JPH07126825A - Production of surface finished by hot dip galvanizing of iron structure to enhance adhesion property of coating and its apparatus for production - Google Patents

Abstract

PURPOSE:To enhance the coating adhesion property of the strongly and intermittently injecting cold water to the surface of the iron structure just prior to a cooling stage in hot dip galvanizing of the iron structure. CONSTITUTION:After the iron structure is put into a hot dip galvanizing tank, the iron structure is pulled out of the plating tank and just before the iron structure is put into a cooling tank 1, the cold water of about <=35 deg.C water temp. is strongly and intermittently injected from plural nozzles 2 to instantaneously and temporarily cool the iron structure. The iron structure is put into the cooling water tank 1 (about >=50 deg.C water temp.) immediately thereafter and is subjected to final cooling. As a result, the plating finished surface of the iron structure is a sandy surface to enhance the adhesion property of coating.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a finished surface of molten zinc plating for increasing the adhesion of coating, and an apparatus for producing the finished surface.

[Prior Art] Conventionally, the finish surface of molten zinc plating was normally finished smoothly.

[Problems to be Solved by the Invention] The conventional method has the following drawbacks. (A) Since the finish surface of the molten zinc plating of the iron structure was finished smoothly, when coating on it, the adhesion to the coating was poor and it was easy to peel off. (B) When painting was performed on the surface of the iron structure that had been galvanized, the surface treatment plant had to be newly treated to make the painting easier.
Therefore, extra time and expense were required. The present invention has been made to eliminate these drawbacks and to minimize extra cost and time.

[Means for Solving the Problems] During the cooling process of the molten zinc plating of the iron structure, it is slowly cooled in water whose temperature is usually raised to 50 ° C. or higher in order to finish the surface smoothly. . According to the present invention, cold water is strongly sprayed onto the plating surface immediately before the cooling step to finish the surface rough, and the cooling water is put into conventional cooling water as it is for cooling.
We have also developed manufacturing equipment that performs these processes.

[Operation] The molten zinc plating process of the iron structure is degreasing, washing with water, pickling, washing with water, flux, plating, cooling, and inspection. In the plating process, 450 zinc was placed in the plating tank.
C. to 470.degree. C., heated and melted, put the iron structure made of iron in it for about 2 to 3 minutes, plating it, pulling it up from the plating tank, immediately cooling water at a temperature of 50.degree. C. or more. Cool in and plate the iron structure. In the present invention, a method for roughening the finished surface in order to improve the adhesion with the coating is incorporated into the cooling step to minimize the manufacturing time and improve the production efficiency. That is, the iron structure is lifted from the plating tank, and immediately before entering the cooling water tank (1), cold water having a water temperature of 35 ° C. or less is intermittently jetted strongly from a plurality of nozzles (2) to temporarily cool the iron structure instantaneously. And immediately after that, the cooling water tank (1)
Put in (water temperature 50 degrees C or higher) and perform final cooling. As a result, the plated surface finish of the iron structure was not smooth, and a rough surface was obtained that increased the adhesion to the coating. The main part of the manufacturing apparatus of the present invention comprises a plurality of nozzles (2) and a cooling water tank (1). Usually, iron structures are lifted from a zinc plating tank by hand with a crane or, if the weight is light, a tool is assembled, and then cooled into a cooling water tank. In the present invention, an iron structure suspended by a crane or the like in a plating tank is moved to a position above this apparatus, and the iron structure is gently lowered from above. When the iron structure descends to the positions of the plurality of nozzles (2), it passes through the place where the cold water is intermittently jetted stronger than the plurality of nozzles (2) and is temporarily cooled. At this time, the surface of the iron structure becomes rough. In order to perform the final cooling, the iron structure is further lowered and put into the cooling water tank (1), the cooling is completed, and the cooling process is completed.

[Embodiment] In the present invention, cold water of 35 ° C. or less was intermittently and strongly jetted by a plurality of nozzles (2) to make the finishing surface rough, and cold water was continuously sprayed. Satisfactory results were obtained even when jetting from the nozzle (2).
Even if cold water was sprayed in a mist state, if the amount of water was sufficient, the effect would decrease, but a rough surface could be achieved. The feature of the present invention is to use cold water having a water temperature of 35 ° C. or less, and another feature is that the most effective water injection method is intermittent injection. Regarding the effect of water temperature, the lower the temperature, the better the result. Water of 35 ° C. or higher reduced the effect of rough surface, but increased the number of nozzles and strongly intermittently sprayed water to achieve the required finished surface. The number of nozzles is small for small iron structures, and the number is determined by the size of the cooling water tank and the spray angle of the nozzle itself.
The same can be said for the number of nozzle array stages.

[Advantages of the Invention] According to this manufacturing method, the adhesion between the coating and the surface of the molten zinc plated finish is remarkably increased, and not only the coating lasts long enough but also the coating which has been problematic in the past is partially peeled off. It's gone. Further, the manufacturing apparatus of the present invention is economical because the manufacturing apparatus can be easily modified by installing an enclosure and a nozzle on the existing cooling water tank and piping.

[Brief description of drawings]

1 is a perspective view

Claims (1)

[Claims] 1. A manufacturing method for molten zinc plating of an iron structure, in which cold water is jetted intermittently stronger than a nozzle immediately before a cooling step to finish a rough surface which increases adhesion of coating. In FIG. 1, a manufacturing device comprising (1) a cooling water tank, (2) a nozzle, (3) a pipe, and (4) an enclosure.