JPS6112988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming an anti-plating film that does not easily react with molten metal on the unplated surface of the plated material, that is, a steel strip, and then coating the entire plated material. The present invention relates to a molten metal plating method that involves immersion in a molten metal plating bath, and particularly to a molten metal plating method suitable for use in manufacturing single-sided continuous galvanized steel sheets.

Various corrosion-resistant films are often formed on the surface of a steel plate for the purpose of imparting corrosion resistance to the steel plate. In this case, it is common to form a corrosion-resistant film on both sides of the steel plate. However, for products that are painted after plating, such as automotive steel sheets, applying paint to the plated surface results in poor image clarity and a significant reduction in commercial value. Further, for example, the weldability of galvanized steel sheets is not good because the difference between the melting point and boiling point of zinc is small, the thermal conductivity is high, and the electrodes are easily contaminated. As mentioned above, imparting corrosion resistance to the surface of a steel sheet has properties that conflict with weldability and image clarity after painting. Therefore, for automobile steel sheets, steel sheets for home appliances, etc., so-called single-sided plated steel sheets are used, in which only one side of the steel sheet is plated to provide corrosion resistance, and the other side has improved paintability and weldability. It is being used.

As a method for manufacturing such single-sided plated steel sheets, there is a method using electroplating, but the thickness of the plated layer obtained by electroplating is generally small and cannot provide sufficient corrosion resistance. In addition, in order to produce products with a large amount of plating using the electroplating method, it is necessary to reduce the threading speed.
This is not preferable because productivity is poor and costs are high.

On the other hand, the hot-dip plating method is widely used because a large amount of plating can be easily obtained and it is advantageous in terms of corrosion resistance, cost, etc. However, since it is difficult to melt-weld steel strips on one side, a method has been adopted in which an extremely thin plating layer is formed on one side, and after applying so-called differential thickness plating, the plating film on the unnecessary side is difficult to peel off. However, it is extremely uneconomical. The method for manufacturing single-sided plated steel sheets using this hot-dip galvanizing method is as follows:
As proposed in Japanese Patent Publication No. 42-24966, one side is subjected to phosphate treatment and then plated, as proposed in Japanese Patent Publication No. 39-7112 or Japanese Patent Publication No. 39-4522, There are several known methods, such as applying water glass to prevent plating, or applying various coating agents containing silicone resin as the main component, as proposed in Japanese Patent Publication No. 51-35174 and Japanese Patent Publication No. 51-8101. It is being However, in a plating line that has heat treatment equipment such as a reduction furnace within the line,
Since steel sheets are exposed to high temperatures of approximately 700℃, treatment agents such as phosphates and water glass cause decomposition and decomposition, resulting in partial peeling and complete one-sided plating. The plating bathtub becomes contaminated with phosphates, water glass, etc. In addition, the uniformity of the silicone resin film is affected by the heat, and
It is difficult to obtain complete one-sided plating, and
It is disadvantageous in that it is expensive. Another option is to use an oxide film as an anti-plating film, but if the oxide film is too thin, the anti-plating ability will be insufficient and it will not be possible to obtain a completely plated steel sheet on one side. When the film becomes thicker, the film tends to peel off due to deformation of the steel plate, etc., which not only makes it impossible to obtain a completely plated steel plate on one side, but also causes problems such as contamination of the plating bath.

An object of the present invention is to provide a plating method that can simply and reliably apply a high-quality molten metal plating film.

The present invention provides a single-sided molten metal plating method for steel strip in which a non-staining agent film is formed on one side of the steel strip and then the steel strip is immersed in a molten metal bath, in which liquid unsaturated hydrocarbons are vaporized. , a method of spraying soot generated by incomplete combustion of the vaporized unsaturated hydrocarbon gas onto one side of a steel strip and making it adhere to form the anti-staining agent, the method comprising: A method for plating a steel strip with a single-sided molten metal, characterized in that the liquid unsaturated hydrocarbon is vaporized by a formed heat source.

The present inventors succeeded in discovering this method by investigating the following points. First, soot as a stain-resistant agent has no physical or chemical affinity for molten metal;
It is possible to completely prevent molten metal from adhering to the steel plate. Moreover, in addition to this, it can be easily removed by a mechanical method after plating is completed. Another point is that liquid unsaturated hydrocarbons, which are the raw material for soot, are the most suitable for forming a soot film, that is, the combustion rate can be easily controlled, and the rate of formation of a non-staining agent film is easy,
It can be selected arbitrarily, is easy to incompletely burn, and has a relatively high carbon atom content, so it generates more soot than other raw materials, and can form a stain-resistant film at a particularly high speed. Not only is it easier to handle than other raw materials, but it is also abundant and easily available.

In the present invention, the liquid unsaturated hydrocarbon is at room temperature,
Things that are liquid at around normal pressure, such as benzene, toluene, xylene, phenol compounds,
Quinoline, naphthalene compounds, light oil or heavy oil, etc. are useful. Also useful are aliphatic unsaturated hydrocarbons such as vegetable oils such as coconut oil or animal oils such as whale oil.

In the present invention, in particular, the incomplete combustion is characterized in that it is easy to adjust the mixing ratio with oxygen or air to achieve incomplete combustion, that is, to easily prepare a mixed gas of liquid unsaturated hydrocarbon and an oxygen source. It has advantages such as easy control of the degree (speed) and easy supply to the burner.

The soot film used as a non-staining agent in the present invention does not peel or fall off even when exposed to high temperatures in a reducing furnace or non-oxidizing furnace for surface cleaning or refining. There is no adhesion and a complete single-sided plated steel plate can be manufactured at low cost. In such a method, it is optimal to form a soot film on the steel strip after both sides of the steel strip are cleaned by electrolytic degreasing or alkaline cleaning, which is a normal degreasing method, but it is not necessarily necessary to degrease both sides. Even if only the plated surface is cleaned and a soot film is formed on the unplated surface with some amount of rolling oil adhering to it, there is almost no problem and the effects of the present invention are exhibited. In addition, in the Senzima type plating line, the purpose is achieved by burning off deposits on the steel plate in an oxidizing furnace and then forming a soot film in a reducing or non-oxidizing atmosphere. The thickness of the soot film is desirably 5 μm or more, but it can be made as thin as about 2 μm in order to increase the rate of formation of the soot film.

In the present invention, after forming a non-plating agent film on one side of a steel strip, this is introduced into a plating bath while maintaining a non-oxidizing or reducing atmosphere in a heated atmosphere. Molten metal does not adhere to the surface on which the glazing agent film is formed, and a completely single-sided plated steel sheet can be manufactured. After plating, if necessary, the soot film can be easily removed by mechanical brushing, etc., and a beautiful single-sided plated steel plate can be obtained. As described in the examples, the single-sided galvanized steel sheet according to the present invention exhibits extremely excellent effects in all types of plating, including hot-dip galvanizing, molten aluminum, and hot-dip galvanizing.

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3, liquid unsaturated hydrocarbons (hereinafter simply abbreviated as liquid hydrocarbons) are shown in advance.
The liquid hydrocarbons supplied from the tank 14 containing
9 and stored in a tank 20 kept at a temperature that maintains a gaseous state. On the other hand, continuous furnace 18
The steel strip 3 passing through the snout 1 is guided by a deflector roll 2 into the snout 1 which maintains a reducing atmosphere.
Then, it is introduced into the masking chamber 6. In the masking chamber, the hydrocarbon vapor accumulated in the tank 20 is sent out by opening the valve 21, and the auxiliary gas supply valve 7 is adjusted so that the amount of soot generated is maximized, and mixed with the liquid hydrocarbon vapor, burner 9
is supplied to cause incomplete combustion, and the generated soot 10 is attached to one side of the steel strip 3. This steel strip is introduced into a molten metal plating bath 4 and plated, and a predetermined single-sided plating is achieved by adjusting the amount of coating with a plating roll 5. On the other hand, the combustion exhaust gas from the masking chamber is led to a bag filter 11, and after separating soot in a filter 12, it enters a gasifier 13. There, the liquid hydrocarbon supplied from the tank 14 is heated by the heat exchanger 15 and becomes a gaseous body. The heat-exchanged exhaust gas passes through the exhaust fan 16 and is exhausted from the exhaust pipe 17. The liquid hydrocarbon vapor that has become a gas is stored in a tank 20 by a gas pump 19. After the masking process is started, the electric heater 8 of the gasifier is turned off, the combustion exhaust gas is used to gasify the liquid hydrocarbons, the masking process is continued continuously, and one side is plated.

In the present invention, before starting masking treatment and gasification using combustion exhaust gas, when partially gasifying hydrocarbons, in addition to heating with an electric heater, heating with steam or an auxiliary boiler is used. It's okay. Furthermore, gasification by ultrasonic vibration by providing an ultrasonic vibrator in the gasifier is also an effective method. In addition, an auxiliary burner is installed in the masking chamber, and the masking process is first performed using a hydrocarbon gas such as acetylene gas, and the gasification is performed simultaneously using exhaust gas to generate liquid hydrocarbon vapor. After accumulation, the auxiliary burner is stopped, and then the auxiliary burner is stopped. , the object of the present invention can be achieved even if masking is performed only by self-cycles. Although air is generally used as the auxiliary combustion gas, a mixed gas in which the blending ratio of N ₂ and O ₂ is appropriately changed may also be used.

With this method, while maintaining a non-oxidizing atmosphere in the masking chamber, it is possible to easily adjust the mixing ratio of liquid hydrocarbon vapor with the auxiliary gas to maximize the amount of soot generated, and it is possible to create completely single-sided plated steel sheets. can be manufactured continuously.

Example 1 Using a continuous plating device shown in Fig. 2, a cold rolled steel strip 3 with a width of 150 mm and a thickness of 0.5 mm was coated with rolling oil etc. on the surface of the steel strip in an oxidation furnace 22 at a line speed of 30 m/min. The kimono is removed by incineration at approximately 650℃, and then the atmosphere is
The oxides on the surface of the steel strip were reduced and activated in a reduction furnace 18 maintained at 20% H ₂ and 80% N ₂ . Next, in the masking chamber 6, the non-plated side of the steel strip is coated with the following method.
A soot film with a thickness of about 10 μm was formed, immersed in a hot-dip galvanizing bath 4 maintained at 460°C, and after cooling with a plating roll 5 to adjust the amount of zinc coating to 1 ^oz /ft ² , a soot film was formed. The soot film on the non-plated surface was removed using a single roll 23. As a result, a beautiful and perfect single-sided galvanized steel plate was obtained. Here, to form a soot film, benzene is used as a liquid hydrocarbon, and first, 30% of benzene is always present in the gasifier 13, and the benzene is heated by a 2KW electric heater 8 installed in the device. A tank 20 with a capacity of 1 m ³ is generated by a gas pump 19.
It was stored until the pressure reached 1.5Kg/ ^cm2 . The tank is
The temperature was maintained at 85°C to 90°C. Next, open the gas supply valve 21 to adjust the benzene vapor flow rate to 2/min, and open the air supply bulk 7 to adjust the air flow rate to 6/min to create a mixed gas, which is then incompletely combusted by the burner 9 to generate soot. A soot film was formed. Further, the electric heater was turned off 5 minutes after the start of the treatment, and thereafter, the exhaust gas was used to generate benzene vapor using the heat exchanger 15 to continue forming the soot film.

Example 2 In the same manner as in Example 1, toluene was used as the liquid hydrocarbon, the toluene vapor flow rate was adjusted to 3/min, and the air flow rate was adjusted to 7/min to form a mixed gas, which was then incompletely combusted and applied to the non-plated surface of the steel plate. Approximately 12μ of soot film
After forming it to a thickness of m, hot-dip galvanizing it,
A beautiful and perfect single-sided plated steel plate was obtained. in this case,
The heating temperature of toluene is 115℃, and the temperature of the tank is 110~
It was held at 115°C.

Example 3 Using the equipment shown in Figure 3, the line speed was 30 m/
A cold-rolled steel strip 3 with a width of 150 mm and a thickness of 0.5 mm is burned and removed in an oxidation furnace 22, and then the atmosphere is changed to H ₂ 20
%, N ₂ The oxides on the surface of the steel strip were reduced and activated in a reducing furnace 18 maintained at 80%. Next, in masking room 6, approximately 10 μm is applied to the non-plated surface of the steel strip using the following method.
After forming a soot film of m, it was introduced into a hot-dip galvanizing bath 4 maintained at 460°C, the amount of zinc coating was adjusted to 1 ^oz / ft ₂ with a plating roll 5, and after cooling,
Soot was removed from the non-plated surface using a brushing roll 23. As a result, a beautiful and perfect single-sided plated steel plate was obtained. To form a soot film, first, acetylene gas was used at a flow rate of 5/min, and the mixing air flow rate was set at 5/min to cause incomplete combustion. In addition, benzene was used as the liquid hydrocarbon, the temperature of the gasifier was kept at 90℃, and the tank 1 was kept so that 30% of benzene was always present in the device.
It was supplied from 4. Gasification was started with the exhaust gas from the masking chamber when the line was started, and after 20 minutes, valve 21 was opened to mix acetylene gas and benzene vapor and supply it to burner 9, and then valve 7 was closed to supply only benzene vapor. At this time, soot generation was continued by mixing the benzene vapor flow rate to 2/min and the air flow rate to 6/min to obtain a soot film thickness equivalent to that in the case of acetylene.

Example 4 Toluene and xylene were used as liquid hydrocarbons, divided into two ways, and the temperature of the gasifier was set at 115°C.
A complete single-sided galvanized steel sheet was obtained in exactly the same manner as in Example 3, except that the temperature was 145° C. (toluene) and 145° C. (xylene).

[Brief explanation of the drawing]

FIGS. 1 to 3 are schematic diagrams showing a racking device used in an embodiment of the present invention. 3... Steel strip, 4... Molten metal plating bath, 6...
Masking chamber, 22... Combustion auxiliary gas supply valve, 7
...Air supply valve, 8...Electric heater, 9...
Burner, 10... Soot, 13... Gasifier, 1
4... Liquid unsaturated hydrocarbon tank, 15... Heat exchanger, 18... Reduction furnace, 19... Gas pump, 2
0...Gas storage tank, 21...Gas supply valve, 23...Brushing roll.

Claims (1)

[Scope of Claims] 1. In a single-sided molten metal plating method for a steel strip in which a non-staining agent film is formed on one side of the steel strip and then the steel strip is immersed in a molten metal bath, liquid unsaturated hydrocarbon is vaporized and the vaporized unsaturated hydrocarbon gas is incompletely combusted so that the generated soot is sprayed onto one side of a steel strip and adhered to form the anti-staining agent, the method comprising: 1. A single-sided molten metal plating method for a steel strip, characterized in that the liquid unsaturated hydrocarbon is vaporized by a heat source formed by a method. 2. Single-sided molten metal plating on a steel strip according to claim 1, wherein the liquid unsaturated hydrocarbon is selected from benzene, toluene, xylene, phenol, light oil, and heavy oil. Method. 3. Claim 1 or 2, characterized in that the anti-stain coating has a thickness of 5 μm or more.
A method for single-sided molten metal plating on a steel strip as described in .