Method and device for cooling a steel strip travelling in a continuous line cooling section

A cooling process for a steel strip (1) running through the cooling section (2) of a continuous line, comprising projecting onto the steel strip a projecting solution, said projecting solution being a liquid solution or a mixture of a liquid solution and a gas,

• wherein the liquid solution has a formic acid concentration of between 0.1% and 6% by mass;
• wherein the projecting solution has a pH between 1.5 and 3;
• wherein the process further comprises recirculating the projecting solution after projection onto the steel strip and also including a continuous or periodic check of the projecting solution prior to being projected, said check including a measurement of at least one physico-chemical datum of the said solution—from the group consisting of pH, density and formic acid concentration, or a combination of these physico-chemical data, and, when this measurement does not fall within a predetermined range of tolerance, a predetermined volume of the projecting solution is drawn off and the same predetermined volume of a formic acid solution is injected into the projection unit (13), said predetermined volume of formic acid solution having a concentration of formic acid such that the projecting solution to be projected is of a concentration of formic acid between 0.1% and 6%;
• and
• wherein the projecting solution drawn off is treated through oxidation with oxygenated water, then filtered to extract hydroxides of iron (III) and other alloying elements.