JP3486003B2 - High adhesion coating method and plating bath for molten Al-Zn-Si alloy and molten Al-Si alloy by flux method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a molten Al-Zn-Si alloy and a molten A using a flux for steel materials.
In l-Si alloy plating, the present invention relates to a plating method for forming a uniform and smooth plating film layer having a high deposition amount on a steel material and a plating bath used therefor.

[0002]

2. Description of the Related Art Conventionally, hot-dip galvanizing has been performed as a measure for improving corrosion resistance of steel towers, building structures such as bridges, overhead wire products made of steel materials, and bolt products which are connecting members thereof. However, along with the development of the ocean and coastal areas, in these severely corrosive environments, hot-dip galvanizing does not provide sufficient corrosion resistance for long-term use, so various maintenance is required. . In addition, acid rain is becoming a problem in recent years, and for the steel materials used for the above-mentioned uses, molten Al-Zn-Si and molten Al having corrosion resistance several times higher than that of zinc plating are used.
-Hot-dip aluminum alloy plating such as Si-based alloy is effective.

Particularly, from the viewpoint of long-term corrosion protection, Al- Zn- S containing 20 to 65 % by weight of zinc and 0.5 to 3.5% by weight of silicon as main components with respect to aluminum .
It is possible to form a molten aluminum-based alloy plating film such as an i-based alloy or an Al-Si-based alloy containing 3 to 12% by weight of silicon as a main component with respect to aluminum in a steel material thickly, that is, with a high deposition amount. It is extremely effective, and development of the plating method is strongly desired.

Corresponding to these circumstances, the above-mentioned method for plating a molten aluminum alloy is industrially advantageous in terms of productivity and equipment, which does not depend on a two-step plating method in which plating is divided into two steps. Various plating methods by a one-step plating method in which a molten aluminum-based alloy plating is directly applied to a steel material without providing an undercoat coating layer have been studied. For example, for steel strips for which it is easy to adopt the continuous plating method, a method of cleaning and activating the surface of the steel sheet with a reducing gas and sealing the plating bath to perform hot dip coating, so-called Sendzimer method, industrialization by NOF method Technology has been established and has been put to practical use. However, molten Al-Zn-Si and molten Al that have been put to practical use by the plating method
-Si-based alloy plated products have a maximum coating amount of about 100 g / m ^{2 on} one side of a steel plate, and it is difficult to provide a high coating amount of the plating layer to thicken the coating layer. .

On the other hand, molten aluminum-based alloys, especially molten Al-Zn-Si-based alloys are used for building structures, overhead wire products, bolt products, etc., where it is industrially advantageous to carry out hot dip plating in the atmosphere using flux. As for the method of performing alloy plating by the one-step plating method, various methods as described below have been studied. For example, the content of aluminum is 1 to
A plating method by a dry flux method for 20% is disclosed in JP-A-58-136759 and JP-A-4-202.
It is disclosed in Japanese Patent Publication No. 751. Further, as a plating method by a dry flux method for molten Al-Zn-Si alloy plating containing aluminum in an amount of 30 to 80%, U.S. Pat. No. 3,860,438, JP-A 3-1
No. 62557 is disclosed. Of these, U.S. Pat. No. 3,860,438 discloses an aqueous solution flux containing potassium fluoride, potassium fluoride, hydrofluoric acid and zinc chloride as a main component. Kaihei 3-162557 proposes a zinc chloride-ammonium chloride-based aqueous solution type flux in which the mixing ratio of zinc chloride and ammonium chloride is specified. further,
In Japanese Unexamined Patent Publication No. 4-323356, a fluoride of an alkali metal containing aluminum and a chloride of an alkaline earth metal, or a molten flux containing an alkali metal chloride is added to a bath surface of a plating bath. Melt on,
A plating method by a molten flux method of floating has been developed.

Regarding the plating of molten aluminum, as a one-step plating method using a flux, conventionally, fluoride of 10% by weight or less (alkali fluoride, cryolite, etc.) is used.
And chlorides (KCl, LiCl, NaC) as main components
(I, CaCl ₂ , ZnCl ₂ etc.) as a main component, a plating method by a molten flux method of melting and suspending a flux composed on the bath surface of a molten Al plating bath has been conventionally known.

However, with respect to the method of plating molten aluminum-based alloys, particularly molten Al-Zn-Si-based alloys or Al-Si-based alloys by the one-step plating method using these fluxes, which have been variously studied, non-plating, etc. Although a plating method for forming a plating film layer with no plating defects is being investigated, most of the development has been done for a method of forming a plating film layer with a high deposition amount.
The situation is not being considered.

As described above, in the prior art, the molten Al--Zn--Si alloy or molten A is added to the steel material.
Regarding 1-Si alloy plating, there is a situation in which a method for forming a thick plating film layer, that is, a high deposition amount, has not been sufficiently studied. For example, the coating weight of these hot-dip galvanized products for steel strips for which continuous plating method by gas reduction method (Sendzier method, NOF method, etc.) is adopted is various documents or product catalogs [eg,
Galvalume steel sheet issued by Nippon Steel Corporation (1990
June issue), Al sheet (issued in October 1993) product catalog], molten Al-Zn-Si
About 85g / m per unit area for system alloy plated products
² , and about 100 g / m ² per unit area is considered to be the limit of the high adhesion plating amount for the molten Al-Si alloy plated product (Al sheet). That is, as compared with general hot dip galvanizing, for example, galvanizing, even in the high-speed plating method in which a high adhesion plating amount is possible by increasing the amount of the hot dipping bath lifted at the time of withdrawal from the hot dipping bath, the molten Al--Zn In the -Si alloy or the molten Al-Si alloy plating, it is difficult to form a plating film layer having a high adhesion amount.

On the other hand, since continuous plating by the gas reduction method is difficult due to the shape, size, etc., the hot dipping method by the flux method is adopted, and the long-term rust prevention is required for the building structure, overhead wire hardware and bolt products. For etc.,
There is a particular need to form a uniform and smooth plating film layer with a high deposition amount by an industrially excellent one-step plating method. However, since it is difficult to perform high-speed plating like the continuous plating method for the steel strips described above, there is a problem that an increase in the amount of hot-dip of the hot dip plating bath during the lifting from the plating bath can hardly be expected. It is difficult to say that the plating method for increasing the amount of adhesion is well established.

[0010]

SUMMARY OF THE INVENTION The present invention addresses the above problems and solves the problems of the prior art by forming a uniform and smooth plating film layer with a high adhesion amount on steel materials. Al-Zn-Si alloys and molten Al-
Regarding Si-based alloy plating, after performing a dry flux treatment effective for forming a uniform and smooth plating film layer with no plating defects by a one-step plating method using flux,
The present invention provides a novel hot-dip Al-Zn-Si-based alloy, a hot-dip Al-Si-based alloy plating method, and a plating bath used in the hot-dip aluminum-alloy plating in which hot-dip plating is performed using a molten flux.

[0011]

Means for Solving the Problems As a result of earnest studies to solve the conventional problems, the present inventors have found that it is difficult to secure a sufficient amount of hot-dip metal. Molten Al-Zn by plating method
-Si-based alloy and hot-dip Al-Si-based alloy plating, the average roughness of the surface of the target steel material is adjusted to a certain range, and immersed in a hot-dip plating bath to which a certain amount of iron component is melted and added. The present invention has been completed by discovering a method capable of forming a uniform and smooth plating film layer with a high adhesion amount on a steel material by treating the steel material and then controlling the adhesion amount of the plating, and a plating bath used for the method. .

That is, the present invention adjusts the surface roughness of the steel material to be plated in hot dip Al-Zn-Si alloy or hot dip Al-Si alloy plating by the one-step plating method using flux. By increasing the viscosity of the hot-dip galvanizing bath, in the process of lifting from the hot-dip galvanizing bath, it is possible to suppress an increase in the amount of hot-dip galvanizing metal adhering to and lifting the steel material and the spontaneous outflow of the hot-dip galvanizing metal. The problem of the conventional method is solved by performing control processing of the amount of plated coating with a large amount of hot-dip metal deposited on the surface and performing smoothing treatment in some cases, resulting in a uniform and smooth coating with a high deposition amount. We have developed a hot dip plating method that enables the formation of various plating film layers and a plating bath used therefor.

That is, according to the present invention, since the formation of an alloy layer due to the reaction between the plating bath and the steel material is suppressed by the action of silicon in the plating bath and the plating bath is remarkably rich in fluidity, In the process of withdrawing from the plating bath, the amount of hot-dip galvanized bath, that is, the amount of hot-dip galvanized metal, which is adhered to the steel material to be plated by the anchoring effect and lifted up and held without flowing out to the surface, is sufficient. Al- Zn that is difficult to secure
-Si alloys and Al-Si alloys have been solved to provide a method for forming a uniform and smooth plating film layer with a high adhesion amount on a steel material by a one-step plating method using flux. To do.

Further, in the present invention, for building structures and bolt products which require long-term rust prevention, 350 g / m ² or more per unit area, which is the high adhesion plating amount adopted in hot dip galvanized products. That is, the molten Al-Zn-Si-based alloy and the molten Al-S having a coating amount corresponding to a plating thickness of about 50 μm (calculated as a specific gravity of 7.14).
Hot-dip Al-Zn-S for i-based alloy plated products
190g per unit area for i-based alloy plated products
/ M ² (calculated as a specific gravity of about 3.80), especially 200
g / m ² or more, and Al-Si-based (calculated as the specific gravity of about 2.64) 132g / m ² per unit area of the alloy plated products or, in particular, it is possible to form a 150 g / m ² or more plating film layer .

That is, the present invention is a molten Al-Zn-S prepared by a one-step plating method using a flux for steel materials.
In the i-based alloy and the molten Al-Si-based alloy plating, the average roughness of the steel material surface from which the oxide film has been removed is 2.5 to 7.
After adjusting to a range of 5 μmRa, activation treatment is performed, and immersion is performed in a hot dip plating bath in which an iron component in a range of 0.25 to 1.5% by weight relative to the total weight of the plating bath excluding flux is melt-added. There is provided a molten Al-Zn-Si alloy and a high deposition plating method for a molten Al-Si alloy, which is characterized by performing a treatment and then a treatment for controlling the deposit amount.

Further, the present invention uses a molten A using flux.
An iron component in the range of 0.25 to 1.5% by weight relative to the total weight of the plating bath excluding the flux is melted and added to the plating bath made of the 1-Zn-Si alloy or the molten Al-Si alloy. A molten Al-Zn-Si alloy and a molten Al-Si alloy plating bath using a flux are provided.

As an embodiment of the present invention, the control processing of the amount of plating adhesion is performed at a peripheral speed of 400 to 1,500 m /
After performing the centrifugal separation method in the range of min and performing the control processing of the amount of plating adhered by the centrifugal separation method, the peripheral speed of 1/3 or more and 2/5 or less and 1
It is particularly preferable to rotate in the opposite direction to the above treatment for a treatment time of / 5 or more and 3/4 or less and add the smoothing treatment.

The present invention will be described in detail below. First, the molten Al-Zn-Si alloy and the method for plating a high amount of molten Al-Si alloy according to the present invention will be described in detail. The plating targeted by the present invention is a molten Al-Zn-Si alloy plating in which a plating temperature of 580 ° C to 700 ° C, preferably 610 ° C to 680 ° C is generally adopted, for example, 20 to 65% by weight with respect to aluminum. -Zn-S containing zinc as a main component and 0.5 to 3.5% by weight of silicon as main components
i-based alloy plating or 3 to 3 for aluminum
Molten A containing 12% by weight of silicon as a main component
1-Si alloy plating and the like.

In the present invention, by the single-step plating by the flux method, a high adhesion amount having a uniform and excellent smoothness of the plating appearance without plating defects such as non-plating, especially an adhesion amount per unit area is molten Al-Zn-Si. system for the alloy plating product (calculated as specific gravity of about 3.80) 190 g / m ² or more, particularly 200 g / m ² or more, and Al-Si alloy coated for products 132g / m ² (specific gravity of about 2.
Calculated as 64) or more, particularly 150 g / m ² or more of the plating film layer is targeted.

The type of steel material that is the material to be plated is not limited. In the present invention, the oxide material is removed and the surface roughness is adjusted on the steel material to be plated. The method is not particularly limited, and after the oxide film is removed by pickling with hydrochloric acid, an aqueous solution of sulfuric acid, etc., the surface roughness is adjusted using mechanical means such as shot blasting and grit blasting. A method of performing the above, or a method of simultaneously removing the oxide film and adjusting the surface roughness by a mechanical means such as shot blasting or grit blasting is adopted. In the molten alloy plating targeted by the present invention, since the generation and growth of the alloy layer due to the action of silicon in the plating bath is suppressed, the amount of the molten alloy plating bath to be lifted when the steel material is lifted from the plating bath. There is a problem that it is difficult to secure enough due to the anchoring effect of. Therefore, in the present invention, the purpose of adjusting the surface roughness is to solve such a problem. That is, by appropriately adjusting the surface roughness of the steel material to be plated and finely roughening the surface, an increase in the amount of the molten alloy plating bath attached to the steel material and lifted up by the anchoring effect is measured. Is done for.

In order to achieve the object of the present invention, the surface roughness of the steel material is 2.5 μmRa to 7.5 μmR in average roughness.
It is defined in the range of a. That is, if the surface roughness of the steel material is less than the average roughness of 2.5 μmRa, it is difficult to secure a sufficient amount of lift of the molten alloy plating bath due to the above-mentioned action in the lifting process from the plating bath. If the average roughness exceeds 7.5 μmRa, the lifted amount of the molten alloy plating bath will be saturated, and problems such as deterioration of the smoothness of the plating film layer surface after the control processing of the coating amount will occur. Not preferable. Therefore, in the present invention, the roughness of the surface of the steel material is defined in the range of average roughness 2.5 μmRa to 7.5 μmRa, preferably 3.0 μmRa to 5.5 μmRa.

As described above, after subjecting the steel material to the surface roughness adjusting treatment, for example, activation treatment using a hydrochloric acid aqueous solution or the like and water washing treatment are performed, and molten Al-Zn by one-step plating using flux is performed. -Si alloy or molten Al-
Si-based alloy plating is performed. The flux used in the present invention and the conditions of use of the flux are not particularly specified, and include, for example, 5 wt% to 70 wt% of one or more calcium chloride and magnesium chloride (one or more calcium chloride and one or more magnesium chloride). And a flux composed of a chloride-based aqueous solution containing one or more of potassium chloride, lithium chloride, and sodium chloride as essential components) as a dry flux, and 15% by weight to 6% by weight.
Contains one or more fluorides containing 0% by weight of aluminum (one or more fluorides containing aluminum and one or more of calcium chloride, magnesium chloride and one or more of potassium chloride, lithium chloride, sodium chloride are essential components (Flux) is used as a molten flux, and hot dip plating is performed using both of these fluxes.

In the present invention, the above-mentioned chloride-based dry flux is applied to the iron and steel material from which the oxide film has been removed, the surface roughness has been adjusted and the activation treatment has been carried out, and the heat-drying treatment has been carried out to give 1 per surface area. After forming a film of 0.5 g / m ^{2 to} 30 g / m ² , the above-mentioned molten flux containing fluoride is melted and suspended, and the melt A is increased in viscosity.
Immersion in an l-Zn-Si alloy or hot dip Al-Si alloy plating bath, holding for a predetermined time and withdrawing from the hot dip plating bath, a treatment for controlling the amount of coating deposit, or a smoothing treatment subsequent to the control treatment. Then, a hot dip coating layer is formed. In order to achieve the object of the present invention, in addition to adjusting the surface roughness of the steel material, molten Al-Z as described above is used.
It is necessary to increase the viscosity of the n-Si alloy or molten Al-Si alloy plating bath. In other words, it is important to control the amount of plating deposit with a large amount of hot-dip metal deposited on the surface of the steel material after being lifted from the plating bath. At the same time, it is taken as a measure for suppressing the spontaneous outflow of the hot dip plating bath and holding it on the surface of the steel material.

Therefore, in order to achieve the object of the present invention, as a result of various studies, it is extremely necessary to melt-add an appropriate amount of iron component into the molten Al-Zn-Si alloy or the molten Al-Si alloy plating bath. It is valid. The iron component to be melt-added in the present invention is not particularly specified, but contains high-purity electrolytic iron or a small amount of C, Mn, Si, P, S, Al, Cr and the like as unavoidable impurities. Steel plates and steel materials are used.

In the present invention, the amount of the iron component added is 0.25% to 1.% with respect to the total weight of the plating bath excluding the flux.
5% by weight (hereinafter referred to as "weight%"). Molten Al-Zn-Si alloy or molten Al-S
The amount of iron component added to the i-based alloy plating bath is 0.2
When the content is less than 5% by weight, the effect of improving the viscosity of these molten alloy plating baths is small, and even if the roughness of the steel material surface is adjusted as described above, the molten steel will melt on the steel material surface after being lifted from the hot dip plating bath. It is difficult to attach and retain a large amount of hot-dip galvanized metal due to the increase in the amount of lift of the alloy plating bath and the suppression of its spontaneous outflow, and the uniform and smooth high-adhesion plating film layer which is the object of the present invention. Formation is inhibited. On the other hand, when the molten addition amount of the iron component exceeds 1.5% by weight, in the plating temperature range of the molten Al-Zn-Si alloy or the molten Al-Si alloy targeted by the present invention, the iron component is added. Unreacted reaction product of the above and the constituent components of the alloy plating bath and its oxide, so-called dross is excessively increased, and it adheres to the plating film layer and deteriorates the uniformity and performance of the plating appearance, which is not preferable. . Therefore, in order to achieve the object of the present invention, the iron component melt-added in the molten alloy plating bath is in the range of 0.25% by weight to 1.5% by weight, preferably 0.35% by weight to 1.2%. weight%
Stipulated in the range of.

The method of adding the iron component to be added by melting to the molten alloy plating bath is not particularly specified, and for example, a molten Al-Zn-Si alloy plating bath or a molten Al-Si alloy plating bath. Of electrolytic iron in the hot dip bath or a method of hot-adding aluminum or zinc containing an iron component as a master alloy at the time of formation of
A method of melting and adding a steel material or the like is adopted. In addition,
The amount of the iron component in the molten alloy plating bath may be adjusted and managed including the amount of the iron component to be added by melting and the plating component, the amount of the iron component inevitably contained by elution from the steel material, It is necessary in the present invention.

As described above, by adjusting the surface roughness of the steel material to be plated and increasing the viscosity of the molten alloy plating bath by adding the iron component, an alloy layer is formed by the reaction with the steel material. It is difficult to increase the amount of molten alloy plating bath that is adhered to the steel material and lifted up during the process of withdrawing from the plating bath, that is, the amount of hot-dip galvanized metal because the plating bath is remarkably rich in fluidity. Al-Zn-Si based alloy or molten Al-Si
In system-based alloy plating, it becomes possible to control the amount of plating deposited when a large amount of hot-dip galvanized metal is deposited on the surface of the steel material after being lifted from the plating bath. That is, in this state, excess molten alloy plated metal that adheres to the steel material can be wiped by a predetermined amount by a method such as high-pressure gas, high-pressure steam, or rotary shaking using a centrifuge, so high adhesion Uniform and smooth molten Al-Zn-Si
A system alloy and a molten Al-Si system alloy plating film layer can be formed, and the object of the present invention is achieved.

In particular, in the method of the present invention, with respect to the method for controlling the amount of plating deposit, a rotary shake-off method using a centrifugal separation method, that is, a peripheral speed of a material to be plated on which hot-dip metal is deposited by a centrifugal separator is used. Is more effective than other control methods to form a uniform and smooth plating film layer with a high deposition amount more effectively than other control methods. That is, with respect to a method for controlling the amount of plating adhered by directly spraying high-pressure gas or high-pressure steam onto the steel material that is the material to be plated with the molten alloy plating bath and wiping the hot-dip metal, in the present invention, Since measures are taken to increase the viscosity, an excess pool of hot-dip galvanized metal is easily generated at the lower end of the material to be plated, and dross contained in the hot-dip galvanized metal is not sufficiently removed. When it remains, it is sometimes observed that a partial pool portion of the hot-dip plated metal is generated due to this. Therefore, depending on the case, there is a drawback that it is necessary to remove the pooled portion of the plating metal by a mechanical means or the like after the control processing of the plating adhesion amount.

On the other hand, the method of controlling the coating amount by adjusting the peripheral speed of the steel material adhered to the molten alloy plating bath by the centrifugal separator is to rotate the surplus deposited hot-dipped metal and dross from the surface to the outside. Can be wiped off by the method described above, and the above problems do not occur, which is particularly effective for achieving the object of the present invention. Therefore, in the present invention, a uniform and smooth molten Al-Zn having a high deposition amount is used.
In order to obtain a plating film layer of a -Si alloy or a molten Al-Si alloy, the steel material to which the molten alloy plating bath has adhered is subjected to a peripheral speed of 400 m / mi using a centrifugal separator.
It is adjusted to a range of n to 1,500 m / min to control the coating amount of plating. That is, the centrifugation method
When the peripheral speed is less than 400 m / min in the process of controlling the amount of plating adhered by adjusting the peripheral speed, the surplus portion of the high-viscosity molten alloy-plated metal adhered to the steel material to be plated is melt-plated. It is difficult to wipe off the metal by solidification until the metal solidifies, and the plating film layer remaining and formed on the surface of the steel material does not always have good smoothness. Also, this peripheral speed is 1,500 m
If it exceeds / min, the effect of wiping off the hot-dip galvanized metal adhering to the steel material is remarkable, and the uniform smoothness of the plating appearance is excellent, but the amount of the coating layer remaining on the surface of the steel material adheres. Is too low, which is not preferable. Therefore, in the present invention, the peripheral speed in the control process of the plating deposition amount using the centrifugal separator is in the range of 400 m / min to 1,500 m / min,
It is preferably regulated to 450 m / min to 1,150 m / min.

Incidentally, in the control processing of the plating adhesion amount, the plating adhesion amount is controlled by the above-mentioned adjustment of the peripheral speed and the processing time. Is not specified. That is, in accordance with the target coating adhesion amount, taking into consideration the lift amount of the hot-dip metal by the steel material at the time of lifting from the hot-dip alloy plating bath, the temperature or treatment amount of the hot-dip metal, treatment size, etc. The peripheral speed in the above range may be set and the processing time may be arbitrarily selected. In the present invention, generally, it is 3 seconds to 3 seconds corresponding to the target plating adhesion amount and the peripheral speed set in consideration of the other factors.
The excess amount of the molten alloy plating metal adhering to the steel material is wiped off for a treatment time of 0 second, preferably 5 to 25 seconds to control the plating adhesion amount and cool to form a plating film layer. It is desirable to do.

Further, in the present invention, a uniform and smooth plating film layer is formed on the material to be plated having a threaded portion such as a bolt and a nut, and the portion other than the threaded portion, that is, the bolt is formed. In order to form a uniform and smooth plating film layer having a high adhesion amount on the head and the body and on the outer surface and the upper and lower surfaces of the nut, the following method is adopted. Using a centrifugal separator for the hot-dip galvanized metal adhering to the steel material, after controlling the plating adhering amount by rotating and wiping in one direction at a predetermined peripheral speed and processing time corresponding to the target plating adhering amount, As compared with the wiping process, a low peripheral speed and a short-time rotation process are performed in the opposite direction. That is, the target amount of plated coating is rotated in one direction, and before the hot-dip galvanized metal controlled by the wiping process is solidified, the hot-dip galvanized metal is wiped to the outside in the opposite direction, under the condition that it is not removed. By adding the rotation process of
Smoothing is promoted by moving the hot-dip galvanized metal on the surface of the steel material in the opposite direction, and a remarkable effect is obtained particularly in the threaded portion of bolts, nuts and the like.

In order to achieve the target by the method, in the present invention, the peripheral speed V during the wiping treatment of the hot dip metal is performed.
Peripheral speed V for ₀ m / min and processing time t ₀ seconds, respectively
_The reverse rotation process is performed in which ₁ m / min is ⅓V ₀ to 4 / 5V ₀ m / min, and the processing time t ₁ second is restricted to the range of 1 / 5t _{0 to} 3 / 4t ₀ second. That is, the peripheral speed V ₁ m / min in the reverse rotation process is 1 / 3V ₀ m / mi.
If it is less than n, it is difficult to sufficiently smooth the molten plated metal by moving it in the opposite direction, and if the peripheral speed exceeds 4/5 V ₀ m / min, the wiping treatment of the molten plated metal is further performed to deposit the plating. It is not preferable because the amount decreases. Further, if the treatment time is less than 1 / 5t ₀ seconds, the treatment time for the reverse movement of the hot-dip plated metal is too short to perform sufficient smoothing treatment, while the treatment time is 3 / 4t ₀
If it exceeds 2 seconds, the smoothing effect is saturated and, depending on the peripheral speed applied, the amount of plating adhered by the wiping treatment of the hot-dip metal is reduced, which is not preferable. Accordingly, in the present invention, the circumferential speed V ₁ m / min wiping processing time of the molten plating metal, the processing time t ₀ seconds, the circumferential speed V ₁ m / min in smooth processing 1 / 3V ₀ m / min
The range of from 4 to 5/5 V ₀ m / min or less, preferably 2
/ 5V ₀ m / min or more to 3 / 4V ₀ m / min or less, and the processing time is 1 / 5t ₀ seconds or more to 3 /
Range of 4t ₀ seconds or less, preferably 2 / 5t ₀ seconds or more to 3 /
It is regulated within the range of 5t ₀ seconds or less. Regarding the molten alloy plating baths that were adhered to and lifted up on the above-mentioned materials to be plated, the excess molten plating baths were wiped off by a centrifugal separation method to control the amount of plating deposits, and then smoothed by rotating in the opposite direction. The effect of the treatment is particularly remarkable for a plated material having a threaded portion such as a bolt or a nut, but the method can be applied to a plated material having other shapes.

As described above, the formation of the alloy layer is suppressed by the action of silicon contained in the plating bath, and the fluidity of the hot-dip plating bath is extremely remarkable, which makes it difficult to form a plating film layer with a high adhesion amount. Regarding the molten Al-Zn-Si alloy and the molten Al-Si alloy plating, in the present invention, a uniform and smooth plating film layer with a high deposition amount is formed on a steel material by a one-step plating method using a flux. It is possible to provide a possible extremely excellent hot-dip alloy plating method.

Next, molten A using the flux of the present invention
The 1-Zn-Si alloy and the molten Al-Si alloy plating bath will be described. Molten A using the flux of the present invention
As a composition of the 1-Zn-Si alloy and the molten Al-Si alloy plating bath, an alloy plating bath having a plating temperature of 580 ° C to 700 ° C, preferably 610 ° C to 680 ° C is used. For example, Al- (20 to 65%) Zn- (0.5 to 3.5%) S containing the above-mentioned aluminum, zinc, and silicon as essential components.
i-based alloy plating bath, or Al- (3 to 12%) Si-based alloy plating bath containing aluminum and silicon as essential components, and a small amount of Mg, Cr, Cu, Ti, Mn,
The target is an alloy plating bath to which Sn or the like is added. The plating bath of the present invention is characterized in that 0.25 to 1.5% by weight of the iron component is melted with respect to the total weight of the plating bath excluding the flux.

[0035]

EXAMPLE Hot-dip Al-Zn-Si alloy plating and hot-dip Al according to the method of the present invention using various shapes of steel materials.
A specific description will be given in order to further clarify the function and effect of the present invention based on an example in which -Si alloy plating is applied. When carrying out the present invention for bolts and nuts, the average roughness is measured centering on the head and body of the bolt, and the outer surface and upper and lower surfaces of the nut. The surface roughness was adjusted.

Example 1 Thickness 5.5 made using hot-rolled steel sheet (equivalent to S40C)
The test piece in the form of an overhead wire having a size of mm × width 50 mm × length 300 mm was degreased and washed with water, and then an oxide film was removed by pickling with a 10 wt% H ₂ SO ₄ aqueous solution, followed by washing with water and drying.
Next, the average roughness of the surface of the test material was adjusted to 3.0 μmRa by grit blasting, and pretreatment was performed by activation treatment using a 10 wt% HCl aqueous solution and water washing treatment. Then, (38 g / l calcium chloride-108 g /
(1 potassium chloride-54 g / l sodium chloride) -based aqueous solution of chloride flux was applied by a dipping method, and heat-drying treatment was performed at 100 ° C. for 15 minutes to deposit 11.8 g / side. A chloride flux film of m ² was formed on the test material and subjected to a water-soluble dry flux treatment. Then, after the treatment, the test material was coated with a molten flux having a composition of (15 wt% cryolite-30 wt% aluminum fluoride-10 wt% calcium chloride-30 wt% potassium chloride-15 wt% sodium chloride). About 20
Molten Al-43.5% to which 0.35% by weight of an iron component at a temperature of 635 ° C. which has been melted and floated to be 0.3 mm is added.
It was immersed in a Zn-1.5% Si-based alloy plating bath and held for 2 minutes. Next, while lifting the test material from the hot dip bath at a speed of 2 m / min, the excess metal adhering to the test material was wiped off using nitrogen gas to control the amount of plating adhered, and then water-cooled and dried. And melted Al-Z on the sample material
An n-Si alloy plating layer was formed.

As a result, on the surface of the plating layer, only 4 to 6 fine projections due to oxides and partial accumulation of the plating bath are converted per 1 m ^{2 of} surface area. Also, the coating weight is 230 g / m ² per surface area.
Met. However, since a pool portion of the plating metal was generated at the lower end portion during the control processing of the coating amount, it was ground and removed. In addition, the amount of plating adhesion was shown by the average value measured in the smooth part excluding the said part. That is, in the state in which a large amount of hot-dip metal was adhered to the test material by the method of the present invention, as a result of the control processing of the plating adhesion amount, the test material had a relatively uniform and smooth plating appearance. It was possible to form the deposited amount of the molten Al-Zn-Si alloy plating film layer.

Comparative Example 1 Using the same test material as in Example 1, the oxide film was removed by the H ₂ SO ₄ aqueous solution under the same conditions as in Example 1, and
Activation treatment using an aqueous HCl solution and pretreatment by washing with water were performed. Subsequently, in the same manner as in Example 1, a water-soluble dry flux treatment with a chloride-based flux was performed.
A molten flux of the same composition as above was suspended, at a temperature of 635 ° C.
Was immersed in a molten Al-43.5% Zn-1.5% Si-based alloy plating bath containing 0.04% of the iron component as unavoidable impurities and held for 2 minutes. Then, the test material is 2m
The coating film layer is lifted from the hot dip bath at a speed of / min, and is immediately water-cooled and dried without controlling the amount of the hot-dip metal that adheres to the test material and is lifted up, without performing a treatment to control the amount of the applied coating. Was formed on the test material.

As a result, on the surface of the plating layer of the comparative material,
Eight to ten fine projections are produced per 1 m ^{2 of} surface area due to oxides and partial accumulation of the plating bath, and the amount of plating adhered is 70 g per surface area.
/ M ² . That is, the surface roughness of the test material obtained by simply removing the oxide film with the H ₂ SO ₄ aqueous solution as described above is 0.95 μmRa, and the hot dip plating bath to which the iron component was not intentionally added was used. , The fluidity is extremely high, and the amount of hot-dip galvanized metal that is adhered to and retained on the sample material after being lifted from the plating bath is small. It was difficult to form the coating layer.

Example 2 A bolt made of SS41 or equivalent was degreased, washed with water and dried, and then the oxide film was removed by grit blasting, and the average roughness of the surface of the test material was 5.3 μmRa.
Was adjusted to 10% by weight, an activation treatment was performed using a 10% by weight HCl aqueous solution, and washing with water was performed. Subsequently, a solution of a chloride-based flux composed of (45 g / l calcium chloride-70 g / l potassium chloride-35 g / l sodium chloride) -based aqueous solution is applied by a dipping method, and heated and dried at 150 ° C. for 20 minutes. Then, a chloride-based flux film having an adhesion amount of 15.5 g / m ² was produced on the test material and subjected to dry flux treatment. Then, a molten flux having a composition of (45% by weight aluminum fluoride-16.5% by weight calcium chloride-25.7% by weight potassium chloride-12.8% by weight sodium chloride) is applied to the treated material to a thickness of about 30 mm. 0.55% by weight of iron components at a temperature of 640 ° C
It was immersed in the added molten Al-44.0% Zn-1.0% Si alloy plating bath and held for 3 minutes. Then, while pulling out from the hot dip plating bath, control processing of the amount of plating adhered was performed using a centrifugal separator, and water cooling and drying were performed. That is, in the plating treatment and the treatment for controlling the coating amount, 15 test bolts of the above size that have been subjected to the chloride-based aqueous solution flux treatment are placed in a plating basket and immersed, and the plating basket is removed from the plating bath by 5 times. ．
After withdrawing at a speed of 4 m / min, the test bolt was transferred to a basket for controlling the amount of plating adhered, which was provided in the centrifugal separator. Then, immediately using a centrifuge, the basket, that is, the test bolt, is rotated at a peripheral speed of 750 m / min.
Then, the excess molten plated metal adhering to the test bolt was wiped off by a rotation treatment for 5 seconds to control the amount of plating adhered.

As a result, each of the test bolts was subjected to a control treatment of the amount of plating deposits in a state where a large amount of hot-dip plated metal was deposited and retained, so that extremely fine protrusions caused by pools in the plating bath were produced. Although 3 to 4 were generated in one row in the vertical direction of the bolt screw part, generally they have a relatively uniform and smooth plating appearance, and the amount of plating adhered is 375 to 392 g.
/ M ² (average plating deposition amount 381 g / m ² ) with a high deposition amount of Al-Zn based plating film layer was formed by the method of the present invention.

Comparative Example 2 Under the same conditions as in Example 2, the surface oxide film of the test bolt was removed by grit blasting, the surface roughness was adjusted to be approximately the same, and activation treatment was performed using an aqueous HCl solution. It was washed with water. Then, a chloride-based water-soluble dry flux treatment similar to that in Example 2 was performed, and a molten flux having the same composition as in Example 2 was melted and suspended. Al-44.0% Z
It was dipped in an n-1.0% Si alloy plating bath and held for 3 minutes. Subsequently, while pulling out from the hot dip plating bath, a centrifugal separator was used to control the amount of coating adhered under the same conditions as in Example 2, followed by water cooling and drying to prepare a comparative material. As a result, in each of the test bolts, extremely fine protrusions due to the pool of the plating bath were generated as in Example 2, but generally the plating film had a relatively uniform and smooth plating appearance. layers are formed, but the coating weight was only 80~102g / m ² (mean 90g / m ^2). That is, the surface roughness of the test bolt was measured in Example 2
Although it was adjusted to 5.3 μmRa, which is the same as the above, the amount of iron component added to the hot-dip galvanizing bath was small and the fluidity of the galvanizing bath was extremely high. The amount of hot-dip galvanized metal was not sufficient, and it was difficult to form a plating film layer with a high adhesion amount.

Example 3 Using the same test bolt as in Example 2, the oxide film was removed, the surface roughness was adjusted, and the activation treatment was performed by the same method and conditions as in Example 2. Then, a chloride-based water-soluble dry flux treatment was applied in the same manner as in Example 2. Subsequently, molten Al-containing the same flux and iron component as in Example 2
Hot-dip plating was performed under the same method and conditions using a Zn-Si alloy plating bath. Then, a plating basket containing 15 test bolts was placed 5.4 m from the plating bath.
/ Centrifuge at a speed of / min, transferred to a basket for coating amount control provided in the centrifuge, and the test bolt was used for 5 seconds at a peripheral speed of 750 m / min in the same manner as in Example 2. By the rotation treatment, the excess hot-dip metal adhering to the test bolt was wiped off. Then, immediately, in the opposite direction, a smoothing treatment was performed by a rotating treatment at a peripheral speed of 375 m / min (1/2 of the peripheral speed) for 3 seconds (3/5 of the processing time), followed by water cooling and drying. As a result, a large amount of hot-dip metal adhered to each test bolt,
In the held state, the plating amount control process and the smoothing process were performed, resulting in a uniform and smooth plating amount 3
68 to 382 g / m ² (average coating weight 375 g /
A high deposition amount of m ² ) Al-Zn based plating film layer was formed by the method of the present invention.

Comparative Example 3 Using the same test bolt as in Example 2, after degreasing, washing with water and drying, the oxide film was removed by grit blasting, and the average roughness of the surface of the test material was 1. It was adjusted to 8 μmRa, activated with 10 wt% HCl aqueous solution, and washed with water. Then, the same chloride-based water-soluble dry flux treatment as in Example 2 was performed, and the molten flux having the same composition as in Example 3 was melted and suspended, and molten Al containing 0.55% by weight of an iron component at a temperature of 635 ° C. was added. -44.0%
The Zn-1.0% Si alloy was immersed in a plating bath and held for 3 minutes. Then, 5.4 m / mi from the hot dip bath
A comparative material was prepared by pulling it up at a speed of n, performing a control treatment of the coating adhesion amount and a smoothing treatment under the same conditions as in Example 3 using a centrifugal separator, cooling with water and drying.
As a result, in each test bolts, but the plating film layer is formed to have a uniform and smooth coating appearance, the coating weight was only 118~135g / m ² (average 120g / m ^2). That is, as for the hot dip plating bath, the same plating bath as in Example 3 in which the iron component was hot-added to increase the viscosity sufficiently was used, but the average roughness of the surface of the test bolt subjected to the surface roughness adjustment treatment was used. Was only 1.8 μmRa, the amount of hot-dip metal lifted during withdrawal from the plating bath was small, and it was difficult to form a plating film layer with a high adhesion amount.

Example 4 A nut (M22 size) made by over-tapping a thread portion for plating using a material having the same steel composition as in Example 2 was degreased, washed with water and dried, and then an oxide film was formed by grit blasting. And the surface roughness of the test material, especially the average roughness of the outer surface and the upper and lower surfaces of the nut is 3.5 μmRa.
Was adjusted to, and activation treatment was performed using a 10% by weight aqueous solution of HCl, followed by washing with water. Subsequently, a chloride-based flux solution composed of (40 g / l calcium chloride-20 g / l potassium chloride-20 g / l sodium chloride) -based aqueous solution was applied by a dipping method, and subjected to heat drying treatment at 180 ° C. for 15 minutes. A chloride flux having an adhesion amount of 6.4 g / m ² was generated on the test material and subjected to a water-soluble dry flux treatment. Then, 20 test nuts were placed in a plating basket (20 wt% cryolite-30 wt% aluminum fluoride-20 wt% calcium chloride-25 wt% potassium chloride-12.5 wt% sodium chloride). A molten Al-38% Zn-1.8% Si-based alloy plating bath containing 0.85% by weight of an iron component at a temperature of 645 ° C. in which a molten flux having a composition is melted and suspended to have a thickness of about 15 mm. And held for 3 minutes. Then, the plating basket was lifted at a speed of 8.5 m / min and vibrated for 10 seconds, and then transferred to a plating adhesion control basket provided in the centrifugal separator. Using a centrifuge, the basket, that is, the nut under test, is rotated at a peripheral speed of 940 m / mi.
The rotation treatment was performed for 5 seconds with n, and the excess hot-dip metal adhering to the test bolt was wiped off. Immediately in the opposite direction, the peripheral speed is 565 m / min (3/5 of the peripheral speed).
Was rotated for 3 seconds (3/5 of the treatment time), and a smoothing treatment was added. The rotation-wiping treatment and the rotation-smoothing treatment under the above conditions were continuously performed three times, followed by water cooling and drying.

As a result, each of the test nuts has a uniform and smooth plating appearance because the plating adhesion amount controlling process and the smoothing process are performed in a state where a large amount of the hot dip plated metal is adhered and retained. , Nut outer surface and upper and lower surface plating coverage 285-303 g / m ² (average plating coverage 2
92 g / m ² ), plating adhesion amount on the inner thread part of the nut 31
0 to 321 g / m ² (average coating weight 316 g / m ² )
A high-adhesion amount Al-Zn-based plating film layer of was formed by the method of the present invention.

Comparative Example 4 Using the same test nut as in Example 4, after degreasing, washing with water and drying, the oxide film was removed by grit blasting, and the surface roughness of the test material, especially the nut The average roughness of the outer surface and the upper and lower surfaces was adjusted to 2.2 μmRa, activation treatment was performed using a 10 wt% HCl aqueous solution, and washing with water was performed. Then, a chloride-based water-soluble dry flux treatment similar to that in Example 4 was performed, and a molten flux having the same composition as in Example 5 was melted and suspended to have a thickness of 15 mm, and the iron component at a temperature of 645 ° C. was adjusted to 0. Molten Al added with 18% by weight
It was immersed in a -38% Zn-1.8% Si alloy plating bath and held for 3 minutes. Then, 8.5m / from the plating bath
After pulling up at a speed of min and applying vibration for 10 seconds, using a centrifugal separator, under the same conditions as in Example 4, a plating adhesion amount control process and a smoothing process were performed, and water cooling and drying were performed to obtain a comparative material. Created.

As a result, a plating film layer having a uniform and smooth plating appearance was formed on each of the nuts to be tested, but the coating amount was 90 on the nut outer surface and the upper and lower surfaces.
Was only ~112g / m ² (average 103g / m ^2). That is, with the adjustment of the surface roughness and the addition amount of the iron component to the hot dip plating bath under the present treatment conditions, a sufficiently large amount of hot dip metal is attached to and retained on the test nut after being lifted from the hot dip bath. Because the effect was not obtained,
It was difficult to form a high adhesion amount of the plating film layer on the outer surface of the nut and the upper and lower surfaces.

Example 5 Low alloy steel containing Cr and Mn (high tensile strength 80 kg / mm
Bolts (M24 x 150m) made using Class ² equivalent
m) was degreased, washed with water and dried, and then the oxide film was removed by grit blasting, the average roughness of the surface of the test material was adjusted to 3.9 μmRa, and activated using a 15 wt% HCl aqueous solution. Chemical treatment was performed and washing with water was performed. Subsequently, a chloride-based flux solution composed of a (30 g / l calcium chloride-10 g / l magnesium chloride-80 g / l potassium chloride-80 g / l sodium chloride) -based aqueous solution was applied by the dipping method, and the resulting mixture was applied at 150 ° C. for 15 minutes. Was heat-dried to produce a chloride flux having an adhesion amount of 17.8 g / m ^{2 on} the test material and a water-soluble dry flux treatment. Then, 10 test bolts were placed in a plating basket (20% by weight cryolite-20% by weight aluminum fluoride-9% by weight calcium chloride-3% by weight magnesium chloride-24% by weight potassium chloride-24% by weight). About 40m thick molten flux composed of sodium chloride type composition
It was immersed in a molten Al-8.5Si-based alloy plating bath to which 1.1% by weight of an iron component having a temperature of 660 ° C., which had been melted and suspended so as to be m, was added and held for 2 minutes. Next, after the plating basket was lifted at a speed of 7.5 m / min, the test bolt was transferred to the plating adhesion control basket provided in the centrifugal separator. Immediately thereafter, use a centrifugal separator to move the basket, that is, the test bolt, to a peripheral speed of 4
The excess hot-dip galvanized metal adhering to the test bolt was wiped off by a rotating treatment at 70 m / min for 6 seconds, and then in the opposite direction at a peripheral speed of 188 m / min (2/5 of the peripheral speed) for 2 seconds (the above-mentioned A control treatment of the amount of plating adhered to which a rotation smoothing treatment for 1/3 of the treatment time) was added and a smoothing treatment were performed, followed by water cooling and drying.

As a result, in each of the test bolts, the coating amount control process and the smoothing process were performed in a state where a large amount of the molten plated metal was deposited and held, so that the plating deposition amount 187 with a uniform and smooth appearance was obtained. ~209g / m ² (average coating weight 201g / m ²⁾ high adhesion amount of Al-Zn-based plating film layer was formed by the method of the present invention.

Comparative Example 5 Using the same test bolts as in Example 5, degreasing, washing with water and drying were performed, and then an oxide film was removed using an aqueous solution of 20 wt% H ₂ SO ₄ and washing with water was performed. An activation treatment was performed with a wt% HCl aqueous solution, and then washing with water was performed. Then, a chloride-based water-soluble dry flux treatment having the same composition as in Example 5 was applied,
In a molten Al-8.5% Si-based alloy plating bath, 1.1 wt% of an iron component at a temperature of 660 ° C., in which a molten flux having the same composition as in Example 5 was melted and suspended, was suspended. It was dipped and held for 2 minutes. Then, while pulling up from the plating bath at a speed of 7.5 m / min, a centrifugal separator was used to perform a control treatment of the coating adhesion amount and a smoothing treatment under the same conditions as in Example 5, followed by water cooling and drying for comparison. I made wood. As a result, a plating film layer having a uniform and smooth plating appearance was formed on each of the test bolts, but the coating adhesion amount was 85 to 115 g / m ² (average 9).
5 g / m ² ). That is, as the hot-dip galvanizing bath, the same galvanic bath as in Example 5 in which the iron component was hot-melted to sufficiently increase the viscosity was used, but the surface roughness adjusting treatment was not performed, so that the test bolt surface Had an average roughness of only 1.2 μmRa, and the amount of the hot-dip metal to be lifted during withdrawal from the plating bath was small, making it difficult to form a plating film layer with a high adhesion amount.

[0052]

In the method of the present invention, the formation of the alloy layer is suppressed by the action of silicon contained in the plating bath, and the fluidity of the hot dip bath is extremely high. Regarding the hot-dip Al-Zn-Si-based alloy and hot-dip Al-Si-based alloy plating method by single-step plating using a flux that has a uniform coating amount and is difficult to form a smooth plating film layer, the surface of the steel material to be plated Roughness adjustment, specification, and increase in viscosity of the molten alloy plating bath due to addition of specific amount of iron component enable increase of lift amount of molten alloy plating bath by steel material when lifting from plating bath Of the molten Al-Zn-Si-based alloy and molten Al-S by solving the above-mentioned problems by wiping the molten alloy plating bath of
It is possible to provide a plating method of the i-based alloy by the flux method. Further, in the present invention, by attaching the steel material, wiping off the surplus amount of the molten alloy plating bath that has been lifted up, and controlling the coating amount by the specified method and conditions, excellent uniform smoothness, high adhesion The amount of molten alloy plating film layer can be formed efficiently, and smoothing treatment is added after the control of the coating amount, which makes it even more uniform with respect to the material to be plated having the threaded portion. It is possible to generate a high-adhesion amount hot-dip alloy plating film layer having excellent smoothness.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-108848 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (4)

(57) [Claims] 1. In hot-dip Al—Zn—Si-based alloy and hot-dip Al—Si-based alloy plating by a one-step plating method using a flux for steel materials, the average roughness of the steel material surface from which the oxide film has been removed is 2.5 to After adjusting to a range of 7.5 μmRa, activation treatment is performed, and in a hot dip plating bath in which iron components in the range of 0.25 to 1.5% by weight relative to the total weight of the plating bath excluding flux are melt-added A method for high-adhesion plating of a molten Al-Zn-Si alloy and a molten Al-Si alloy, which is characterized in that it is subjected to a dipping treatment and then a treatment for controlling the amount of plating deposited. 2. The molten Al according to claim 1, wherein the control process of the coating amount described above is performed by a centrifugal separation method at a peripheral speed of 400 to 1,500 m / min.
-Zn-Si system alloy and molten Al-Si system alloy high deposition amount plating method. 3. The plating adhesion control process described above is performed for a certain period of time by a centrifugal separation method at a peripheral speed of 400 to 1,500 m / min, and then 1/3 or more to 4/5 of the peripheral speed.
The melting according to claim 1, wherein the smoothing process is performed by rotating in the opposite direction to the process at the following peripheral speed and a process time of ⅕ or more and 3/4 or less of the process time. A
A high deposition amount plating method for 1-Zn-Si based alloy and molten Al-Si based alloy. 4. A flux for a steel material is melted and suspended.
In the plating bath composed of the molten Al-Zn-Si alloy or the molten Al-Si alloy, the iron component in the range of 0.25 to 1.5% by weight relative to the total weight of the plating bath excluding the flux is melted. A molten Al-Zn-Si alloy and a molten Al-Si alloy plating bath using a flux characterized by being added.