Technology for producing strip steel continuous hot-dip galvanized thin coating

Abstract

The invention discloses technology for producing a strip steel continuous hot-dip galvanized thin coating. Excessive zinc solution is scraped by an air knife after the strip steel is discharged from a zinc pot. The technology can guarantee the surface quality of the thin coating, is convenient to be switched with common coatings, and meets the production requirements of different coatings. The technology comprises the following parameters: the zinc solution comprises 0.14 to 0.18 weight percent of effective aluminum, 0.015 to 0.03 weight percent of Fe and the balance of Zn, wherein the temperature of the zinc solution is between 455 and 465 DEG C, the temperature for putting the strip steel into the zinc pot is between 410 and 470 DEG C, the cutting edge gap in the middle of the air knife is 1.0 to 1.3mm, a distance from the air knife to the strip steel is 7 to 12mm, the height of the air knife is 150 to 380mm, and the wind pressure of the air knife is 20 to 45KPa. The technology is suitable for producing thin-coating galvanized plates.

Description

technical field [0001] The invention relates to a hot-dip galvanizing process, in particular to a strip steel continuous hot-dip galvanizing thin coating production process. Background technique [0002] Galvanizing is an economical and effective method that is often used for steel plate corrosion protection. Among them, the hot-dip galvanizing method is commonly used, that is, the strip steel is continuously hot-dip galvanized. After the strip steel is cleaned and annealed, it enters the zinc pot containing molten zinc liquid with a clean surface. After the strip steel comes out of the zinc pot, the surface is attached A layer of hot zinc liquid. At this time, the surface of the strip steel is a pure zinc layer, and the action of aluminum in the steel base and zinc liquid produces Fe 2 AL 5 The middle layer is used for adhesion to ensure the adhesion between the zinc layer and the strip steel. At the same time, the air knife blows the airflow with a certain momentum to ...

AI Technical Summary

Problems solved by technology

However, its cost is high, the environment is polluted, and it is very different from the hot-dip galvanizing unit and process, so it is not comparable

However, it is difficult to control the thickness of the thin coating and the surface quality of the coating by using an air knife to control the thickness of the coating in the continuous hot-dip galvanizing process of the strip steel.

In the published document with the application number 200710092982.1, a hot-dip galvanizing process with low alloy consumption is disclosed, but the distance between the air knife and the steel strip is relatively large, reaching 50mm, and there are problems of low zinc scraping efficiency and a lot of zinc dross , and will make the galvanized layer prone to defects such as bright spots and zinc flow lines, which will affect the surface quality of the product

The application number is 200810197544.6, which adopts a method of adding mixed rare earths such as Ce and La to the zinc pot to improve the fluidity of the zinc solution. The aluminum content is controlled in the range of 0.9% to 1.5% by weight, which is the same as that of ordinary hot-dip plating. Compared with the zinc process, the composition of the zinc pot is quite different. The effective aluminum content of the common coating zinc solution is generally around 0.18-0.2%, and it is very difficult and long to realize the conversion from 0.18-0.2% to 1%. Therefore, its interchangeability is poor

In addition, since the aluminum content in the previous production process was obtained by ordinary chemical tests, it is the total aluminum in the zinc pot, which includes the dissolved aluminum in the zinc liquid and the aluminum condensed in the zinc slag. Completely and truly reflect the aluminum content in the zinc solution