JPS59145770A - One-side metal hot dipping method - Google Patents

Abstract

PURPOSE:To make plating thickness uniform by heating the surface of a steel strip to be plated to the temp. at which a plating metal is remelted after a metal hot dipping treatment to spread the plating metal in the part where the plating thickness on the surface to be plated is large to the part where it is small. CONSTITUTION:A steel strip 1 is dipped via a deflector roll 11 into a molten plating metal 12, and is subjected to hot dipping on one side, thereafter the strip is pulled via a sink roll 13 into the atmosphere and is adjusted to a prescribed plating thickness by a gas squeezer 14. The plating surface of the strip 1 is then heated by a high-frequency heater 15 to the temp. at which the plating metal is remelted to spread the plating metal in the part where the plating thickness on the plated surface is large to the part where it is small and to make the plating thickness uniform. Water or an aq. soln. is thereafter ejected from a force cooler 17 to the strip and further the strip is cooled with a usual cooler 17'. The non- plated surface is polished with a device 20 for removing a stop-off agent after cooling and the strip is subjected to skin pass rolling in a skin pass mill 21.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a method for single-sided hot-dip metal plating of copper strips.

[Prior art]

A so-called plated steel strip, which is a copper strip plated on both or one side, is being used in a wide variety of applications because of its excellent corrosion resistance. In this method of manufacturing a plated steel strip, it can be used as a product even if it is immersed in a hot-dip metal plating bath, but it is often subjected to skin pass rolling in order to further improve the surface quality. However, since the thickness of the copper band wave plated metal while immersed in the hot-dip metal plating bath fluctuates, applying skin pass rolling to the copper band to be plated causes uneven gloss on the surface of the copper band, which significantly reduces the commercial value. was there. The above problem caused uneven gloss in a single-sided plated steel strip that was plated on one side, particularly on both the plated and non-plated sides of the copper strip.

[Purpose of the invention]

The present invention has been made in view of the above facts, and aims to reduce and equalize variations in the thickness of the metal to be plated, and to prevent uneven gloss caused by skin pass rolling after plating.

[Summary of the invention]

The present invention involves heating the surface of the steel strip to be plated to a temperature at which the plated metal re-melts after hot-dipping the copper strip.
) The above purpose was achieved by pouring the plating metal on the dog surface into a small area, thereby equalizing the plating thickness on the surface of the copper strip. .

The present inventors researched the causes of uneven gloss that occurs on the plated and non-plated surfaces when skin-pass rolling is applied to a dark-colored steel strip. As a result, the inventors found that such uneven gloss can be caused by vibrations of the plating equipment and changes in the plating thickness. The plating thickness fluctuates due to the effects of gas vibrations in the controlling gas throttling device, a decrease in the melting temperature of the plating bath, etc., and as a result, the thickness of the plated steel strip changes, and the coating thickness of the steel strip changes during skin bath rolling. The degree of work (rolling reduction) is large in the sag dog part, and the degree of work is small in the small part, resulting in uneven work. It became clear that uneven gloss occurred. Now, when we compare the rolling reduction due to variations in plating thickness in the case of single-sided plated steel strip, as shown in Figure 1, the plated metal M coated with hot-dip metal on steel strip 1 is thicker in part a and thicker in part b. It's getting thinner. For this reason, if the thickness of the steel strip is HO, the minimum plated metal thickness is Hl, the difference between the maximum and minimum plated metal thickness is ΔH1, and the thickness after skin pass is H2, then the rolling reduction ratio of the 93 part and b part is Since Hs is sufficiently smaller than HO, it can be seen that the thinner the thickness Ho of the copper strip and the larger the difference ΔH between the plated metal thicknesses, the larger the rolling reduction ratio becomes. As a result, uneven gloss occurs on the surface of the copper strip during skin pass rolling.

As a result of research, the present inventors found that it is most effective to heat the surface of the copper strip after plating in order to reduce variations in plating thickness. In other words, in the case of hot-dip galvanizing, the temperature at which the plated zinc on the surface of the copper strip starts to melt again is 40
0C to temperature 5 at which oxidation phenomenon due to excessive temperature rise can be prevented
By heating the surface of the copper strip to be plated to 00C, or in the case of hot-dip aluminization, to 600C, the temperature at which the plated aluminum on the surface of the copper strip starts to melt again, to 700C, the temperature at which oxidation phenomenon due to excessive temperature rise can be prevented. This is to equalize the plating thickness by bringing the plating metal on the surface of the steel strip into a molten state and flowing the plating metal in the areas where the plating thickness is a little thicker to the smaller areas. In addition, by blowing air or a gas such as nitrogen onto the heated surface to be plated, the plated metal on the molten surface of the copper strip is forced to flow, which increases the effect of equalizing the thickness of the copper strip plating. .

After the plating surface is further heated to make the plating surface uniform and smooth with little variation in thickness, it is preferable to uniformly spray or spray water or an aqueous solution as a forced cooling means, so that the plating surface has no crystal grain formation. A shimmering appearance with a fine spangled pattern is obtained. By spraying an aqueous solution of water-soluble phosphate dissolved in water as a cooling refrigerant, the spangles generated on the plating surface are fine and of uniform particle size, which works well with equalizing the plating thickness. The effect will be even greater. The phosphates used in this case include sodium phosphate, potassium phosphate, magnesium phosphate, ammonium phosphate, and ammonium dihydrogen phosphate, which can be used alone or in combination. The concentration used is preferably 3% or less, which is as thin as possible, since the spraying of the chemical worsens the working environment.

After this forced cooling treatment, the steel plate is subsequently cooled by a conventional method, and then a polishing process is started for the purpose of removing the anti-stick agent applied to the non-plated surface. There are two methods for polishing: mechanical methods using brushes, etc., and methods such as hydrochloric acid treatment, which chemically penetrates the interface between the plating inhibitor and the iron base and promotes interfacial deterioration. The inhibitor has a composition mainly composed of clay minerals, to which are added 5 to 30 units of phosphate and silicate as binders, and can be used with any polishing method. , bamboo can also be used in combination to ensure removal under appropriate conditions.

To give an example of mechanical polishing conditions, 3 to 5 stands of nylon brushes containing abrasive grains with a wire diameter of 1.0 to 25 m are installed, and the steel strip is passed through at a line speed of 60 to 120 m/-. If so, the plating inhibitor can be removed. As an example of chemical polishing conditions, the anti-plating agent is removed from the interface by treatment for 2 to 3 seconds using hydrochloric acid at a concentration of 3 to 15%.

The single-sided hot-dip coated steel strip from which the plating inhibitor has been removed is subsequently subjected to a skin pass rolling process to improve the material quality and surface quality. Naoko\ has a reduction rate of 0.5 to 2.
．． It is rolled into a product within a range of 5%.

Through the series of steps described above, it is possible to obtain a product with uniform molten metal on one side, no gloss 2, and excellent appearance quality on both the plated and non-plated surfaces.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the single-sided galvanizing method to which the present invention is applied, in which the steel strip 1 is coated with an inhibitor coating device consisting of a pick-up roll 2, an applicator roll 3, a backup roll 4, and a plating inhibitor tray 5. After the plating inhibitor 7 in the pan 5 is applied to this non-plated surface, the oxidation furnace 8
to go into. In the oxidation furnace 8, oil adhering to the plated surface of the copper strip is burned off, and then the throat 9 is passed through the reduction furnace 1o.
to go into. In the reduction furnace 10, oxides on the plated surface of the copper strip are reduced and cleaned. Next, the steel strip 1 is deflector roller 11
It is immersed in the hot-dip plated metal 12 through a zinc roller 13, and then pulled up into the atmosphere and adjusted to a predetermined plating thickness by a gas throttling device 14. Next, # band 1 is heated by the high frequency heating device 15, and the plated metal is remelted.
Alternatively, if the attached plating metal is in a molten state, the fluidity of the plating metal will be even higher, and the plating metal will be thicker in areas with larger plating thickness than in smaller parts due to the tension of the mating surface of the metal itself. It flows and promotes thickness uniformity.

At this time, the gas is sprayed onto the heating surface of the steel strip 1 by blowing air or gas such as nitrogen using the device 15', which forces the plating metal to flow, thereby making the plating thickness uniform. The effect will be greater. The gas to be sprayed is preferably an inert gas such as nitrogen, which is advantageous in terms of preventing oxidation of the steel strip, but air may also be used. The support row 216 is provided in contact with the steel strip 1 on the non-plated side facing the high-frequency heating device to prevent vibration of the steel strip 1 and to keep the gap G between the high-frequency heating device 15 and the steel strip 1 constant. It has the role of holding the

As a device for heating the copper strip 1, in addition to the above-mentioned high-frequency heating device, there are a method in which the flame of a burner is directly applied to the steel strip to heat it;
There are other methods, such as heating with a drowsiness heater, which can be applied as the heating device of the present invention, but in any case, it is desirable to be able to heat in a short time in order to reduce the length of the device and suppress oxidation of the plated metal. The most desirable method is the high-frequency heating method, which can heat only the surface layer by using an appropriate frequency.

Next, the steel strip 1 is cooled with 2% sodium phosphate using a forced cooling device 17.
Spray the aqueous solution uniformly onto the plating surface at a pressure of 2'q/cd,
After the spangles on the plating surface have been made extremely fine, the spangles on the plating surface are subsequently cooled in a conventional cooling device 17', and then the inhibitor removing device 20 is placed under υ tension by the A1 bridle roller 18 and the A2 bridle roller 19. The plating inhibitor was completely removed under the following polishing conditions: abrasive-containing snylon brush wire diameter of 1.6 mm, 3 stands, and line speed of 60 m/Mm.

Next, the steel strip 1 is put into the skin bath mill 21 and the tension of the 9 steel strips is increased to the mill 3.
Controlled by the bridle roller 22 and the A2 bridle roller 19, skin pass rolling is performed with an elongation rate of 0.5% to improve material quality and surface quality. Since the plating thickness is sufficiently uniform, uneven gloss does not occur on both the plated and non-plated surfaces even during skin bath rolling.

According to experiments conducted by the present inventors, one-sided hot-dip galvanizing of P1 steel strip was carried out using the single-sided plating method illustrated in FIG. The device maintains the gap between the high-frequency coil and the copper strip at 10 mm, and the surface temperature of the copper strip is 45 mm.
Heat to 0C and use a skin bath mill to reduce the pressure to 0.5%.
In both the rolling treatment and the one in which the heating surface was sprayed with air or nitrogen gas, no uneven gloss was observed on either the plated or non-plated surfaces, which would pose a practical problem, and each side weighed 173 g. A beautiful single-sided plated copper strip with a zinc coverage of 1/m" was obtained.
As a result of conducting a salt spray corrosion resistance test, it was confirmed that there was no red rust on the plated surface and that the plating was reliable, and the problems of the conventional technology were resolved.

〔Effect of the invention〕

As described above, according to the present invention, in single-sided hot-dip metal plating of a copper strip, after the plating process, the plated metal is placed in a heating furnace and heated to a temperature at which the surface of the plated metal re-melts, and then the threshold of the plated metal is still molten. By performing forced cooling when the copper strip is in this state, the plating thickness can be made uniform, and as a result, it is possible to produce a plated steel strip with even luster on the surface of the copper strip after skin bath rolling, and its industrial value is extremely high. big.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a single-sided plated steel strip showing unevenness in plating thickness, and FIG. 2 is a diagram of a single-sided plating apparatus showing an embodiment of the present invention.

Claims (1)

[Claims] 1. In a method for producing a single-sided hot-dip metal-plated steel strip by immersing a copper strip in a plating bath, after plating, the copper strip is placed in a heating furnace and heated to a temperature at which the surface of the plated metal remelts; Single-sided melting is characterized in that when the surface of the plated metal is still in a molten state, forced cooling is performed by spraying water or an aqueous solution, followed by normal cooling, followed by polishing and skin pass rolling of the non-plated surface. Metal plating method. 2. Claim 1, characterized in that the heating temperature is 400C to 500C in the case of hot-dip galvanizing.
Single-sided hot-dip metal plating method described in Section 1. 3. The heating temperature is 600C for hot-dip aluminum plating.
700c to 700c, the single-sided hot-dip metal plating method according to claim 1. 4. The forced cooling aqueous solution is a water-soluble salt/acid in water.
The single-sided hot-dip metal plating method according to claim 1, characterized in that 5 to 3% of the metal is melted.