JPS62136589A - Method and installation for producing alloyed galvanized steel sheet - Google Patents

Abstract

PURPOSE:To form an alloy layer having excellent workability and to improve the quality of a galvanized steel sheet by coating a high melting metal on a steel strip after hot dip galvanization then subjecting the plating to an alloying treatment by bringing the same into contact with a heating roll. CONSTITUTION:The steel strip 2 is conducted into a galvanizing bath 4 and is plated. The plated strip is cooled by a cooler 5 and is conducted to a one side electroplating device 8. The metal such as iron or nickel having the m.p. higher than the m.p. of zinc is coated on the steel strip 1 as a cathode. After the steel strip 2 is passed through a cleaning device 9 and a dryer 10, the one-side electroplated surface is brought into contact with the heating roll 11 by which the steel strip 2 is heated and the iron of the steel strip is diffused into the hot dip galvanized layer. The plating layer is thus galvanized. The steel strip is then cooled in a quenching tank 12 to prevent an overalloying and thereafter the steel strip is passed through a temper rolling mill 13 and a leveler 14, etc. and is subjected to a chemical conversion treatment by a chemical conversion treatment device 15, by which the product is obtd. The coating of the high melting metal may be formed on both faces as well. The energy consumption is reduced by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an alloyed galvanizing method and its equipment.

(Prior art) As a method for manufacturing alloyed hot-dip galvanized steel sheets, for example,
JP-A No. 60-149760 discloses that after hot-dip galvanizing, the sheet is heated in an alloying furnace to diffuse the iron of the plated original sheet into the plated layer to form an iron-zinc alloy.

As is well known, in such alloyed galvanized steel sheets, the surface of the alloy layer determines the iron content, and the portions close to the underlying plated original plate have a higher iron content than the surface.
It is a hard, brittle layer. However, this method has the disadvantage that the plating layer peels off during processing, which is referred to as 4-doubling.

In addition, when differential thickness plating is applied to the surface of a steel plate and alloying treatment is performed, the thickly plated side becomes properly alloyed (if iron is used in the plating layer, the thinly plated side becomes overalloyed, and conversely, the thinly plated side becomes properly alloyed). This results in the disadvantage that the thicker plated side becomes insufficiently alloyed.

Furthermore, such alloying treatment has drawbacks such as extremely low thermal efficiency because air is sucked in from the lower part of the furnace and high-temperature gas is discharged from the upper part due to the draft effect of the alloying furnace.

(Object of the Invention) The present invention has been made to advantageously solve these drawbacks.

(Means for Solving the Problems) The present invention provides a method of coating at least one side with a metal with a higher melting point than zinc after hot-dip galvanizing, and then moving the coated side in contact with a heating roll to perform alloying treatment. A method for producing a single-alloyed galvanized steel sheet, characterized by:

An alloyed galvanizing equipment characterized by a hot-dip galvanizing device, an electroplating device, a roll heating device, a temper rolling mill, a leveler, and a chemical conversion treatment device.

The present invention relates to an alloyed galvanizing equipment characterized in that a hot-dip galvanizing device, an electroplating device, a preheating device, a roll heating device, a temper rolling mill, a leveler, and a chemical conversion treatment device are installed in series.

That is, in the present invention, after hot-dip galvanizing, at least one side is coated with one or more metals having a higher melting point than zinc, such as iron, nickel, phosphorus, aluminum, manganese, magnesium, and chromium. . This coating prevents the molten zinc from adhering to the roll when the iron of the plated original plate is later heated and diffused into the zinc layer and the zinc-iron alloying process is performed. When plating is applied, iron diffuses into the zinc layer from both the plated original plate and the iron plating layer on the surface, so the hard and brittle R layer is thin and consists of 20 layers with excellent workability. If an alloy layer can be formed to improve quality, or if chemical conversion treatment such as chromate treatment after alloying treatment can be improved, the upper layer of iron plating as described above is coated with nickel or the like.

Furthermore, depending on the application, it may be coated with a high melting point metal such as zinc.

In order to exhibit the above-mentioned functions, such a metal coating may have a coating density of at most 3 g/rrr' or less, and coating methods include electroplating, flash plating, etc.

In this way, after coating the upper layer of the hot-dip galvanized layer with a high-melting point metal, the iron and zinc layer of the plated original plate are alloyed by heating the roll, and the roll surface temperature is 480 to 600°C. The plate can be heated to a temperature of 48.0° C. or higher, and alloying with an iron content of about 10% can be performed by contacting for 5 to 20 seconds.

Prior to this roll heating, the galvanized steel sheet can be preheated to about 400° C. and then the roll heating can be performed. In such a case, there is an effect that the roll heating can be made smaller.

The roll can be heated by, for example, electric induction, gas combustion, or the like.

That is, the plating layer thickness is about several microns, and the thermal conductivity is 450 to 50% of the alloying temperature from the thermal conductivity of the steel plate itself.
The temperature conductivity of a steel plate at 0°C is as follows: plate thickness 1. For a thin plate of about 0 mm, even if it is heated from one side with a roll, the difference between the center temperature of the plate and the surface temperature at the contact line is about 10°C, and this difference disappears in a few seconds, ensuring uniform alloying on both sides. .

The galvanized steel sheet that has been alloyed in this way is then plated with non-ferrous metals as necessary, and then the shape of the plated steel sheet is corrected using a temper rolling leveler, and after chemical conversion treatment such as chromate treatment, it is made into a product. It is.

(Example) Next, an example of the device of the present invention will be described.

Example 1 In FIG. 1, a steel strip 2 is unwound from a reel la, and the surface of the steel strip 2 is cleaned in a pretreatment furnace 3, and if necessary, heat treatment such as annealing is performed to reach a temperature suitable for plating. Then, it is introduced into a galvanizing bath 4, and after plating, it is passed through a cooling machine 5.
The steel strip is cooled, guided to a single-sided electroplating device 8 consisting of a conductive roll 6 and an electrode 7, a plating solution is introduced between the roll 6 and the electrode 7, plating is performed using the steel strip 1 as a cathode, and then plating is carried out in a cleaning device 9. After washing the steel strip 2 and drying it in a drier 10, the steel strip 2 is guided so that one side of the electroplated surface is in contact with the heating roll 11, and the plated steel strip 2 is heated by moving it into contact with the roll 11, thereby removing the iron of the plated original plate (copper strip). is diffused into the hot-dip galvanized layer and alloyed.

After being cooled in a quench tank 12 to prevent overalloying, the shape is corrected in a temper rolling mill 13 and a leveler 14, and then chemical conversion treatment such as chromate treatment is performed in a chemical conversion treatment device 15 to form a reel 1b as a product. Turn it up.

Example 2 In FIG. 2, a steel strip 2 is unwound from a reel 1a, and the surface of the steel strip 2 is cleaned in a pretreatment furnace 3, and if necessary, heat treatment such as annealing is performed to reach a temperature suitable for plating. Then, it is introduced into a galvanizing bath 4, and after plating, it is passed through a cooling machine 5.
The plating solution is introduced between the roll 6 and the electrode 7, and plating is performed using the steel strip 2 as a cathode. The strip 2 is washed and dried in a dryer 10, and then the plated steel strip 2 is preheated in a preheating device 16, and heated by a heating roll 1.
Roll 1 so that one side of the electroplated surface is in contact with Roll 1.
1, the plated steel strip 2 is heated, and the iron of the plated original plate (steel strip) is diffused into the hot-dip galvanized layer and alloyed.

Next, after cooling in a quench tank 12 to prevent overalloying, the surface of the alloy layer is plated in a post-processing device 17, and the shape of the plated steel strip 2 is corrected in a temper rolling mill 13 and a leveler 14, and chemical conversion is performed. A processing device 15 performs a chemical conversion treatment, and the product is wound onto a reel 1b.

Example 3 Next, an example of the method of the present invention will be described together with a comparative example. Q,
A 13 mm thick copper strip (common steel, width 1500 mm) was coated with 3[1/r11 (layer thickness 5μ) on the front side and 60p/lf (layer thickness 10μ) on the back side, and this was then air-cooled. After cooling to 50°C, 1
F! /lo' iron plating is applied to the back side, then this plated steel strip is preheated to 400℃ (gas heating), and the iron plated surface is moved in contact with a heating roll (gas heating in the roll) with a roll surface temperature of 500℃ for 7 seconds. After alloying treatment, temper rolling (elongation rate 1.0%) and leveler, the third
As shown in the figure, a good alloy layer i was obtained consisting of approximately 88 thin F layers on the base iron side.

Energy consumption is COG 452Nr11 for preheating.
s/h.

With roll heating, COG 205 Nrr? /h Comparative Example As described above, the hot-dip galvanized plated steel strip was alloyed by heating it in an alloying furnace (gas combustion furnace, furnace temperature 800°C, processing time 18 seconds). As shown in Fig. 3, the brittle alloy layer containing a large amount of iron is thicker on the base iron side than in the present invention.

Energy consumption is COG 750 Nm”/h
It became.

(Effects of the Invention) By carrying out the present invention, the quality of the iron-zinc alloy layer can be significantly improved because the iron-zinc alloy layer is almost composed of a thin, easily workable alloy layer with a brittle alloy layer containing a large amount of iron. .

Further, excellent effects such as being able to significantly reduce the amount of energy used for alloying can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing examples of the apparatus of the present invention, and FIG. 3 is an explanatory chart showing the iron content distribution in the direction of the plating layer thickness of plated steel sheets according to the method of the present invention and a comparative example. l: Reel, 2: Copper strip, 3: Pretreatment furnace, 4: Galvanizing bath, 5: Cooler, 6: Conductive roll, 7: Electrode, 8
: Single-sided electroplating device, 9: Washing device, 10: Dryer, 11: Heating roll, 12: Quench tank, 13:
Temper rolling mill, 14 Nirepera-115: Chemical conversion treatment equipment,
16: Preheating device, 17: Post-processing device.

Claims (1)

[Claims] 1. After hot-dip galvanizing, at least one side is coated with a metal with a higher melting point than zinc, and then the coated side is moved while in contact with a heating roll to undergo an alloying treatment.
Method of manufacturing alloyed galvanized steel sheet. 2. Alloyed galvanizing equipment characterized by having a hot-dip galvanizing device, an electroplating device, a roll heating device, a temper rolling mill, a leveler, and a chemical conversion treatment device installed in series. 3.Hot-dip galvanizing equipment, electroplating equipment, preheating equipment,
Alloyed galvanizing equipment characterized by being equipped with a roll heating device, skin pass rolling mill, leveler, and chemical conversion treatment device.