JPH04259362A - Manufacture of hot dip metal coated steel sheet and apparatus therefor - Google Patents

Abstract

PURPOSE:To eliminate heating before hot dip metal coating and to stably and continuously manufacture a hot dip metal coated steel sheet of good-quality at the time of applying hot dip metal coating to the surface of a steel sheet by preliminarily applying the electroplating of a metal same as the hot dip metal. CONSTITUTION:The surface of a cold rolled steel sheet 2 finished with annealing is degreased and cleaned by a cleaning apparatus 3, and the steel sheet 2 is introduced into an electroplating tank 4 of a metal same as the hot dip coating metal. Then the steel sheet 2 is used as the cathode, and energizing is executed between the above and the anode to electrically plate the steel sheet 2 with the metal. Next, a hot dip metal coating layer is formed on the surface of the steel sheet in a plating bath 6 charged with the hot dip metal for plating, and the coating weight of the hot dip metal is regulated by a gas wiper 13. If required, the coating metal and Fe in the steel sheet are alloyed, which is cooled by a cooling apparatus 8, and after that, temper rolling 10 is executed. The hot dip metal coated steel sheet free from the need of heating before hot dip metal coating and having stabilization at a certain line speed even in the joint of the steel sheet can be obtd.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to hot-dip metal plated steel sheets,
For example, the present invention relates to a method and apparatus for producing hot-dip galvanized steel sheets and hot-dip aluminized steel sheets.

0002

2. Description of the Related Art A hot-dip galvanized steel sheet will be described below as an example. Hot-dip galvanized steel sheets have excellent corrosion resistance and workability, and are therefore used for automobiles, electrical products, and the like. Conventionally, as a manufacturing apparatus for this hot-dip galvanized steel sheet, as shown in, for example, Japanese Patent Application Laid-Open No. 60-224791,
A continuous hot-dip galvanizing apparatus (CGL) shown in FIG. 2 is common.

[0003] This continuous hot-dip galvanizing equipment has the following features:
The steel plate 2 from the payoff reel 1 is cleaned in the cleaning device 3 on the entry side, then annealed in the non-oxidation heating furnace 12, passed through the snout 14 and galvanized in the hot-dip galvanizing tank 6, and then zinc drawn. The amount of zinc deposited is controlled to a predetermined level by the device 13, and the alloying furnace 7 is heated as necessary.
Alloying heat treatment is performed by ■ Exit side temper rolling mill 1
0 to correct the shape, and then wind it up with a tension reel 11.

However, this hot-dip galvanized steel sheet manufacturing apparatus has the following problems. ■ The non-oxidation heating furnace required before plating is long. ■ It is necessary to change the operating conditions of the non-oxidation heating furnace at the coil joint, but since there is a time delay in the response of the furnace, the yield will decrease by the length equivalent to (response time x line speed). ■
When changing the plate thickness, it is necessary to change the line speed as it is regulated by the furnace capacity. For this reason, it becomes difficult to control the amount of zinc deposited using the zinc squeezing device, and the amount of deposited zinc is off. ■ It is necessary to maintain a reducing atmosphere from the furnace to the hot-dip galvanizing tank using a snout, making it extremely difficult to clean the bath at the bath entry point.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, eliminates the need for the heating furnace, maintains a constant line speed even at coil joints, stabilizes the amount of metal deposited, and improves the stability of the molten bath. It is an object of the present invention to provide a method for manufacturing a hot-dip metal-plated steel sheet and an apparatus therefor, which allows easy cleaning of the entrance part.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides the following steps:
A method for producing a hot-dip metal-plated steel sheet characterized by electroplating the same kind of metal as the molten metal, and an electroplating tank for the same kind of metal as the molten metal upstream of the hot-dip metal plating tank for the steel sheet in the direction in which the steel sheet travels. The present invention provides an apparatus for manufacturing a hot-dip metal-plated steel sheet, which is characterized by the following:

[0007]

[Operation] The present invention will be explained below using the apparatus of the present invention shown in FIG. Steel plate 2 rewound by payoff reel 1
passes through the inlet looper 15 and enters the cleaning device 3. In the cleaning device 3, the steel plate 2 is degreased so as not to interfere with subsequent electroplating.

[0008] Thereafter, the plated steel sheet 2 is electrogalvanized in an electrogalvanizing bath 4. Conventionally, in order to prevent oxidation of the steel sheet surface, the steel sheet is heated to the required temperature while being held in a reducing atmosphere, and hot-dip galvanizing is performed in a hot-dip galvanizing bath 6. However, in the present invention, a predetermined coating amount is applied in advance. Electrogalvanizing has made it possible to produce hot-dip galvanized steel sheets that maintain good adhesion without heating.

In order to find the optimal operating conditions, the present inventors investigated the hot-dip galvanizing property (unplated occurrence rate) and plating adhesion (impact test), the electrolytic galvanizing coating amount, and the penetration rate of the plate into the hot-dip galvanizing tank. The influence of temperature was investigated. The incidence of non-plating was determined visually, and the impact test was performed by ball impact. The survey results are shown in Figures 3 and 4. According to Figure 3, even when the infiltration plate temperature is 50°C, the electrolytic galvanizing coating amount is about 1.0 g/m2 (one side) and the incidence of non-plating is 0.
becomes.

Further, according to FIG. 4, it was found that the plating adhesion was good if the intrusion plate temperature was 50° C. or higher and the electrogalvanized coating amount was 0.8 g/m 2 (one side) or higher. Therefore, it is appropriate to set the electrolytic galvanizing coating amount to 1 g/m2 (one side) and the immersion plate temperature to 50°C. The electrogalvanizing tank has a conductor roll 18 as shown in FIG.
The steel strip 2 supported by the anode 17 is sandwiched between the anodes 17, and a sulfate bath having a pH of about 1.5 is used.

[0011] The electrogalvanizing tank length is determined by the line speed and current efficiency, and the current density is 70A/dm2.
, current efficiency 90%, electrogalvanized coating amount 1g/m2
(one side), the immersion time in the plating bath is approximately 0.5 seconds.
If the maximum line speed is 150 m/min based on the capacity of the zinc drawing device, it will be 1.25 m, which is a very compact device compared to the conventional heating furnace.

Furthermore, since there is no snout 14, the bath entry area is visible from the outside, making it easy to remove dross. By performing electrogalvanizing in this manner, hot-dip galvanizing can be performed without a heating furnace. Thereafter, after alloying heat treatment is performed in the alloying furnace 7 as necessary, the temper rolling mill 1
0 through the tension reel 1 through the exit looper 16.
1.

Next, the production of a hot-dip aluminized steel sheet will be explained. Hot-dip aluminized steel sheets have conventionally been manufactured using the equipment shown in Figure 2, but by using the equipment of the present invention shown in Figure 1, the problems with conventional techniques can be solved in the same way as hot-dip galvanized steel sheets. We were able to. In order to find the optimal operating conditions, the inventors
Regarding hot-dip aluminum plating properties (non-plating occurrence rate) and plating adhesion (impact test), the influence of electrolytic aluminum plating deposition amount and board temperature entering the hot-dip aluminum plating bath 6 was investigated. The survey results are shown in Figures 5 and 6.

According to FIG. 5, even when the immersion plate temperature is 50° C., the rate of non-plating becomes 0 when the coating amount is about 0.5 g/m 2 (one side). Figure 6 shows the relationship with plating adhesion. As a result, it was found that the plating adhesion was good if the infiltration plate temperature was 50° C. or higher and the electrolytic aluminum plating amount was 0.4 g/m 2 (one side) or higher.

[0015] Therefore, it is appropriate that the electrolytic aluminum plating deposition amount is 0.5 g/m2 (one side) and the immersion plate temperature is 50°C. As shown in FIG. 1, the electrolytic aluminum plating tank has a steel strip 2 supported by a conductor roll 18 and an anode 17.
It is composed of a chloride bath with a pH of 1.5.
Use something of a certain degree.

[0016] The electrolytic aluminum plating tank length is determined by line speed and current efficiency, and the current density is 70A/
dm2, current efficiency 90%, electrolytic aluminum plating coating weight 0.5 g/m2 (one side), the immersion time in the plating bath is 0.3 sec, and if the line speed is 150 m/min based on the capacity of the aluminum squeezing device, 0.5 g/m2 (one side).
The length is 75m, so a very compact device is required.

Furthermore, since there is no snout, the bath entry area can be seen from the outside, making it easy to remove dross. By performing electrolytic aluminum plating in this manner, hot-dip aluminum plating can be performed without a heating furnace. Thereafter, after alloying heat treatment is performed in an alloying furnace 7 as necessary, the material is passed through a temper rolling mill 10 and wound onto a tension reel 11 via an outlet looper 16.

The present invention will be explained below in comparison with the prior art. 1) Even when changing the coil joint or coil size, there is no need to change the line speed due to heating furnace rate control, so the coating amount can be controlled stably. 2) Since there is no snout, it is easy to remove dross from the part of the plated steel sheet that has entered the molten bath, reducing dross defects. 3) Plating adhesion and non-plating occurrence rate are both at the same level as the conventional method.

[0019]

EXAMPLES Example 1 A hot-dip galvanized steel sheet was manufactured using the apparatus of the present invention whose system diagram is shown in FIG. The target amount of zinc plating was 45g/m2 (one side), and the electroplating was carried out in a zinc sulfate bath (pH approximately 1.
5), temperature 55℃, current density 70A/dm2, coating amount 1g/m2 (single side), hot dip galvanizing Al=0.1
4% by weight (bath temperature 475°C). Example 2 Same as Example 1 except that an aluminum chloride bath (pH about 1.5) was used instead of the zinc sulfate bath in Example 1, and hot-dip aluminum plating (bath temperature 670°C) was used instead of hot-dip galvanizing. And so. Comparative Example Using the conventional apparatus whose system diagram is shown in Figure 2, in place of the electroplating tank in Example 1, a 10% H2 atmosphere, 80
The same procedure as in Example 1 was conducted except that a 0° C. heating furnace and a snout were used.

The test results for Examples 1 and 2 and Comparative Examples are shown in Tables 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Effects of the Invention] By performing electroplating using an electroplating bath of the same type of metal as the molten metal, instead of heating using a conventional heating furnace that was performed before molten metal plating, 1
) Even when changing coil joints or coil sizes, the line speed can be kept constant, allowing stable control of the amount of plating deposited. 2) A snout part is no longer required, and dross can be easily removed at the part that enters the bath, reducing dross defects. 3) Since an electroplating tank is used instead of a heating furnace, the equipment has become more compact.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of the device of the present invention.

FIG. 2 is a system diagram of a conventional device.

FIG. 3 is a graph showing the relationship between electrogalvanizing deposition amount and non-plating occurrence rate.

FIG. 4 is a graph showing the relationship between electrogalvanizing coating weight and plating adhesion.

FIG. 5 is a graph showing the relationship between the amount of electrolytic aluminum plating and the rate of occurrence of non-plating.

FIG. 6 is a graph showing the relationship between electrolytic aluminum plating deposition amount and plating adhesion.

[Explanation of symbols]

1 payoff reel
2 Steel plate 3 Cleaning device
4 Electroplating tank 6 Hot dip metal plating tank
7 Alloying furnace 8 Cooling device
9 Metal deposition meter 10 Temper rolling mill
11 Tension reel 12 Non-oxidation heating furnace
13 Metal drawing device 14 Snout
15 Inlet looper 16 Outlet looper
17 Anode 18 Conductor roll

Claims (2)

[Claims] 1. A method for manufacturing a hot-dip metal-plated steel sheet, characterized in that, prior to hot-dip metal plating on the steel sheet, electroplating is performed with a metal of the same type as the molten metal. 2. An apparatus for manufacturing a hot-dip metal-plated steel sheet, characterized in that an electroplating tank for the same type of metal as the molten metal is disposed upstream of the hot-dip metal plating tank for the steel sheet in the direction in which the steel sheet travels.