Method for controlling zinc flow ripples of heavy-weight material and thick-coating hot-galvanizing products

Abstract

The invention relates to the field of hot galvanizing, in particular to a method for controlling zinc flow ripples of heavy-weight material and thick-coating hot-galvanizing products. The method is characterized in that aiming at the reasons caused by the defect of zinc flow ripples, the temperature of an injection medium is adjusted, the cooling capacity of the injection medium to strip steel is improved, and meanwhile technological parameters of an air knife are optimized, so that the purpose of controlling the defect of the zinc flow ripples is achieved; the specific parameters are selected as follows: 1, before production, indoor temperature of a draught fan is within the range between 0-10 DEG C; 2, parameters of the air knife are optimized: the distance between the lip of the air knife and the liquid surface is 600-1,000 mm, the distance between the lip of the air knife and the strip steel is 15-30 mm; according to the unit speed and coating depth, the pressure of the air knife is 100-300 mbar. Compared with the prior art, the method has the benefits as follows: surface quality of heavy-weight material and thick-coating hot-galvanizing products of which the heavy-weight material is not less than 2.0 mm and the thick coating is not less than 220 g / m<2> is effectively controlled, and the percent of pass is improved to 96.2 percent from 90.5 percent before implementation.

Description

technical field [0001] The invention relates to the field of hot-dip galvanizing, in particular to a method for controlling zinc flow lines of hot-dip galvanized products with thick material and thick coating. Background technique [0002] The continuous hot-dip galvanizing line for strip steel usually adopts air blowing method to control the thickness of the coating, that is, it is controlled by an air knife. The air knife is not only to control the adhesion of the coating, but also an important equipment to determine the surface quality of the product. In zinc, the main factors affecting the thickness of the galvanized layer are: air knife pressure, air knife distance, height of air knife from zinc liquid surface, and air knife angle. [0003] After the strip comes out of the zinc pot and before reaching the air knife, the coating is in a liquid state, and the excess zinc liquid flows from top to bottom under the action of gravity, and the liquid zinc sticking to the surfa...

AI Technical Summary

Problems solved by technology

[0003] After the strip comes out of the zinc pot and before reaching the air knife, the coating is in a liquid state, and the excess zinc liquid flows from top to bottom under the action of gravity, and the liquid zinc sticking to the surface of the strip decreases as the distance from the zinc liquid surface increases, hindering The air flowing in the zinc liquid will reduce the temperature of the coating, and after the coating reaches the position of the air knife, it will mix with the air sprayed by the air knife to reduce the liquid zinc on the strip and cool it at the same time, and the excess zinc will accumulate under the action of the air flow Corrugations are formed; after cooling with mixed air, the surface temperature of the strip steel drops below 419°C and solidifies, forming "zinc corrugations", such as figure 1 As shown, this defect refers to the horizontal stripes of the protruding zinc layer that appear on the surface of the strip. The length and spacing of the stripes are not equal. When the situation is serious, it will form a defect that resembles water ripples. "The coating moiré, zinc undulation, and zinc protrusion that we usually say belong to this kind of defect, but the severity and surface shape are different. Zinc flow ripple is actually the uneven thickness of the longitudinal coating on the surface of the strip, and the surface protrusion The part feels hand-touched by hand, and the thickness of the coating is larger than other parts. Due to the unevenness of the strip surface, it will seriously affect the surface quality of the strip, and cannot meet the inspection standards of high-level surfaces and the requirements of users for surface quality.

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