Method of manufacturing a steel strip and coated steel sheet obtainable thereby

A method of manufacturing a steel strip for use in an automobile body, comprising the subsequent steps of hot rolling the strip into a hot rolled strip, cold rolling the hot rolled strip and hot dip coating the cold rolled strip with a Zn based coating by leading the strip through a bath comprising molten zinc and wiping the strip after said coating using a gas knife having a knife slot from which a wiping gas is projected, wherein:

• the steel strip is cold rolled to a final cold rolled thickness of between 0.40 mm and 1.00 mm in a multi-stand cold rolling mill wherein cold rolling in the last stand takes place such that:
• SRF
• AWR
• ≥
• 21000
• ⁢
• kN
• /
• m
• 2
• wherein SRF is the specific rolling force expressed in kN/m calculated as the rolling force in kN divided by the strip width in m, and AWR is the average work roll radius in m of a top work roll and a bottom work roll at mid roll position, and wherein GKD is the average distance between the knife slot from which the wiping gas is projected and the surface of the coated strip that is being wiped, wherein GKD≤10 mm;
• wherein a bath of molten metal has a composition comprising Zn, Al and Mg, wherein the strip after coating and wiping is cooled in a cooling section between the location where the strip is wiped and a downstream location where the strip is first contacted by a guiding roll;
• wherein an active cooling gas flow Q in m3/hr is used which is required to maintain the strip temperature within 20° C. of a target strip temperature in the range between 200° C. and 300° C. at said guiding roll;
• wherein the cooling gas flow in the second half of the cooling section is a percentage p of Q and the cooling gas flow in the first half of the cooling section is a percentage of (100-p) of Q, wherein p is set at 70% or more;
• and
• wherein cold rolling in the last stand takes place using work rolls that have a roughness Ra which is 7 μm or less but in all cases 1.0 μm or more.