JPH06299312A - Surface-treated steel material excellent in corrosion resistance and its production - Google Patents

Surface-treated steel material excellent in corrosion resistance and its production

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Publication number
JPH06299312A
JPH06299312A JP8825993A JP8825993A JPH06299312A JP H06299312 A JPH06299312 A JP H06299312A JP 8825993 A JP8825993 A JP 8825993A JP 8825993 A JP8825993 A JP 8825993A JP H06299312 A JPH06299312 A JP H06299312A
Authority
JP
Japan
Prior art keywords
steel
aluminum
bath
weight
corrosion resistance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP8825993A
Other languages
Japanese (ja)
Inventor
Tomio Kajita
Kazuo Okumura
Masaki Tanigawa
和生 奥村
富男 梶田
正樹 谷川
Original Assignee
Kobe Steel Ltd
株式会社神戸製鋼所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kobe Steel Ltd, 株式会社神戸製鋼所 filed Critical Kobe Steel Ltd
Priority to JP8825993A priority Critical patent/JPH06299312A/en
Publication of JPH06299312A publication Critical patent/JPH06299312A/en
Pending legal-status Critical Current

Links

Abstract

(57) [Abstract] [Purpose] To provide a zinc-aluminum alloy plated steel material having excellent corrosion resistance and a method for producing the same. [Structure] F with a thickness of 1 μm or less at the interface with the steel material that is the base material
It has an intermetallic compound layer made of e-Al, and a coating film made of 20 to 80% by weight of aluminum and the balance being essentially zinc is provided thereon. Such a surface-treated steel material is obtained by immersing the steel material in a molten metal consisting of 0.1 to 20% by weight of aluminum and the balance being zinc, and at the interface between the steel material and the plated layer, Fe-Al having a thickness of 1 μm or less. It can be obtained by forming an intermetallic compound layer and then immersing it in a molten metal consisting of 20 to 80% by weight of aluminum and the balance being essentially zinc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel material having excellent corrosion resistance, which can be widely used in various industrial fields including construction materials, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, the surface of steel products such as steel plates and steel wires has been widely galvanized to improve the corrosion resistance of steel products, and even today, such products have a wide range of uses. Steel is used. However, in recent years, with the diversification of the environment in which such galvanized steel materials are used, the corrosion resistance of galvanization is especially high, especially in coastal areas that are strongly affected by sea salt particles and heavy industrial areas that are strongly affected by acid rain. Is not enough.

Against this background, a zinc-aluminum alloy plated steel material having better corrosion resistance than conventional zinc plating has been developed, and the amount thereof used is increasing year by year.
The zinc-aluminum alloy plating containing 20 to 80% by weight of aluminum has excellent corrosion resistance because it has both the sacrificial anticorrosion ability for galvanized steel and the effect of the passivation film of aluminum plating.

By the way, aluminum 20 to 80% by weight
In the zinc-aluminum alloy plating containing, an Fe-Al alloy layer is formed at the interface with the steel material that is the base material. This Fe
Since the Al alloy layer is hard and brittle, when the alloy layer grows thick, the workability of the plated steel sheet is significantly deteriorated. Therefore,
Conventionally, Si of about 3% of aluminum content was added to the plating bath, and thin Fe-Al-S was added to the interface with the steel plate substrate.
The i alloy layer is formed to suppress the growth of the Fe-Al alloy layer.

However, according to such a conventional method,
The added Si will be included not only in the alloy layer but also in the plating layer, and Si in the plating layer will be present as Si particles at the interface between the Al-rich dendrite and the Zn-rich dendrite interphase. It will be segregated. The segregated Si particles are likely to be a starting point of corrosion, the Si particles serve as a cathode, promote the elution of zinc in the vicinity of the Si particles, and promote the progress of local corrosion of the plating layer. When such localized corrosion of the plating layer reaches the steel plate substrate, spot-like rust is generated, which not only causes a problem in appearance but also causes many problems such as deterioration of plating adhesion.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in conventional zinc-aluminum alloy plated steel products, and is a surface-treated steel product having excellent corrosion resistance and its production. The purpose is to provide a method.

[0007]

A surface-treated steel material excellent in corrosion resistance according to the present invention has an intermetallic compound layer made of Fe-Al having a thickness of 1 μm or less at an interface with a steel material as a base material, and further on it. Is characterized by having a coating of 20 to 80% by weight of aluminum and the balance being essentially zinc.

According to the present invention, such a surface-treated steel material is obtained by immersing the steel material in a molten metal consisting of 0.1 to 20% by weight of aluminum and the balance being essentially zinc to form a thick film at the interface between the steel material and the plating layer. It can be obtained by forming an Fe-Al intermetallic compound layer having a thickness of 1 μm or less and then immersing it in a molten metal consisting of 20 to 80% by weight of aluminum and the balance being essentially zinc.

According to the present invention, the Fe-Al intermetallic compound layer serves as a barrier layer against diffusion of iron from the steel material which is the base material, and Fe-A which adversely affects the workability.
Suppress excessive growth of 1-alloy and Zn-Fe alloy. Further, the Fe-Al intermetallic compound layer also serves as a barrier against corrosion factors, improves corrosion resistance, and firmly adheres to both the steel sheet that is the base material and the plating layer that is the upper layer. However, it has an effect. However, since the intermetallic compound layer made of Fe-Al itself is hard and brittle, if the thickness exceeds 1 μm, the workability deteriorates. Therefore, according to the present invention, Fe-A is used.
The thickness of the intermetallic compound layer made of 1 must be 1 μm or less.

In the plated steel product according to the present invention, the upper layer is a coating layer consisting of 20 to 80% by weight of aluminum and the balance being essentially zinc. This coating layer consists of a dendrite phase rich in aluminum and a dendrite phase rich in zinc. Due to the passivation coating of aluminum and the sacrificial anticorrosive ability of zinc,
It has excellent corrosion resistance in a wide variety of environments. When the content of aluminum in the coating layer is less than 20% by weight, improvement in corrosion resistance due to passivation of aluminum cannot be expected, and when it exceeds 80% by weight, the sacrificial anticorrosive ability against steel disappears. . Therefore, according to the present invention,
In order to have both the passive film and the sacrificial anticorrosive ability of zinc,
The content of aluminum in the coating must be 20 to 80% by weight. Furthermore, according to the present invention, since Si is not contained in the coating layer, Si particles that are likely to be the starting point of local corrosion are not segregated, and thus local corrosion does not proceed. The excellent corrosion resistance and adhesion of the coating layer are maintained over a long period of time.

The method for producing the surface-treated steel material having excellent corrosion resistance according to the present invention will be described below. In the present invention, first, the steel material is cleaned by a conventionally known ordinary method, and then the aluminum material is cleaned.
By immersing in a molten metal bath (hereinafter referred to as the first bath) consisting of 0.1 to 20% by weight and the balance being essentially zinc, the thickness of the interface between the steel material and the plating layer is 1 μm or less. F
An e-Al intermetallic compound layer is formed, and the steel material treated in this manner is then immersed in a molten metal bath (hereinafter referred to as the second bath) consisting of 20 to 80% by weight of aluminum and the balance essentially of zinc. Can be obtained by

In the present invention, the method of cleaning the steel material is a method such as degreasing, flux treatment, gas reduction treatment, etc., which is capable of obtaining an active surface by removing fats and oils, dirt and oxide film on the surface of the steel material. There is no particular limitation so long as it is a conventional method known in the art. In the present invention, the composition of the first bath consists of 0.1 to 20% by weight of aluminum and the balance essentially zinc. When the content of aluminum in the molten bath is less than 0.1% by weight, the growth of the Zn-Fe alloy layer is promoted by the reaction between iron and zinc, while the content of aluminum is 2%.
When it exceeds 0% by weight, the growth of the Fe-Al intermetallic compound layer becomes excessive and the thickness cannot be made 1 μm, and thus the workability of the plated steel material is significantly deteriorated. Therefore, according to the present invention, the aluminum content in the first bath should be in the range of 0.1 to 20% by weight.

In addition to aluminum and zinc, the first bath may contain inevitable impurities such as iron, and additional third elements such as lead and antimony. These third elements are not particularly problematic in the step of immersing the steel material in the first bath to form the Fe-Al intermetallic compound layer, but when the third element is mixed in the second bath, plating It may adversely affect the corrosion resistance of steel materials. Therefore, it is desirable that the above-mentioned third element is suppressed to 0.1% by weight or less in the useful bath.

According to the present invention, the steel material is immersed in the first bath to form the Fe-Al intermetallic compound layer, and then the steel material is pulled up from the first bath and then immersed in the second bath. Aluminum over the Fe-Al intermetallic compound layer 2
A coating layer is formed consisting of 0-80% by weight, the balance essentially zinc. The composition of this second bath is aluminum 20-
80% by weight with the balance essentially zinc.

The aluminum content in the second bath is 2
When it is less than 0% by weight, improvement in corrosion resistance due to the aluminum passivation film is not expected, while it is 80% by weight.
When it exceeds, the sacrificial anticorrosive ability for steel disappears. Therefore, in the present invention, in order to have the effect of improving the corrosion resistance due to the passivation film and the sacrificial anticorrosion ability, and exhibiting the excellent corrosion resistance, the content of aluminum in the second bath is in the range of 20 to 80% by weight. It is necessary to

In the present invention, the Fe-Al intermetallic compound, which is a barrier layer against the diffusion of iron, is formed before the dipping in the second bath.
It is not necessary to add the third element such as silicon, which has been added to suppress the excessive growth of the -Al intermetallic compound layer, to the second bath. Accordingly, the upper layer of the surface-treated steel sheet according to the present invention, which contains 20 to 80% by weight of aluminum and the balance being essentially zinc, does not contain a third element such as silicon and thus local corrosion. It is possible to obtain a surface-treated steel sheet that does not progress.

According to the present invention, when the steel material is immersed in the first bath and then withdrawn from the first bath, a coating layer corresponding to the composition of the first bath is formed on the Fe-Al intermetallic compound layer. It is formed. This coating layer elutes when immersed in the second bath, and instead forms a coating layer corresponding to the composition of the second bath. Therefore, it is not necessary to remove the coating layer film layer corresponding to the composition of the first bath formed in the first bath before dipping in the second bath, but the first bath component is mixed in the second bath. Since the composition control of the second bath may be complicated, in the present invention, the coating layer corresponding to the first bath component formed in the first bath may be removed before dipping in the second bath. desirable.

As described above, as a method for removing the coating layer corresponding to the components of the first bath formed in the first bath before dipping in the second bath, a gas squeezing method, mechanical grinding, chemical etching or the like is used. However, the present invention is not limited to these and may be selected as appropriate. Furthermore, in the present invention, the plating conditions such as plating bath temperature and plate temperature are
In both cases of the first bath dipping and the second bath dipping, there is no particular limitation, and it may be carried out according to a conventionally known conventional method.

[0019]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. In each of the following Examples and Comparative Examples, an aluminum-killed cold-rolled steel sheet having a thickness of 0.77 mm was used as a base material and was cleaned by a conventional method known in the art.
A surface-treated material was obtained by treating with a batch-type hot dip plating apparatus under the conditions shown in. The following samples were subjected to the following corrosion resistance test and workability test. Corrosion resistance test A cross-cut to the base material was performed on the surface of the steel sheet, and a salt spray test was carried out in accordance with JIS Z-2371 using this as a sample, and the time until the occurrence of red rust was evaluated. Workability test A steel plate was subjected to close contact bending, and the occurrence of cracks in the worked portion was visually observed, and the degree of cracking was evaluated.

Table 2 shows the test evaluation results of the respective examples and comparative examples. As is clear from Table 2, the surface-treated steel materials obtained in Examples 1 to 17 according to the present invention are
Both have excellent corrosion resistance and workability. However, in Comparative Examples 1 to 6 in which the aluminum content in the first bath or the second bath does not satisfy the conditions specified in the present invention, or in the conventional method in which silicon is added to the bath and the treatment is performed in one bath. According to certain Comparative Examples 7 to 9, all are inferior in both corrosion resistance and workability, or one of them is inferior. In Comparative Example 1, since the aluminum concentration in the first bath was low, the Fe-Al intermetallic compound layer was not confirmed and the Zn-Fe alloy layer was excessively grown.

[0021]

[Table 1]

[0022]

[Table 2]

The corrosion resistance evaluation criteria are as follows. ◎ Red rust occurrence 1000 hours or more ○ Red rust occurrence 800 to 1000 hours △ Red rust occurrence 500 to 800 hours × Red rust occurrence 500 hours or less The workability evaluation criteria are as follows.

◎ No cracks in the processed part ○ Little cracks in the processed part △ During cracking in the processed part × Large cracks in the processed part

[0025]

As described above, according to the present invention, an intermetallic compound layer of Fe-Al having a thickness of 1 μm or less is formed at the interface with a steel material as a base material, and an aluminum 20- A surface-treated steel material having excellent corrosion resistance can be obtained by forming a coating film consisting of 80% by weight and the balance being essentially zinc.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Kajita 2222, Ikeda, Ikeda, Ikeda, Onoe-machi, Kakogawa-shi, Hyogo Prefecture Kakogawa Research Area, Kobe Steel Co., Ltd.

Claims (2)

[Claims]
1. An intermetallic compound layer made of Fe-Al having a thickness of 1 μm or less is formed at an interface with a steel material as a base material, and 20 to 80% by weight of aluminum and the balance being essentially zinc. A surface-treated steel material that has a coating and has excellent corrosion resistance.
2. A Fe-Al intermetallic compound having a thickness of 1 .mu.m or less at the interface between the steel material and the plated layer by immersing the steel material in a molten metal consisting of 0.1 to 20% by weight of aluminum and the balance being essentially zinc. The method for producing a surface-treated steel material having excellent corrosion resistance according to claim 1, wherein after the layer is formed, the surface-treated steel material is immersed in a molten metal having 20 to 80% by weight of aluminum and the balance being essentially zinc.
JP8825993A 1993-04-15 1993-04-15 Surface-treated steel material excellent in corrosion resistance and its production Pending JPH06299312A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP8825993A JPH06299312A (en) 1993-04-15 1993-04-15 Surface-treated steel material excellent in corrosion resistance and its production

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP8825993A JPH06299312A (en) 1993-04-15 1993-04-15 Surface-treated steel material excellent in corrosion resistance and its production

Publications (1)

Publication Number Publication Date
JPH06299312A true JPH06299312A (en) 1994-10-25

Family

ID=13937889

Family Applications (1)

Application Number Title Priority Date Filing Date
JP8825993A Pending JPH06299312A (en) 1993-04-15 1993-04-15 Surface-treated steel material excellent in corrosion resistance and its production

Country Status (1)

Country Link
JP (1) JPH06299312A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008169478A (en) * 2006-12-11 2008-07-24 Nippon Steel Corp Hot dip coated steel member and method of producing the same
JP2008538384A (en) * 2005-02-24 2008-10-23 ティッセンクルップ スチール アクチェンゲゼルシャフトThyssenKrupp Steel AG Method for coating steel strip and steel strip with said coating
JP2009179865A (en) * 2008-01-31 2009-08-13 Nisshin Steel Co Ltd A1-plated steel wire, and method for producing the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008538384A (en) * 2005-02-24 2008-10-23 ティッセンクルップ スチール アクチェンゲゼルシャフトThyssenKrupp Steel AG Method for coating steel strip and steel strip with said coating
KR101287168B1 (en) * 2005-02-24 2013-07-16 티센크루프 스틸 유럽 악티엔게젤샤프트 Method for steel strip coating and a steel strip provided with said coating
JP2008169478A (en) * 2006-12-11 2008-07-24 Nippon Steel Corp Hot dip coated steel member and method of producing the same
JP2009179865A (en) * 2008-01-31 2009-08-13 Nisshin Steel Co Ltd A1-plated steel wire, and method for producing the same

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