JPS6058786B2 - Cooling method and equipment for hot-dip plating of steel structures, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling method and apparatus for hot-dip plating of large steel structures, typically over 10 meters in length.

Large structures such as bridges are painted on the surface to prevent construction.
Furthermore, although painting was carried out regularly, it had the drawback of requiring a great deal of labor and expense. Recently, surface treatment methods such as hot-dip plating have attracted attention from the viewpoint of durability.
It is becoming popular. This hot-dip plating method is a plating method that creates a metal coating layer on the surface of a steel material or steel structure that has been cut and drilled by immersing it in molten metal such as zinc or tin.The general process is as follows: Pre-treatment process such as degreasing and cleaning, flux treatment process to smooth the progress of plating reaction, molten metal bath process to create a diffusion coating layer on the surface layer by immersing it in molten metal, and bringing the plated item to room temperature. It consists of a cooling process. The temperature of the above-mentioned molten metal bath is, for example, 450° C. or higher in galvanizing, and the cooling process is usually performed by immersion in cold water. However, this hot-dip plating method has the disadvantage that the steel material or steel structure may be bent, twisted, or otherwise deformed. This is because the plate thickness, cross-sectional area, etc. of each part are different, so naturally there is a difference in heat capacity, and the temperature difference when cooling this causes thermal stress. Conventionally, deformation due to cooling was considered unavoidable. It was considered. However, deformation of steel structural members is not preferable because it poses a problem, especially with respect to load-bearing capacity, and new strains are generated by forcibly assembling the structure using deformed objects.

The present invention has been made in view of the above, and provides for the following:
Since the cooling water level reaches the cooling water level from the bottom of the structure toward the top, there is a difference in the cooling start time depending on the height of each part, resulting in temperature differences between each part.2 Even if the structure is instantly immersed in the water tank, each part It is an object of the present invention to provide a cooling method and device that allows each part of a structure to be cooled uniformly and that does not cause distortion due to temperature differences. It is.

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the apparatus of the present invention.

Cooling tank 1 has a width of approximately 2 TrL, a length of approximately 15 m, and a depth of approximately 2 m.
This is a rectangular tank, usually located adjacent to the plating tank.

A girder holder 2 for receiving a girder is provided at an appropriate position on the inner wall of the cooling tank 1. This girder pedestal 2 is rotated manually or by a motor around a vertical axis, and is placed in the girder support state shown in Fig. 1 and in the retracted state in which it is in close contact with the inner wall after 900 turns. Can be switched. Water spray nozzles 3...3 that spray water into the water tank along the tops of the left and right side walls of the cooling tank are arranged in a line, and a valve 4...4 is provided for each nozzle, and several nozzles are grouped together. Each group is connected to a water sprinkling pipe 6 via a manual valve 5, the inlet of this water sprinkling pipe 6 is connected to the discharge port of a pump 8 via a three-way electromagnetic valve 7, and the outlet of the water sprinkling pipe 6 is connected to a motor valve 9. It is released into the aquarium through the water. Further, the branch port of the three-way electromagnetic valve 7 is also discharged into the water tank. An intake port 10 at the bottom of the cooling tank 1 is connected to a water intake port of a pump 8, so that water is returned. In addition,
A flow meter 11 and a pressure gauge 12 are provided at the inlet of the water sprinkler pipe 6, and a flow meter 13 is provided at the outlet of the motor valve 9. Motor valve 9, three-way solenoid valve 7 and pump 8
The valves 4, . . . 4 and manual valves 5, .
Ru. There is a crane above the plating tank and the cooling tank 1, and the object to be plated G is suspended from the plating tank to the cooling tank 1.
The specimen is transferred to a cooling tank, immersed in a suspended state in a cooling tank, and then pulled out after cooling.

For example, electric resistance type temperature sensors 15...15 are attached to the surface of each part of the object G to be plated, and the temperature of each sensor is digitally displayed by being transmitted to the operation panel 14. Next, how to use this device will be explained with reference to FIGS. 2 and 3.

In advance, the three-way valve 7 is switched to the direct discharge side into the water tank to fill the water tank with cooling water, and the opening and closing of the manual valve 5 is adjusted according to the length of the object to be plated to be cooled.

Further, the girder holder 2 is kept in the girder receiving state. Next, by operating the crane, the object G to be plated is placed on the girder pedestal 2 as shown in Fig. 2.
Put it on top. What should be noted here is that the device should be placed in a position where the overall height is the lowest, that is, a position where the time difference between each part reaching the cooling water surface is as small as possible. Further, it is preferable that the plate be mounted such that the parts having a large plate thickness and requiring cooling are located on both the left and right sides. Next, temperature sensors 15 are installed at several locations on each part of the object to be plated, such as the upper flange, lower flange, and web.
・Install 15. Next, the pump 8 is activated to start watering. What is important here is the temporal control of the pressure applied to the object to be plated by water spraying.

In other words, the high-temperature zinc/lead plating layer is soft, and high-pressure spraying will cause discoloration and pockmarks on its surface, so the water pressure should be lowered when starting watering to reduce the pressure applied to the surface of the plated object. After cooling down and confirming that the temperature measured by the temperature sensor on the surface has become lower than the melting point of zinc, gradually increase the amount of water sprinkled by tightening the motor valve 9 while watching the water pressure gauge. In addition, spray water uniformly over the entire length of the object to be plated to avoid temperature differences between parts, and spray more water on areas with large cross-sectional areas, such as the upper and lower flanges, and avoid areas with small cross-sectional areas. For example, the direction and range of water sprayed by the nozzles 3...3 are set in advance so that the web is not sprayed with water or only a small amount of water is sprayed, and each part in the same cross section is uniformly cooled at a uniform temperature. .By performing watering in this way,
When the measured value of the temperature sensor reaches the predetermined temperature, water sprinkling is stopped, the object to be plated is lifted up by crane operation, the girder pedestal 2 is switched to the retracted state, and the object to be plated is placed in the cooling tank as shown in Fig. 3. Cool by immersing it in the air.

After cooling, it is lifted up and transported to a predetermined location. The device of the present invention can further automate a series of processes using a central control device such as a microcomputer.

Further, temperature measurement etc. can also be carried out manually.
According to the present invention, deformation and distortion in hot-dip plating of large copper structures can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the apparatus of the present invention, and FIGS. 2 and 3 are perspective views illustrating how to use the above embodiment. 1... Cooling water tank, 2... Girder pedestal (holding device), 3... Water nozzle, 6... Water sprinkling pipe, 7... Three-way solenoid valve, 8●●●●●●pump, 9●●●●◆●motor valve, 15...Temperature sensor.

Claims (1)

[Scope of Claims] 1 Pre-cooling only a predetermined portion of the object to be plated after the molten metal bath by spraying water, and immersing the entire object to be plated into a cooling water tank after the temperature of each part has decreased to a predetermined value or less. Features: Cooling method for hot-dip plating of steel structures, etc. 2. A cooling method for hot-dip plating of steel structures, etc. according to claim 1, characterized in that the object to be plated is immersed in a cooling water tank in a state where the height of the object to be plated is the lowest. 3. A holding device for holding the object to be plated after the molten metal bath in a cooling water tank, a water spraying device for selectively sprinkling water only on a predetermined portion of the object to be plated, and A cooling device for hot-dip plating of steel structures, comprising a temperature measuring device for measuring the temperature of each part of the structure, and an immersion device for suspending the object to be plated, immersing it in the cooling water tank, and pulling it up.