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Characteristics and solutions of under-pickling on the surface of packaging steel strip
by：Hongmei
2021-03-15
(1) Defect features: the surface of the packaging steel strip shows horizontal black stripes. Often accompanied by a black floating gray layer, horizontal fine lines similar to 'head-up lines' are distributed in strips or sheets on the surface of the packaging steel strip.
(2) Cause
①The iron oxide film on the surface of the packaging steel strip is not cleaned by pickling, but is pressed into the plate surface during cold rolling.
② Poor operation of the scale breaking machine, so that the iron sheet is not sufficiently loosened and peeled off, which affects the pickling effect.
③Improper pickling process, such as inconsistent acid concentration, low temperature, high ferrous iron, short pickling time, fast speed, etc.
④ The packaging steel has a large sickle bend, wave shape, or the packaging steel belt is stretched straight to expose the acid surface due to excessive curling tension.
⑤ There is oil stain on the surface of the packaging steel strip, which prevents acid erosion.
⑥Alloy steel and cold rolled materials are prone to under-pickling due to the compact structure of the oxide scale.
(3) Prevention and elimination methods
①Operate the scale breaking machine correctly. Improve the scale breaking effect.
② Adjust the temperature and concentration of the acid solution, and control the pickling speed according to the steel specifications and the shape of the incoming plate.
(4) Inspection and judgment: According to the specific conditions of the product, slight under-pickling can be judged as 3 groups of high-quality boards, or qualified products in the national standard ordinary boards, and generally judged as partial standard ordinary boards Qualified products in the middle, especially serious ones are judged as scrap products.
(2) Cause
①The iron oxide film on the surface of the packaging steel strip is not cleaned by pickling, but is pressed into the plate surface during cold rolling.
② Poor operation of the scale breaking machine, so that the iron sheet is not sufficiently loosened and peeled off, which affects the pickling effect.
③Improper pickling process, such as inconsistent acid concentration, low temperature, high ferrous iron, short pickling time, fast speed, etc.
④ The packaging steel has a large sickle bend, wave shape, or the packaging steel belt is stretched straight to expose the acid surface due to excessive curling tension.
⑤ There is oil stain on the surface of the packaging steel strip, which prevents acid erosion.
⑥Alloy steel and cold rolled materials are prone to under-pickling due to the compact structure of the oxide scale.
(3) Prevention and elimination methods
①Operate the scale breaking machine correctly. Improve the scale breaking effect.
② Adjust the temperature and concentration of the acid solution, and control the pickling speed according to the steel specifications and the shape of the incoming plate.
(4) Inspection and judgment: According to the specific conditions of the product, slight under-pickling can be judged as 3 groups of high-quality boards, or qualified products in the national standard ordinary boards, and generally judged as partial standard ordinary boards Qualified products in the middle, especially serious ones are judged as scrap products.
