Surface treatment of metal strip
AssigneeCentre de Recherches Metallurgiques-Centrum voor Research in de Metallurgie
InventorsPhilippe Paulus, Jules Hancart
Life of this patent
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Abstract
Metal strip, particularly steel strip, is heated to above 250.degree. C. and quenched in a phosphating bath, at 80.degree. C. or more, containing one or more phosphates of the type Me (H.sub.2 PO.sub.4).sub.n, where Me=Zn, Ni, Mn, or an alkali metal, at a concentration of 1 to 20 g/l.
Claims17
A method of treating the surface of a steel strip and coating it with a phosphate layer, during thermal treatment which comprises quenching after recrystallization, the method comprising the following steps:
- (a) heating the strip to a temperature higher than the recrystallization temperature and holding at this temperature;
- and
- (b) quenching the strip in a phosphating bath having a temperature of at least 80.degree. C. and containing at least one phosphate of the type Me(H.sub.2 PO.sub.4).sub.n, where Me is selected from Zn, Ni, Mn, and alkali metals, at a concentration in the range 1 to 20 g/l.
A method of treating the surface of a steel strip and coating it with a phosphate layer, during thermal treatment, comprising introducing the strip into a first hot aqueous solution in order to rapidly cool it after recrystallization treatment and then introducing the strip into a second hot aqueous solution in order to finally cool it after a thermal overaging treatment, the second aqueous solution is a phosphating bath having a temperature of at least 80.degree. C. and containing at least one phosphate of the type Me(H.sub.2 PO.sub.4).sub.n, where Me is selected from Zn, Ni, Mn, and alkali metals, at a concentration in the range 1 to 20 g/l.
Dependencies are inferred from the claim text.