Device for improving preoxidation in an annealing furnace

A method for improving temperature longitudinal homogeneity of a steel strip comprising a low carbon alloyed steel strip dedicated to liquid metal coating, the method comprising:

• continuously running the steel strip at a line speed in a temperature homogenization section provided with electric resistances, the temperature homogenization section being located before a post-treatment section and after a furnace section, the furnace section being configured to provide a radiative or electric heating of the steel strip to a predetermined average temperature, the temperature homogenization section including at least one contact roll comprising refractory stainless steel, the at least one contact roll having a strip wrapping angle higher than 90°,
• wherein a total contact time and a total contact length, respectively, of the strip with the at least one contact roll are selected to be greater or equal to
• ContactTime
• ⁢
• 1
• =
• (
• A
• *
• exp
• ⁢
• (
• B
• *
• RSTGDP
• )
• )
• *
• strip
• ⁢
• thickness
• and
• ContactLength
• ⁢
• 1
• =
• ContactTime
• ⁢
• 1
• *
• line
• ⁢
• speed
• where
• -
• :
• RSTGDP
• =
• (
• 1
• -
• Initial
• ⁢
• roll
• ⁢
• temperature
• -
• Actual
• ⁢
• strip
• ⁢
• temperature
• Initial
• ⁢
• roll
• ⁢
• temperature
• -
• Initial
• ⁢
• strip
• ⁢
• temperature
• )
• ×
• 100
• ContactLength1 is in m, ContactTime1 in sec, line speed in m/sec, and
• 0.34<A<0.92 and 0.035<B<0.045,
• wherein ContactTime1 is limited to a value necessary to attain a predetermined upper value of RSTGDP, the initial roll temperature, and
• wherein the initial and actual strip temperatures in the temperature homogenization section are measured by temperature measurement devices.