different grades. Two modes of operating the bar cooler have been developed and optirnized, the mode full bar cooling (adjustrnent of rolling temperature) and the mode bar head end cooling (reduction of rolled-in-scale defects). "Ultra Fast Cooling " is a powerful technology particularly well adapted to produce high strength steels in hot strip mills. Two possible installations are envisaged: 1)The "early UFC situated just after the finishing mill, 2) The "late UFC" located at the exit of the runout table, before the downcoiler. The main advantages of UFC concern high strength hot rolled steels. The mechanical properties can be improved or obtained with cheaper alloying elements. The reproducibility and the consistency of these properties are significant. Thanks to high cooling rates at the exit of the finishing mill, the "early UFC" is particularly well adapted to improve the properties of HSLA and fine grain steels. Laminar Cooling - Ultra Fast Cooling combinations generate multiphase microstructures and improved mechanical properties. The proportion of each phase (ferrite-bainite-martensite) is adapted changing the cooling profile.

The "Transfer Bar Cooling" unit, placed after the last roughing stand of the Sidmar HSM (Arcelor), cools the transfer bar in a very fast and controllable way in order to fulfil the very diversified rolling thermal constraints as required for the different grades. Two modes of operating the bar cooler have been developed and optirnized, the mode full bar cooling (adjustrnent of rolling temperature) and the mode bar head end cooling (reduction of rolled-in-scale defects). "Ultra Fast Cooling " is a powerful technology particularly well adapted to produce high strength steels in hot strip mills. Two possible installations are envisaged: 1)The "early UFC situated just after the finishing mill, 2) The "late UFC" located at the exit of the runout table, before the downcoiler. The main advantages of UFC concern high strength hot rolled steels. The mechanical properties can be improved or obtained with cheaper alloying elements. The reproducibility and the consistency of these properties are significant. Thanks to high cooling rates at the exit of the finishing mill, the "early UFC" is particularly well adapted to improve the properties of HSLA and fine grain steels. Laminar Cooling - Ultra Fast Cooling combinations generate multiphase microstructures and improved mechanical properties. The proportion of each phase (ferrite-bainite-martensite) is adapted changing the cooling profile.

Keywords

cooling, bar, strip

cooling, bar, strip