Technological process of pickling treatment of strip steel continuous pickling unit

The pickling treatment of the strip steel continuous pickling unit is widely used to remove the oxide scale on the surface of the cold-rolled slab, that is, the hot-rolled sheet. For example, the scale of hot-rolled steel needs to be removed before surface treatment such as phosphating or coating; surface pretreatment of welded pipes before galvanizing or other hot-dip galvanizing and electroplating; surface treatment of annealed steel before cold drawing, such as Pipes, profiles and wires; descaling and similar treatments before electroplating and brush plating in the production of stainless and special steels. At present, pickling is still a process used in steel production and steel surface treatment, regardless of environmental risks. However, the pickling process of the strip steel continuous pickling unit also brings the following problems:

(1) Large consumption of steel and acid In the pickling process, some iron sheets are mainly removed by the chemical reaction between the acid and the iron sheets and the dissolution of the corresponding metal oxides. For example, when pickling steel with sulfuric acid, the iron oxide scale should be removed by the stripping action of hydrogen bubbles generated by the chemical reaction between the acid and the steel. Therefore, a large amount of acid is inevitably consumed during the pickling process. Although the use of pickling in the pickling process can reduce the metal consumption of the steel, large amounts of metal and iron are still lost.

(2) May reduce the physical properties of steel: During the pickling process, a chemical reaction occurs between metallic iron and acid to generate hydrogen. Since the hydrogen chemical content in the pickling solution is higher than that in the pickling steel, the generated hydrogen will penetrate into the steel and accumulate, resulting in hydrogen embrittlement, which affects the mechanical properties of the steel or subsequent processing

(3) It will bring a series of environmental pollution problems: the pickling process is used to treat the surface of steel or parts. Due to the differences in steel varieties, product specifications and production scales, there are great differences in production equipment and production environments. For example, the sealing of pickling tanks, corrosion of production equipment, ventilation and exhaust of pickling workshops, acid mist discharge and treatment, sewage treatment and discharge, etc., there are great differences in treatment methods and treatment levels. This will bring many problems to environmental protection, which need to be dealt with and solved one by one.