JPH09263923A - Production of galvannealed steel sheet having iron-nickel-oxygen film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a galvannealed steel sheet having an Fe-Ni-O film capable of reducing a fluctuation in the coating weight. SOLUTION: At the time of producing a galvanealed steel sheet having an Fe-Ni-O film in such a manner that, in a continuous galvanizing line, a steel sheet is applied with galvanizing and is thereafter subjected to alloying treatment and skinpass rolling to form an Fe-Ni-O film thereon, feedback control in which rolling loads in a skinpass rolling mill are corrected is executed based on the information on the surface roughness measured by a steel sheet surface roughness measuring device provided in the poststage of the skinpass rolling mill and also in the prestage of Fe-Ni-O film treating equipment, and the skinpass rolling is executed so as to regulate the surface roughness of the steel sheet after the skinpass rolling to a prescribed range to produce the galvannealed steel sheet having the Fe-Ni-O film.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a press formability,
Further, the present invention relates to a method for producing an alloyed hot dip galvanized steel sheet which is further excellent in spot weldability, adhesiveness, chemical conversion treatment property, or in which molten metal such as welding dust hardly adheres, if necessary.

[0002]

2. Description of the Related Art Galvanized steel sheets are widely used as various kinds of rust-proof steel sheets because they have various excellent characteristics. In order to use this zinc-based plated steel sheet as an anticorrosive steel sheet for automobiles, in addition to corrosion resistance, paint compatibility, etc., the performance required in the vehicle body manufacturing process includes press formability, spot weldability, adhesiveness and chemical conversion. It is important that the processability is excellent.

In some cases, it is required that the molten metal that scatters at a high speed, such as welding dust generated during spot welding, is unlikely to adhere to the surface.

By the way, the zinc-based plated steel sheet generally has a drawback that the press formability is inferior to that of the cold-rolled steel sheet. This is because the sliding resistance between the zinc-based plated steel sheet and the press die is higher than that of the cold-rolled steel sheet. That is, since the sliding resistance is large, the zinc-plated steel sheet hardly flows into the press die in a portion where the sliding resistance between the bead and the galvanized steel sheet is extremely large, and the steel sheet is easily broken.

As a method for improving the press formability of a zinc-based plated steel sheet, a method of applying a high-viscosity lubricating oil is generally widely used. However, this method has problems that, due to the high viscosity of the lubricating oil, a coating defect occurs due to poor degreasing in the coating process, and the press formability becomes unstable due to oil shortage during pressing. Accordingly, there is a strong demand for improving the press formability of a zinc-based plated steel sheet.

On the other hand, in a zinc-based plated steel sheet, the copper of the electrode easily reacts with molten zinc to form a brittle alloy layer during spot welding. There is a problem that the continuous hitting property is inferior to.

Furthermore, in the manufacturing process of automobile bodies,
Various adhesives are used for the purpose of rust prevention and vibration control of car bodies, but in recent years it has become clear that the adhesiveness of zinc-based plated steel sheets is inferior to that of cold-rolled steel sheets. It was

As a method for solving the above-mentioned problems, JP-A-53-60332 and JP-A-2-90483 disclose electrolytic treatment, dipping treatment, coating oxidation treatment, or heat treatment on the surface of a zinc-based plated steel sheet. Is disclosed to form an oxide film mainly composed of ZnO to improve weldability or workability (hereinafter referred to as Prior Art 1).

Japanese Unexamined Patent Publication (Kokai) No. 4-88196 discloses that the surface of a zinc-plated steel sheet contains 5 to 60 g / l of sodium phosphate at a pH of 2 to 6.
A technique to improve the press formability and chemical conversion treatability by forming an oxide film mainly of P oxide by immersing the plated steel sheet in the aqueous solution, electrolytic treatment, or spraying the above aqueous solution ( Hereinafter, the prior art 2) is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 3-191093 discloses press formability and chemical conversion by producing Ni oxide on the surface of a zinc-based plated steel sheet by electrolytic treatment, dipping treatment, coating treatment, coating oxidation treatment or heat treatment. A technique for improving processability (hereinafter referred to as Prior Art 3) is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 58-67885 discloses a technique for improving the corrosion resistance by producing a metal such as Ni and Fe on the surface of a zinc-based plated steel sheet by, for example, electroplating or chemical plating (hereinafter referred to as prior art. 4) is disclosed.

[0012]

However, the above-mentioned prior art has the following problems.

The prior art 1 uses the above-described various processes to
Since it is a method of generating an oxide mainly composed of ZnO on the surface of the plating layer, the effect of reducing the sliding resistance between the press die and the plated steel sheet is small, and the effect of improving the press formability is small. If the oxide is present on the surface of the plating layer, there is a problem that the adhesiveness is deteriorated.

Prior art 2 is a method of forming an oxide film mainly composed of P oxide on the surface of a zinc-plated steel sheet, so that it has a great effect of improving press formability and chemical conversion treatability, but spot weldability, There is a problem that the adhesiveness deteriorates.

Prior art 3 is a method of forming a Ni oxide single-phase film, so that the corrosion resistance is improved, but the adhesion is deteriorated.

Prior art 4 is a method of forming only a metal such as Ni, so that the corrosion resistance is improved, but the effect of improving the press formability is not sufficient because the metallic property of the coating is strong. Furthermore, there is a problem that the wettability of the metal to the adhesive is low and sufficient adhesiveness cannot be obtained.

Therefore, there is no zinc-based plated steel sheet which is excellent in press formability and, if necessary, is also excellent in spot weldability, adhesiveness and chemical conversion treatment property.

At the present time, no zinc-based plated steel sheet has been developed which can suppress the adhesion of welding spatter which is generated and scattered during spot welding.

In order to solve the above-mentioned problems, the present applicant has
As a result of intensive research, by forming an appropriate Fe-Ni-O-based coating on the surface of the plating layer of zinc-based plated steel sheet, in addition to press formability, spot weldability, adhesion and chemical conversion treatment It has been found that the properties can be improved, and a patent application was filed for Japanese Patent Application No. 6-257499 for a zinc-plated steel sheet having excellent press formability and, if necessary, excellent spot weldability, adhesiveness and chemical conversion treatability. In addition, the above-mentioned Fe-Ni-
It was also found that the O 2 -based coating can reduce the adhesion of welding spatter that is generated and scattered during welding.

In the above-mentioned steel sheet, a predetermined Fe-Ni-O-based film as defined below is formed on the surface of at least one plating layer of the zinc-based plated steel sheet according to the required performance. (1) In order to obtain excellent press formability, the amount of Fe-Ni-O-based coating deposited (hereinafter referred to as coating deposition): 10 to 10 in terms of the total amount of metallic elements in the Fe-Ni-O-based coating 1500mg / m ² , Fe-
Oxygen content of Ni-O coating (hereinafter referred to as oxygen content of coating): 0.5 to less than 30 wt%. (2) In order to have excellent press formability and spot weldability, the coating amount is 10 to 1500 mg / m ² , the oxygen content of the coating is 0.5 to less than 30 wt%, and the Fe content in the Fe-Ni-O coating is Content (wt%) and Ni content (wt%) + Fe content (wt
%) Ratio (hereinafter referred to as Fe / Fe + Ni in the film): 0 to 0.9
And (3) In order to have excellent press formability and adhesiveness, the amount of coating film is 10 to 1500 mg / m ² , and the oxygen content of the film is 0.5 to 3
Less than 0 wt%, Fe / Fe + Ni in the coating: 0.05 to less than 1.0. (4) In order to have excellent press formability, spot weldability, adhesiveness and chemical conversion treatability, the amount of coating film: 10 to 1500mg
/ m ² , oxygen content of the coating: 0.5-10 wt%, Fe / Fe + Ni in the coating: 0.05-0.9. (5) In the above (4), in order to further excel in press moldability and adhesiveness, the amount of coating film: 10 to 1200 mg
/ m ² , oxygen content of the coating: 0.5-10 wt%, Fe / Fe + Ni in the coating: 0.1-0.3. (6) In order to suppress the adhesion of molten metal such as welding spatter that occurs and scatters during spot welding, the amount of coating film: 50-
10000mg / m ² , oxygen content of the film: Fe / Fe + Ni in the film becomes Fe
When c is set, the range is 0.5 to 9 × Fec + 21.

The action of the Fe-Ni-O-based coating described above is considered as follows. The conventional zinc-based plated steel sheet is inferior in press formability to the cold rolled steel sheet.
This is because the sliding resistance between the zinc-plated steel sheet and the press die is large. The reason for this is that, under high surface pressure, the low melting point zinc and the mold cause an adhesion phenomenon. In order to prevent this, it is effective to form a film having a higher melting point than the zinc or zinc alloy plating layer on the surface of the plating layer of the zinc-based plated steel sheet. Fe-Ni-
Since the O-based coating is hard and has a high melting point, by forming the Fe-Ni-O-based coating on the surface of the zinc-based plated steel sheet, the sliding resistance between the plating layer surface and the press die during press forming can be improved. As a result, the zinc-based plated steel sheet easily slips into the press die, and press formability is improved.

The conventional galvanized steel sheet is inferior to the cold-rolled steel sheet in continuous hitting property in spot welding. The reason for this is that the molten zinc at the time of welding diffuses into the copper of the electrode to form a fragile alloy layer, which causes an increase in the electrode tip diameter due to peeling of the alloy layer. Therefore, as a method for improving the continuous hitting property of zinc-based plated steel sheet,
It is effective to form a high melting point film on the surface of the plating layer to suppress the reaction between the plating metal and the copper electrode. As a result of examining various coatings in order to improve the spot weldability of galvanized steel sheets, it was found that Ni or Ni oxide coatings are particularly effective. The reason for this is not clear, but a very high melting point Ni oxide suppresses the diffusion of zinc to the copper electrode and reduces the wear of the copper electrode, or Ni reacts with Zn to form a high melting point Zn-Ni alloy. It is presumed that this is due to the formation of the metal and suppressing the reaction between the zinc and the copper electrode.

It has been known that the adhesiveness of a conventional galvanized steel sheet is inferior to that of a cold-rolled steel sheet, but the cause has not been clarified. Then, as a result of investigating this cause, it became clear that the adhesiveness is controlled by the composition of the oxide film on the surface of the steel sheet. That is, in the case of a cold-rolled steel sheet, the oxide film on the surface of the steel sheet is mainly Fe oxide, whereas in the zinc-based plated steel sheet, Zn oxide is mainly. The adhesiveness was different depending on the composition of this oxide film, and Zn oxide was inferior to Fe oxide in adhesiveness.
Therefore, the adhesiveness can be improved by forming the Fe oxide film on the surface of the zinc-based plated steel sheet.

The conversion treatment property of the conventional galvanized steel sheet is as follows:
Inferior to cold-rolled steel sheet due to high Zn concentration on the steel sheet surface, resulting in coarse and uneven phosphate crystals formed and different quality of phosphate crystals I do. When the Zn concentration on the surface of the steel sheet is high, the phosphate crystals are mainly composed of whipite, and the secondary adhesion of hot water after coating is poor. This is because the Fe concentration in the phosphate crystals is low, so that when exposed to a wet environment after coating, the chemical conversion treatment film condenses and loses its adhesion to the steel sheet.

In order to suppress the condensed water of the chemical conversion coating,
It is effective to include metals such as Fe and Ni in the phosphate crystals. By forming the above Fe-Ni-O-based coating, Ni and Fe in the coating are taken into the phosphate crystals during chemical conversion treatment, resulting in a chemical conversion coating with good adhesion, and a dense A uniform phosphate crystal is formed,
Not only secondary contact with warm water but also corrosion resistance is improved.

Further, it was considered that the phenomenon that the molten metal such as welding dust scattered at the time of spot welding adheres to the surface of the steel sheet is as follows. That is, in the conventional zinc-based plated steel sheet, the zinc of the surface plating layer is easily deformed, so that the plating layer is deformed by the molten metal flying at high speed to form irregularities. If the melting point of the molten metal is low,
While the plating layer is melted to form an alloy layer, it is rapidly cooled and solidifies and adheres. Therefore, when the melting point of the steel sheet surface layer is low and the yield stress is low and the steel sheet is easily deformed, the molten metal easily adheres and solidifies.

Since the Fe-Ni-O-based coating has a high hardness and a high melting point, it prevents deformation and melting due to the molten metal rushing onto the surface of the zinc-based plating layer at high speed. It is considered that the flying molten metal becomes difficult to adhere.

Further, a Fe-Ni-O-based coating having the above-mentioned constitution is formed on the zinc-based plated layer by a dipping treatment or an electrolytic treatment using a treatment liquid containing Fe ions and Ni ions as essential components. A method of manufacturing a zinc-based plated steel sheet was examined. As a result, a method by immersion treatment using an aqueous solution of a sulfuric acid / nitric acid bath containing Fe ions and Ni ions as essential components.
(Japanese Patent Application No. 7-303132), a method of dipping treatment using an aqueous solution of a chloride bath (Japanese Patent Application No. 7-216589), a method of electrolytic treatment using an aqueous solution of a sulfuric acid bath (Japanese Patent Application No. 7-303131). It has been found that the above-mentioned zinc-based plated steel sheet can be produced by various treatment liquids and treatment methods of

The above-mentioned method of dipping treatment using a chloride bath aqueous solution according to Japanese Patent Application No. 7-216589 is performed using FeCl ₂ and NiCl.
₂ , the ratio of the Fe content (g / l) to the sum of the Fe content (g / l) and the Ni content (g / l) is in the range of 0.004 to 0.9, and the pH is 2.0. In the range of up to 3.5 and temperature of 20 to 70 ° C
The zinc-plated steel sheet is treated with an aqueous solution adjusted to fall within the range, or an aqueous solution containing an oxidizing agent in the aqueous solution, or further treated with the above-mentioned aqueous solution, and then further treated in an oxidizing atmosphere at 500 to 600 ° C. It is a method for producing a zinc-based plated steel sheet having a Fe-Ni-O-based coating by heating in a temperature range.

Further, the method by electrolytic treatment using a sulfuric acid bath according to Japanese Patent Application No. 7-303131 discloses a method of electrolyzing a zinc-based plated steel sheet as a cathode in an aqueous solution containing nickel sulfate and ferrous sulfate. The total concentration of nickel sulfate and ferrous sulfate in the aqueous solution is in the range of 0.1 to 2.0 mol / l, the sum of nickel ion concentration and ferrous ion concentration: M (mol / l), and the plating solution Between the average flow velocity U: (m / s) and the current density in the electrolysis: I _k (A / dm ² ), I _k /
This is a method for producing a zinc-based plated steel sheet having the above-mentioned Fe-Ni-O-based coating by performing electrolytic treatment so as to satisfy the relationship of (U ^1/2 × M) = 50 to 150.

By the way, the inventors of the present invention, in the continuous galvanizing line, after hot dip galvanizing, the steel sheet is heated to form a galvanized layer containing a zinc-iron alloy plated layer containing about 7 to 17 wt% of iron. For galvanized steel sheet, when using a treatment liquid containing Fe ions and Ni ions as described above as essential components, by dipping treatment or electrolytic treatment, to form a Fe-Ni-O-based coating of the above-mentioned configuration In some cases, there was a large variation in the amount of coating film.

It has also been found that when the amount of coating film is large, the surface of the steel sheet after the film formation turns brownish black. If the surface of the steel sheet is blackened, it becomes difficult to detect harmful small grain dross defects and defects such as minute flaws, which causes problems in product quality assurance. In addition, if the variation in the amount of coating film is large, there is also the problem that the appearance differs between the obtained product lots.

On the other hand, in the case of spot welding, in order to prevent the welding dust from adhering to the steel plate during spot welding,
Since it is more advantageous to set the Fe-Ni-O-based coating amount to 200 mg / m ² or more, it may be desirable to secure a certain amount of coating amount.

That is, from the viewpoint of ensuring stable quality, it is advantageous to be able to reduce the variation in the amount of Fe—Ni—O-based coating adhered, and to reduce the variation in the amount of adhered film. If stable production of coatings in the range of 200 to 500 mg / m ² is possible, press formability, spot weldability, adhesiveness, chemical conversion treatment, and the effect of preventing the adhesion of welding spatter that occurs during welding and scatters It is possible to stably provide the alloyed hot-dip galvanized steel sheet that also has the advantage that the same steel sheet can be used for various purposes.

Therefore, Fe-Ni- which is formed during the production of the galvannealed steel sheet on which the Fe-Ni-O system coating is formed
It would be beneficial if fluctuations in the amount of O-based coating deposited could be reduced.

The present invention has been made in consideration of the above-mentioned circumstances, and in producing the alloyed hot-dip galvanized steel sheet having the Fe-Ni-O-based coating, the Fe-Ni-O-based coating is used. It is an object of the present invention to provide a method for manufacturing an alloyed hot-dip galvanized steel sheet capable of reducing fluctuations in the amount of adhesion.

[0037]

[Means for Solving the Problems] The present inventors have examined factors that affect the amount of Fe-Ni-O-based coatings deposited on a plated layer of a galvannealed steel sheet by immersion treatment or electrolytic treatment. .

As a result, the following was found. (1) In both the immersion method and the electrolytic method, the amount of the Fe-Ni-O-based coating deposited depends on the surface condition of the plated steel sheet before forming the Fe-Ni-O-based coating (oxide coating). State, surface roughness) and temper rolling conditions. this is,
It is considered that this is due to the following reasons. (2) For example, when a Fe-Ni-O-based coating is formed by immersion treatment, the main reaction for forming the coating is a substitution reaction between metal ions in the treatment liquid and Zn in the galvanized coating, and The more the outermost oxide film of the plating layer is destroyed by rolling, the more the Fe-Ni-O-based film is deposited and the more stable the film is formed. When the alloyed hot-dip galvanized steel sheet is subjected to the immersion treatment using the treatment liquid of the chloride bath under the same immersion treatment conditions, the area ratio B (%) of the degree of destruction of the oxide film is formed.
The relationship shown in Fig. 4 is observed between the Fe-Ni-O-based coating film deposition amount W. The area ratio (%) of the degree of destruction of the oxide film was determined by enlarging the range of 2 × 2 mm by 500 times on the surface of the plated steel sheet after temper rolling by a scanning electron microscope (SEM), The formed portion was visually judged and determined as an average value of n = 3 or more. (3) When the Fe-Ni-O-based coating is formed by electrolytic treatment, the reaction efficiency of the electrolytic reaction is affected by the electrolytic current density. When the surface roughness is small and the surface is flat, the current density in the vicinity of the electrolytic reaction surface is large, so that the amount of coating adhered is large. For galvannealed steel sheets, when electrolytic treatment using a treatment solution in a sulfuric acid bath and under the same electrolytic treatment conditions, surface roughness Ra (μm) and the amount of Fe-Ni-O-based coating film formed A relationship as shown in Fig. 5 is recognized between the two. (4) Therefore, keep the amount of Fe-Ni-O-based coating adhered to
In order to manufacture products of stable quality, it is necessary to control the surface condition (state of oxide film, surface roughness) of the plated steel sheet before treatment within a certain range. (5) However, the surface roughness of the alloyed hot-dip galvanized steel sheet after the alloying treatment largely depends on the steel composition, the steel sheet size, the alloying treatment conditions, etc., particularly the alloying treatment temperature. It is difficult to always keep the surface roughness of a galvannealed steel sheet with different steel components, steel sheet dimensions, and alloying treatment conditions before forming the Fe-Ni-O-based coating within a certain range. Also,
Up to now, no consideration has been given to the degree of destruction of the oxide film. (6) Regarding alloyed hot-dip galvanized steel sheet, various studies were conducted on the surface roughness after temper rolling and the degree of destruction of the oxide film, and these were correlated with the rolling load of the temper rolling. It was found that the surface roughness of the steel sheet and the degree of destruction of the oxide film can be controlled by controlling

FIG. 6 is a diagram showing the relationship between the rolling load (Ton / mm) and the surface roughness of the plated steel sheet after temper rolling. The surface roughness decreases as the rolling load increases. Figure 7 shows the relationship between the rolling load (Ton / mm) and the area ratio (%) of the destroyed part of the oxide film on the plating layer surface after temper rolling. The area ratio (%) of the broken part of the film is increasing. By appropriately controlling the temper rolling load, it is possible to control the surface roughness of the steel sheet after temper rolling and the degree of destruction of the oxide film within a required range. (7) Incidentally, it may be considered that the treatment condition of the Fe-Ni-O-based coating is changed according to the surface condition of the plated steel sheet before the Fe-Ni-O-based coating forming treatment. However, in this case, it is necessary to change the treatment liquid conditions such as treatment liquid temperature, pH, liquid concentration / liquid composition, and treatment time as the treatment conditions for the Fe-Ni-O-based film. Since it takes time to change the condition of the treatment liquid and lacks responsiveness, it is practically impossible to change the condition of the treatment liquid for each coil to be processed and control it rapidly.

The present invention is based on the above findings, and the characteristic features thereof are as follows. (1) In a continuous hot-dip galvanizing line, after hot-dip galvanizing the steel sheet, alloying treatment, temper rolling, then Fe-N
When producing the alloyed hot-dip galvanized steel sheet with the Fe-Ni-O-based coating by applying the treatment to form the iO-based coating,
Feedback control that corrects the rolling load of the temper rolling mill based on the surface roughness information measured by the steel plate surface roughness measuring device installed in the subsequent stage of the temper rolling mill and in the preceding stage of the Fe-Ni-O coating treatment equipment. A method for producing an alloyed hot-dip galvanized steel sheet having a Fe—Ni—O 2 -based coating, which performs the temper rolling so that the surface roughness of the steel sheet after temper rolling falls within a predetermined range (first invention). (2) In a continuous hot-dip galvanizing line, after hot-dip galvanizing the steel sheet, alloying treatment, temper rolling, then Fe-N
When producing the alloyed hot-dip galvanized steel sheet with the Fe-Ni-O-based coating by applying the treatment to form the iO-based coating,
The rolling load of the temper rolling mill is calculated based on the Fe-Ni-O-based coating amount information measured by the Fe-Ni-O-based coating amount measuring device installed after the Fe-Ni-O-based coating forming device. A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O-based coating, in which tempering rolling is performed so that the surface roughness of the steel sheet after temper rolling is adjusted by performing feedback control for correction (second invention) ). (3) In a continuous hot-dip galvanizing line, after hot-dip galvanizing the steel sheet, alloying treatment, temper rolling, then Fe-N
When producing the alloyed hot-dip galvanized steel sheet with the Fe-Ni-O-based coating by applying the treatment to form the iO-based coating,
Based on the surface roughness information measured by the steel plate surface roughness measuring device provided after the alloying treatment device and before the temper rolling mill, feedforward control is performed to correct the rolling load of the temper rolling mill, and A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O 2 -based coating, which is temper-rolled so that the surface roughness of the steel sheet after the quality rolling is within a predetermined range (third invention). (4) In a continuous hot dip galvanizing line, after hot dip galvanizing steel sheet, alloying treatment, temper rolling, then Fe-N
When producing the alloyed hot-dip galvanized steel sheet with the Fe-Ni-O-based coating by applying the treatment to form the iO-based coating,
The feedback control according to claim 1 or claim 2 and the feedforward control according to claim 3 are used together, and the condition change point is a steel plate surface roughness measuring device or Fe-Ni-O provided after the temper rolling mill. Fe-N provided in the latter stage of the system film forming device
Feed-forward control is performed until it passes the iO-based coating amount measuring device, and after the condition change point, it is switched to feedback control so that the surface roughness of the steel sheet after temper rolling falls within a predetermined range. A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O 3 -based coating, which performs control to correct the rolling load of a temper rolling mill (4th invention). (5) The invention according to any one of the first to fourth inventions
In the method for manufacturing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O-based coating, the steel sheet surface roughness Ra after temper rolling is 0.5 to
Assuming that the area ratio of the area where the surface roughness Ra is 1.5 μm and the surface roughness Ra is A (μm) and the film is crushed by temper rolling and the oxide film is destroyed is B (%), A / B × 100 is 1 to 3 After the temper rolling was performed so that the Fe-Ni-O system coating amount was 200 to 500 mg /
A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O-based coating forming an Fe-Ni-O-based coating of m ² (fifth invention).

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
It will be explained by 2.

FIG. 2 is a diagram showing a main part of a continuous hot dip galvanizing line. In Figure 2, 1 is an annealing furnace, 2 is a galvanizing bath, 3 is a wiping nozzle, 4 is an alloying furnace, and 5 is
Is a temper rolling mill, 6 is an Fe-Ni-O system coating treatment device, 7 is a steel plate surface roughness measuring device installed in the preceding stage of the temper rolling mill,
8 is a steel plate surface roughness measuring device provided at the latter stage of the temper rolling mill, 9 is a Fe-Ni-O system coating amount measuring device, 10 is a temper rolling mill controller, 11 is a process computer,
12 is a steel plate, 15 is a bridle roll on the side of the temper rolling mill, 16
Is a bridle roll on the exit side of the temper rolling mill, 17a and 17b are work rolls, and 18a and 18b are backup rolls.

A case of producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O 3 -based coating using this apparatus will be described.

The steel sheet 12 which has been unwound and fed by an unwinding device (not shown) and which has been subjected to predetermined annealing in the annealing furnace 1 is dipped in the zinc plating bath 2 for melting and holding the plated metal. After that, the wiping nozzle 3 provided on the galvanizing bath 2 adjusts the coating amount to a predetermined amount, and then it is heated in the alloying furnace 4 so that a predetermined concentration of iron is formed in the plating layer from the base steel plate. After being diffused to form a zinc-iron alloy plated layer having an iron concentration in the plated layer of about 7 to 17 wt%, it is cooled by a cooling device (not shown).

The cooled steel sheet was subjected to a temper rolling mill 5 to
Temper rolling is performed for the purpose of straightening the shape, improving the surface appearance, smoothing the surface, or improving the mechanical properties.

By the process computer 11, the rolling load based on the steel composition, steel plate size, material grade, etc.,
Tension, elongation, etc. are determined, and this data is instructed to the temper rolling mill controller 10.

In the temper rolling mill 5, the temper rolling mill controller 10 controls the temper rolling mill based on instructions such as rolling load, tension and elongation output from the process computer 11. At that time, the rolling load, the surface roughness information measured by the steel plate roughness measuring device provided in the pre-stage or the post-stage of the temper rolling mill or Fe-Ni-O-based film deposition amount measuring device measured Fe-Ni- The rolling load is adjusted so that the surface roughness of the steel sheet after temper rolling falls within a predetermined range, based on the O 2 -based coating amount information. Temper rolling mill controller 10
Applies a prescribed rolling load to the backup rolls 18a and 18b, and temper-rolls the work rolls 17a and 17b backed up by the backup rolls.

Further, the elongation rate of the steel sheet in temper rolling is calculated based on the pulse oscillators provided at the shaft ends of the entrance-side bridle roll 15 and the exit-side bridle roll 16, respectively.
The temper rolling mill controller 10 controls the tension between the entrance-side bridle roll and the exit-side bridle roll so that this elongation rate becomes constant.

Next, in a Fe-Ni-O type coating treatment apparatus, a tempered rolled steel sheet was treated with a treatment liquid having a predetermined composition by an immersion method and an electrolytic method under a predetermined condition of Fe-N.
After the iO 2 -based film treatment is applied to form a predetermined amount of Fe-Ni-O 2 -based film, the film is wound by an unillustrated take-up winding device.

Further, in the above line, the tail end of the preceding coil and the tip of the following coil are connected by a welding machine (not shown) provided after the inlet side rewinding device, and the coil is changed at the inlet side. Even if there is such a problem, the steel plate continuously runs in the processing part such as the plating bath. The attributes of the steel sheet running before and after this connection often change. The condition change point in the present invention means a point of changing manufacturing conditions such as alloying conditions in a running steel plate represented by the above-mentioned connecting portion.

In the case of the embodiment of the first invention, a temper rolling mill
5 The steel plate surface roughness after temper rolling measured by the surface roughness measuring device 8 installed in the latter stage of 5 is fed back to the temper rolling mill controller 10 and the difference between the target surface roughness and the measured surface roughness is measured. Then, the rolling load of the temper rolling mill 5 is corrected, and the rolling load is controlled so that the surface roughness of the steel sheet after temper rolling falls within a predetermined roughness range.

At this time, the rolling load for temper rolling is set as follows. Rolling load P is steel type, steel plate size, target elongation rate, operating conditions (operating speed, temper rolling in / out of temper rolling mill),
It is affected by the alloying degree of the plating layer. For example, the rolling load P is set based on each manufacturing condition by the following formula (1).

P = a ₀ + a ₁ t + a ₂ ω + a ₃ T _{E +} + a ₄ T _D + a ₅ ε + a ₆ V + a ₇ S (1) where t: plate thickness ( mm), ω: Strip width (mm), T _E : Tension on the temper rolling mill entrance side (kg), T _D : Tension on the temper rolling mill exit side (kg), ε: Target elongation (%), V: Operating speed (mpm), S: Fe concentration in the plating layer
(wt%) a _{0 to} a ₇ : Constants, which are set in a table in the line computer for each component system of steel types.

A method for setting the rolling load will be described with reference to FIGS. 8 and 9 and FIG. 10 showing the procedure for setting the rolling load.
Figure 8 shows the relationship between rolling load and surface roughness.
According to the deviation between the measured surface roughness A ₀ and the target surface roughness A ₁ , the rolling load ΔP is corrected so that the target surface roughness A ₁ is obtained, and the rolling load P ₁ is estimated. On the other hand, rolling load P and A / B × 10
Since the relationship of 0 has a relationship as shown in FIG. 9, the value of A ₁ / B ₁ × 100 of the steel sheet after temper rolling is estimated from the corrected rolling load P ₁ estimated above, It is checked whether this value is within a predetermined range. When the estimated value of A / B × 100 is within the predetermined range, the rolling load P ₁ estimated above is set as the rolling load P ₁ . When the value of A / B × 100 of the steel sheet estimated above is not within the predetermined range, the steel sheet surface roughness A is further corrected within a predetermined range by further correcting the rolling load by ΔP ₁ , The corrected rolling load P ₂ is calculated. Then, from the estimated rolling load after correction P ₂ , the value of A / B × 100 after temper rolling was estimated, and further, the estimated A / B × 100
It is checked whether the value of is within a predetermined range. When the estimated value of A / B × 100 is within the predetermined range, the rolling load P ₂ estimated above is set as the rolling load. Further, when the estimated value of A / B × 100 is not within the predetermined range, the above calculation is further continued, and the value of the steel sheet surface roughness A after temper rolling and A / B × 100 Set the rolling load P so that the value of is within the specified range.

In this way, the rolling load P is set and the variation in the Fe—Ni—O 2 -based film deposition amount formed by temper rolling can be reduced.

In the case of the second embodiment of the present invention, the Fe-Ni-O system coating amount measuring device 9 provided at the subsequent stage of the Fe-Ni-O system coating treatment device 6 measures the Fe-Ni-O system. The coating amount is fed back to the temper rolling mill controller 10, the rolling load of the temper rolling mill 5 is corrected according to the deviation between the target deposition amount and the measured deposition amount, and the steel sheet surface roughness after temper rolling is corrected. The rolling load is controlled so that is within a predetermined roughness range.

The rolling load for temper rolling is set as follows. Based on the relationship between the surface roughness and the adhered amount shown in FIG. 5, the correction amount ΔA of the surface roughness according to the adhered amount deviation between the target adhered amount W ₁ and the measured adhered amount W ₀ is obtained. Then, the rolling load is set according to the procedure described in the embodiment of the first invention described above.

In this way, the rolling load P is set, and the variation in the Fe-Ni-O 2 -based film deposition amount formed by temper rolling can be reduced.

In the case of the embodiment of the third invention, the alloying furnace 4
Subsequent to the temper rolling, the temper rolling was measured by the surface roughness measuring device 7 installed in the former stage of the temper rolling mill 5.The temper rolling of the steel plate surface roughness measured by the steel plate surface roughness measuring device provided in the former stage was performed. It is sent to the machine controller 10 and feed-forward control is performed to correct the rolling load of the temper rolling mill 5 according to the deviation between the target surface roughness and the measured surface roughness. Control to be within the roughness range.

The temper rolling load is set as follows.
Rolling load P, ratio of surface roughness A (Ra: μm) after temper rolling and area ratio B (%) of the broken part of oxide film, A / B × 100
There is a relationship as shown in Fig. 12, and F = A / B
When × 100 is F, the relationship between F and P is expressed by the following equation (2).

F = k ₁ / P (2) k ₁ is a constant determined by the surface roughness of the plated steel sheet after the alloying treatment before temper rolling, and is the plate temperature invading the plating bath. , It changes depending on the alloying processing conditions, so it is possible to previously obtain the relationship between them by a multiple regression equation or to make a table of these relationships. FIG. 11 is a table set in the line computer in which k ₁ corresponding to the surface roughness of the steel sheet after the alloying treatment is set according to the combination of the plate temperature entering the plating bath and the alloying treatment temperature. It is an example, and is prepared for each component system of the steel type. From this table, based on the surface roughness measurement value measured by the steel plate surface roughness measuring device in the preceding stage of the temper rolling mill, the corresponding k ₁ is obtained (hereinafter, k _{1 is referred} to as original plate roughness constant k ₁ ) .

A value of A / B × 100 is estimated from FIG. 12 and the measured value of the surface roughness of the steel sheet before temper rolling. Rolling force P and
Since the relationship of A / B × 100 has a relationship as shown in FIG. 13, the rolling load ΔP is corrected so that the value of A / B × 100 estimated above becomes the target value.

These procedures will be described with reference to the flow chart of FIG. First, the initial load P ₀ is calculated based on the equation (1). Next, based on the table shown in FIG. 11, the original plate roughness constant k ₁ is obtained based on the surface roughness of the steel sheet after the alloying treatment, and the value of A / B × 100 is further estimated. Then, from FIG. 13, the rolling load is corrected by ΔP ₀ so that the estimated value of A / B × 100 becomes the target value of A / B × 100, and the corrected rolling load P ₁ is calculated. Next, the estimated steel plate surface roughness A ₁ after temper rolling is estimated from the corrected estimated load P ₁ . Then, it is checked whether the estimated steel plate surface roughness A ₁ is within a predetermined steel plate surface roughness range. When the estimated steel plate surface roughness A ₁ is within the range of the predetermined steel plate surface roughness, the rolling load P ₁ obtained above is set as the rolling load P ₁ .

Further, when the estimated steel plate surface roughness A ₁ is not within the range of the predetermined steel plate surface roughness, the value of A / B × 100 is further set to the target A / B × 100 as shown in FIG. Correct the rolling load by ΔP ₁ so that it is within the range of B × 100,
The corrected rolling load P ₂ is calculated. Next, the estimated load after correction
From P ₂ , the estimated steel plate surface roughness A ₂ after temper rolling is estimated.
Next, it is checked whether the estimated steel plate surface roughness A ₂ is within a predetermined steel plate surface roughness range. Estimated steel plate surface roughness A ₂
Is within the range of the predetermined steel plate steel plate roughness, the rolling load P ₂ obtained above is set as the rolling load. Further, when the estimated steel plate surface roughness A ₂ is not within the range of the predetermined steel plate surface roughness, the above calculation is further continued, and the value of the steel plate surface roughness A after temper rolling and A / Obtain the rolling load P within which the value of B × 100 falls within the specified range. In this way, the rolling load P can be set to reduce the fluctuation of the Fe-Ni-O 2 -based film deposition amount formed by temper rolling.

In the case of the embodiment of the fourth invention, the first
Feedback control described in the embodiment of the invention and feedforward control described in the third embodiment of the invention, or feedback control described in the second embodiment of the invention and implementation of the third invention When the Fe-Ni-O-based coating is formed on the hot dip galvanized layer by the immersion treatment or the electrolytic treatment in combination with the feedforward control described in the above embodiment, the feedback described in the embodiment of the first invention is used. When the control and the feedforward control described in the embodiment of the third aspect of the invention are used together, until the condition change point passes through the surface roughness measuring device 8 in the subsequent stage of the temper rolling mill 5, the feed is performed. By performing the forward control and thereafter performing the feedback control, the feedback control described in the second embodiment of the invention and the third invention When used in combination with the feedforward control described in the embodiment, the feed rate is changed until the condition change point passes through the Fe-Ni-O-based coating amount measuring device 9 in the subsequent stage of the Fe-Ni-O-based processing device. By performing forward control and thereafter performing feedback control, control is performed so that the steel sheet surface roughness after temper rolling falls within a predetermined roughness range.

The rolling load is set by the above-mentioned first invention.
The method described in the embodiment of the third invention can be used.

By performing such control, it is possible to reduce fluctuations in the amount of Fe—Ni—O 2 -based film formed, including the vicinity of the condition change point. Generally, the condition change point is often the coil connection portion. By performing such control, it is possible to reduce the variation in the coating amount in the longitudinal direction of the coil, particularly in the vicinity of the coil connecting portion.

In the case of the embodiment of the fifth invention, the first
~ In the case of the embodiment of the fourth invention, the steel plate surface roughness Ra after temper rolling is 0.5 to 1.5 μm, and the surface roughness Ra is
A (μm), where B (%) is the area ratio of the part where the film is crushed by temper rolling and the oxide film is destroyed, A / B × 100 is 1 ~
Control to become 3.

The above-mentioned limited range is shown by a hatched area in FIG. The reason for limiting this range is as follows.

The surface roughness Ra is preferably 0.5 to 1.5 μm. When used for automobile parts and the like, it is often the case that the small plate is blanked and then press-formed. If the surface roughness Ra is less than 0.5 μm, the steel sheet is likely to slip during blanking, resulting in poor dimensional accuracy of the length after blanking. Further, when the surface roughness Ra exceeds 1.5 μm, the surface roughness is too large, and the press formability deteriorates.

When A / B × 100 is less than 1, the surface roughness Ra is small, the area ratio of the oxide film destroyed by temper rolling is large, and the amount of coating film formed is too large.

When A / B × 100 exceeds 3, surface roughness
Ra is large, and the oxide film is not sufficiently destroyed by temper rolling, and it becomes impossible to obtain a predetermined coating amount.

By doing so, in the Fe-Ni-O-based coating forming treatment performed after temper rolling, the Fe-Ni-O-based coating with a coating adhesion amount of 50 to 500 mg / m ² can be stabilized. Can be formed.

A known surface roughness measuring device can be used as the steel plate surface roughness measuring device.

A fluorescent X-ray adhesion amount measuring device can be used as the Fe-Ni-O 2 film adhesion amount measuring device.

[0076]

【Example】

(Example 1) A plate thickness of 0.60 to 1.20 mm, a plate width of 914 to 1524 mm and a tensile strength of 30 to 40 kgf / mm ² level IF steel is used as the material, and the plating adhesion amount is 32 to 67 g / m ² per side. For a hot-dip galvanized steel sheet with a Fe concentration in the plating layer of 7.8 to 15.5 wt%, an aqueous solution of Fe / (Fe + Ni): 0.004 to 0.9 in a chloride bath was used, pH: 2.0 to 3.5, Temperature: The Fe-Ni-O system treatment by immersion treatment was performed under the conditions of 20 to 70 ° C. At that time, the above-mentioned first
The steel plate surface roughness was controlled by changing the rolling conditions of the temper rolling described in the embodiments of the invention to the third embodiment of the invention.

Table 1 shows the variation of the coating amount of the coil middle part (steady part) when the above-mentioned respective controls were performed with the target coating amount range of 200 to 500 mg / m ² . In Table 1, Invention Example 1, Invention Example 2, and Invention Example 3 are respectively the first
Examples corresponding to the embodiment of the invention, the embodiment of the second invention, and the embodiment of the third invention. For comparison, without performing the above control, the tension between the inlet bridle and the outlet bridle of the temper rolling mill is kept constant,
Table 1 also shows the variation of the coating amount when the elongation control is performed by controlling the rolling load.

FIG. 3 shows the transition of the adherence amount tolerance deviation rate in the above case.

[0079]

[Table 1]

From Table 1, in the case of the comparative example according to the prior art, 70
The standard deviation in mg / m ² front and rear, are reduced to the case 40 mg / m ² about the present invention embodiment.

Further, from FIG. 3, the adherence amount tolerance deviation rate, which was 1 to 2% in the prior art, is reduced to 0.05% or less in the example of the present invention.

Example 2 A plate thickness is 0.60 to 1.20 mm and a plate width is 914.
And tensile strength of the material of 30~40kgf / mm ² level of the IF steel ~1524mm, Fe concentration in the plating layer amount plating adhesion in per side 32~66g / m ² is 7.9 ~16.3wt% of molten alloying Fe-Ni- with the same dipping treatment as in Example 1 for galvanized steel
O 2 type film forming treatment was performed. At that time, if the coil top portion, which is a condition change point, passes through the steel plate surface roughness measuring device provided in the preceding stage of the temper rolling mill, the feedforward control described in the embodiment of the third invention is performed. The coil top portion is a feedback control (invention example 4) described in the embodiment of the first invention after the steel plate surface roughness measuring device in the latter stage of the temper rolling mill is passed, or, the coil top portion is After passing through the Fe-Ni-O-based treatment film deposition amount measuring device in the subsequent stage of the Fe-Ni-O-based treatment device, the feedback control (Invention Example 5) described in the embodiment of the second invention was switched to.

[0083]

[Table 2]

Table 2 shows the variation of the film adhesion amount at a position 30 m from the coil top when each of the above controls is performed. For comparison, Table 2 also shows the variation of the coating amount when the above control is not performed.

From Table 2, in the case of the comparative example according to the prior art,
A standard deviation of around 80 mg / m ² is 40 mg / m ^{2 in} the case of the present invention.
It has been reduced to the front and back.

(Example 3) The plate thickness of Ti-IF steel was 0.8.
mm, width 1219 mm, standard SGCD2, SGCD3 material, and galvannealed galvanized steel sheet with a coating weight of 45 ± 5 g / m ² per side, surface roughness was variously changed by changing the temper rolling conditions.
Ra, the degree of destruction of the oxide film B (%) for different steel sheets,
Fe-Ni-O system treatment with the same treatment solution as in Example 1,
About steel sheets with different coating amount, press formability, spot weldability, adhesiveness, adhesion resistance to welding dust generated during spot welding, surface appearance, and slippage of steel sheets when blanked It was evaluated by the following. (1) Press Formability The press formability was evaluated by evaluating the friction coefficient between the test piece and the bead using the following device. FIG. 15 is a schematic front view showing the friction coefficient measuring device. As shown in the figure, a friction coefficient measurement sample 21 collected from a sample is fixed to a sample table 22, and the sample table 22 is fixed to an upper surface of a horizontally movable slide table 23. On the lower surface of the slide table 23, there is provided a slide table supporting base 25 having a roller 24 in contact with the slide table supporting base 25, and by pushing up the slide table supporting base 25, the pressing load N on the friction coefficient measurement sample 21 by the bead 26 is increased. A first load cell 27 for measuring is attached to the slide table support 25. A second load cell 28 for measuring a sliding resistance force F for moving the slide table 23 in the horizontal direction is provided at one end of the slide table 23 in the horizontal movement direction while the pressing force is applied. Is installed. As the lubricating oil, Noxlast 550HN manufactured by Nippon Parkerizing Co., Ltd.
It was applied to the surface of and tested.

The friction coefficient μ between the specimen and the bead is
Formula: Calculated by μ = F / N. However, pressing load N: 400 kgf, sample withdrawing speed (horizontal moving speed of slide table 23): 10
It was set to 0 cm / min.

FIG. 16 is a schematic perspective view showing the shape and size of the bead used. The lower surface of the bead 26 slides while being pressed against the surface of the sample 21. Its bottom surface has a width of 10
mm, the length in the sliding direction is 3 mm, and the width of the front and rear faces is 10
The 1/4 cylindrical surface with 4.5mmR on each line of mm touches as shown in the figure.

The press formability was evaluated as follows according to the numerical value of the friction coefficient obtained by the above test. ○: Friction coefficient is 0.16 or less, △: Friction coefficient is over 0.16, less than 0.18, ×: Friction coefficient is over 0.18

(2) Spot Weldability Spot weldability was evaluated by the following continuous point number test.

Resistance test (spot welding) in which two test pieces under the same conditions are stacked, sandwiched between a pair of electrode tips from both sides, and current is concentrated by applying pressure is continuously performed under the following welding conditions. did.

・ Electrode tip: Dome type with 6 mm tip diameter ・ Pressure force: 250 kgf ・ Welding time: 0.2 seconds ・ Welding current: 11.0 KA ・ Welding speed: 1 point / second Melted and solidified metal part generated at the joint of the welded base metal (sample)
(Shape: Go-stone, hereinafter referred to as nugget) diameter is 4 ×
The number of dots that were continuously welded until t ^1/2 (t: thickness of one sheet) was used.

The spot weldability was evaluated as follows according to the numerical value of the number of continuous dots obtained by the above test.

○: The number of continuous dots is 5,000 or more, △: The number of continuous dots is 50
Less than 00 points, more than 3000 points x: The number of consecutive points is less than 3000 points

(3) Adhesiveness The following adhesiveness test specimens were prepared from each specimen. Fig. 17
FIG. 3 is a schematic perspective view illustrating the assembling process. As shown in the figure, two test pieces with a width of 25 mm and a length of 200 mm 31
Then, a test body 34 is prepared by laminating and bonding the adhesive 33 through a spacer 32 having a diameter of 0.15 mm so that the thickness of the adhesive 33 becomes 0.15 mm, and baking at 150 ° C. × 10 min.
The test specimen prepared in this way was bent into a T-shape as shown in Fig. 18, and a tensile test was performed at a speed of 200 mm / min using a tensile tester to determine the average peel strength when the test specimen peeled.
(n = 3 times) was measured. Peel strength is calculated by calculating the average load from the load chart of the tensile load curve during peeling, and the unit is kgf / 25m.
Expressed in m. In FIG. 18, P indicates tensile load. The adhesive used was a PVC-based hemming adhesive.

Adhesiveness was evaluated as follows according to the numerical value of the peel strength obtained by the above test.

◯: Peel strength is 10 kgf / 25 mm or more, Δ: Peel strength is less than 10 kgf / 25 mm, 5 kgf / 25 mm or more, ×: Peel strength is less than 5 kgf / 25 mm

(4) Chemical conversion treatment test The following test was conducted to evaluate the chemical conversion treatment.

Each sample was treated with an immersion type zinc phosphate treatment liquid for automobile coating (PBL3080 manufactured by Nippon Parkerizing Co., Ltd.) under normal conditions to form a zinc phosphate film on the surface thereof. The crystalline state of the zinc phosphate film thus formed was observed with a scanning electron microscope (SEM). The crystalline state was evaluated as follows.

◯: The crystals of the phosphate film are dense and small. Δ: The crystals of the phosphate film are rather coarse and large. X: The crystals of the phosphate film are coarse.

(5) Anti-sticking resistance to scattering Each test piece was subjected to a spot welding scattering occurrence test under the following conditions. As shown in Fig. 19, the thickness of the two stacked sheets is 0.8m.
amount plating adhesion on both sides with m 60 g / m ² of alloyed hot-dip galvanized steel sheet (10 wt% Fe, the balance Zn) of 35, 10 mm from the end portion
Spot welding under the following conditions at the location of No. 3, and the spatter 37 generated at that time was attached to the specimen 31 installed vertically at a location 500 mm away from the end of the material to be welded and attached to 10 cm square (100 cm ² ). The number of solidified scatters was counted.

・ Electrode: DR type Tip diameter 6mm-40R ・ Pressure force: 200kgf ・ Electrification time: 0.2 seconds ・ Welding current: 11kA According to the value of the number of scattered particles obtained by the above test,
The adhesion resistance to scattering was evaluated by the following according to the number of welding dispersion adhered per unit area. ○: The number of scattered deposits is 0, △: The number of scattered deposits is 1 or more, 3
Less than, ×: The number of scattered particles exceeds 3,

(6) Surface Appearance The appearance of the test piece was visually observed and its color tone was compared with that of a standard sample and evaluated as follows. ◯: In the oil-free state, almost no blackening was observed as compared with the standard sample, but in the oiling state it was slightly blackened. Δ: Oil-free, slightly blackened compared to the standard sample. X: Oil-free state, which is significantly blackened compared to the standard sample.

For the standard sample, the adhesion amount (one side): 60 g /
m ² , Fe% in plating layer: 10 wt%, surface roughness Ra: 1.0 μm, area ratio (B) of oxide film destroyed by temper rolling (B): 50%
The alloyed hot-dip galvanized steel sheet before forming the -Ni-O system coating treatment was used.

By applying oil, the difference in color tone between the steel sheet after the Fe—Ni—O type coating treatment and the steel sheet before this treatment becomes remarkable, so the surface after oiling was also evaluated. The oiling condition was NOXLAST 550HN manufactured by Nippon Parkerizing Co., Ltd., and the oiling amount was 1.0 g / m ² per side.

(7) Sliding property As for the sliding property, after forming a Fe-Ni-O type film, Knoxlast 550HN manufactured by Nihon Parkerizing Co., Ltd. was applied at 1.0 g / m ² per side.
Using the shearing device shown in Fig. 20, the oiled alloyed molten zinc plated steel sheet was tensioned between the payoff reel 40 and the pinch roll 42 in front of the shear 41: 0.5 kgf / mm ² , the pinch roll pressure in front of the shear (contact pressure ): 10 kgf / cm, set shear length: 1200 mm
The degree of error in the measured shear length with respect to the set shear length was evaluated as follows.

◯: The error is 1.0 mm or less, Δ: The error is 1.
0 to 5.0 mm or less, ×: Error exceeds 5.0 mm The evaluation results are also shown in Table 3.

[0108]

[Table 3]

In Table 3, the basic properties are evaluations that combine press formability, spot weldability, adhesiveness, and chemical conversion treatability, and are the lowest of the evaluations obtained in each of the above tests. Was evaluated as the basic characteristic. Moreover, the lowest evaluation in each characteristic evaluation was made into the comprehensive evaluation.

Inventive Example 6 in which the surface roughness Ra and A / B are within the range of the fifth invention of the present invention and the coating amount is 200 to 500 mg / m ² is excellent in evaluation of all properties.

On the other hand, No. 19 having a surface roughness Ra of less than 0.5 μm
Has poor slipperiness. No. 18 having a surface roughness Ra of more than 1.5 has poor press formability.

No. 4 and No. 9 with A / B less than 1 have a large amount of coating film and have poor surface appearance. No.1 and N with A / B over 3
o.5, No.10, No.11, No.14 to No.16 have a small amount of coating film, and scattering easily adheres.

The above-mentioned embodiment is a case of immersion treatment using a chloride-based treatment liquid containing Fe ions and Ni ions, but the present invention is not limited to this embodiment.
Immersion treatment using an aqueous solution containing Fe ions and Ni ions,
Similar results can be obtained when performing electrolytic treatment.

[0114]

According to the present invention, an alloyed hot-dip galvanized steel sheet with reduced fluctuations in the Fe-Ni-O-based coating film deposition amount can be produced. Therefore, when the target range of the Fe-Ni-O-based coating film deposition amount is narrow. Also in this case, the sticking amount deviation rate can be significantly improved, and as a result, the yield can be improved. In addition, it has excellent performance in all of press formability, spot weldability, adhesiveness, and chemical conversion treatability, and it also stabilizes hot dip galvanized steel sheet with Fe-Ni-O based coating that does not easily adhere to molten metal such as welding dust. It will be possible even if manufactured.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a range of a steel plate surface roughness and an area ratio of a broken portion of an oxide film in the present invention.

FIG. 2 is a diagram showing a main part of a continuous galvanizing line.

FIG. 3 is a diagram showing changes in the adherence amount tolerance deviation rate of the Fe—Ni—O system coating.

[Fig. 4] Degree of destruction of oxide film on the plating layer surface and Fe-Ni-
The figure explaining the relationship with the amount of O 2 system coatings.

FIG. 5 is a diagram for explaining the relationship between the surface roughness of a plated steel sheet and the amount of Fe—Ni—O 2 -based film deposition.

FIG. 6 is a diagram illustrating the relationship between the rolling load of temper rolling and the surface roughness of the plated steel sheet after temper rolling.

FIG. 7 is a diagram illustrating the relationship between the rolling load of temper rolling and the degree of destruction of the oxide film of the plated steel sheet after temper rolling.

FIG. 8 is a diagram illustrating a method of obtaining an estimated rolling load corrected from the surface roughness measured in the embodiment of the first invention.

FIG. 9 is a diagram illustrating a method for correcting a rolling load according to the embodiment of the first invention.

FIG. 10 is a flowchart illustrating a procedure for setting rolling load in the embodiment of the first invention.

FIG. 11: k ₁ Corresponding to Surface Roughness of Steel Sheet after Alloying
A table showing a table for setting the.

FIG. 12 is a diagram showing the relationship between rolling load, steel plate surface roughness after alloying treatment (before temper rolling), and A / B value of the steel sheet after temper rolling.

FIG. 13 is a diagram illustrating a method of correcting a rolling load in the embodiment of the third invention.

FIG. 14 is a flowchart illustrating a procedure for setting a rolling load in the embodiment of the third invention.

FIG. 15 is a schematic perspective view showing a friction coefficient measuring device.

FIG. 16 is a schematic perspective view showing the shape and dimensions of a bead used for measuring a friction coefficient.

FIG. 17 is a schematic perspective view illustrating an assembling process of the adhesive test specimen.

FIG. 18 is a schematic perspective view illustrating a load of a tensile load when measuring peel strength in an adhesion test.

FIG. 19 is a diagram for explaining a method for testing the adhesion resistance of welding dust.

FIG. 20 is a diagram illustrating shearing equipment used for evaluation of slipperiness.

[Explanation of symbols]

 1 Annealing furnace 2 Zinc plating bath 3 Air wiping nozzle 4 Alloying furnace 5 Temper rolling mill 6 Fe-Ni-O type coating treatment device 7, 9 Steel plate surface roughness measuring device 8 Fe-Ni-O type coating amount measurement Equipment 10 Temper rolling mill controller 11 Process computer 12 Steel plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (3)

[Claims] 1. A continuous hot-dip galvanizing line, in which hot-dip galvanizing is applied to a steel sheet, and then alloying treatment, temper rolling, and then Fe-Ni-O-based film forming treatment are performed to obtain Fe-Ni. -O
When manufacturing alloyed hot-dip galvanized steel sheet with a system coating, the surface roughness information measured by the steel sheet surface roughness measuring device provided after the temper rolling mill and before the Fe-Ni-O coating processing equipment is used. Based on this, feedback control is performed to correct the rolling load of the temper rolling mill, and temper rolling is performed so that the surface roughness of the steel sheet after temper rolling falls within a predetermined range. A method for producing a galvannealed steel sheet having a coating. 2. A continuous type hot dip galvanizing line is used to apply hot dip galvanizing to a steel sheet, and then alloying treatment, temper rolling, and then treatment to form a Fe—Ni—O-based coating to obtain Fe—Ni. -O
Fe-Ni-O, which was installed in the latter stage of the Fe-Ni-O system film forming device, was used to manufacture the alloyed hot-dip galvanized steel sheet with the system film.
Feedback control is performed to correct the rolling load of the temper rolling mill, based on the Fe-Ni-O system coating amount information measured by the O system coating amount measuring device, and the steel plate surface roughness after temper rolling is specified. A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O-based coating, characterized by performing temper rolling so as to fall within a range. 3. A continuous hot-dip galvanizing line, wherein hot-dip galvanizing of a steel sheet is followed by alloying treatment, temper rolling, and then treatment for forming a Fe-Ni-O-based coating to obtain Fe-Ni. -O
When manufacturing a galvannealed steel sheet with a system coating, based on the surface roughness information measured by the steel sheet surface roughness measuring device provided after the alloying treatment device and before the temper rolling mill, An alloy with Fe-Ni-O based coating characterized by performing feed-forward control to correct the rolling load of the rolling mill and temper-rolling so that the surface roughness of the steel sheet after temper-rolling falls within a specified range. Method for producing hot-dip galvanized steel sheet. 4. A continuous type hot dip galvanizing line is used to apply hot dip galvanizing to a steel sheet, and then alloying, temper rolling, and then form a Fe-Ni-O-based coating to form Fe-Ni. -O
In producing an alloyed hot-dip galvanized steel sheet having a system coating, the feedback control according to claim 1 or claim 2 and the feedforward control according to claim 3 are used together, and the condition change point is after the temper rolling mill. Feed-forward control is performed until it passes the Fe-Ni-O-based coating amount measuring device installed in the subsequent stage of the steel plate surface roughness measuring device or the Fe-Ni-O-based film forming device installed in The Fe-N is characterized in that after passing through the above, the control is switched to feedback control to correct the rolling load of the temper rolling mill so that the steel sheet surface roughness after temper rolling falls within a predetermined range.
A method for manufacturing an alloyed hot-dip galvanized steel sheet having an iO coating. 5. The method for producing an alloyed hot-dip galvanized steel sheet having the Fe—Ni—O-based coating according to claim 1, wherein the steel sheet surface roughness after temper rolling is used. Ra is 0.
5 to 1.5 μm, surface roughness Ra is A (μm), and the area ratio of the part where the oxide film is destroyed by crushing the film by temper rolling
When B (%) is set, A / B × 100 is 1 to 3 after temper rolling, and Fe-Ni-O system coating amount is 200 to
Characterized by forming a Fe-Ni-O-based film of 500 mg / m ^2.
A method for producing an alloyed hot-dip galvanized steel sheet having a Fe-Ni-O system coating.